Proposal for a New Test of the Time Independence Of The Fine Structure Constant, alpha, Using Orthogonally Polarised Whispering Gallery Modes in a Single Sapphire Resonator

TL;DR

This paper proposes a novel experiment using orthogonally polarized whispering gallery modes in a sapphire resonator to test the potential variation of the fine structure constant, alpha, over time, with enhanced sensitivity at microwave frequencies.

Contribution

It introduces a new dual-mode sapphire resonator setup leveraging anisotropy and impurity effects to improve sensitivity in detecting changes in alpha.

Findings

Potential for high sensitivity measurement at infrared frequencies.

Electron Spin Resonance effects enable alpha variation detection at microwave frequencies.

The anisotropic sapphire resonator can serve as a precise test for alpha's time independence.

Abstract

A new experiment to test for the time independence of the fine structure constant, alpha, is proposed. The experiment utilizes orthogonally polarized Transverse Electric and Transverse Magnetic Whispering Gallery Modes in a single sapphire resonator tuned to similar frequencies. When configured as a dual mode sapphire clock, we show that the anisotropy of sapphire makes it is possible to undertake a sensitive measurement from the beat frequency between the two modes. At infrared frequencies this is possible due to the different effect of the lowest phonon frequency on the two orthogonally polarized modes. At microwave frequencies we show that the phonon effect is too small. We show that the Electron Spin Resonance of paramagnetic impurities (such as Cr3+) in the lattice effects only one polarization with an alpha^6 dependence. This enables an enhancement of the sensitivity to temporal changes in a at microwave frequencies.