Hybrid multinary modulation using a phase modulating spatial light modulator and a low-pass spatial filter

Author(s):

Abstract:Zoltán Göröcs, Gábor Erdei, Tamás Sarkadi, Ferenc Ujhelyi, Judit Reményi, Pál Koppa, and Emoke Lorincz

“We propose a method for performing binary intensity and continuous phase modulation of beams with a spatial light modulator (SLM) and a low-pass spatial filtering 4-f system. With our method it is possible to avoid the use of phase masks in holographic data storage systems or to enhance the phase encoding of the SLM by making it capable of binary amplitude modulation. The data storage capabilities and the limitations of the method are studied.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 32, Issue 16, pp. 2336-2338 (2007)
DOI: 10.1364/OL.32.002336

Twisted-nematic liquid-crystal-on-silicon adaptive optics aberrometer and wavefront corrector

Author(s): Seow-Hwang Eng, Douglas Chai, Fred Reinholz

Abstract:

“A Hartmann-Shack wavefront sensor (HSWS) has been proven to be a reliable tool for the quantitative analysis of human ocular aberrations. In an active adaptive optics (AO) system, it has the role to monitor wave aberrations. To ensure the exclusive retrieval of Zernike coefficients for the measured ocular wavefronts, we first nullify the AO system’s aberrations. This is of particular importance in our setup with a twisted-nematic (TN) liquid-crystal-on-silicon (LCoS) chip as the wavefront manipulator due to its strong unwanted zero-order diffractive beam. We characterize the AO system’s performance—before and after ocular corrections—by means of different parameters, including experimental and simulated point spread functions (PSFs). An iterative closed-loop algorithm reduces the residual wavefront error to typical values of 0.1 μm. This system constitutes a wavefront corrector that can possibly be used for high resolution retinal imaging purposes or for visual psychophysical experiments.”

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Publication: Journal of Biomedical Optics
Issue/Year: J. Biomed. Opt. 14, 044014 (Jul 27, 2009)
DOI: 10.1117/1.3183814

Optical ferris wheel for ultracold atoms

Author(s): S. Franke-Arnold, J. Leach, M. J. Padgett, V. E. Lembessis, D. Ellinas, A. J. Wright, J. M. Girkin, P. Ohberg, and A. S. Arnold

Abstract:

“We propose a versatile optical ring lattice suitable for trapping cold and quantum degenerate atomic samples. We demonstrate the realisation of intensity patterns from pairs of Laguerre-Gauss (exp(iℓө) modes with different ℓ indices. These patterns can be rotated by introducing a frequency shift between the modes. We can generate bright ring lattices for trapping atoms in red-detuned light, and dark ring lattices suitable for trapping atoms with minimal heating in the optical vortices of blue-detuned light. The lattice sites can be joined to form a uniform ring trap, making it ideal for studying persistent currents and the Mott insulator transition in a ring geometry. ”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 15, Issue 14, pp. 8619-8625 (2007)
DOI: 10.1364/OE.15.008619

Ultrashort Laguerre-Gaussian pulses with angular and group velocity dispersion compensation

Author(s): I. Zeylikovich, H. I. Sztul, V. Kartazaev, T. Le, and R. R. Alfano

Abstract:

“Coherent optical vortices are generated from ultrashort 6.4 fs pulses. Our results demonstrate angular dispersion compensation of ultrashort 6.4 fs Laguerre-Gaussian (LG) pulses as well as what is believed to be the first direct autocorrelation measurement of 80 fs LG amplified pulses. A reflective-mirror-based 4f-compressor is proposed to compensate the angular and group velocity dispersion of the ultrashort LG pulses.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 32, Issue 14, pp. 2025-2027 (2007)
DOI: 10.1364/OL.32.002025

How to create and detect N-dimensional entangled photons with an active phase hologram

Author(s): Martin Stütz, Simon Gröblacher, Thomas Jennewein, Anton Zeilinger

Abstract:

“The experimental realization of multidimensional quantum states may lead to unexplored and interesting physics, as well as advanced quantum communication protocols. The orbital angular momentum of photons is a well suitable discrete degree of freedom for implementing high-dimensional quantum systems. The standard method to generate and manipulate such photon modes is to use bulk and fixed optics. Here the authors demonstrate the utilization of a spatial light modulator to manipulate the orbital angular momentum of entangled photons generated in spontaneous parametric downconversion. They show that their setup allows them to realize photonic entanglement of up to 21 dimensions, which in principle can be extended to even larger dimensions.”

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Publication: Applied Physics Letters
Issue/Year: Appl. Phys. Lett. 90, 261114 (2007)
DOI: 10.1063/1.2752728

Generation of fractal speckles by means of a spatial light modulator

Author(s): Hideki Funamizu and Jun Uozumi

Abstract:

“It was shown in previous studies that, when a diffuser is illuminated by coherent light with an average spatial intensity distribution obeying a negative power function, the scattered field in the Fraunhofer diffraction region exhibits random fractal properties. The method employed so far for producing such fields has a disadvantage in that generated speckle intensities are low due to small transmittance of fractal apertures used in the illumination optics. To overcome this disadvantage, a generation of fractal speckles by means of a spatial light modulator is proposed. The principle is explained and experimental results are also shown.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 15, Issue 12, pp. 7415-7422 (2007)
DOI: 10.1364/OE.15.007415

Depth Analysis of Polymer-Coated Steel Samples Using Near-Infrared Femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry

Author(s): M. Paz Mateo, Carmen C. Garcia, R. Hergenröder

Abstract:

“The viability of near-infrared femtosecond laser ablation (fs-LA) inductively coupled plasma mass spectrometry (ICPMS) for the in-depth analysis of polymer coatings over galvanized steel substrates has been studied. A good depth resolution was obtained modifying the femtosecond Gaussian beam to a flat-top beam by using a liquid-crystal display. In order to avoid mixing of information coming from successive shots, a low repetition rate was accomplished and signals were monitored shot by shot. Different kinds of coatings were used to demonstrate the capability of femtosecond ablation for depth-profiling analysis. Ablation was conducted under He atmosphere, after sample cell Ar was admixed. The depth profiles obtained by LA-ICPMS are in good agreement with those obtained by GD-OES for the three analyzed samples. In cases where due to averaging over several millimeter sample roughness determines the depth resolution of GD-OES, it was found that LA-ICPMS achieves better depth resolution due to the better lateral resolution. The depth resolution obtained by LA-ICPMS was found to be 240 nm and 2.3 μm, for a hot-dip galvanized steel (HDGS) and a polymer−polymer-coated HDGS, respectively, compared to the 2.2 and 4.5 μm achieved with GD-OES for the same samples. ”

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Publication:Analytical Chemistry
Issue/Year: Anal. Chem., 2007, 79 (13), pp 4908–4914
DOI: 10.1021/ac070241q

HoloTrap: Interactive hologram design for multiple dynamic optical trapping

Author(s): E. Pleguezuelos, A. Carnicer, J. Andilla, E. Martín-Badosa, M. Montes-Usategui

Abstract:

“This work presents an application that generates real-time holograms to be displayed on a holographic optical tweezers setup; a technique that allows the manipulation of particles in the range from micrometres to nanometres. The software is written in Java, and uses random binary masks to generate the holograms. It allows customization of several parameters that are dependent on the experimental setup, such as the specific characteristics of the device displaying the hologram, or the presence of aberrations. We evaluate the software’s performance and conclude that real-time interaction is achieved. We give our experimental results from manipulating 5 μm microspheres using the program.”

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Publication: Computer Physics Communications
Issue/Year: Computer Physics Communications, Volume 176, Issues 11-12, Pages 701-709, (2007)
DOI: 10.1016/j.cpc.2007.03.003

Dynamic speckle illumination microscopy with wavelet prefiltering

Author(s): Cathie Ventalon, Rainer Heintzmann, and Jerome Mertz

Abstract:

“Dynamic speckle illumination (DSI) provides a simple and robust technique to obtain fluorescence depth sectioning with a widefield microscope. We report a significant improvement to DSI microscopy based on a statistical image-processing algorithm that incorporates spatial wavelet prefiltering. The resultant gain in sectioning strength leads to a fundamentally improved scaling law for the out-of-focus background rejection.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 32, Issue 11, pp. 1417-1419
DOI: 10.1364/OL.32.001417

Holographic and single beam optical manipulation of hyphal growth in filamentous fungi

Author(s): D. R. Burnham, G. D. Wright, N. D. Read and D. McGloin

Abstract:

“We report on the ability of holographic light fields to alter the normal growth patterns of filamentous fungi. The light fields are produced on a microscopic scale by borrowing methods from the field of optical tweezers, but without the aim of directly trapping or manipulating objects. Extended light fields are shown to redirect and constrict hyphal tip growth, and induce hyphal branching in a highly reproducible manner. The merits of using discrete and continuous light fields produced using a spatial light modulator are discussed and the use of three-dimensional ‘pseudowalls’ of light to control the growth patterns is reported. We also demonstrate the dependence of hyphal tip growth on the wavelength of light, finding that less power is needed at shorter wavelengths to effect changes in the growth dynamics of fungal hyphae.”

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Publication: Journal of Optics A: Pure and Applied Optics
Issue/Year: J. Opt. A: Pure Appl. Opt. 9 S172-S179 (2007)
DOI: 10.1088/1464-4258/9/8/S09
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