Patent ID: 6943889

Claim:
An interferometer comprising a beam splitter and combiner for splitting an input beam into two sub-beams and for combing two sub-beams into a single beam; a first arm having a length l 1 optically coupled to the beam splitter and combiner, said first arm defining a first path within a first material having a refractive index n 1 and a coefficient of expansion α 1 ; and, a second arm having a length l 2 optically coupled with the beam splitter and combiner, said second arm defining a second path within a second material having a refractive index n 2 and a coefficient of expansion α 2 wherein the lengths of the two arms are selected such that they satisfy the equation: l 1 ⁡ [ n 1 ⁢ α 1 + ⅆ n 1 ⅆ T ] - l 2 ⁡ [ n 2 ⁢ α 2 + ⅆ n 2 ⅆ T ] = 0.