Binocular adaptive optics vision analyzer with full control over the complex pupil functions

December, 2011

Author(s): Christina Schwarz, Pedro M. Prieto, Enrique J. Fernández, and Pablo Artal

Abstract:

“We present a binocular adaptive optics vision analyzer fully capable of controlling both amplitude and phase of the two complex pupil functions in each eye of the subject. A special feature of the instrument is its comparatively simple setup. A single reflective liquid crystal on silicon spatial light modulator working in pure phase modulation generates the phase profiles for both pupils simultaneously. In addition, another liquid crystal spatial light modulator working in transmission operates in pure intensity modulation to produce a large variety of pupil masks for each eye. Subjects perform visual tasks through any predefined variations of the complex pupil function for both eyes. As an example of the system efficiency, we recorded images of the stimuli through the system as they were projected at the subject’s retina. This instrument proves to be extremely versatile for designing and testing novel ophthalmic elements and simulating visual outcomes, as well as for further research of binocular vision.”

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Publication: Optics Letters, (subscription required)

Issue/Year/DOI: Optics Letters, Vol. 36, Issue 24, pp. 4779-4781 (2011)
doi:10.1364/OL.36.004779


Generation of Optical Vortices by Linear Phase Ramps

July, 2011

Author(s): Sunil Vyas

Abstract:

“Generation of optical vortices using linear phase ramps is experimentally demonstrated. When two regions of a wavefront have opposite phase gradients then along the line of phase discontinuity vortices can be generated. It is shown that vortices can evolve during propagation even with the unequal magnitude of tilt in the two regions of the wavefront. The number of vortices and their location depend upon the magnitude of tilt. vortex generation is experimentally realized by encoding phase mask on spatial light modulator and their presence is detected interferometrically. Numerical simulation has been performed to calculate the diffracted intensity distribution from the phase mask, and presence of vortices in the diffracted field is detected by computational techniques.”

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Publication: International Journal of Optics, (free download)

Issue/Year/DOI: International Journal of Optics, Volume 2012, Article ID 794259, 6 pages, (2012)
doi:10.1155/2012/794259


Binary-Phase Spatial Light Filters for Mode-Selective Excitation of Multimode Fibers

July, 2011

Author(s): Stepniak, G.; Maksymiuk, L.; Siuzdak, J.;

Abstract:

“In this paper, spatial light modulation is proposed to increase the transmission capacity of graded-index multimode fibers. In the method, selected linearly polarized eigenmodes of the fiber are excited using simple binary-phase spatial filters. Numerical results indicate that the selectivity of the method is very high, also for fibers with perturbed profiles. The excess attenuation of the method is very low. In the experiment, a threefold increase of fiber bandwidth for several filters is obtained.”

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Publication: Journal of Lightwave Technology, (subscription required)

Issue/Year/DOI: Journal of Lightwave Technology, Volume: 29 Issue: 13, P.1980 – 1987 (2011)
doi:10.1109/JLT.2011.2155621


Dynamic space shaping of intense ultrashort laser light with blazed-type gratings

November, 2010

Author(s): I. Marienko, V. Denisenko, V Slusar, and M. Soskin

Abstract:

“A beam shaper for dynamic transversal shaping of broadband laser pulses that utilizes a blazed ruled grating and a blazed-type grating simulated on Spatial Light Modulator was demonstrated. The introduced shaper scheme is an extension of 2f-2f scheme [Mariyenko, et al., Opt. Express 13, 7599 (2005)] where the two thin holograms with matched grating constants performed light shaping. The new scheme utilizes the diffraction gratings with different grating constants. Dispersion-free light shaping is achieved by means of the intermediate transversal light beam magnification. The magnification balances the mismatch in the grating constants resulting in total residual angular dispersion compensation. In turn, the magnified beam covers a greater area on the modulator matrix thus reducing the incident light power density by a value equal to square of the magnification factor. It translates to the safe-operation threshold extension of the modulator allowing shaping pulses that are powerful enough to be used in the applications. With a proper components selection, the throughput efficiency of the shaper can be well above 40%. A proper shaper operation was demonstrated with the 140-fs Ti:Sapphire oscillator. Theoretical calculations support the conclusions.”

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Publication: Optics Express, (free download)

Issue/Year/DOI: Optics Express, Vol. 18, Issue 24, pp. 25143-25150 (2010)
doi:10.1364/OE.18.025143


Increasing multimode fiber transmission capacity by mode selective spatial light phase modulation

September, 2010

Author(s): Stepniak, G.; Maksymiuk, L.; Siuzdak, J.;

Abstract:

“We propose spatial light modulation with binary phase filters to increase the transmission bandwidth of multimode fibers. In the experiment more than 300 % of bandwidth enhancement is obtained.”

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Publication: ECOC Proceedings, (subscription required)

Issue/Year/DOI: 36th European Conference and Exhibition on Optical Communication (ECOC), 2010
doi:10.1109/ECOC.2010.5621465


A portable laser photostimulation and imaging microscope

July, 2010

Author(s): Volodymyr Nikolenko , Darcy S Peterka, Rafael Yuste

Abstract:

“We describe a compact microscope that uses a spatial light modulator (SLM) to control the excitation laser light. The flexibility of SLMs, which can mimic virtually any optical transfer function, enables the experimenter to create, in software, arbitrary spatio-temporal light patterns, including focusing and beam scanning, simply by calculating the appropriate phase mask. Our prototype, a scan-less device with no moving parts, can be used for laser imaging or photostimulation, supplanting the need for an elaborate optical setup. As a proof of principle, we generate complex excitation patterns on fluorescent samples and also perform functional imaging of neuronal activity in living brain slices.”

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Publication: Journal of Neural Engineering, (free download)

Issue/Year/DOI: J. Neural Eng., Volume 7, Number 4 (2010) 045001
doi: 10.1088/1741-2560/7/4/045001


Nonlinear response studies and corrections for a liquid crystal spatial light modulator

June, 2010

Author(s): RAVINDER KUMAR BANYAL, B. RAGHAVENDRA PRASAD

Abstract:

“The nonlinear response of light transmission characteristics of a liquid crystal (LC) spatial light modulator (SLM) is studied. The results show that the device exhibits a wide range of variations with different control parameters and input settings. Experiments were performed to obtain intensity modulation that is best described by either power-law or sigmoidal functions. Based on the inverse transformation, an appropriate pre-processing scheme for electrically addressed input gray-scale images, particularly important in several optical processing and imaging applications, is suggested. Further, the necessity to compensate the SLM image nonlinearities in a volume holographic data storage and retrieval system is demonstrated.”

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Publication: PRAMANA Journal of Physics (free download)

Issue/Year/DOI: PRAMANA Journal of Physics, Vol. 74, No. 6, June 2010, pp. 961-971


Spatial light modulator as a reconfigurable intracavity dispersive element for tunable lasers

September, 2009

Author(s): Lin Dong, Sergei Popov, Sergey Sergeyev and Ari T. Friberg

Abstract:

“An improved approach for narrow-band wavelength selection in tunable lasers is described. To provide the tunability, a reconfigurable diffractive optical element (DOE) based on a programmable spatial light modulator (PSLM) is applied. With a proper choice of the phase transfer function of the PSLM, the device can be used as a dispersive intra-cavity component for precise tuning within the lasing spectral band of a solid-state dye laser. The suggested design allows avoiding the mechanical movement of any cavity components. The tunability performance and simulation are demonstrated using the Fourier optics method. ”

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Publication: Central European Journal of Physics, (subscription required)

Issue/Year/DOI: Central European Journal of Physics, Volume 8, Number 2, 228-234, (2009)
DOI: 10.2478/s11534-009-0151-4


Superhydrophobic surface structures in thermoplastic polymers by interference lithography and thermal imprinting

September, 2009

Author(s): Christian W.J. Berendsen, Marek Škereň, David Najdek and František Cerný

Abstract:

“We present a method to produce superhydrophobic surfaces in thermoplastic polymer substrates. The method involves the creation of a nickel stamp using a customized laser interference lithography technique and electroplating processes. This stamp is used to emboss sub-micrometer periodic structures into the thermoplastic. The modified surface is coated with a hydrophobic plasma-polymerized hexafluoropropene layer. Surfaces with different periodicity and relief depth were created. On the surface with the highest aspect ratio, advancing water contact angles of 167° were measured with a water contact angle hysteresis of below 5°.”

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Publication: Applied Surface Science – ScienceDirect.com (subscription required)

Issue/Year/DOI: Applied Surface Science, Volume 255, Issue 23, 15 September 2009, Pages 9305-9310
doi:10.1016/j.apsusc.2009.07.001


Systematic errors of an optical encryption system due to the discrete values of a spatial light modulator

February, 2009

Author(s): David S. Monaghan, Unnikrishnan Gopinathan, Damien P. Kelly, Thomas J. Naughton, John T. Sheridan

Abstract:

“An optical implementation of the amplitude encoded double random phase encryption/decryption technique is implemented, and both numerical and experimental results are presented. In particular, we examine the effect of quantization in the decryption process due to the discrete values and quantized levels, which a spatial light modulator (SLM) can physically display. To do this, we characterize a transmissive SLM using Jones matrices and then map a complex image to the physically achievable levels of the SLM using the pseudorandom encoding technique. We present both numerical and experimental results that quantify the performance of the system. ”

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Publication: SPIE – Optical Engineering, (subscription required)

Issue/Year/DOI: Opt. Eng., Vol. 48, 027001 (2009);
doi:10.1117/1.3076208