Study of Liquid Crystal on Silicon Displays for Their Application in Digital Holography

Due to the significant capability of Liquid Crystal Displays (LCDs) to spatially manipulate the phase information of an incident light beam, this technology is been widely applied in a large number of optical applications. Nowadays, they are employed as Spatial Light Modulators (SLMs) in many areas, as for instance, in Optical Image Processing (Liu et al., 1985), in Holography Data Storage (Coufal et al., 2000), in Programmable Adaptive Optics (Dou & Giles, 1995), in Medical Optics (Twietmeyer et al., 2008), or in Diffractive Optics (Marquez et al., 2005), among others. Recently, a new type of reflective LCDs, the Liquid Crystals on Silicon (LCoS) displays, have awakened a great interest due to their specific technical characteristics, which in general, are superior in many aspects to the ones provided by transmissive LCDs (Lee et al., 2004; Wu & Yang, 2005). For instance, as LCoS displays work in reflection, the light impinging such devices performs a double pass through the LC cell, leading to a larger phase modulation than that related to transmissive LCDs with the same thickness. This greater phase modulation capability allows LCoS displays to become very suitable devices for digital holography applications, as for instance, for laser beam shaping (Dickey et al., 2005; Rodrigo et al., 2011) or for optical micro-particle manipulation (Ashkin, 2006). To maximize the efficiency of digital holograms generated by using LCoS displays, it is required to apply a suitable methodology for optimizing the performance of these devices when generating the specific phase and amplitude distributions. Nowadays, there exist different theoretical models proposed to improve the performance of LCDs (Azzam & Bashara, 1972; Gagnon, 1981; Marquez et. al., 2001). In general, most of these models are based on mathematical formalisms describing fully polarized light, as the Jones formalism (Jones, 1941) or the Berreman formalism (Berreman, 1972). However, some authors have discovered that LCoS displays may introduce non-negligible values of effective depolarization at the reflected beam (Lizana et al., 2008a; Marquez et al., 2008; Wolfe & Chipman, 2006), which are originated by the electrical addressing schemes applied in these devices (Hermerschmidt et al., 2007). This effective depolarization depends on the incident