A G-Band Reconfigurable Waveguide-Based Bandstop Filter Enabled by High-Performance Optically Controlled RF Switches

We report the design, simulation, and analysis of a G-band (140-220 GHz) reconfigurable bandstop filter (BSF) using the waveguide-based configuration. The reconfigurability is enabled by novel optically controlled RF switches with superior performance in the millimeter-to-terahertz (mmW-THz) region. For a prototype demonstration, multiple such switches are integrated into three pairs of split-ring resonators coupled to a microstrip transmission line for operation. By turning on/off these switches using a 100 W/cm
²
light from fiber-coupled 550 nm LEDs, the center frequency of the bandstop filter can be reconfigured to 148 GHz, 182 GHz or 212 GHz as expected. For all three states, a center frequency suppression of larger than 15 dB, and an average 3 dB fractional bandwidth of 17.14 % have been achieved. The optically controlled reconfigurable waveguide filter reported here is of unique and high performance, demonstrating the approach for developing tunable/reconfigurable THz circuits using the optically controlled RF switches is promising and transformative for applications in advanced THz sensing, imaging, and adaptive communications.