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Harmonic generation from YBCO microwave resonators

Durga P. Choudhury, John S. Derov, S. Sridhar

cond-mat.supr-conarXiv:cond-mat/9904080

Abstract

Measurement of harmonic power on a suspended stripline microwave resonator patterned out of thin film YBa2Cu3O7 (YBCO) has been carried out as a function of temperature and microwave power. The third harmonic power P3 shows a subtle nonlinear dependence on the fundamental power P1 on a log-log scale. Fit to a straight line yields slopes of P3 vs. P1 between 1.5 to 3, contrary to elementary calculations that predict a slope of exactly 3. It is shown that third harmonic power generated from higher order terms in the nonlinear impedance could account for the discrepancy quantitatively without resorting to any additional ad-hoc assumptions. Results of measurement of fifth harmonic power is presented as a confirmation. A small second harmonic power is also observed that does not show anomalous power dependence within the experimental accuracy.

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