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

Abstract:

“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: Optical Trapping Applications 2009
Issue/Year: Advances in Imaging, OSA Technical Digest (CD) (Optical Society of America, 2009), paper OMB3
DOI: 10.1364/OTA.2009.OMB3

Sagnac-interferometer-based characterization of spatial light modulators

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

Abstract:

“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
Issue/Year: Applied Optics, Vol. 48, Issue 12, pp. 2236-2242 (2009)
DOI: 10.1364/AO.48.002236

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

Abstract:

“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
Issue/Year: Optics Express, Vol. 17, Issue 8, pp. 6209-6217 (2009)
DOI: 10.1364/OE.17.006209

Zero order synthetic hologram with a sinusoidal phase carrier for generation of multiple beams

Author(s): V. Arrizón, U. Ruiz, G. Mendez, and A. Apolinar-Iribe

Abstract:

“We discuss a phase synthetic hologram, for encoding arbitrary complex fields, whose design is based on a sinusoidal phase grating with a spatially modulated phase depth. An important feature of the hologram is that it encodes the complex field at the zero diffraction order of the carrier grating. The smoothness of this sinusoidal carrier grating facilitates the implementation of the hologram with a pixelated spatial light modulator. We take advantage of the hologram reconstruction at the zero-diffraction order for the simultaneous generation of a collection of complex beams.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 17, Issue 4, pp. 2663-2669 (2009)
DOI: 10.1364/OE.17.002663

Holographic twin traps

Author(s): S Zwick, T Haist, Y Miyamoto, L He, M Warber, A Hermerschmidt and W Osten

Abstract:

“We present a new method that enables the generation of arbitrary positioned dual-beam traps without additional hardware in a single-beam holographic optical tweezers setup. By this approach, stable trapping at medium numerical aperture and long working distance is realized on a standard Zeiss Axiovert 200 M research microscope. Simulations of focus separations and spherical aberrations were performed and first experimental results are presented.”

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Publication: Journal of Optics A
Issue/Year: J. Opt. A: Pure Appl. Opt. (2009), 11 034011 (11pp)
DOI: 10.1088/1464-4258/11/3/034011

Color holographic reconstruction using multiple SLMs and LED illumination

Author(s): Fahri Yaras and Levent Onural

Abstract:

“A color holographic reconstruction technique by using three light emitting diodes (LEDs) is described. Reflective type phase-only spatial light modulators (SLMs) are used since they are suitable for in-line phase holograms. Gerchberg-Saxton iterative algorithm is used for computing phase holograms. Three phase holograms are calculated separately for red, green and blue colors, for a color reconstruction, and separately loaded to corresponding SLMs. Three LEDs are used for illuminating those phase holograms and reconstructions are combined and captured. Experimental results are satisfactory. ”

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Publication: SPIE Proceedings
Issue/Year: Proc. SPIE, Vol. 7237, 72370O (2009);
DOI: 10.1117/12.806875

SLM Microscopy: Scanless Two-Photon Imaging and Photostimulation with Spatial Light Modulators

Author(s): Volodymyr Nikolenko, Brendon O. Watson, Roberto Araya, Alan Woodruff, Darcy S. Peterka and Rafael Yuste

Abstract:

“Laser microscopy has generally poor temporal resolution, caused by the serial scanning of each pixel. This is a significant problem for imaging or optically manipulating neural circuits, since neuronal activity is fast. To help surmount this limitation, we have developed a “scanless” microscope that does not contain mechanically moving parts. This microscope uses a diffractive spatial light modulator (SLM) to shape an incoming two-photon laser beam into any arbitrary light pattern. This allows the simultaneous imaging or photostimulation of different regions of a sample with three-dimensional precision. To demonstrate the usefulness of this microscope, we perform two-photon uncaging of glutamate to activate dendritic spines and cortical neurons in brain slices. We also use it to carry out fast (60 Hz) two-photon calcium imaging of action potentials in neuronal populations. Thus, SLM microscopy appears to be a powerful tool for imaging and optically manipulating neurons and neuronal circuits. Moreover, the use of SLMs expands the flexibility of laser microscopy, as it can substitute traditional simple fixed lenses with any calculated lens function.”

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Publication: Frontiers in Neural Circuits
Issue/Year: Front Neural Circuits. 2008; 2: 5.
DOI: 10.3389/neuro.04.005.2008

Calibration of dynamic holographic optical tweezers for force measurements on biomaterials

Author(s): Astrid van der Horst and Nancy R. Forde

Abstract:

“Holographic optical tweezers (HOTs) enable the manipulation of multiple traps independently in three dimensions in real time. Application of this technique to force measurements requires calibration of trap stiffness and its position dependence. Here, we determine the trap stiffness of HOTs as they are steered in two dimensions. To do this, we trap a single particle in a multiple-trap configuration and analyze the power spectrum of the laser deflection on a position-sensitive photodiode. With this method, the relative trap strengths can be determined independent of exact particle size, and high stiffnesses can be probed because of the high bandwidth of the photodiode. We find a trap stiffness for each of three HOT traps of ? ~26 pN/µm per 100 mW of laser power. Importantly, we find that this stiffness remains constant within ± 4% over 20µm displacements of a trap. We also investigate the minimum step size achievable when steering a trap with HOTs, and find that traps can be stepped and detected within ~2 nm i our instrument, although there is an underlying position modulation of the traps of comparable scale that arises from SLM addressing. The independence of trap stiffness on steering angle over wide ranges and the nanometer positioning accuracy of HOTs demonstrate the applicability of this technique to quantitative study of force response of extended biomaterials such as cells or elastomeric protein networks.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 25, pp. 20987-21003
DOI: 10.1364/OE.16.020987

Dynamic control of higher-order modes in hollow-core photonic crystal fibers

Author(s): T. G. Euser, G. Whyte, M. Scharrer, J. S. Y. Chen, A. Abdolvand, J. Nold, C. F. Kaminski, and P. St. J. Russell

Abstract:

“We present a versatile method for selective mode coupling into higher-order modes of photonic crystal fibers, using holograms electronically generated by a spatial light modulator. The method enables non-mechanical and completely repeatable changes in the coupling conditions. We have excited higher order modes up to LP31 in hollow-core photonic crystal fibers. The reproducibility of the coupling allows direct comparison of the losses of different guided modes in both hollow-core bandgap and kagome-lattice photonic crystal fibers. Our results are also relevant to applications in which the intensity distribution of the light inside the fiber is important, such as particle- or atom-guidance. ”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 22, pp. 17972-17981
DOI: 10.1364/OE.16.017972

Applications of LCoS-based adaptive optical elements in microscopy

Author(s): Andreas Hermerschmidt, Jan Haffner, Tobias Haist, Wolfgang Osten

Abstract:

“Liquid crystal on silicon (LCoS)-based spatial light modulators (SLMs) are versatile adaptive optical elements. In microscopy, among their applications are aberration sensing and correction in wide-field microscopy and also the implementation of holographic optical tweezers. For aberration correction, the required scene-based wavefront sensing can be implemented as a modified correlation-based Shack-Hartmann approach where a high-resolution SLM first senses and then corrects the aberrations. For the implementation of holographic optical tweezers, the SLM serves as a variable optical beam-splitter which is addressed with holograms computed by fast algorithms implemented on the graphics processing unit (GPU) of a common PC almost in real-time.”

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Publication: Proceedings IEEE/LEOS Internationall Conference on Optical MEMs and Nanophotonics
Issue/Year: Proceedings IEEE/LEOS Internationall Conference on Optical MEMs and Nanophotonics, 2008,
DOI: 10.1109/OMEMS.2008.4607842