Patent ID: 6452725
Filing Date: 2002-09-17
Classification: G02B

Abstract:
A thermally stable etalon filter, including:a pair of reflective surfaces disposed in parallel, spaced apart relationship; an optical medium disposed between said reflective surfaces to define a cavity, said optical medium having a net thermal expansion coefficient and a net thermal refractive index coefficient that are opposite in effect and offsetting, whereby the refractive effect of said etalon is unaffected by temperature variations; said optical medium including a pair of optically transmissive materials; one of said pair of materials having a coefficient of thermal expansion that is countervailing to the coefficient of thermal refractive index of the other of said pair of materials; the thickness of said pair of materials being selected to establish an optical path through said cavity that exhibits an optical path length that is essentially constant with changes in temperature in said pair of materials.