Microwave Quenching in DC-biased Coplanar Waveguide Based on $YBa_2Cu_3O_{7-\delta}$ Thin Film

TL;DR

This study investigates microwave loss quenching in YBCO-based coplanar waveguides under DC bias, revealing how film thickness and input power influence the quenching behavior and associated heating effects.

Contribution

It provides new insights into the power and current-dependent microwave quenching phenomena in HTS coplanar waveguides with different film thicknesses.

Findings

Quenching occurs at lower current for thinner films at low input power.

At higher input power (>1W), thicker films quench at lower current due to heating.

Different behaviors are observed depending on input power and film thickness.

Abstract

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 $P_{in}$ and direct current (DC) $I_{dc}$. Two waveguides were studied: CPW-150 and CPW-75, fabricated of epitaxial 150 nm and 75 nm YBCO films. The insertion loss of CPW, $IL = 10 lg (P_{out} / P_{in})$, was measured versus both the operating temperature and the bias DC current $I_{dc}$ when a fixed level of the input X-band pulsed MW signal $P_{in}$ was applied. Here $P_{out}$ is the power measured at the CPW output. A pulse duration ${\tau}_i$ was 5 ${\mu}s$ with pulse repetition period T = 40 ${\mu}s$. Experiments showed a noticeable difference in specific values of $I^*= I_{dc}$ corresponding to the $P_{in}$ 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 $P_{in}>1W$ the situation is opposite, i.e., quenching for CPW-150 takes place at a lower $I^*$. This is explained by stronger microwave heating of CPW-150.