  Factors that contribute to the temperature dependence of a resonant frequency
in a low-expansion optical cavity are discussed, including deformation at the
cavity ends due to different coefficients of thermal expansion (CTE) of the
spacer, optically-contacted mirror substrate and coating. A model of the
temperature dependence is presented that incorporates finite-element-analysis
of the cavity ends. A measurement of frequency versus temperature of a cavity
mode is used along with the model to deduce a spacers CTE versus temperature
profile. The measured profile correlates very well with a separate experiment
utilizing a temporary surface-mounted Fabry-Perot cavity fabricated on the
outside of the spacer with hydroxy-catalysis bonding.

Optics