Fabry-Pérot resonator for high-field multi-frequency ESR at millimetre and submillimetre wavelengths

Abstract

The design and performance of a Fabry-Pérot (FP) resonator for high-field multi-frequency electron spin resonance (ESR) at microwave frequencies from 110 GHz to 330 GHz and corresponding Zeeman fields between 3.9 T and 12 T (at g = 2) is described. The tunable semiconfocal FP arrangement includes an inductive copper mesh that can be mechanically adjusted to obtain best performance in the entire temperature range from room temperature to 4 K. Sensitivity improvements (as compared to transmission mode experiments without a resonator) of about two orders of magnitude are obtained at 330 GHz. The potential of the configuration for investigating spin systems of low concentration with millimetre and submillimetre ESR is demonstrated on three examples.