High-precision phase profile modeling for liquid crystal on silicon devices

High-precision modeling of the phase profile in liquid crystal on silicon (LCoS) devices is challenging yet crucial for high-precision wavefront modulation applications. This work proposes a two-step phenomenological model to characterize the actual phase profile in LCoS by integrating the interpolation with super-Gaussian convolution. The actual phase at a pixel center is determined by convolving the setting phase values of neighboring pixel centers to capture overall pixel response characteristics, while the detailed phase profile between adjacent pixels is described using an error function. The convolution step is employed to model the fringing field effect, while the interpolation step is employed to account for elastic interactions among liquid crystal molecules and nonlinear effects, resulting in a more flexible and precise characterization and modeling of the phase profile in LCoS devices. Furthermore, to determine the model parameters more accurately, a measurement method for diffraction efficiency is presented, featuring insensitivity to fluctuations of laser power and polarization state by introducing an optical power monitoring branch. Predictions of diffraction efficiencies based on the proposed model achieve close agreement with experimental measurements, with a mean error of 0.71% for standard blazed gratings and 1.64% for optimized blazed gratings, thereby contributing to high-precision phase manipulation.