All-optically Controlled Microwave Analog Phase Shifter with Insertion Losses Balancing

An all-optically driven microwave phase shifter is designed and experimentally demonstrated for 1-10 GHz. The proposed optical addressing is realised in nematic liquid crystals (NLC) mixed with novel mesogenic azobenzene (azo) dyes, allowing a dielectric constant variation from a surface anchoring nematic state to a photo-induced isotropic state when exposed to a laser beam with a wavelength of 465 nm. The phase shifter device is implemented in a compact meandered inverted microstrip with impedance matched by a novel light-intensity-dependent method for insertion loss balancing between tuning states. Prototyped by photolithography, the device is assembled with an azo NLC mixture of GT3-24002 and CPND-7 (10wt%). Measurements report a continuously tunable differential phase shift of 0-184 degrees at 10 GHz with a maximum insertion loss of -3.53 dB and negligible insertion loss variations (up to 9%) between phase-shifting states, which eliminates complex phase-biasing networks and amplitude-compensating circuits for the standalone high-resolution phased array beamforming application with reduced distortions.