Laser-interferometric dilatometry from 100 K to 325 K

Abstract

To enable high precision optical measurements highly dimensionally stable materials are needed. Dimensional stability is an important material property describing the dependency of geometrical dimensions of an optical setup due to temperature fluctuations. Optical setups are often built with components made of glass-ceramics or composite materials which exhibit low coefficients of thermal expansion (CTE). These materials have to be characterized over the full operating temperature range to accurately predict the response of the optical system and the impact on its measurement performance. Our laser dilatometer setup is designed to characterize these low expansion materials in a temperature range from 100 K to 325 K, using a heterodyne laser interferometer to measure the dimensional changes of a sample due to well-controlled temperature variations. In this talk, we present the current status of our test facility, and recent improvements to decrease the uncertainty budget to levels of 10 ppb/K over the temperature range from 100 K to 325 K.