Using crystalline materials to control the thermo-optic behavior of an optical path

Abstract

The thermo-optic behavior of an optical path over a range of temperatures ΔT is controlled by determining a figure-of-merit (FOM) for the optical path and including in the path a body of crystalline material that enables the conditions specified by the FOM to be satisfied. The crystalline material is highly transparent at a wavelength λ of radiation propagating in the path, and it has a coefficient of thermal expansion (CTE) and a refractive index n such that the CTE and dn/dT are mutually adapted to satisfy the FOM over the range ΔT. In one embodiment, the CTE and dn/dT of an etalon compensate one another so as to perform frequency discrimination that is essentially temperature insensitive over the range ΔT. In a preferred embodiment of the optical etalon the crystalline material comprises LiCaAlF6.

Dependencies are inferred from the claim text.