GaAs on quartz coplanar waveguide phase shifter

摘要

An optically controlled Schottky-contacted coplanar waveguide (CPW) phase shifter on a thin epitaxial GaAs film bonded to a quartz substrate has been fabricated using the epitaxial lift-off (ELO) technique. This allows the original semi-insulating GaAs substrate to be replaced by an optically transparent, low-dielectric-constant quartz substrate. A significant reduction in insertion loss and increase in phase shift was observed after lift-off. The ELO device allows the use of backside illumination for optical control, avoiding any metal shadowing effects, thus producing higher sensitivity to the optical signal. From 5 to 40 GHz, the ELO device gave an insertion loss of approximately -0.1 dB per degree of phase shift. At a backside illumination intensity of 0.65 mW/cm/sup 2/, a 1-cm-long device produced over 350 degrees of phase shift at 30 GHz.