GHz-rate optical phase shift in light-matter interaction-engineered, silicon-ferroelectric nematic liquid crystals

Abstract

Organic electro-optic materials have demonstrated promising performance in developing electro-optic phase shifters. Their integration with other silicon photonic processes, nanofabrication complexities, and durability remains to be developed. While the required poling step in electro-optic polymers limits their potential and large-scale utilization, devices made of paraelectric nematic liquid crystals suffer from slow bandwidth. In ferroelectric nematic liquid crystals, we report an additional GHz-fast phase shift that ultimately allows for significant second-order nonlinear optical coefficients related to the Pockels effect. It avoids poling issues and can pave the way for hybrid silicon-organic systems with CMOS foundry compatibility. We report DC and AC modulation efficiencies of ≈ 0.25 V ⋅ mm (from liquid crystal orientation) and ≈ 25.7 V ⋅ mm (from the Pockels effect), respectively, an on-chip insertion loss of ≈ 2.6 dB, and an electro-optic bandwidth of f−6dB>4.18 GHz, employing improved light-matter interaction in a waveguide architecture that calls for only one lithography step.