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Proceedings Paper

Optimization of the diffraction efficiency of a spatial light modulator through phase error minimization
Author(s): Matthew A. Cibula; David H. McIntyre
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Paper Abstract

Spatial light modulators (SLMs) are used to diffract light beams for a variety of applications. In particular, optical tweezer trapping has greatly benefited from the advent of phase-mostly and phase-only SLMs to write holograms that produce multiple traps. We are using holographic optical tweezers to trap multiple sensor particles in a lab-on-a-chip measurement platform. As part of this program, we have developed a method for optimizing the diffraction efficiency of a SLM. This general method can be applied in situ and addresses the issues of nonlinear phase modulation and phase modulation less than 2π. The method employs a one-dimensional blazed phase grating written on the SLM. For an ideal SLM, the phase shift is linear and covers 0 - 2π, yielding a first-order diffraction efficiency of unity. For a realistic SLM with nonlinear or reduced phase shift, the efficiency is approximately η = 1 - σ2, where σ2 is the variance of the phase error from the ideal case. Because each pixel contributes to the phase error independently, this suggests a method to maximize the efficiency by adjusting the phase encoding of the SLM pixel-by-pixel. In practice, we do this by adjusting the gray-scale of each pixel while measuring the first-order diffracted power. The collection of optimal gray values comprises the optimized gray-scale lookup table, which exhibits the nonlinearity required to produce a linear phase grating and the saturated phase encoding that maximizes the efficiency of phase limited SLMs. We have successfully applied this optimization method to two different SLMs.

Paper Details

Date Published: 12 September 2013
PDF: 11 pages
Proc. SPIE 8810, Optical Trapping and Optical Micromanipulation X, 88102N (12 September 2013); doi: 10.1117/12.2023374
Show Author Affiliations
Matthew A. Cibula, Oregon State Univ. (United States)
David H. McIntyre, Oregon State Univ. (United States)


Published in SPIE Proceedings Vol. 8810:
Optical Trapping and Optical Micromanipulation X
Kishan Dholakia; Gabriel C. Spalding, Editor(s)

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