Ultrahigh optical Q factors of crystalline resonators in the linear regime

Abstract

Experimental demonstration of record optical quality factor of $(6.3\ifmmode\pm\else\textpm\fi{}0.8)\ifmmode\times\else\texttimes\fi{}{10}^{10}$ corresponding to cavity ring-down time of $\ensuremath{\tau}\ensuremath{\simeq}36\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{s}$ is made possible by avoiding nonlinear effects in a crystalline whispering gallery mode resonator. We discuss various loss mechanisms in $\mathrm{Ca}{\mathrm{F}}_{2}$ cavities and ways of achieving higher quality factors. Possible applications in quantum optics and photonics are discussed.