CONICET | Buscador de Institutos y Recursos Humanos

Liquid crystals displays (LCDs) have found to be very useful in a large number of optical applications because of their notably capability to spatially manipulate the phase information of an incident light beam. Therefore, they are nowadays used as spatial light modulators (SLMs) in many applications, as for instance, in Optical Image Processing [1], in Holography Data Storage [2], in Programmable Adaptive Optics [3], in Medical Optics [4], or in Diffractive Optics [5], among other. Recently, a new type of reflective LCDs, the Liquid Crystals on Silicon (LCoS) displays, have awaken a great interest due to their specific technical characteristics, which in general, are superior in many aspects to the provided by trasmissive LCDs [6,7]. For instance, as LCoS displays work in reflection, the light impinging such devices performs a double pass through the LC cell, leading to a large phase modulation than the related to trasmissive LCDs with the same thickness. Therefore, at the present, they are broadly employed in optical applications and in particular, they result to be very interesting devices when performing digital holography applications. In order to achieve high efficiencies for the addressed holograms, an optimized LCoS display performance is required (i.e. it is needed to address a stable and accurate phase distribution). In this framework, a characterization and optimization procedure arises important. However, some authors have observed different non-desired physical phenomena when working with LCoS displays. We refer to the effective depolarization [8,9], the time-fluctuation of the phase [10] and the anamorphic phenomenon [11]. Such phenomena may be damaging for optical applications, decreasing the corresponding efficiency and so, for an appropriate LCoS display response, they have to be taken into account in the optimization methodology. In this chapter, we propose an LCoS display characterization and optimization procedure [12] based on the combination of the Stokes-Mueller and the Jones formalisms. This procedure is able to deal with polarized, partial polarized or unpolarized light and so, the effective depolarization related to LCoS displays is taken into account. Moreover, some results of a commercial LCoS display optimization are provided as a function of the wavelength [13] and the incident angle [14], being the LCoS display response strongly dependent with these two physical parameters. Besides, we include a thoroughly study of the physical phenomena stated above. In this sense, we show their impact in the efficiency of digital holograms addressed to the LCoS display and their physical origin is also discussed. Afterwards, a method based on the Minimum Euclidian Principle, which is befitting for minimize the influence of those phenomena in digital holography [15], it is also proposed. Finally, some digital holograms are experimentally applied with the best configuration obtained.

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