Thermal-noise-limited optical cavity

Abstract

A pair of optical cavities are designed and set up so as to be insensitive to both temperature fluctuations and mechanical vibrations. With the influence of these perturbations removed, a fundamental limit to the frequency stability of the optical cavity is revealed. The stability of a laser locked to the cavity reaches a floor $<2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ for averaging times in the range $0.5\ensuremath{-}100$ s. This limit is attributed to Brownian motion of the mirror substrates and coatings.