Testing Lorentz Invariance by Comparing Light Propagation in Vacuum and Matter

TL;DR

This experiment tests the isotropy of light speed in vacuum and matter using a rotating optical resonator setup, setting new upper limits on anisotropy and aiming to improve sensitivity with cryogenic cooling.

Contribution

It introduces a Michelson-Morley type experiment comparing light speed in vacuum and matter with a rotating setup, providing new upper bounds on anisotropy.

Findings

Upper limit for anisotropy in sapphire: Δc/c < 4×10^(-15)

Experiment setup achieves rotation every 45 seconds

Work is ongoing to improve sensitivity with cryogenic cooling

Abstract

We present a Michelson-Morley type experiment for testing the isotropy of the speed of light in vacuum and matter. The experiment compares the resonance frequency of a monolithic optical sapphire resonator with the resonance frequency of an orthogonal evacuated optical cavity made of fused silica while the whole setup is rotated on an air bearing turntable once every 45 s. Preliminary results yield an upper limit for the anisotropy of the speed of light in matter (sapphire) of \Delta c/c < 4x10^(-15), limited by the frequency stability of the sapphire resonator operated at room temperature. Work to increase the measurement sensitivity by more than one order of magnitude by cooling down the sapphire resonator to liquid helium temperatures (LHe) is currently under way.