Computer simulation of liquid crystal spatial light modulator based on surface plasmon resonance

Spatial resolution is an important performance characteristic of spatial light modulators (SLM). This parameter depends on the physical properties of the electro-optical material, as well as on the design features of the SLM. One of the key factors affecting the spatial resolution of liquid crystal (LC)-based SLM is the fringing field effect. This effect can be reduced in thin LC cells with corresponding reduction in the electro-optical response. A strong electro-optic response in thin LC layer can be attained using the Surface Plasmon Resonance (SPR) phenomenon. While SPR-based LC SLMs were already demonstrated about 15 years ago, their development has been hampered by the fact that these devices are expected to have a relatively low resolution, due to the finite propagation length (several tens of micrometers) of the surface plasmons (SP). This study is aimed at improving the spatial resolution of the SPR-SLM by optimizing the metal-dielectric structure of the device. In particular, a small-scale patterning of the metal layer supporting the propagation of SPs is considered a possible solution for reducing the spatial blurring associated with long propagation length of SPs. Detailed computer simulations of the spatial resolution of the SPR-based LC SLM structure have been carried out using both the rigorous coupled wave analysis (RCWA) and the finite difference time domain (FDTD) method. These simulations were performed for an SLM structure based on the well-known prism-type, Kretschmann excitation configuration. The SLM performance for various spatial resolutions was simulated by introducing a dielectric layer with periodically modulated refractive index. The RCWA technique was used for an initial estimate of the SP excitation angle and the optimal thickness of the silver layer supporting the SP propagation. The FDTD method was used for detailed analysis of near and far field spatial distribution of the modulated light. The results of this study showing improved resolution LC-SP-SLM are presented here.