Optically Controlled Millimeter-wave Switch with Stepped-Impedance Lines

A photoconductive grounded coplanar waveguide (GCPW) millimetre-wave switch controlled by a single infrared light-emitting diode is presented. By converting a straight GCPW transmission line into an alternating stepped-impedance line structure, the proposed device shows an on-state insertion loss of <2.9 dB and an off-state isolation of more than 15 dB over a wide-frequency range of 12–30 GHz, with a particularly good radio-frequency performance in the K-band (18–27 GHz). The required optical power and electrical power of the switch are only 199 and 364 mW, respectively. This device also demonstrates an absorptive characteristic with a low reflection coefficient of <−13.5 dB within this frequency range for both the on and off states. In addition, by employing through-holes for illumination of a silicon superstrate, the proposed device can be fabricated with rapid and low-cost laser etching and can be easily integrated with other microwave and millimetre-wave circuits.