Sensitive measurement of stress birefringence of fused silica substrates with cavity ring-down technique.

A polarized cavity ring-down technique was employed to precisely measure the residual stress birefringence of fused silica substrates with greatly enhanced measurement sensitivity. Intracavity birefringence resulted in beating of two orthogonally resonant modes in a Fabry-Perot cavity. The beating frequency of the ring-down decay was directly related to phase retardation induced by stress birefringence of optical components inside the cavity. For fused silica substrates, measurement reproducibilities of phase retardation of 2.38×10-6 rad and of optical path difference of 2.4×10-4 nm were experimentally achieved. In addition, spatially resolved mapping of stress birefringence of a fused silica substrate was obtained, which was in good agreement with that measured with a commercial stress birefringence measurement instrument. The experimental results demonstrated that cavity ring-down is a sensitive technique for stress birefringence measurements of optical components.