Position and Intensity Modulations in Holographic Optical Traps Created by a Liquid Crystal Spatial Light Modulator

Author(s): Astrid van der Horst, Benjamin P. Downing, and Nancy R. Forde


“The addressing of the liquid crystals in spatial light modulators gives rise to temporal modulation of the phase pattern. Here we investigate the effect of this on the intensity and position of holographic optical traps.”

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Publication: Optics InfoBase, (subscription required)

Issue/Year/DOI: Conference Paper, Optical Trapping Applications (OTA), OSA/DH/FTS/HISE/NTM/OTA 2009

Programmable ultrashort-pulsed flying images

Author(s): M. Bock, S. K. Das, and R. Grunwald


“We report the generation of programmable two-dimensional arrangements of ultrashort-pulsed fringe-less Bessel-like beams of extended depth of focus (referred to as needle beams) without truncating apertures. A sub-20-fs Ti:sapphire laser and a liquid-crystal-on-silicon spatial light modulator (LCoS-SLM) of high-fidelity temporal transfer in phase-only operation mode were used in the experiments. Axicon profiles with ultrasmall conical angles were approximated by adapted gray scale distributions. It was demonstrated that digitized image information encoded in amplitudephase maps of the needle beams is propagated over considerably large distances at minimal cross talk without the need for additional relay optics. This experiment represents a physical realization of Saari’s proposal of spatio-temporally nondiffracting “flying images” on a few-femtosecond time scale. ”

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Publication: Optics Express (free download)

Issue/Year/DOI: Optics Express, Vol. 17, Issue 9, pp. 7465-7478

Model-free method for measuring the full Jones matrix of reflective liquid-crystal displays

Author(s): Christian Kohler, Tobias Haist, Wolfgang Osten


“We present a method for measuring all eight parameters (including the signs) of the Jones matrices of liquid-crystal displays. The method can be applied to measure the Jones matrices for all addressable gray levels thus delivering the specifications needed for calculating characteristic curves for arbitrary input and output polarizations. Unlike other approaches, we do not rely on a physical model of the LCD. Thus, it is possible to measure the Jones matrices of a more complex optical system in one step (e.g., when a reflective LCD is used in combination with a beamsplitter). Though the method presented is, in principle, applicable for transmissive and reflective LCDs, calculations and experiments are only shown using the example of a reflective liquid-crystal-on-silicon display. ”

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Publication: SPIE – Optical Engineering, (subscription required)

Issue/Year/DOI: SPIE – Optical Engineering, Vol. 48, 044002 (2009)

Sagnac-interferometer-based characterization of spatial light modulators

Author(s): Jian Wei Tay, Michael A. Taylor, Warwick P. Bowen


“A method for characterizing the phase response of spatial light modulators (SLMs) by using a Sagnac interferometer is proposed and demonstrated. The method represents an improvement over conventional diffraction-based or interferometric techniques by providing a simple and accurate phase measurement while taking advantage of the inherent phase stability of a Sagnac interferometer. As a demonstration, the phase response of a commercial liquid crystal on a silicon SLM is characterized and then linearized by using a programmable lookup table. The transverse phase profile over the SLM surface is also measured.”

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Publication: Applied Optics, (subscription required)

Issue/Year/DOI: Applied Optics, Vol. 48, Issue 12, pp. 2236-2242 (2009)

Multiplexed force measurements on live cells with holographic optical tweezers

Author(s): Cecile O. Mejean, Andrew W. Schaefer, Eleanor A. Millman, Paul Forscher, and Eric R. Dufresne


“We describe open-loop and closed-loop multiplexed force measurements using holographic optical tweezers. We quantify the performance of our novel video-based control system in a driven suspension of colloidal particles. We demonstrate our system’s abilities with the measurement of the mechanical coupling between Aplysia bag cell growth cones and beads functionalized with the neuronal cell adhesion molecule, apCAM. We show that cells form linkages which couple beads to the underlying cytoskeleton. These linkages are intermittent, stochastic and heterogeneous across beads distributed near the leading edge of a single growth cone.”

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Publication: Optics Express, (free download)

Issue/Year/DOI: Optics Express, Vol. 17, Issue 8, pp. 6209-6217 (2009)