Features and Statistics of S-parameters in Nonlinear Wave Chaotic Systems*

The Random Coupling Model (RCM) has been shown to successfully predict the statistical properties of linear wave chaotic cavities in the highly over-moded regime. It is of interest to extend the RCM to strongly nonlinear systems. Besides the statistics of harmonics we recently studied, in this talk, we discuss measurements of the nonlinear S-parameters in two nonlinear systems. One system is a diode-loaded ¼-bowtie quasi-2D microwave cavity where the diodes act as point nonlinearities in a wave chaotic system. Another is a cut-circle quasi-2D microwave cavity which is made of Pb plated copper. In the superconducting state, the cavity is very nonlinear. By taking advantage of the high power (up to +35 dBm) vector network analyzer (VNA), we observe that the S-parameters are power dependent. Some features, such as time reversal symmetry breaking, hot spot statistics, nonlinear impedance etc. are observed in these nonlinear systems. The goal is to study how RCM needs to be modified to quantitatively explain these features.