Del Mar Photonics

Optics and Photonics 2009 Presentations attended by Del Mar Photonics team.

Brooke Hester is a PhD student working in the Optical Tweezers Lab at the National Institute of Standards and Technology (NIST). In this video she tells about trapping polystyrene spheres and nanoshells using Trestles CW - continuum wave tunable Ti:Sapphire laser from Del Mar Photonics.
 

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A nanoshell is composed of a spherical core of a particular compound surrounded by a shell of a few nanometers in thickness. One of the promising applications concerns the biological field. Research is being performed to create nanoshells with high absorptions at biologically useful wavelengths by altering the thickness of the shells. Particularly, the Near Infra Red region, which corresponds with low absorption by tissue, may be useful.
In the literature, special attention is given to gold nanoshell with a dielectric core (gold sulfide, silicon dioxide,...). Gold is a biocompatible compound, making it a useful material for medical applications. However the overall size of silica/gold nanoshells may make clearance of these particles a problem in use in the body. To be removed from the body via the kidneys (renal system), a particle's hydrodynamic diameter must be approximately less than 6nm. Long term in vivo toxicity studies must be undertaken to determine the toxicity of any nanoparticle.
Nanoshells are currently being investigated as:
• a treatment for cancer similar to chemotherapy but without the toxic side-effects [1]
• inexpensive, quick analysis of "samples as small as a single molecule" and builds on Raman spectroscopy [2]
Gold (Au) nanoshells exhibit tunable plasmonic resonance based on the ratio of the shell to core thickness. In addition the overall size of such a particle allows independent control of its scattering cross section.

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Towards spatio-temporal control in optical trapping
Paper 7400-15 of Conference 7400
Date: Sunday, 02 August 2009
Time: 4:30 PM – 4:50 PM

Author(s): Debjit Roy, Arijit K. De, Debabrata Goswami, Indian Institute of Technology Kanpur (India)

 
Since its first implementation in the end of seventies last century, optical trapping has been one of the forefront of present day research having wide ranging applications from Bose-Einstein condensate to measurement of tiny forces (of the order of few pico-Newtons) exerted by molecular motors inside living cell. Starting with a discussion on a simplistic method for force calibration and implementation of gigantic instantaneous forces offered by ultrashort laser pulses in holding Rayleigh particles, the idea of spatio-temporal control achieved by simultaneously shaping the spatial as well as time-frequency profile of laser pulses will be discussed.

Measurement of trap length for an optical trap
Paper 7400-83 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 5:30 PM

Author(s): Susan Y. Wrbanek, NASA Glenn Research Ctr. (United States)

 
A discussion of the technique used to measure the trap length along the z-axis of an optical trap formed with an upright microscope is presented. The experimental approach was to drop a microsphere of known size and mass from its various positions within a water chamber and time its fall, noting whether or not the microsphere could be re-trapped at the end of the time. If a falling microsphere reaches terminal velocity early in its fall, computing the distance over which the microsphere may be re-trapped is straightforward. Difficulties encountered near the top and bottom of the water chamber are noted, and compared to two modifications of Stokes equation. The results allow more precise control using optical micromanipulation to assemble miniature devices by providing information about the distance over which that optical trap is effective, and how much a trapped object can be raised, lowered, and re-trapped.

Bacterial swimming studied using optical traps
Paper 7400-7 of Conference 7400
Date: Sunday, 02 August 2009
Time: 11:30 AM – 12:00 PM

Author(s): T. Lance Min, Patrick Mears, Lon Chubiz, Christopher Rao, Ido Golding, Yann R. Chemla, Univ. of Illinois at Urbana-Champaign (United States)

 
Bacterial chemotaxis serves as a model system for studying cellular response to external stimuli. Current chemotaxis assays usually examine the response of individual motors, while true bacterial swimming results from the cooperative activity of multiple motors that often turn asynchronously. On the other hand, when the response of freely swimming bacteria is assayed, only the ensemble-averaged response is typically recorded, since the single-cell data is often noisy and too short-term to be meaningful.
We have developed a novel assay where individual E. coli cells are optically trapped in liquid medium, and the motion of cell body within the trap is monitored with millisecond time-resolution. Under conditions conducive to motility, the trapped bacteria remain motile for periods exceeding one hour. Cell body motion exhibits rich behavioral patterns, consisting of wobbly rotation interspersed with sudden cessation of rotation corresponding to "runs" and "tumbles". Analyzing body motion for an extended time period yields run and tumble statistics for individual cells.
We have also built a microfluidic chamber where parallel streams of laminar flow establish chemical gradients perpendicular to flow direction. Moving the trapped cell along a chemoeffector gradient allow us to probe the response of a single cell under precisely defined stimuli conditions.

Theoretical prediction for cell deformation in the optical traps
Paper 7400-12 of Conference 7400
Date: Sunday, 02 August 2009
Time: 2:50 PM – 3:10 PM

Author(s): Paul Brule-Bareil, Yunlong Sheng, Univ. Laval (Canada); Arthur E. Chiou, National Yang-Ming Univ. (Taiwan)

 
We present optical and mechanical models for cell’s deformation in the optical traps. The morphological deformation of the cell is calculated from the local stress distribution on the cell using the linear theory of thin elastic membrane, which is valid for the cells without cytoskeletal structure, such as the red blood cells. This approach is generic allows computing for a variety of experimental configurations and predicting cell’s deformation. The coupling coefficient from one fiber to another through the deformed trapped cell in the fiber-optical dual-beam stretcher was calculated for monitoring of the cell deformation by measuring the coupling coefficient.

Encapsulation of gold nanoparticles in thermoresponsive microgels: molecular traps for SERS
Paper 7394-89 of Conference 7394
Date: Wednesday, 05 August 2009
Time: 5:30 PM

Author(s): Rafael Contreras-Cáceres, Univ. de Almería (Spain); Ramón Álvarez-Puebla, Isabel Pastoriza-Santos, Jorge Pérez-Juste, Luis M. Liz-Marzán, Univ. de Vigo (Spain)

 
Nanocomposite materials consisting of a colloidal metal nanoparticle within a synthetic polymer hydrogel shell have attracted great attention due to potential applications in several fields such as catalysis, photonics, electronics, optics and biomedicine. Gold metal nanoparticles has been successfully incorporated inside thermoresponsive poly(N-isopropylacrylamide) (pNIPAM) microgels. Control over the NIPAM shell thickness can be easily achieved by using appropriate amounts of NIPAM monomer. The thermoresponsive properties of the systems allow us to control the optical and catalytic properties of metal nanoparticles. Recently, we have shown its applicability as molecular traps for surface-enhanced, spectroscopic, ultra-sensitive analysis.

Multiple optical traps created with an inclined fiber optical tweezers
Paper 7400-81 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 5:30 PM

Author(s): Yuxiang Liu, Miao Yu, Univ. of Maryland, College Park (United States)

 
Most of the current multiple optical traps are realized with optical tweezers based on microscope objectives. We created multiple traps with a fiber-based trapping system. The traps were formed at different vertical levels with adjustable separations and positions. We demonstrated that this fiber-based trapping system can perform multiple functions, such as particle selection, separation, and stacking. Compared with the multiple traps formed with objective-based optical tweezers, the fiber-based multiple traps are independent of the objective or the substrate and are potential to be integrated in microfluidic systems for on-chip parallel manipulation and characterization of interactions of colloidal and biological systems.

Dynamic properties of a micro-sphere optically trapped in air by radially polarized laser beam
Paper 7400-69 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 4:40 PM – 5:00 PM

Author(s): Masaki Michihata, Yasuhiro Takaya, Terutake Hayashi, Osaka Univ. (Japan)

 
Recently the trapping technique is used in air, for example, a precision probe for sensing surface of an object. We studied the dynamic properties of a micro-sphere (ϕ8um) optically trapped in air by using radially or linearly polarized beam. We realized the optical trapping of the micro-sphere in air with objective of NA0.80. Then the vertical and lateral force working on the micro-sphere are analyzed numerically by means of ray-trace method and measured experimentally. The results are qualitatively coincident with numerical calculations.

Thermal motion of an optically trapped nano-tool
Paper 7400-71 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 5:20 PM – 5:40 PM

Author(s): Stephen H. Simpson, Mervyn J. Miles, Simon Hanna, Univ. of Bristol (United Kingdom)

 
By using multiple optical traps suitably sized complex bodies can be bound with respect to their positions and orientations. One recent application of this involves the use of an elongated object, equipped with a probe (a "nano-tool"), to measure and apply pico-Newton sized forces to, for example, the surface of a cell. Calculations of the mechanical susceptibility of trapped probes and their hydrodynamic resistance, are presented. These quantities are used to assess the subsequent thermal motion in the context of the Ornstein-Uhlenbeck process. Implications for the resolution and general behavior of the nanoprobe referred to above are discussed.

Optically tunable surfaces via trapped particles in microcavities
Paper 7400-77 of Conference 7400
Date: Thursday, 06 August 2009
Time: 11:00 AM – 11:20 AM

Author(s): Rebecca Sainidou, Fransisco Javier Garcia de Abajo, Consejo Superior de Investigaciones Científicas (Spain)

 
We introduce optically tunable surfaces based upon metallic gold nanoparticles trapped in open, waterfilled gold cavities. The optical properties of the surfaces change dramatically with the presence and location of the particles inside the cavities. The precise position of the particles is shown to be controllable through optical forces exerted by external illumination, thus leading to all-optical tunability, whereby the
optical response of the surfaces is tuned through externally applied light. We discuss the performance of the cavity-particle complex in detail and provide theoretical support for its application as a novel concept of a large-scale optically tunable system.

Measurement of the axial rotation of nanorods trapped by a laser beam
Paper 7400-79 of Conference 7400
Date: Thursday, 06 August 2009
Time: 11:40 AM – 12:00 PM

Author(s): Sun-Uk Hwang, Gwangju Institute of Science and Technology (Korea, Republic of); Yong-Jin Kim, Gyu-Chul Yi, Pohang Univ. of Science and Technology (Korea, Republic of); Yong-Gu Lee, Gwangju Institute of Science and Technology (Korea, Republic of)

 
Optical trapping of nanorods has attracted many researchers due to the many potential applications of nanorods in sensor technologies. It is well known that nanorods align with the propagation axis or the polarization direction of a laser beam. However, there are only few studies about the axial rotation of nanorods. In this study, we present a method for the measurement of the rotational frequency of nanorods trapped by a laser beam.

Brooke Hester is a PhD student working in the Optical Tweezers Lab at the National Institute of Standards and Technology (NIST). In this video she tells about trapping polystyrene spheres and nanoshells using Trestles CW - continuum wave tunable Ti:Sapphire laser from Del Mar Photonics.
 

Request a quote for laser suitable for optical trapping

Optical trapping of individual quantum dots and other challenging particles
Paper 7400-14 of Conference 7400
Date: Sunday, 02 August 2009
Time: 4:00 PM – 4:30 PM

Author(s): Lene B. Oddershede, Univ. of Copenhagen (Denmark)

To optically trap nanoparticles it is important to have an efficient
optical trap. Through improvements, e.g. canceling spherical aberrations
(Optics Letters vol.32, p.1998 2007), we significantly increased the
performance of a single beam optical trap thus allowing trapping of
individual nanoparticles in three dimensions in a single laser trap
using very low laser powers. Anther crucial point is to choose
particles and laser wavelengths such that the absorption and
scattering cross sections for the nanoparticles are low. Using
a 1064 nm laser gold nano-spheres with diameters 18 to 250 nm
(Nano Letters vol. 5 p.1937 2005) as well as gold nano-rods with
thicknesses down to 8 nm and aspect ratios between 1.7 and 5.6
(Nano Letters vol. 8 p. 2998 2008) were individually optically trapped
in three dimensions, and optical forces of tenths of pico-Newton easily
applied. The gold nano-rods aligned with the electrical field, this
property making the rods excellent as nano-rotators in single molecule
experiments. In contrast to gold nanoparticles, which are known to
quench fluorescence, silver nanoparticles enhance fluorescence, and
silver spheres with diameters down to 18 nm were also easily
individually optically manipulated (Nano Letters vol. 8 p.1486, 2008).
Hence, silver nanoparticles are obvious choices as handles for
experiments where a clear fluorescent signal is desirable. Even
individual quantum dots have been proven individually trapped
(Nano Letters, vol.8, p.3376 2008). Their narrow emission bands
combined with a very low degree of photo-bleaching make quantum
dots superior as markers or donors in the study of, e.g., single
molecule systems. Also, the trapping spring constant carries
information about the interaction between the electrical field and
the quantum dot, thus allowing a calculation of physical characteristics
of the quantum dot such as the polarizability of an individual colloidal
quantum dot. A further advantage is that two photon absorption is
very efficient, hence, only a single laser is needed in a setup
which allows both for visualization, manipulation, and force measurements.

Towards spatio-temporal control in optical trapping
Paper 7400-15 of Conference 7400
Date: Sunday, 02 August 2009
Time: 4:30 PM – 4:50 PM

Author(s): Debjit Roy, Arijit K. De, Debabrata Goswami, Indian Institute of Technology Kanpur (India)

 
Since its first implementation in the end of seventies last century, optical trapping has been one of the forefront of present day research having wide ranging applications from Bose-Einstein condensate to measurement of tiny forces (of the order of few pico-Newtons) exerted by molecular motors inside living cell. Starting with a discussion on a simplistic method for force calibration and implementation of gigantic instantaneous forces offered by ultrashort laser pulses in holding Rayleigh particles, the idea of spatio-temporal control achieved by simultaneously shaping the spatial as well as time-frequency profile of laser pulses will be discussed.

Nano-optical trapping of Rayleigh particles and E-coli bacteria with optical resonant antennas
Paper 7400-16 of Conference 7400
Date: Sunday, 02 August 2009
Time: 4:50 PM – 5:10 PM

Author(s): Romain Quidant, Maurizio Righini, Petru V. Ghenuche, Sudhir Cherukulappurath, ICFO - Instituto de Ciencias Fotónicas (Spain); Viktor Myroshnychenko, Fransisco Javier Garcia de Abajo, Consejo Superior de Investigaciones Científicas (Spain)

 
We report on the first experimental implementation of autonomous integrated optical nano-tweezers. We pattern metallic nanoantennas on a glass substrate to create strong light intensity gradients able to efficiently trap low-contrast objects under low laser intensity. First we show trapping in water of Rayleigh polystyrene beads. Further to that, we demonstrate the applicability of our method to parallel trapping of E-coli bacteria. Several individual bacteria are trapped at the same time, with their orientation imposed by the geometry of the antennas. After few hours the trapped bacteria keep on growing and dividing demonstrating that no serious damage is provoked.

Dynamics of colloidal particles on optical trap arrays
Paper 7400-18 of Conference 7400
Date: Monday, 03 August 2009
Time: 2:00 PM – 2:30 PM

Author(s): Charles M. Reichhardt, Los Alamos National Lab. (United States)

 
Using numerical simulations, we examine the types of dynamics that can occur
for colloidal particles interacting with a periodic optical trap array.
For repulsively interacting colloids, the ground state can form a series of
ordered states known as colloidal molecular crystals when the number of
colloids is an integer multiple of the number of optical trap minima. The
colloidal molecular crystals have orientational degrees of freedom that can
be coupled to an external drive. We show that a remarkable variety of
dynamical states can arise for the colloidal molecular crystals when a
circular external drive is applied. These include polarization transitions,
field induced martensitic transitions, sliding states, and avalanche
behaviors. We map the dynamical phase diagram for these states and discuss
possible applications for electrooptics as well as connections to condensed
matter and atomic systems.

Calculation of optical forces on a dielectric bead in a geometrically aberrated trap
Paper 7428-8 of Conference 7428
Date: Monday, 03 August 2009
Time: 6:00 PM

Author(s): Artur Carnicer, Denis Garnier, Salvador Bosch Puig, Ignasi Juvells, Univ. de Barcelona (Spain)

 
In this communication we describe a computational tool for obtaining the force exerted by a beam on micron-sized spherical dielectric particles in real conditions. The system (a water immersion objective) is simulated using an optical system design software whereas the information provided by the output rays feeds the application developed. The calculation of the force is carried out using the ray-optics approach.

Trestles femtosecond Ti:Sapphire laser
Trestles Finesse femtosecond Ti:Sapphire laser with integrated DPSS pump laser
Trestles Opus femtosecond Ti:Sapphire laser with built in 3 Watt DPSS laser

The physical limits of light trapping in thin-films and structures operating near the limit
Paper 7411-17 of Conference 7411
Date: Tuesday, 04 August 2009
Time: 9:40 AM – 10:00 AM

Author(s): Mukul Agrawal, Peter Peumans, Stanford Univ. (United States)

 
We have rigorously derived the physical limits of light trapping for arbitrary optical structures. The limit was derived using information theory to place an upper bound on the maximum number of optical degrees of freedom from which the local photon density of states can be derived. We conclude that even in the wave regime, the limits for light trapping derived for in the geometrical optics regime cannot be surpassed. We illustrate these limits through the example of optimized thin-film amorphous silicon solar cells with broadband grating incoupling.

Plasmonic and biomimetic light-trapping for photovoltaics
Paper 7411-19 of Conference 7411
Date: Tuesday, 04 August 2009
Time: 2:00 PM – 2:20 PM

Author(s): Darren M. Bagnall, Tristan L. Temple, Stuart A. Boden, Univ. of Southampton (United Kingdom)

 
Nanotechnology and nanophotonics will have a significant role within photovoltaics over the coming years. In particular the application of plasmonics and biomimetics appear exciting prospects with an number of recent advances and insights. The particular strength of each system lies in the ability to control sizes and distributions to features and thereby match the solar spectrum. The reduction of reflection using moth-eye schemes, and the use of plasmonic layers that can enhance light-trapping and the filter spectral components in multi-junction devices, will be discussed.

Power spectral analysis trap calibration using high-speed camera position detection with limited bandwidth
Paper 7400-43 of Conference 7400
Date: Tuesday, 04 August 2009
Time: 3:00 PM – 3:20 PM

Author(s): Astrid V. D. Horst, Benjamin P. B. Downing, Nancy R. Forde, Simon Fraser Univ. (Canada)

 
For trap stiffness calibration, determining the corner frequency from the power spectrum is a reliable and often preferred method. When using camera imaging for particle tracking, however, the corner frequency can be close to the Nyquist frequency, making fitting a Lorentzian problematic. This is true even for high-speed camera imaging when dealing with stiff optical traps. Here, we explore whether the absolute height of the low-frequency plateau in the power spectrum can be used for trap calibration, thereby taking into account the effects of image integration blur, position detection error and aliasing.

Mapping fluid velocity in a microfluidic device using optical trapping
Paper 7400-48 of Conference 7400
Date: Tuesday, 04 August 2009
Time: 4:30 PM – 4:50 PM

Author(s): Daniel J. Day, Jing Wu, Min Gu, Swinburne Univ. of Technology (Australia)

 
We present the concept of velocity mapping in a microfluidic device using optical trapping. Direct measurement of the Stokes force on a polymer microsphere can be determined from the gradient force in an optical trap generated by a high numerical aperture objective. The transverse velocities across straight and u-shaped channels are measured and compared with computational fluid dynamic simulations. The effect of bead diameter on the Stokes force is also characterized.

Three dimensional holographic optical trapping and manipulation of multiple particles and defects in liquid crystals
Paper 7400-50 of Conference 7400
Date: Tuesday, 04 August 2009
Time: 5:10 PM – 5:30 PM

Author(s): Ivan I. Smalyukh, Rahul P. Trivedi, Taewoo Lee, Gabriel Stockdale, Dennis F. Gardner, Jr., Suman Anand, Univ. of Colorado at Boulder (United States)

 
Simultaneous manipulation of multiple colloidal particles and defects in liquid crystals is performed using holographic optical trapping implemented with a liquid-crystal phase-only spatial light modulator. We have determined the trap stiffness at different laser powers by studying the viscous drag forces and also from Brownian motion of the particles. Trap stiffness variation along the depth of the liquid crystal is also analyzed. These measurements are then used to probe inter-particle and defect-particle interaction forces as well as to characterize the line tension of disclinations and linear defect clusters in the bulk of liquid crystals.

Possibility of constructing a standard comparison for laser radiation based on a combined trap detector
Paper 7419A-35 of Conference 7419A
Date: Tuesday, 04 August 2009
Time: 8:00 PM

Author(s): Alexander Kovalev, Andrey Kotyuk, Sergey Moskaluk, All-Russian Research Institute for Optical and Physical Measurement (Russian Federation); Eugene Yankevich, Kompaniya Medkorporaziya (Russian Federation)

 
It is suggested to use a combined trap detector as a standard comparison for laser radiation. Such detector will consist of thermal as well as photoelectric receivers. As a result of consecutive reflection, radiation will end up in the photoelectric receiver. It is suggested to use layered structures as thermal receivers. Such structures will consist of a thin metal layer with a blackened outer surface connected to a dielectric layer. Such dielectric will be fused to the surface of a thermostat. Each thermal receiver has electrical substitution winding and is calibrated separately. Behavior of such thermal receiver is analyzed for both radiative and convective heat loss. Errors related to zonal characteristics of the receiver as well as errors related to ambient temperature have been analyzed. Minimal radiation output for required measurement accuracy of the thermal receiver has been identified.

Depletion-driven selective optical trapping in nanoparticle suspensions
Paper 7400-51 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 8:30 AM – 8:50 AM

Author(s): Joseph Junio, H. Daniel Ou-Yang, Lehigh Univ. (United States)

 
For certain proportions of different sized particles in suspension, entropic effects can induce a net depletion attraction if smaller particles are precluded from the space between the larger particles. We show that depletion can be induced for size mixtures not exclusive to the depletion phenomenon by concentrating larger particles in the presence of smaller particles. Using the radiation pressure from a tightly focused laser, we can locally concentrate nanoparticles in suspension; and fluorescence excitation enables quantification of particles in the region as a function of trapping intensity. Since larger particles favorably trapped, we demonstrated the effects of depletion with a mixture of optically trapped 160nm and 63nm particles. A detailed analysis of the trapping enhancement due to depletion will be presented and implications to particle sorting will be addressed.

Optical trapping and binding in evanescent optical landscapes
Paper 7400-54 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 9:30 AM – 9:50 AM

Author(s): Luen Y. Wong, Colin D. Bain, Durham Univ. (United Kingdom)

 
Evanescent optical landscapes are created by the total internal reflection of two counterpropagating laser beams, and used to trap large numbers of submicron particles. We present experimental observations of array formation for dielectric particles, and show that different arrays are obtainable by varying the size of the particles and the wavelength and polarisations of the incident beams. Other interesting phenomena have been observed such as the ejection of large numbers of particles from the array, even beyond the evanescent field. Au colloidal microparticles show stable long range optical binding, but do not form a regular predictable array.

A comprehensive software suite for optical trapping and manipulation
Paper 7400-62 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 1:50 PM – 2:10 PM

Author(s): Daryl C. Preece, Richard Bowman, Graham M. Gibson, Graeme Whyte, Miles J. Padgett, Univ. of Glasgow (United Kingdom)

 
We present a comprehensive laser tweezers software package comprising the fundamental software components for any laser tweezers system. This includes fast hologram generation software, implemented on a graphics card, thereby allowing 100 hundred independently moving traps at video frame rate. The software also includes comprehensive camera suit and image recognition software for multi-particle tracking and analysis. The software will be freely available from the authors and online.

Wavefront correction for holographic optical trapping
Paper 7400-64 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 2:30 PM – 2:50 PM

Author(s): Tomáš Cižmár, Michael Mazilu, Kishan Dholakia, Univ. of St. Andrews (United Kingdom)

Optical trap assisted direct write nanolithography
Paper 7400-70 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 5:00 PM – 5:20 PM

Author(s): Craig B. Arnold, Euan R. McLeod, Princeton Univ. (United States)

 
We use Bessel beam optical traps to position polystyrene microspheres near surfaces, and illuminate them using a second pulsed laser in order to take advantage of the near-field intensity enhancement to create subwavelength features on the substrate. Due to the 2-D nature of the trap, the microbeads reach an equilibrium spacing above the surface that is independent of large scale features and allows for easy parallization of the process without the need for active feedback control of the bead-surface spacing. We show 100 nm and smaller feature sizes and demonstrate 2x2 arrays of parallel features produced in a direct-write fashion.

Analysis of the trapping forces on a spheroidal microparticle
Paper 7400-85 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 5:30 PM

Author(s): Hector Sosa-Martinez, Julio C. Gutiérrez-Vega, Instituto Tecnológico y de Estudios Superiores de Monterrey (Mexico)

 
Based on the standard classical optics approximation, we present a numerical study of the trapping forces exerted on an arbitrary oriented micron-sized dielectric spheroid by means of a counterpropagating dual-beam optical trap with a Gaussian transverse field pattern. Our analysis includes the calculation of the transverse and axial trapping efficiencies as function of the normalized beam waist separation distance, normalized spheroid size, effective index of refraction of the microparticle and ellipticity of the spheroid. The trapping forces produced are compared with those obtained for spheres.

Optical trapping of hydrosomes
Paper 7400-41 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 5:30 PM

Author(s): Carlos Lopez-Mariscal, Kristian Helmerson, National Institute of Standards and Technology (United States)

 
We demonstrate the controlled production and optical trapping and manipulation of of sub-micron sized hydrosomes on demand. We use optical trapping techniques to study the dynamics of single molecules encapsulated in the hydrosomes.

Optical trapping and guiding of absorbing nanoclusters in air
Paper 7400-73 of Conference 7400
Date: Thursday, 06 August 2009
Time: 9:00 AM – 9:30 AM

Author(s): Vladlen G. Shvedov, Yana V. Izdebskaya, Anton S. Desyatnikov, Andrei V. Rode, Yuri S. Kivshar, Wieslaw Z. Krolikowski, The Australian National Univ. (Australia)

 
We introduce a novel approach for all-optical trapping and
manipulation of absorbing aerosol particles based on a photophoretic force and singular beams. We demonstrate experimentally, in open air, the robust three-dimensional trapping and manipulation of agglomerates of carbon
nanoparticles over the distances of a few millimeters, as well as their acceleration up to velocities of 1 cm/s.

Detaching and optical trapping of micro-part solidified using microstereolithography
Paper 7400-76 of Conference 7400
Date: Thursday, 06 August 2009
Time: 10:10 AM – 10:30 AM

Author(s): Md. Tallal Bin Najam, Yong-Gu Lee, Gwangju Institute of Science and Technology (Korea, Republic of)

 
Curing of resins for making a solidified micro-scaled part is in use of researchers for quite a long time now. Microstereolithography is one such process for the generation of micro-scaled parts using pulsed laser systems. In the process, a photocurable resin is used for the curing of a micro-scaled structure. However, detaching of such a part solidified using a photocurable resin is a difficult thing. In this paper, we will put our concentration on the detaching and optical trapping of a micro-scaled object formed using microstereolithography. The process is accordingly evaluated and a precise analysis is provided for the detaching as well as the optical trapping.

The optical force induced by an angular momentum carrying beam alone can never trap a particle: the damping force from the water medium is working in harmony
Paper 7400-68 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 4:20 PM – 4:40 PM

Author(s): Jack Ng, The Hong Kong Univ. of Science and Technology (Hong Kong, China); Zhi Fang Lin, Fudan Univ. (China); Che Ting Chan, The Hong Kong Univ. of Science and Technology (Hong Kong, China)

 
In an angular momentum carrying beam (AMCB), particles can be trapped at the center. It is assumed that gradient force is responsible. However, a symmetry analysis reveals that the natural vibration frequencies are complex, which means the particle is gaining energy from AMCB and it will eventually escape. The situation is different when the medium provides damping that absorbs the particle’s energy. At sufficient damping a particle can be stably trapped, whereas for insufficient damping a particle cannot be trapped. There is an intermediate range of damping in which the particle will be driven into exotic orbital motion.

Sensitivity of DNA-hairpins dynamics to the mechanism of force feedback probed using a surface-coupled passive force clamp
Paper 7400-1 of Conference 7400
Date: Sunday, 02 August 2009
Time: 8:50 AM – 9:20 AM

Author(s): Yeonee Seol, National Institute of Health (United States); Thomas T. Perkins, Univ. of Colorado at Boulder (United States)

 
Optical-trapping experiments have yielded new insight into the
mechanical behavior of individual biomolecules. A common experimental
assay consists of an enzyme or nucleic acid molecule attached to a
cover slip at one end and to a small polystyrene bead at the other.
The bead is captured and held under tension with an optical trap.
Active feedback maintains constant force, often called a force clamp,
to increase measurement precision. Yet, active feedback is inherently
bandwidth limited. This limited bandwidth leads to significant
fluctuations in force that are particularly pronounced for rapid,
large changes in molecule extension (e.g. DNA hairpin unfolding). A
novel, passive force clamp circumvents this limitation by pulling the
bead to a non- linear region of the trap where ktrap = 0. To date,
this passive force clamp has required a specialized dual optical
trapping apparatus where one trap measures position and the other
measures force. Here, we demonstrate a passive force clamp achieved
with a single trap in a surface-coupled assay using a previously
characterized DNA hairpin. In an active force clamp, rapid back-and-
forth transition between open and closed hairpins states were observed
within the update period of the active force clamp (2 or 10 ms) as
well as a change in the long term dynamics. By using a passive force
clamp, these spurious transitions were eliminated and the correct
dynamics measured. By analyzing the fluctuations in the bead position
in conjunction with the known elasticity of DNA, we simultaneously
measured force and position in a single-beam, passive force clamp.
Thus, the benefits of the passive force clamp are now available to the widely used surface-coupled optical trapping assays.

Spectral properties and nonlinear dynamics of spontaneous emission of a resonance photon by two-level atom trapped in damped nanocavity with a resonance mode b
Paper 7421-2 of Conference 7421
Date: Monday, 03 August 2009
Time: 9:40 AM – 10:00 AM

Author(s): Vladislav F. Cheltsov, Moscow State Mining Univ. (Russian Federation)

 
Time dependent spectral distribution and nonlinear dynamics of separate photons emitted spontaneously by two-level atom, trapped in damped nanocavity and coupled to a single resonance mode, have been investigated The results have been obtained with the help of new nonperturbative theory by solving exactly the Schrödinger equation. The theory accounts exactly and simultaneously processes of emission, reabsorptions and leakage of photon. The obtained distributions and emission dynamics are presented with plots as functions of the photon frequency detuning and time for various values Г/4g. For Г/4g < 1 the spectrum is a triplet inside the cavity and a doublet outside it. In this case the total emission probability is described by decaying oscillations. For Г/4g >=1 and Г/4g >> 1 the spectrum consists of a single central line, profile of which depending on value Г/4g.

Manipulating vanadium oxide nanotubes with optical tweezers
Paper 7400-78 of Conference 7400
Date: Thursday, 06 August 2009
Time: 11:20 AM – 11:40 AM

Author(s): Woei-Ming Lee, Univ. of St. Andrews (United Kingdom); Jose Luis Hernández-Pozos, Liliana I. Vera-Robles, Antonio Campero Celis, Univ. Autónoma Metropolitana-Iztapalapa (Mexico); Kishan Dholakia, Univ. of St. Andrews (United Kingdom)

 
We describe the optical trapping characteristic of vanadium nanotubes and demonstrate a simple but powerful dielectric microsphere tagging technique to manipulate absorptive nanotubes. A steerable optical tweezers system is shown for the efficient trapping and transportation of these absorptive nanotubes via the tagged functionalized microspheres. The very same optical tweezers serves as a form of optical scissors that performs precise trimming of these nanotubes. The versatility of this optical technique allows the selective tagging, manipulation, and trimming of independent or bundles of nanotubes onto a chosen substrate and minimizes physical damage due to any absorption.

Combining optical trapping and gold post arrays: nanometer-scale localization of DNA to gold with a high strength, biocompatible bond
Paper 7400-13 of Conference 7400
Date: Sunday, 02 August 2009
Time: 3:40 PM – 4:00 PM

Author(s): Thomas T. Perkins, D. Hern Paik, Yeonee Seol, Wayne Halsey, Univ. of Colorado at Boulder (United States)

 
Surface conjugation of biomolecules onto an array of nano-structures provides a unique way to carry out repeatable measurements of single-molecules. For optical trapping experiments, we covalently linked DNA to gold nanoposts (r = 50-150 nm, 1 mm2 array) at one end and to a polystyrene bead at the other. The gold-DNA linkage was formed by six thiol bonds using dithiolphosphoramidite (DTPA). The DNA molecules remained attached in the presence of 1-10 mM mono- and di-thiolated chemicals, allowing passivation by methoxy-(polyethylene glycol)-thiol as well as addition of dithireitol. We demonstrated the mechanical strength of the gold-DTPA bond by overstretching DNA.

Simulation of electric field profile in semi insulating Metal/CdZnTe/Metal structure under flux
Paper 7449-9 of Conference 7449
Date: Monday, 03 August 2009
Time: 1:50 PM – 2:20 PM

Author(s): Jan Franc, Roman Grill, Charles Univ. in Prague (Czech Republic); Ralph B. James, Brookhaven National Lab. (United States); Jan Kubat, Eduard Belas, Pavel Moravec, Pavel Hoschl, Petr Praus, Charles Univ. in Prague (Czech Republic)

 
Charge collection in CdZnTe X-ray detectors is influenced by profile of electric field, which is governed by the space charge accumulated at deep levels. The type of the space charge and electric field distribution in the Metal/CdZnTe/Metal structure is at low fluxes mostly influenced by the charge injected from electrodes and subsequently trapped at deep levels. With an increasing flux additional space charge from trapped photo carriers is accumulated at deep levels further modifying the electric field. The purpose of the present contribution is to simulate distribution of the electric field in the metal/CdZnTe/metal structure in dependence of the flux of incoming radiation in order to estimate the influence of contacts on operation CZT detectors under high fluxes of X-ray photons. The simulation is based on the self-consistent steady state solution drift-diffusion equation coupled with Poisson equation. The effects of Au, Pt and In on the profile of electric field will be discussed.

Microcavity effects on light extraction efficiency of blue phosphorescent organic light emitting devices
Paper 7415-77 of Conference 7415
Date: Tuesday, 04 August 2009
Time: 8:00 PM

Author(s): Jaewon Lee, Neetu Chropa, Franky So, Univ. of Florida (United States)

 
It is known that OLEDs microcavity structure have a strong directional emission compared with non-cavity devices with a Lambertian emission pattern. We have found that more light is trapped in the substrate due to strong cavity effect. Micro-cavity blue PHOLEDs were fabricated on the substrates with two dielectric mirror structures. The amount of the substrate guided mode was measured with direct contact to the photodiode with refractive index matching gel to study the cavity effects on light extraction efficiency. We found that the 4QWS device has a stronger trapped substrate mode than the 2QWS or noncavity device due to a secondary cavity mode at the high viewing angle. Simulation results also confirmed the experimental data.

Optimum applied bias in CZT detectors
Paper 7449-10 of Conference 7449
Date: Monday, 03 August 2009
Time: 2:20 PM – 2:40 PM

Author(s): Salah A. Awadalla, Redlen Technologies (Canada)

 
We report an experimental work on the effect of applied bias on the detector performance. The study shows an optimum applied bias (HV) exists where the detector figures of merit are optimized. The optimum applied bias is much dependent of the transport properties of the device. Detectors with low electron trapping, (μτ)e better than 10-2 cm2/V, can operate efficiently at relatively low HV values: as low as 200V for 5mm thick detectors; while detectors with high electron trapping,(μτ)e greater than 5x10-3 cm2/V, require relatively high bias: as high as 700V for 5mm thick detectors. To provide more details and understanding of the results, we developed a Monte-Carlo simulation that simulates Charge drift, diffusion, and collection under electric field produced by the bias voltage.

Defect level measurements in CZT detectors
Paper 7449-24 of Conference 7449
Date: Tuesday, 04 August 2009
Time: 11:30 AM – 11:50 AM

Author(s): Rubi Gul, Zheng Li, Brookhaven National Lab. (United States); Rene Rodriguez, Kara Keeter, Idaho State Univ. (United States); Aleksey E. Bolotnikov, Ralph B. James, Brookhaven National Lab. (United States)

 
The point defects levels and the electrical and radiation response of two CdZnTe detectors were studied by Current Deep-Level Transient Spectroscopy (I-DLTS), Transient Current Technique (TCT), Current Voltage (I-V), , and gamma-ray spectroscopy. I-DLTS was employed to measure the parameters of the defects, such as the energy levels in the band gap, the carrier capture cross-sections and their densities. Three main energy traps, one shallow donor and two deep electron traps with energies of 9-620 meV from the conduction band edge were identified with capture cross sections of 10-18-10-17 cm2 and trap densities of 108-1011 cm-3. Transport properties, such as the carrier lifetime ~3.5 µs and mobility ~1100 cm2/Vs of the detectors were studied using TCT. The current induced by the laser-generated carriers and the charge collected were also determined using TCT data. The detector’s electrical characteristics were explored, and its performance tested using I-V, and gamma-ray spectroscopy

Measurement of interparticle capillary forces in colloidal self-assembly with holographic optical tweezers
Paper 7400-45 of Conference 7400
Date: Tuesday, 04 August 2009
Time: 3:50 PM – 4:10 PM

Author(s): Supone Manakasettharn, Ryan J. Kershner, Kevin T. Turner, Univ. of Wisconsin-Madison (United States)

 
We have used holographic optical tweezers to measure the interparticle capillary forces that drive colloidal self-assembly processes. A dilute colloidal suspension containing micron-sized polystyrene particles is loaded into a microfluidic channel. A 1064-nm fiber laser is modulated using a Hamamatsu LCOS device to generate multiple holographic optical traps. Identically sized particles are trapped and directed to the water-air interface. The forces between the particles are quantified by measuring the deviation of the particles from the center of the calibrated traps. The particle size and center-to-center distance is systematically varied to measure the effect of these parameters on interparticle capillary forces.

SONOPTICS: spatio-temporal micromanipulation by light and sound
Paper 7400-86 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 5:30 PM

Author(s): Paul A. Campbell, Univ. of Dundee (United Kingdom); Kishan Dholakia, Univ. of St. Andrews (United Kingdom)

 
Optical trapping has evolved to a technologically mature state, capable of routine application, especially in physics and biophysics environents, but also retaining an intrinsic power and versatility for specialist cutting-edge applications. In this paper we highlight the usefulness of optical trapping [of microbubbles] when combined with ultrasonic stimulus, for achieving a controlled disruption of cell membranes. This is an area that we pioneered in 2005, and which has grown in both popularity and breadth of application since then. We will highlight the power of this unique fusion of light and sound with a raft of new observations that also include parallel in-situ electrophysiological measurements. These provide a new level of control and understanding of the hydrodynamic causes leading to membrane breaching, together with their specific biological effects.

Development of an Yb optical lattice clock using a fermionic isotope
Paper 7431-15 of Conference 7431
Date: Wednesday, 05 August 2009
Time: 4:40 PM – 5:00 PM

Author(s): Masami Yasuda, National Institute of Advanced Industrial Science and Technology (Japan) and Japan Science and Technology Agency (Japan); Takuya Kohno, Japan Science and Technology Agency (Japan) and National Institute of Advanced Industrial Science and Technology (Japan); Kazumoto Hosaka, Hajime Inaba, Yoshiaki Nakajima, Atsushi Onae, National Institute of Advanced Industrial Science and Technology (Japan); Hidetoshi Katori, The Univ. of Tokyo (Japan) and Japan Science and Technology Agency (Japan); Feng-Lei Hong, National Institute of Advanced Industrial Science and Technology (Japan) and Japan Science and Technology Agency (Japan)

 
We report the development of an ytterbium (Yb) optical lattice clock. In fermionic isotopes (171Yb, 173Yb), the hyperfine splitting in the ground state leads to a lower temperature of laser-cooled atoms than that of the bosonic isotope (174Yb) due to the polarization gradient cooling mechanism. We have succeeded in magneto-optically trapping 171Yb and 173Yb using the 1S0-3P1 spin-forbidden transition. The temperature of the ultracold atomic ensemble was measured to be 15 and 30 uK for 173Yb and 171Yb, respectively by using the time-of-flight method. Development is under way to trap atoms in the lattice far off resonant trap.

Shaping the phase of a single photon
Paper 7465-39 of Conference 7465
Date: Thursday, 06 August 2009
Time: 5:10 PM – 5:40 PM

Author(s): Eden Figueroa, Holger Specht, Joerg Bochmann, Martin Muecke, Christian Noelleke, Stephan Ritter, David Moehring, Gerhard Rempe, Max-Planck-Institut für Quantenoptik (Germany)

 
Recently, sources with the capability to tailor the bandwidth of single photons have been developed. Using either DCLZ schemes in atomic ensembles or atoms trapped in QED cavities the production of long photons (as compared to the detection time) has been achieved. This characteristic enables the high frequency modulation of the photon shape, opening interesting avenues for research [1]. In this work we extend these ideas, by studying the effect of phase modulation in the interference of two photons produced by atoms trapped in a QED cavity. One single photon is sent through a fiber electro-optical modulator, and the result of the applied phase change is studied via its interference with a second un-modulated reference photon. If no modulation is introduced, a Hong-Ou-Mandel behavioris expected. Interestingly, if a phase change is applied within the photon envelope, the coalescence behavior of the interference can be altered. This scheme can be applied in the context of quantum key distribution as proposed by Inoue et al. [2], and might compare favorably to the latter, since intrinsically it does not require phase stability.

[1] P. Kolchin, et al. Phys. Rev. Lett. 101, 103601 (2008) [2] K. Inoue et al. Phys. Rev. Lett. 89, 037902 (2002)

The nano-world at your fingertips
Paper 7400-61 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 1:30 PM – 1:50 PM

Author(s): James A. Grieve, Arturas Ulcinas, Sriram Subramanian, Univ. of Bristol (United Kingdom); Graham M. Gibson, Miles J. Padgett, Univ. of Glasgow (United Kingdom); David M. Carberry, Mervyn J. Miles, Univ. of Bristol (United Kingdom)

 
Recent developments in multitouch computing promise intuitive, many point-of-contact control with feedback directly beneath the user's fingers. By coupling this innovative interface to a holographic optical tweezers system we are able to demonstrate the independent but simultaneous real-time control of multiple optical traps. The system readily accomodates multiple users and further opens the technology to use by non-specialists.

Single molecule chemical reactions within femtoliter volume containers
Paper 7400-40 of Conference 7400
Date: Tuesday, 04 August 2009
Time: 2:20 PM – 2:40 PM

Author(s): Ana M. Jofre, Ben Faulk, The Univ. of North Carolina at Charlotte (United States)

 
We create and observe controlled single molecule chemical reactions within femtoliter containers called hydrosomes, which are stable optically trapped aqueous nanodroplets.
Optical tweezers are used to manipulate the hydrosomes, to fuse one with another, thereby mixing the encapsulated components. Custom fabricated microfluidic channels are used to sort the hydrosomes containing different molecule species. We demonstrate the use of hydrosomes as microreactors by fusing two hydrosomes, each containing a complementary single strand of DNA, and observing the subsequent hybridization via FRET (Fluorescence Resonance Energy Transfer).

Nanometer scale imaging and spectroscopy of organic semiconductor film
Paper 7395-18 of Conference 7395
Date: Sunday, 02 August 2009
Time: 4:40 PM – 5:00 PM

Author(s): Dai Zhang, Ute Heinemeyer, Frank Schreiber, Eberhard Karls Univ. Tübingen (Germany); Reinhard Scholz, Technische Univ. München (Germany); Alfred J. Meixner, Eberhard Karls Univ. Tübingen (Germany)

 
Molecular domains of diindenoperylene organic film with sizes of several hundreds of nanometer and the thickness of 1 to 4 molecular layers are resolved both topographically and optically by nanoimage using a home-built parabolic mirror assisted near-field optical microscope. The boundaries of the molecular domains exhibit stronger intensity and red-shifted photoluminescence as compared to those of the regions inside the domain. Defects induced exiton trapping effects and tip plasmon and DIP thin film polariton coupling are suggested for the interpretations of the observed phenomena.

Trestles femtosecond Ti:Sapphire laser
Trestles Finesse femtosecond Ti:Sapphire laser with integrated DPSS pump laser
Trestles Opus femtosecond Ti:Sapphire laser with built in 3 Watt DPSS laser

Characterization of a 14-mm-long virtual Frisch-grid CZT detector array
Paper 7449-8 of Conference 7449
Date: Monday, 03 August 2009
Time: 1:20 PM – 1:50 PM

Author(s): Aleksey E. Bolotnikov, Giuseppe S. Camarda, Yonggang Cui, Anwar M. Hossain, Ge Yang, Ki Hyun Kim, Ralph B. James, Brookhaven National Lab. (United States)

 
We present new results from testing an array of 14-mm long virtual Frisch-grid CdZnTe detectors with a cathode signals readout scheme implemented to improve spectral response by correcting the electron trapping. In this paper, we discuss the characterization of the array and show our preliminary results obtained with gamma-ray sources.

Shaping of elliptical photonic lattices
Paper 7430-35 of Conference 7430
Date: Monday, 03 August 2009
Time: 6:00 PM

Author(s): Adrian Ruelas, Servando Lopez-Aguayo, Tecnológico de Monterrey (Mexico); Julio C. Gutiérrez-Vega, Tecnológico de Monterrey Chapter (Mexico)

 
We study the problem of shaping the transverse intensity pattern of an optical beam to induce a photonic lattice for trapping and propagating optical solitons in an elliptic motion with varying rotation rate. The transverse pattern is described by a suitable superposition of helical Mathieu beams. We discuss the properties of the lattice and the criteria to stabilize the motion of the solitons.

Photons as momentum-energy eigenmodes
Paper 7421-21 of Conference 7421
Date: Tuesday, 04 August 2009
Time: 9:40 AM – 10:00 AM

Author(s): Michael Mazilu, Univ. of St. Andrews (United Kingdom)

 
Optical micromanipulation offers a unique insight into light-matter interaction at the mesoscopic level within the classical framework. Using a generalized energy-momentum tensor, I introduce a decomposition of the classical electromagnetic field into eigenmodes having properties similar to the ones associated with photons i.e. modes with uniquely defined energy, momentum and polarization. Potential experiments are discussed that could verify the implications of this decomposition in the case of single-photo optical trapping.

Optical rotation of the shrunken multi-lamellar vesicle in optical tweezers
Paper 7400-82 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 5:30 PM

Author(s): Chungil Ha, Hyuk Kyu Pak, Pusan National Univ. (Korea, Republic of); Kipom Kim, Univ. of California, Santa Barbara (United States)

 
Shrunken multi-lamellar vesicle (SMLV) has a geometrically anisotropic internal nano-layered structure, known as a form birefringence. In this work, by trapping the SMLV using the optical tweezers with an elliptically polarized laser beam, we rotate the SMLV and measure the angular speed of SMLV. This rotational motion is explained using a simple model of optical torque, where lipid bi-layers are treated as thin parallel plates. This experimental and theoretical study can be applied to control the rotational motion of biological materials or ellipsoidal shape particle with form birefringence.

Electronic structures and electric properties of OLED-related interfaces
Paper 7415-19 of Conference 7415
Date: Sunday, 02 August 2009
Time: 4:30 PM – 4:50 PM

Author(s): Hisao Ishii, Yutaka Noguchi, Yasuo Nakayama, Chiba Univ. (Japan)

 
Interface is a key to understand and improve organic light emitting diodes (OLEDs). In this study, we will report on two topics in relation to the interfaces of OLEDs.　One is interfacial charges at organic-organic interfaces. For Alq3 and TPBi, we found that the orientation polarization of these molecules induce interfacial charges with carrier blocking at the interfaces by measuring displacement current. We also found that Light illumination and ion gauge radiation during the device fabrication significantly modify the amounts of polarization charges and traps. Second topic is the interfacial electronic structure of F8BT-MoO3 interfaces studied by photoemission. The reason of injection improvement will be discusses.

Brooke Hester is a PhD student working in the Optical Tweezers Lab at the National Institute of Standards and Technology (NIST). In this video she tells about trapping polystyrene spheres and nanoshells using Trestles CW - continuum wave tunable Ti:Sapphire laser from Del Mar Photonics.
 

Request a quote for laser suitable for optical trapping

Characterization of single electron effects in nanoscale MOSFETs
Paper 7402-20 of Conference 7402
Date: Wednesday, 05 August 2009
Time: 9:20 AM – 9:40 AM

Author(s): Leonard Forbes, Drake A. Miller, Oregon State Univ. (United States)

 
The future of mixed-signal, memory, and microprocessor technologies are dependent on ever increasing analog and digital integration and higher cell densities. However, device variability creates challenges at each new technology node which decreases yield, performance, and noise margins. At these device dimensions the low-frequency noise is dominated by the influence of one or more traps capturing and emitting charge in the oxide creating wide variations in noise from otherwise identical devices. Existing processes of record have been extended well beyond the ranges previously deemed feasible or reliable and single electron events and random telegraph noise signals become important.

Pool-Frenkel emission and hopping conduction in semiconducting carbon nanotube transistor
Paper 7399-6 of Conference 7399
Date: Wednesday, 05 August 2009
Time: 11:10 AM – 11:50 AM

Author(s): Minhee Yun, David Perello, Univ. of Pittsburgh (United States); Moon J. Kim, The Univ. of Texas at Dallas (United States); Dong Jae Bae, Woo Jung Yu, Seung Jin Chae, Young-Hee Lee, Sungkyunkwan Univ. (Korea, Republic of)

 
We report carbon nanotube field effect transistors (CNT FET) utilizing semiconducting single-walled carbon nanotubes (SWCNTs). Multiple devices, each of different metal source and drain contacts, were fabricated on a single SWCNT. Transport properties of the devices were consistent with the Bethe theory of thermionic emission for Schottky contacts and the Poole-Frenkel Emission was dependent on the device position. Further, single-walled CNTFET were irradiated with 20 keV electrons using an e-beam lithography exposure method. Analysis of conduction data in the temperature range 25 K to 300 K indicated the creation of traps along the nanotube channel. Ballistic electrical conduction is reduced to a tunneling-assisted hopping model – Poole-Frenkel emission.

Opto-mechanics of liquid crystal droplets
Paper 7414-2 of Conference 7414
Date: Sunday, 02 August 2009
Time: 1:30 PM – 1:55 PM

Author(s): Saulius Juodkazis, Hokkaido Univ. (Japan); Etienne Brasselet, Univ. Bordeaux 1 (France)

 
We overview recent progress in the field of laser trapping and manipulation of liquid crystal droplets. The mechanisms of optical molecular reordering are discussed in terms of light-induced birefringence inside micrometer-sized droplets. Statics and dynamics of laser-generated liquid crystal reorientation are compared in planar and three-dimensional configurations, i.e., films vs. droplets. Application potential of optical angular manipulation of liquid crystal particles trapped in laser tweezers for microphotonics and microfluidics is discussed.

Charge carrier injection in organic light emitting diodes studied by impedance spectroscopy
Paper 7415-15 of Conference 7415
Date: Sunday, 02 August 2009
Time: 2:45 PM – 3:00 PM

Author(s): Stefan Nowy, Wei Ren, Julia Wagner, Josef A. Weber, Wolfgang Brütting, Univ. Augsburg (Germany)

 
Impedance spectroscopy (IS) is a powerful method for characterizing the
electrical properties of materials and their interfaces. In this study
we use IS to investigate the charge carrier injection properties of
different anodes and anode treatments in bottom-emitting organic
light-emitting diodes (OLEDs). These are ITO-based (indium tin oxide)
hetero-layer devices with TPD
(N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4-diamine) as
hole transporter and Alq3 (tris-(8-hydroxyquinoline) aluminum) as
emission and electron transporting layer. A detailed analysis of the
(not very well known) interfaces yields information about trapped and
interfacial charges as well as the dynamics of injected charges.
Furthermore, we use IS to study degradation processes in OLEDs.

Confined modes in periodic planar particle arrays
Paper 7392-23 of Conference 7392
Date: Monday, 03 August 2009
Time: 4:20 PM – 4:40 PM

Author(s): Xesus M. Bendaña, Fransisco Javier Garcia de Abajo, Consejo Superior de Investigaciones Científicas (Spain)

 
We find the conditions for the existence of trapped modes in planar periodic particle arrays.
Confined modes of TM and TE symmetry are observed in self-standing arrays sitting in a symmetric
environment, originating in lattice resonances signalled by the proximity of a Wood anomaly. This
mechanism of mode formation is shown to be inhibited by the presence of a dielectric substrate in an asymmetric environment. Intrinsic surface modes of the substrate are modified by the presence of the array. Perfect-conductor particles are considered to illustrate mode degeneracy and the interplay between electric and magnetic polarization. Our results provide a common framework to understand surface modes in structured surfaces and modes in particle arrays.

Proton radiation damage study of the next generation of swept charge devices
Paper 7435-30 of Conference 7435
Date: Monday, 03 August 2009
Time: 6:00 PM

Author(s): Jason P. Gow, Andrew D. Holland, The Open Univ. (United Kingdom); Peter J. Pool, e2v technologies plc (United Kingdom)

 
The first generation of Swept Charge Device (SCD) the e2v technologies plc CCD54 was used in the Demonstration of a Compact Imaging X-ray Spectrometer (D-CIXS) launched in 2003 and again in the Chandrayaan-1 X-ray Spectrometer (C1XS) instrument currently in orbit around the Moon. The main source of decreased energy resolution in both cases is proton damage, from trapped and solar protons respectively. This paper presents the results from an experimental study to evaluate the performance of the next generation of SCD the CCD234 and CCD236 irradiated with a 10 MeV equivalent proton fluence of 3.0E8 protons.cm-2 demonstrating the factor of two increase in radiation hardness when compared to the CCD54. In particular the increased leakage current, decrease in energy resolution and the degradation of charge transfer efficiency (CTE) are described.

A combined double-tweezers and wavelength-tunable laser nanosurgery microscope
Paper 7400-10 of Conference 7400
Date: Sunday, 02 August 2009
Time: 2:10 PM – 2:30 PM

Author(s): Qingyuan Zhu, Univ. of California, Irvine (United States); Shahab Parsa, Linda Z. Shi, Marcellinus Harsono, Univ. of California, San Diego (United States); Michael W. Berns, Univ. of California, Irvine (United States)

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We describe a combined laser scissors and tweezers microscope that (1) has two trapping 1.06 µm cw laser beams (2) uses a tunable 200 fs 710-990 nm Ti:Sapphire laser for nanosurgery, and (3) has the option to use a 337 nm 4 ns UV laser for subcellular surgery. The two laser tweezers and either of the laser ablation beams can be used in a cell surgery experiment. The system is integrated into the robotic-controlled RoboLase system (Botvinick and Berns, Microscopy Res. & Technique 68: 65-74, 2005). Chromosomes of rat kangaroo PTK2 cells are cut with the laser scissors and the individual chromosome fragments are manipulated in the living cell during mitosis.

The interaction of Escherichia coli with its surrounding three dimensional substrate measured by optical tweezers
Paper 7400-11 of Conference 7400
Date: Sunday, 02 August 2009
Time: 2:30 PM – 2:50 PM

Author(s): Novia Yen, Ming-Tzo Wei, Arthur E. Chiou, National Yang-Ming Univ. (Taiwan)

 
It has been known that the shape, locomotion, and growth of cells and bacteria are often affected by their interactions with extra cellular matrix (ECM). However, it is difficult to quantify such interactions with conventional biochemical methods. In this paper we report the application of oscillatory optical tweezers to trap and oscillate three types of E. coli, namely, BW25113 (normal with flagellum), BW25113 (normal with flagellum but subjected to UV light exposure for 1 hr for deactivation), and JW1923 (JW1923 a null-flagellum mutant of BW25113), in 0.2% LB agar substrate to quantify the E. coli - substrate interactions in terms of the elasticity modulus G’. Our results are consistent with our studies via biochemical methods.

Transparent white organic light emitting diode with improved cathode transparency
Paper 7415-33 of Conference 7415
Date: Monday, 03 August 2009
Time: 11:45 AM – 12:00 PM

Author(s): Jeong-Ik Lee, Hye-Yong Chu, Jeonghee Lee, Jae-Heon Shin, Chi-Sun Hwang, Electronics and Telecommunications Research Institute (Korea, Republic of)

 
For the hybrid WOLED, we have fabricated the device with the structure of ITO/HTL/ph-EMLs/interlayer/fl-EML/ETL/LiF/Al. The balanced emissions from the fluorescence layer and the phosphorescence layer have been obtained by using appropriate carrier (hole) trapping effects in the phosphorescence layer, which resulted in 15 % of external quantum efficiency and 29 lm/W of power efficiency, respectively at 1000 cd/m2 in the bottom emission structure. Moreover, the transparent WOLED has been successfully fabricated by the combination of the hybrid WOLED and the cathode of n-doped ETL(200 Å)/Ag (150 Å) and over 17 lm/W of power efficiency at 1000 cd/m2 with over 70 % of transmittance at 550 nm has been achieved.

A comparative study of proton radiation damage in p- and n-channel CCDs
Paper 7435-14 of Conference 7435
Date: Monday, 03 August 2009
Time: 1:50 PM – 2:10 PM

Author(s): Jason P. Gow, Neil J. Murray, Andrew D. Holland, The Open Univ. (United Kingdom); David J. Burt, Peter J. Pool, e2v technologies plc (United Kingdom)

 
It has been demonstrated that p-channel charge coupled devices (CCDs) are more radiation hard than conventional n-channel devices as they are not affected by the dominant electron trapping caused by the displacement damage defect the E-centre (phosphorus-vacancy). This paper presents a summary of the results from a comparative study the e2v technologies plc CCD47-20 fabricated using the same mask to form n-channel and p-channel devices and the high resistivity p-channel CCD227 and the n-channel CCD247 devices based on the popular astronomy format of the CCD42. The n-channel devices were irradiated to a 10 MeV equivalent proton fluence of 1.68E9 protons.cm-2, with the p-channel devices irradiated to 10 MeV equivalent proton fluence of 5.03E9 protons.cm-2 and 15.09E9 protons.cm-2. The charge transfer efficiency, leakage current, leakage current non-uniformity, and energy resolution were measured as a function of radiation dose.

High efficiency phosphorescent OLEDs based on the heterostructured light emission and charge injection layers
Paper 7415-35 of Conference 7415
Date: Monday, 03 August 2009
Time: 1:50 PM – 2:10 PM

Author(s): Byung-Doo Chin, Dankook Univ. (Korea, Republic of); Yu-Ri Choi, Korea Institute of Science and Technology (Korea, Republic of); Heume-Il Baek, Changhee Lee, Seoul National Univ. (Korea, Republic of)

 
The light emitting efficiency and the stability of the phosphorescent devices, whose emission characteristics are strongly dominated not only by the energy transfer but also by the charge carrier trapping influenced by the heterostructured emissive layers and charge injection layer, are studied by differences in the spectral behavior, carrier balance of devices, and energy levels. The enhancement of the light emitting properties by use of heterostructures at emitting layer, either multilayer or mixing of hole- and electron-transporting materials (such as 4,4',4''-tris(N-carbazolyl)-triphenylamine); TCTA and bis(10-hydroxybenzo[h]quinolinate) beryllium; Bebq2) was characterized and explained with relevant time-resolved analysis and photophysical behavior.

Simultaneous laser particle guidance and fluid counterflow in single-mode hollow core photonic crystal fibres
Paper 7400-25 of Conference 7400
Date: Monday, 03 August 2009
Time: 5:00 PM – 5:30 PM

Author(s): Tijmen G. Euser, Martin K. Garbos, Jocelyn S. Y. Chen, Philip S. J. Russell, Max Planck Institute for the Science of Light, Erlangen (Germany)

 
Photonic crystal fibers (PCFs) have proved very useful for strongly enhancing light-matter interactions. For example, hollow-core photonic crystal fiber (HC-PCF) offers both low loss and a fundamental optical mode that is strongly confined to the core. We present controlled optical trapping and guidance of silica microparticles in the fundamental mode of D2O-filled hollow-core PCF, and show that a particle can be held stationary against an opposing fluid flow using optical propulsion. A well-defined optical mode propagating through a microfluidic channel offers a new way of measuring drag forces acting on single particles.

Electron structure of AgCl nanocrystal with silver ion adsorbed on atomic-rough surface and quantum transitions
Paper 7396-2 of Conference 7396
Date: Monday, 03 August 2009
Time: 6:00 PM

Author(s): Yury Timoshenko, Voronezh State Univ. (Russian Federation); Valentina Shunina, Voronezh State Technical Univ. (Russian Federation)

 
Adsorption was considered as on the atomically-rough surface as on the smooth surface. The electron structure of AgCl nanocrystals with the adsorbed silver ion were calculated by semi-empirical tight-binding method and in frame of DFT method B3LY P/HW. The quantum transitions were investigated in semi-empirical approach. Basing on the obtained data a conclusion is specifically made that the most efficient trapping of photoelectron should occur under adsorption on a smooth surface rather than near the steps and their fractures as it was assumed previously. Also probabilities of quantum transitions for different variants of adsorption were been discussed.

Optical manipulation using silicon nanophotonics
Paper 7400-29 of Conference 7400
Date: Tuesday, 04 August 2009
Time: 8:00 AM – 8:30 AM

Author(s): David Erickson, Cornell Univ. (United States)

 
In this talk I will discuss some of our recent work on optical manipulation and transport of nanoparticles and nucleic acids using silicon photonic devices. It will be demonstrated how the concentration and amplification of the optical field inside slot waveguides and ring resonators results in extremely large scattering and polarization forces. We demonstrate how these forces can be used to trap organic and inorganic targets ranging in size from tens of microns to handfuls of nanometers. The potential for a highly resolute optical chromatography device will also be demonstrated. Some of the advanced analytical, numerical and experimental techniques used to investigate and design these systems will be discussed.

Microfluidic design and fabrication of wafer-scale varifocal liquid lens
Paper 7426-2 of Conference 7426
Date: Tuesday, 04 August 2009
Time: 8:40 AM – 9:00 AM

Author(s): Jeong Yub Lee, Seung-Tae Choi, Seung Wan Lee, Woon Bae Kim, Samsung Advanced Institute of Technology (Korea, Republic of)

 
We developed microfluidic design and fabrication for wafer-scale varifocal liquid lens of auto macro and focusing. This lens close to human eye consists of Si frame with inner hole, elastomer membrane, glass plate and optical fluid confined by these structures. Si frame is fabricated using MEMS processes. To prevent void trapping and improve liquid filling, we developed wafer-based microfabrications of seal line dispensing, accurate dropping of optical fluid, pressing & bonding process in vacuum and UV sealant curing. Afterward, electro-active polymer actuators which change lens shape, was attached. The ultra-slim & highly-tunable liquid lens suitable for mass production was realized.

Effect of intergrain defects on transport in semicrystalline polymeric semiconductors
Paper 7417-27 of Conference 7417
Date: Tuesday, 04 August 2009
Time: 9:20 AM – 9:35 AM

Author(s): Alberto Salleo, Leslie H. Jimison, Chenchen Wang, Stanford Univ. (United States); Michael F. Toney, SLAC National Accelerator Lab. (United States); Alexander Ziegler, Max-Planck-Institut für Biochemie (Germany); Martin J. Heeney, Queen Mary, Univ. of London (United Kingdom); Iain McCulloch, Imperial College London (United Kingdom)

 
Charge transport in organic semiconductors is limited by defects. We use a directional crystallization technique to engineer known grain-boundaries in P3HT. X-ray diffraction is used to characterize the relative orientation of the P3HT chains wrt the grain-boundaries. A study of the transport characteristics of these grain-boundaries reveals that grain-bridging by polymer chains may be an effective transport pathway. Furthermore, we show that polymers that exhibit terracing over large areas (~µm2) and high mobilities, such as PBTTT, have a similar areal trap density as P3HT. We derive consequences in terms of transport limiting factors.

Hydrodynamic interactions at a fluid wall
Paper 7400-46 of Conference 7400
Date: Tuesday, 04 August 2009
Time: 4:10 PM – 4:30 PM

Author(s): Roberto Di Leonardo, Univ. degli Studi di Roma, La Sapienza, CNR (Italy); Carol López Quesada, Univ. de Barcelona (Spain)

 
Macro and mesoscopic flow close to solid walls is very well described byno-slip boundary condition at the interface.
As a result, colloidal dynamics,in the close proximity of a wall, is dominated by particle wall hydrodynamic
interactions which reduce single particle mobilities and "screen" interparticle couplings.
Liquid-gas interfaces, instead, provide an almost perfect slipboundary condition.
In such situations, flows resulting from colloidal dynamics can be easily reproduced considering
image particles appearing behind the wall and mirroring the dynamics of real ones.
Optically trapping particles at a liquid-air interface, we show that flow contributions from image particles
doubles the strength of hydrodynamic interactions, with respect to the bulk value, and enhances single particle mobility.

Photon counting using amorphous selenium: Achieving hole dispersion limited count-rate using the Frisch grid detector design
Paper 7449-31 of Conference 7449
Date: Tuesday, 04 August 2009
Time: 4:10 PM – 4:30 PM

Author(s): Amir H. Goldan, Karim S. Karim, Univ. of Waterloo (Canada)

 
Incomplete charge collection due to poor electron mobility in amorphous selenium (a-Se) results in depth-dependent signal variations. The slow signal rise-time for the portion of the induced charge due to electron-movement towards the anode and significant electron trapping cause ballistic deficit. In this paper, we investigate Frisch-grid detector design to reduce the depth dependent noise and improve the spectral performance of a positively biased amorphous selenium radiation detector for emerging photon counting applications. In addition, we show that using the Frisch grid, we can improve the photon-count rate substantially and achieve the maximum rate fundamentally limited by hole dispersion inside the material. Preliminary results based on theory are presented.

Pulse electrodeposited tin sulfide films for photovoltaic applications
Paper 7409-41 of Conference 7409
Date: Tuesday, 04 August 2009
Time: 8:00 PM

Author(s): Hirian Berenice N. Anaya, Ildefonso Zamudio Torres, Nini Rose Mathews, Univ. Nacional Autónoma de México (Mexico)

 
In this work we report the cathodic pulse electrodeposition and characterization of tin sulfide on F-doped tin oxide coated glass substrates. Films of thickness 80-300 nm were deposited by varying the pulse duration at the deposition potential from 0.8 V to 1 V vs. SCE. Structural studies suggest that the predominant phase obtained is orthorhombic SnS with an average crystalline grain size of 15 nm. An optical band gap of 1.2 eV is typical for the electrodeposited SnS, but a systematic increase in the band gap value was observed with increase in the applied potential in the electrodeposition. Electrical parameters and charge transport mechanism of the films were studied using Schottky diodes fabricated by depositing Al. Two trap levels with activation energies 0.045 and 0.142 eV were detected from the I-V measurements at 200-340 K. We shall discuss the relevance of these results in the application of such films in photovoltaic structures.

Optical binding forces acting on two colloidal particles in a dual optical tweezers
Paper 7400-53 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 9:10 AM – 9:30 AM

Author(s): Ming-Tzo Wei, Lehigh Univ. (United States); Jack Ng, Ping Sheng, Che Ting Chan, The Hong Kong Univ. of Science and Technology (Hong Kong, China); H. Daniel Ou-Yang, Lehigh Univ. (United States)

 
Optical binding has been proposed as being responsible for the cluster formation of micron size dielectric spheres in coherent light fields. However, direct supporting experimental evidence has been missing. We report an experimental study of optical forces between two dielectric spheres in a dual optical tweezers. Results for optical forces are presented for three conditions: interparticle separation, particle size, and respective polarizations of the optical trapping beams relative to the separation direction of the particles. A comprehensive calculation based on the generalized Mie scattering theory for the same experimental conditions have also been conducted. This paper will present a comparison between experimental and theoretical results.

Frequency measurement of the 40Ca+ clock transition using a LD-based clock laser and UTC(NICT)
Paper 7431-7 of Conference 7431
Date: Wednesday, 05 August 2009
Time: 11:00 AM – 11:20 AM

Author(s): Kensuke Matsubara, Ying Li, Shigeo Nagano, Hiroyuki Ito, Masatoshi Kajita, Reiko Kojima, Kazuhiro Hayasaka, Mizuhiko Hosokawa, Yuko Hanado, National Institute of Information and Communications Technology (Japan)

 
We have developed an optical frequency standard based on the 4 2S1/2 – 3 2D5/2 quadrupole transition of single calcium (40Ca+) ions. Using a simple LD-based clock laser system, we determined the clock transition frequency at 729 nm with an uncertainty of 1.7 x 10-14 with respect to the definition of the second through the UTC(NICT). This uncertainty was mainly limited by the residual magnetic fluctuation. We are now developing a new ion trap surrounded with a magnetic shield to reduce the magnetic fluctuation and consequently to determine the clock transition frequency at the 10-15 level accuracy.

Preparation and characterization studies of amorphous silicon (a-Si) thin films prepared using RF magnetron sputtering
Paper 7404-32 of Conference 7404
Date: Wednesday, 05 August 2009
Time: 5:30 PM

Author(s): Detty P. Alappatt, Vellara P. Mahadevan Pillai, Geo Rajan, Univ. of Kerala (India)

 
Highly transparent amorphous silicon thin films were prepared using RF Magnetron sputtering. The absence of characteristic peaks in the XRD and Raman analysis reveals the amorphous nature of the films. Surface morphology of the films were analyzed using Atomic Force microscopy, which revealed a highly textured surface features with distributed nanoparticles. This is suitable for solar cell applications where trapping of light may be induced, thus significantly inhibiting the reflection of photons incident on the device surface. The films show strong PL emission in near UV-visible region.

Using holographic optical tweezers to measure forces with SPM-like probes
Paper 7400-72 of Conference 7400
Date: Wednesday, 05 August 2009
Time: 5:40 PM – 6:00 PM

Author(s): David M. Carberry, Leo Ikin, Univ. of Bristol (United Kingdom); Graham M. Gibson, Miles J. Padgett, Univ. of Glasgow (United Kingdom); Mervyn J. Miles, Univ. of Bristol (United Kingdom)

 
Using holographic optical tweezers we demonstrate the optical assembly and control of SPM-like probes. The probes are formed from cadmium sulphide rods or silica, and silica microspheres. Calibration of the trap stiffness allows us to use a precise measure of probe displacement to calculate the applied forces. We demonstrate that the optically controlled probe can exert a force in excess of 60pN, over an area of $1 \times 10^{-13}$m$^{2}$, with a force sensitivity of 50fN. Probes, similar to the ones presented here, are likely to have applications as nanotools in probing laser-sensitive cells and materials.

Charge transport characterisation of single crystal CdMnTe for x-ray detection
Paper 7449-46 of Conference 7449
Date: Thursday, 06 August 2009
Time: 9:10 AM – 9:30 AM

Author(s): James M. Parkin, Univ. of Surrey (United Kingdom) and Lab. Impex Systems (United Kingdom); Paul J. Sellin, Annika Lohstroh, Spryos Gkoumas, Matthew C. Veale, Univ. of Surrey (United Kingdom)

 
CdMnTe samples doped with varying concentrations of Vanadium and Indium have been investigated for use as radiation detectors . Alpha Hecht analysis displays mobility-lifetime products around 4 x 10-5 cm2/V for electrons. Spatial variations of mobility-lifetime product are studied by Ion beam induced charge imaging, showing good uniformity of charge transport. Temperature dependent alpha Time of Flight (TOF) measurements yield electron mobility around 260 cm2/Vs and charge trap activation energy of 0.145 eV. X-ray spectra from the Tb 44.2 keV line show the resolution of a planar device to be around 11 %.

Optical paddle-wheel
Paper 7400-75 of Conference 7400
Date: Thursday, 06 August 2009
Time: 9:50 AM – 10:10 AM

Author(s): Theodor Asavei, Vincent L. Y. Loke, Timo A. Nieminen, Norman R. Heckenberg, Halina H. Rubinsztein-Dunlop, The Univ. of Queensland (Australia)

 

Using optical tweezers to probe the elasticity of short molecules
Paper 7400-5 of Conference 7400
Date: Sunday, 02 August 2009
Time: 10:50 AM – 11:10 AM

Author(s): Benjamin P. B. Downing, Astrid V. D. Horst, Marjan Shayegan, Nancy R. Forde, Simon Fraser Univ. (Canada)

 
Probing relatively short molecules, such as the protein elastin (~200 nm), with optical tweezers requires manipulating trapped polystyrene beads at separations small compared to their micron dimensions. We discuss experimental complications arising from this proximity, such as optical, electrostatic and hydrodynamic interactions, and our efforts to minimize them. In our instrument, using a single beam optical trap to manipulate one bead and a micropipette to manipulate a second, we show that an appropriate choice of bead sizes minimizes unwanted optical effects. However, we find and characterize significant hydrodynamic effects, which must be taken into account during quantitative data collection.

Ångström-resolution optical tweezers for investigating DNA-binding/translocating molecular motors
Paper 7400-6 of Conference 7400
Date: Sunday, 02 August 2009
Time: 11:10 AM – 11:30 AM

Author(s): Anders E. Wallin, Heikki Ojala, Edward Haeggström, Univ. of Helsinki (Finland)

 
Aiming to investigate how DNA-binding/translocating molecular motors work, we have constructed a double-trap optical tweezers instrument with high spatial resolution. We report on the instrument design, construction, calibration, and proof-of-principle experiments. To achieve high spatial resolution DNA-constructs are tethered between two optically trapped beads in a ’dumbbell’-assay. Single molecule experiments are performed in a microfluidic laminar flow-channel which allows efficient delivery of beads, DNA, proteins, and buffers to the focal volume. Preliminary results on DNA-translocation by a viral packaging motor, and transcription by an RNA-polymerase will be presented.

2D modeling of silicon based thin film dual and triple junction solar cells
Paper 7409-15 of Conference 7409
Date: Sunday, 02 August 2009
Time: 3:10 PM – 3:30 PM

Author(s): Yegao Xiao, Crosslight Software Inc. (Canada); Kentaro Uehara, Crosslight Software Inc. (Japan); Michel Lestrade, Zhiqiang Li, Zhanming S. Li, Crosslight Software Inc. (Canada)

 
Si-based thin film dual and triple junction solar cells are modeled based on the Crosslight APSYS in this work. Basic physical quantities like band diagrams, optical absorption and generation are obtained. Quantum efficiency and I-V curves are presented for current matching analyses. The results are discussed with respect to TCO ZnO:Al affinity and amorphous trap states. Crosslight modules, FDTD and/or ray tracing, are also being used to model light trapping and optic absorption enhancement effect for such thin film solar cells grown on textured substrate. The modeling results give possible clues to achieve high efficiency.

Photon: quantum representation versus field representation seen from a new stand point
Paper 7421-18 of Conference 7421
Date: Tuesday, 04 August 2009
Time: 8:40 AM – 9:00 AM

Author(s): Erich H. Berloffa, Leopold-Franzens-Univ. Innsbruck (Austria)

 
Recently anew interpreted old experiments as well as the ongoing debate, "What is the nature of light?" force one to illuminate the photon's character from an other side.
In particular, the question is discussed: Can the quantum properties of a single photons transferable to a manifold of correlated ones of them (laser)? A sketch is given how helically polarized laser radiation focused onto a metal alloy target, such that moiré fringes appear, generate tremendous locally inductances (B-field) underneath "hot spots". This is possible due to the fact that the group velocity of light underneath the laser interaction zone tends to approach zero but not reaching it. An imbalance in absorption of E-and B-field of the degenerated electromagnetic wave is responsible of it, however, as B -> ∞ underneath a "hot spot" the energy density ρ -> 0. Experiments revealed the B-field can grow so strong that trapped nuclei may be dismantled (Nuclear Cluster Jet). The origin of the observed phenomena are caused by light, but the quantum nature of photons can not made responsible for it, it is mere a feature of special optical fields in association with target conditions.

Measuring the surface tension of oil droplets using optical tweezers
Paper 7400-42 of Conference 7400
Date: Tuesday, 04 August 2009
Time: 2:40 PM – 3:00 PM

Author(s): Graham M. Gibson, Alison M. Yao, Richard Bowman, Jonathan M. Cooper, Miles J. Padgett, Univ. of Glasgow (United Kingdom)

 
We demonstrate the use of holographic optical tweezers to form hydrodynamically coupled arrangements of silica beads for trapping and measuring the mechanical properties of micron sized droplets of fluorinated oil.

An oil droplet, ~2-10 microns diameter, in water is confined between 4 trapped silica beads, each 2 micron diameter. The thermal motion of each bead is monitored simultaneously; continuous monitoring at 1kHz is achieved using a high speed CMOS camera and centre of mass tracking algorithm. Measurement of the cross-correlation functions and power spectra of the Brownian motion of the beads provide information on the mechanical properties of the confined oil droplet.

Laser transmission and scattering studies of bio-molecules and bio-chemical simulations: relationship to mutagenesis and carcinogenesis
Paper 7397-36 of Conference 7397
Date: Wednesday, 05 August 2009
Time: 6:00 PM – 6:20 PM

Author(s): Gary C. Vezzoli, Lebanon College (United States); Jessica K. Willett, Dartmouth Hitchcock Medical Ctr. (United States)

 
We present experimental research and interpretations on laser transmission and scattering studies of DNA from several sources, and of seminal fluid, both as a function of temperature, showing a major anomaly at ~ 42 degrees Celsius in both materials -- in DNA due to the incipient unwinding of the double helix, and in seminal fluid, presumably due to the relationship with specific DNA. These results are also supported by in-situ electrical charge transport measurements, as well as pH and thermal studies. We also report resuts from studies addressing: chirality and broken symmetry in frog egg embryos; trapped kidney stones in the urethra leading to cancer of the bladder in men; chelate chemistry of the prostate gland related to zinc/aqueous-salt/matrix chemical interaction and leading to prostate enlargement or prostate cancer; the denaturing of DNA by urea; and the temperatue-dependent classical Casimir effect in organic materials. In all of these studies, the technique of laser transmission, laser scattering, and laser speckle and interference patterns has been very telling in elucidating properties in biomoleucles that relate to mutagenesis in DNA, and carcinogenesis of the bladder and of the prostate gland.
This work extends our previous free electron laser studies of inorganic ring and chain molecules by THz spectroscopy.

Laser guidance based cell detection
Paper 7400-22 of Conference 7400
Date: Monday, 03 August 2009
Time: 4:00 PM – 4:20 PM

Author(s): Zhen Ma, Julie X. Yun, Yangzhang Wei, Karen J. L. Burg, Xiaocong Yuan, Bruce Z. Gao, Clemson Univ. (United States)

 
Laser guidance is the technique that uses weakly convergent beam to trap particles radially in the center of the beam and simultaneously propel them along the beam propagation axis with a travelling distance over millimeters. In this paper, the laser guidance was applied to detect cells with different types, phenotype transformation or gene modification, especially for the situation that fluorescent markers used in flow cytometry for cell detection are not available or their application is contraindicated by clinical restriction. The optical force, which determines the guidance speed of the cell, is dependent on the parameters of the cell being guided, such as size, shape, composition and refractive index. Therefore, by measuring the guidance speed of the cell along the laser beam, cells with different properties can be effectively distinguished. As examples, we report two experimental results: 1) the laser guidance system could significantly distinguish the metastatic cancer cell type 4T1 from its non-metastatic counterpart 4T07, which could not be achieved by using a high magnification microscope; 2) L-10 are genetically modified TC-1 cells (mouse lung-carcinoma tumor cells) that stably express a fusion protein of the extracellular domain of mouse UL16-binding protein-like transcript 1 “MULT1” and the transmembrane and intracellular domains of Fas. Under a high magnification microscope (63X, 1.4), L-10 and TC-1 cells showed no difference in phenotype. For example, cell-diameter measurement showed no statistical difference between the two cell diameters D: DTC-1=11.5±0.7 μm and DL-10=11.5±1.1 μm. The laser guidance experiment conducted with these two cell types demonstrated that only one gene modification resulted in ~40% decrease in guidance speed. These experimental data indicate that laser guidance can be used to detect subtle difference between sub-cell types.
 

Brooke Hester is a PhD student working in the Optical Tweezers Lab at the National Institute of Standards and Technology (NIST). In this video she tells about trapping polystyrene spheres and nanoshells using Trestles CW - continuum wave tunable Ti:Sapphire laser from Del Mar Photonics.
 

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