We show that temperature compensation based on differential thermal expansion between sapphire and fused silica can be used to create a Fabry–Perot cavity with an exceptionally low coefficient of thermal expansion at low temperatures. We describe the design of such a cavity that utilizes shaped fused silica mirrors and a sapphire spacer. The geometry of the fused silica mirror was designed using a finite element model to have a small platform, giving a frequency temperature turning point of 16.6 K. The measured turning point was 16.2 K and the curvature was 6 × 10−10 K−2, both of which were consistent with the model.
© 1997 Optical Society of America
Eng K. Wong, Mark Notcutt, Colin T. Taylor, Anthony G. Mann, and David G. Blair, "Temperature-compensated cryogenic Fabry-Perot cavity," Appl. Opt. 36, 8563-8566 (1997)