Experimental Characterization of Optically Tunable High-Temperature Superconducting Microwave Resonators and Delay Lines

This paper reports the design, fabrication, and measurements of optically tunable superconducting microwave resonators and delay lines. The devices are comprised of superconducting coplanar waveguide (CPW) transmission lines fabricated from a 100 nm-thick YBCO film, interrupted by 3- and 5-m YBCO meander structures of the same thickness on top of an LAO substrate. The CPW is tested at 77 K up to a frequency of 50 GHz, where it exhibits a transmission loss of about 0.12 dB/mm. The measurements are done in a cryogenic microwave probe station, where all the calibrations have been performed at 77 K. It has been observed that the resonance frequencies of the superconducting resonators can be changed by more than 2 GHz under the optical illumination at a wavelength of 1550 nm. The delay lines also exhibit a phase retardation of up to 90 at the same operating conditions.