Fast parallel diffractive multi-beam femtosecond laser surface micro-structuring

Author(s): Zheng Kuang, Dun Liu, Walter Perrie, Stuart Edwardson, Martin Sharp, Eamonn Fearon, Geoff Dearden, Ken Watkins

Abstract:

“Fast parallel femtosecond laser surface micro-structuring is demonstrated using a spatial light modulator (SLM). The Gratings and Lenses algorithm, which is simple and computationally fast, is used to calculate computer generated holograms (CGHs) producing diffractive multiple beams for the parallel processing. The results show that the finite laser bandwidth can significantly alter the intensity distribution of diffracted beams at higher angles resulting in elongated hole shapes. In addition, by synchronisation of applied CGHs and the scanning system, true 3D micro-structures are created on Ti6Al4V.”

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

Issue/Year/DOI: Applied Surface Science, Volume 255, Issues 13-14, 15 April 2009, Pages 6582-6588
doi:10.1016/j.apsusc.2009.02.043

Correction of aberration in holographic optical tweezers using a Shack-Hartmann sensor

Author(s): Carol López-Quesada, Jordi Andilla, Estela Martín-Badosa

Abstract:

“Optical aberration due to the nonflatness of spatial light modulators used in holographic optical tweezers significantly deteriorates the quality of the trap and may easily prevent stable trapping of particles. We use a Shack-Hartmann sensor to measure the distorted wavefront at the modulator plane; the conjugate of this wavefront is then added to the holograms written into the display to counteract its own curvature and thus compensate the optical aberration of the system. For a Holoeye LC-R 2500 reflective device, flatness is improved from 0.8λ to λ/16 (λ=532 nm), leading to a diffraction-limited spot at the focal plane of the microscope objective, which makes stable trapping possible. This process could be fully automated in a closed-loop configuration and would eventually allow other sources of aberration in the optical setup to be corrected for.”

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Publication: Applied Optics, (subscription required)

Issue/Year/DOI: Applied Optics, Vol. 48, Issue 6, pp. 1084-1090 (2009)
doi:10.1364/AO.48.001084

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, (free download)

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

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

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