Resonance widths in open microwave cavities studied by harmonic inversion

TL;DR

This paper uses harmonic inversion to measure resonance widths in open microwave cavities, successfully resolving overlapping resonances and confirming predictions from random matrix theory with experimental data.

Contribution

It introduces the application of harmonic inversion to resolve broad resonances in microwave cavities, extending the measurable regime beyond previous limitations.

Findings

Resonances were successfully extracted even when line widths exceeded mean level spacing by a factor of 10.

Experimental distributions of line widths matched random matrix theory predictions.

The method enables analysis of complex resonance spectra in open systems.

Abstract

From the measurement of a reflection spectrum of an open microwave cavity the poles of the scattering matrix in the complex plane have been determined. The resonances have been extracted by means of the harmonic inversion method. By this it became possible to resolve the resonances in a regime where the line widths exceed the mean level spacing up to a factor of 10, a value inaccessible in experiments up to now. The obtained experimental distributions of line widths were found to be in perfect agreement with predictions from random matrix theory when wall absorption and fluctuations caused by couplings to additional channels are considered.