Multilayer optical interferometer based on programmable tilted liquid crystal gratings on glass substrates

This study presents a tunable optical system based on liquid crystal gratings, specifically designed for operation in the infrared (IR) spectrum. The system features a compact design, occupying only a few square millimeters, and adopts a multilayer architecture with gratings positioned between two stacked BK7 glass substrates. An externally applied voltage activates a secondary optical pathway, configured as a Mach-Zehnder interferometer (MZI), by directing light through the upper glass layer into two optical channels on the system’s surface. The light is subsequently coupled back into the internal waveguide through the top glass layer before reaching the system’s output. Finite-difference time-domain (FDTD) simulations confirm the successful optical coupling of an incoming out-of-plane light beam into the MZI’s bottom arm, facilitated by the liquid crystal tilted grating structure. These results lay the groundwork for the development of a versatile, compact, and programmable Mach-Zehnder interferometer, offering strong potential for applications in optical communication systems and optical biosensing.