Multiwavelength study of etalon effects in LCOS-based spatial light modulators

Abstract

Spatial light modulators (SLM) offer a broad range of opportunities in optics. Especially liquid crystal on silicon (LCOS) devices are in common use, due to their extreme high spatial resolution and up-scalable production capabilities compared to other technologies. Still, the architectural complexity of these displays causes well known phase errors, such as the inherent backplane curvature, crosstalk between adjacent pixels or spatial varying phase response (SVPR). In our latest work we presented a robust method to characterize the 2D resolved phase response of a SLM by means of a Twyman-Green interferometer and how to calculate a compensation phase mask. Based on the non-linear deviation of the pixel retardation measurements, it was indicated that a pure LC layer thickness variation is not the only contributor to the SVPR. In this work we want to propose a more representative model by taking interfering reflections of different layers, the socalled Etalon effect, into account. The 2D pixel phase response was simulated via Ericksen-Leslie equation and included in the transfer matrix method. The introduced Etalon model is validated by complementary measurements for different center wavelengths. A white-light monochromator was added to the setup to adjust these properties accordingly. First implications of systematic error compensation will be discussed.