Design and evaluation of phase-deviation sensitive DOEs with possible application in SLM characterization

Abstract

The spatial light modulator (SLM) is a component which permits dynamic phase and/or amplitude shaping of the cross section of a light beam. Thanks to a high efficiency, its wide range of applications includes e.g. optical beam steering and applications in signal processing. This Master thesis presents a method for designing pixelated diffractive optical elements (DOEs) producing spots whose intensities are optimized to heavily depend on a particular phase modulation level. A theoretical expression for the sensitivity is derived and both simulations as well as experiments show that the achieved sensitivities are several times higher than when using conventional, intensity-maximizing, DOE design methods. Eventually, a non-interferometric way of determining the phase modulation characteristics of an 8-bit SLM unit using these DOEs is suggested. The results in one case show an agreement within 20◦ with measurements made by interferometry. As the method is subjected to a different setting of the SLM unit yielding a higher residual amplitude modulation, interferometry and phase retrieval using DOEs agree to a lesser extent.