Microwave Quenching in DC-Biased Coplanar Waveguide Based on $\text{YBa}_{2}\text{Cu}_{3}\text{O}_{7-\delta}$ Thin Film

In this paper, we report on the results of features in the discovered effect of a strong change in the microwave losses (quenching) in HTS-based coplanar waveguide (CPW) at certain values of the input power $P_{\mathrm{in}}$ and direct current (dc) $I_{\mathrm{dc}}$ . Two waveguides were studied: CPW-150 and CPW-75, fabricated of epitaxial 150- and 75-nm YBCO films. The insertion loss of CPW $IL = 10\ \text{lg}\ (P_{\mathrm{out}} / P_{\mathrm{in}})$ was measured versus both the operating temperature and the bias dc current $I_{\mathrm{dc}}$ when a fixed level of the input X-band pulsed MW signal $P_{\mathrm{in}}$ was applied. Here $P_{\mathrm{out}}$ is the power measured at the CPW output. A pulse duration $\tau_{i}$ was 5 $\mu\text{s}$ with pulse repetition period $T = 40\ \mu\text{s}$ . Experiments showed a noticeable difference in specific values of $I^\ast = I_{\mathrm{dc}}$ corresponding to the $P_{\mathrm{in}}$ -dependent quenching phenomenon in CPW-150 and CPW-75. With a weak input signal, the difference in behavior of CPWs is anticipated, i.e., quenching occurs at a lower current for thinner film. For $P_{\mathrm{in}} > 1$ W the situation is opposite, i.e., quenching for CPW-150 takes place at a lower $I^\ast$ . This is explained by stronger microwave heating of CPW-150.