Discovery of higher order reentrant modes by constructing a cylindrical symmetric ring and post cavity resonator

TL;DR

This paper reports the discovery and experimental verification of higher order reentrant modes in a cylindrical symmetric ring and post cavity, revealing modes with improved or reduced displacement sensitivity for precision measurements.

Contribution

It introduces the existence of higher order reentrant cavity modes in a novel ring and post structure, demonstrating modes with enhanced and reduced sensitivities compared to single post resonators.

Findings

Two re-entrant modes identified, one with higher sensitivity and one with lower sensitivity.

The more sensitive mode outperforms single post resonators by a factor of 1.5 to 2 below 100 μm gap.

Potential for use as a highly sensitive transducer in precision measurement applications.

Abstract

Analysis of the properties of resonant modes in a reentrant cavity structure comprising of a post and a ring was undertaken and verified experimentally. In particular we show the existence of higher order reentrant cavity modes in such a structure. Results show that the new cavity has two re-entrant modes, one which has a better displacement sensitivity than the single post resonator and the other with a reduced sensitivity. The more sensitive mode is better than the single post resonator by a factor of 2 to 1.5 when the gap spacing is below 100 $ \mu$m. This type of cavity has the potential to operate as a highly sensitive transducer for a variety of precision measurement applications, in particular applications which require coupling to more than one sensitive transducer mode.