We report two high birefringence and low viscosity nematic mixtures for phase-only liquid-crystal-on-silicon spatial light modulators. The measured response time (on + off) of a test cell with 2π phase change at 1550 nm, 5 V operation voltage, and 40 °C is faster than 10 ms. To improve the photostability, a distributed Bragg reflector is designed to cutoff the harmful ultraviolet and blue wavelengths. These materials are promising candidates for future 6G optical communications.

This project aims to develop novel frame buffer pixel circuit-based silicon backplanes using 180nm process technology for polarization-independent liquid crystal on silicon (PI-LCOS) phase modulators. Three unique pixel circuits, which exclusively utilize NMOS transistors, have been designed to minimize pixel size and improve production yield. Additionally, the "Voltage Booster” (VBOOST) technique extends the dynamic voltage range, crucial for stable phase modulation and high grayscale. Efforts are also underway to enhance stability against voltage fluctuation by incorporating the auxiliary capacitor or refined active-driving pixel-electrode stage. The prototype silicon backplane features a 64 x 64-pixel matrix with column and row decoders for individual pixel addressing, facilitating optical testing. By employing a two-stage analog dynamic random-access memory (DRAM), the pixel circuit supports sequential data loading row by row throughout the array while simultaneously displaying previously loaded frame data. This ‘frame-at-a-time’ data refresh capability is vital for displaying images with full contrast, which is particularly advantageous for holographic and color sequential display applications. Simulation and experimental assessments on the silicon backplane chips demonstrate that these pixel circuits can support a high-resolution LCOS device with approximately 4.15 um x 4.15 um pixel pitch in the 180nm process technology, a high voltage holding ratio exceeding 94%, and substantial grayscale modulation depth.

Phase-only liquid crystal on silicon (LCoS) spatial light modulators are used in a variety of applications. Despite their wide use, current phase-only LCoS devices are hindered by their single-polarization modulation. We propose a polarization independent LCoS device which uses a polymer quarter-wave plate for polarization conversion. We designed a custom pixel circuit which enables high driving voltage and high pixel grayscale by utilizing an analog driving frame buffer pixel circuit. Our pixel circuit is optimized for small pixel size and the silicon backplanes can be fabricated at a traditional foundry. We demonstrate polarization independent phase modulation through optical beam steering tests for various input polarizations. Our fabricated device lays the foundation for commercial LCoS devices highly suitable for wavelength selective switches, holographic display, wavefront correction, and optical beam shaping.

This project presents the design and fabrication of a polarization-independent liquid crystal-on-a-silicon (PI-LCoS) phase modulator that utilizes a polymer quarter-wave plate (QWP) for polarization conversion. The device features a novel silicon backplane including DRAM-based analog pixel circuit with fine grayscale control, and small pixel size, achievable using standard foundry processes. We demonstrate polarization-independent phase modulation through beam steering tests under various input polarizations, achieving high optical efficiency and low polarization-dependent loss (PDL) of less than 0.6 dB. The proposed device, with its frame-at-a-time update and simplified waveplate fabrication process, offers significant advantages for commercial applications such as wavelength-selective switches, holographic displays, adaptive optics, and free-space optical communication systems.