Computer-generated holograms with optimum bandwidths obtained with twisted-nematic liquid-crystal displays

Author(s): Victor Arrizón, Luis A. González, Rodrigo Ponce, and Alfonso Serrano-Heredia

Abstract:

“We discuss a computer-generated hologram for encoding arbitrary complex modulation based on a commercial twisted-nematic liquid-crystal display. This hologram is implemented with the constrained complex modulation provided by the display in a phase-mostly configuration. The hologram structure and transmittance are determined to obtain on-axis signal reconstruction, maximum bandwidth, optimum efficiency, and high signal-to-noise ratio. We employed the proposed holographic code for the experimental synthesis of first-order Bessel beams.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Vol. 44, Issue 9, pp. 1625-1634, 2005
DOI: 10.1364/AO.44.001625

Structure and scaling of helical modes of light

Author(s): Steven Sundbeck, Ilya Gruzberg, and David G. Grier

Abstract:

“Modes of light that contain topological defects such as screw dislocations can be focused into optical traps with interesting and useful properties. The way in which the intensity distribution within helical modes of light varies with topological charge is discussed, and new scaling predictions for their radial profiles that are consistent with experimental observations are introduced.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 30, Issue 5, pp. 477-479 , 2005
DOI: 10.1364/OL.30.000477

Vortex knots in light

Author(s): J. Leach, M. R. Dennis, J. Courtial and M. J. Padgett

Abstract:

“Optical vortices generically arise when optical beams are combined. Recently, we reported how several laser beams containing optical vortices could be combined to form optical vortex loops, links and knots embedded in a light beam (Leach et al 2004 Nature 432 165). Here, we describe in detail the experiments in which vortex loops form these structures. The experimental construction follows a theoretical model originally proposed by Berry and Dennis, and the beams are synthesized using a programmable spatial light modulator and imaged using a CCD camera.”

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Publication:New Journal of Physics
Issue/Year:New J. Phys. 7, 55 (2005)
DOI: 10.1088/1367-2630/7/1/055

Spiral phase contrast imaging in microscopy

Author(s): Severin Fürhapter, Alexander Jesacher, Stefan Bernet, and Monika Ritsch-Marte

Abstract:

“We demonstrate an optical method for edge contrast enhancement in light microscopy. The method is based on holographic Fourier plane filtering of the microscopic image with a spiral phase element (also called vortex phase or helical phase filter) displayed as an off-axis hologram at a computer controlled high resolution spatial light modulator (SLM) in the optical imaging pathway. The phase hologram imprints a helical phase term of the form exp(i ??) on the diffracted light field in its Fourier plane. In the image plane, this results in a strong and isotropic edge contrast enhancement for both amplitude and phase objects.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 13, Issue 3, pp. 689-694, 2005
DOI: 10.1364/OPEX.13.000689

Photoporation and cell transfection using a violet diode laser

Author(s): L. Paterson, B. Agate, M. Comrie, R. Ferguson, T. Lake, J. Morris, A. Carruthers, C. T. Brown, W. Sibbett, P. Bryant, F. Gunn-Moore, A. Riches, and Kishan Dholakia

Abstract:

“The introduction and subsequent expression of foreign DNA inside living mammalian cells (transfection) is achieved by photoporation with a violet diode laser. We direct a compact 405 nm laser diode source into an inverted optical microscope configuration and expose cells to 0.3 mW for 40 ms. The localized optical power density of ~1200 MW/m2 is six orders of magnitude lower than that used in femtosecond photoporation (~104 TW/m2). The beam perforates the cell plasma membrane to allow uptake of plasmid DNA containing an antibiotic resistant gene as well as the green fluorescent protein (GFP) gene. Successfully transfected cells then expand into clonal groups which are used to create stable cell lines. The use of the violet diode laser offers a new and simple poration technique compatible with standard microscopes and is the simplest method of laser-assisted cell poration reported to date.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 13, Issue 2, pp. 595-600, 2005
DOI: 10.1364/OPEX.13.000595

Determination of the phase- and polarization-changing properties of reflective spatial light modulators in one set-up

Author(s): Kay Gastinger, Ola D. Hunderi and Mikael Lindgren.

Abstract:

“The use of liquid crystal spatial light modulators in applications, require good characterization of phase, polarization and amplitude shifting properties. This report presents a new approach for simultaneously characterizing the depolarization and controlling the polarization properties of a reflective twisted nematic liquid crystal spatial light modulator (LC SLM). The SLM was set up as a part of a Michelson interferometer. The phase response was determined by using a piezo-electric actuator for phase stepping in the reference arm. During the polarization measurement the reference beam was removed and the polarization state of the input and output was determined by a polarization state generator (PSG) and a polarization state analyzer (PSA), each consisting of a polarizer and a quarter-wave plate. Hereby, both phase response and polarization control properties could be determined independently in the same measurement configuration simply by changing static polarization components. The systematic rotation of the quarter wave plates of the PSG and the PSA using stepper motors gives out-put data whose Fourier transform in terms of angular frequency components can be used to determine all the elements of the Mueller matrix. The Mueller matrix of a commercial SLM (Holoeye LC-2500) was determined for 17 evenly spaced voltage levels addressed to the SLM.”

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Publication: SPIE Proceedings
Issue/Year: Proc. SPIE, Vol. 5618, 174 (2004)
DOI: 10.1117/12.578438

Assembly of 3-dimensional structures using programmable holographic optical tweezers

Author(s): Gavin Sinclair, Pamela Jordan, Johannes Courtial, Miles Padgett, Jon Cooper, and Zsolt Laczik

Abstract:

“The micromanipulation of objects into 3-dimensional geometries within holographic optical tweezers is carried out using modified Gerchberg-Saxton (GS) and direct binary search (DBS) algorithms to produce the hologram designs. The algorithms calculate sequences of phase holograms, which are implemented using a spatial light modulator, to reconfigure the geometries of optical traps in many planes simultaneously. The GS algorithm is able to calculate holograms quickly from the initial, intermediate and final trap positions. In contrast, the DBS algorithm is slower and therefore used to pre-calculate the holograms, which are then displayed in sequence. Assembly of objects in a variety of 3-D configurations is semi-automated, once the traps in their initial positions are loaded.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 12, Issue 22, pp. 5475-5480, 2004
DOI: 10.1364/OPEX.12.005475

Full-color autostereoscopic 3D display system using color-dispersion-compensated synthetic phase holograms

Author(s): Kyongsik Choi, Hwi Kim, and Byoungho Lee

Abstract:

“A novel full-color autostereoscopic three-dimensional (3D) display system has been developed using color-dispersion-compensated (CDC) synthetic phase holograms (SPHs) on a phase-type spatial light modulator. To design the CDC phase holograms, we used a modified iterative Fourier transform algorithm with scaling constants and phase quantization level constraints. We obtained a high diffraction efficiency (~90.04%), a large signal-to-noise ratio (~9.57dB), and a low reconstruction error (~0.0011) from our simulation results. Each optimized phase hologram was synthesized with each CDC directional hologram for red, green, and blue wavelengths for full-color autostereoscopic 3D display. The CDC SPHs were composed and modulated by only one phase-type spatial light modulator. We have demonstrated experimentally that the designed CDC SPHs are able to generate full-color autostereoscopic 3D images and video frames very well, without any use of glasses.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 12, Issue 21, pp. 5229-5236, 2004
DOI: 10.1364/OPEX.12.005229

Size selective trapping with optical ”cogwheel” tweezers

Author(s): Alexander Jesacher, Severin Fürhapter, Stefan Bernet, and Monika Ritsch-Marte

Abstract:

“We experimentally investigate the size-selective trapping behavior of Laguerre-Gaussian beams (”doughnut-beams”) and ”cogwheel”-shaped beams which are collinear superpositions of two doughnut beams of equal opposite helical index. Experimentally they are created by diffraction of a Gaussian laser beam at a high resolution refractive spatial light modulator (SLM). In the focus of an optical microscope such a beam looks similar to a ”cogwheel”, i.e. the light intensity is periodically modulated around the circumference of a sphere with a precisely adjustable diameter. In an optical tweezers setup these modes can be used to trap particles or cells, provided their sizes exceed the ring diameter by a fixed amount. This promises a convenient method of constructing an optical tweezers system in microscopy which acts as a passive sorter for particles of differing sizes.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 12, Issue 17, pp. 4129-4135, 2004
DOI: 10.1364/OPEX.12.004129

Multiple Optical Trapping by Means of Diffractive Optical Elements

Author(s): Dan Cojoc, Valentina Emiliani, Enrico Ferrari, Radu Malureanu, Stefano Cabrini, Remo Zaccaria Proiettiand Enzo Di Fabrizio

Abstract:

“In this paper we report multiple optical trapping of microscopic dielectric particles using diffractive optical elements implemented on twisted nematic liquid crystal spatial light modulators. The particles are trapped in arrays disposed in plane or in volume and can be moved independently in x-y-z by changing the configuration of the diffractive optical element. We show also multiple trapping using Laguerre-Gaussian and Gaussian beams simultaneously. The orbital angular momentum of the Laguerre-Gaussian beam is transferred to the particle, making it to move on a circular trajectory defined by the intensity pattern specific to this beam. We use sample cells built with two microscope slides separated by 120 µm with a sticky tape. The space between the two slides is filled with 2 µm diameter silica spheres diluted in water (concentration 0.026% wt). We show that optical trapping is also possible in a small glass capillary with a diameter of 100 µm. ”

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Publication: Japanese Journal of Applied Physics
Issue/Year: Jpn. J. Appl. Phys. 43 (2004) pp. 3910-3915
DOI: 10.1143/JJAP.43.3910