Full-field mapping of the stress-induced birefringence using a polarized low coherence interference microscope

A polarization-sensitive optical coherence microscope (PS-OCM) has been developed to non-destructively measure birefringence distribution at the surface and internal interfaces of multi-layer structures. The PS-OCM can make two-dimensional en face measurement by exploiting the parallel sensing capability of the CCD sensors. PS-OCM utilizes the low coherence interference principle to enable the depth-resolved mapping of the birefringence distribution inside the materials. By simultaneous detection of interference fringes in two orthogonal polarization states allows determination of the Strokes parameters of light. Comparison of the Strokes parameters of the incident state to that reflected light from the sample can yield a depth-resolved map of optical properties such as birefringence and refractive index. Because many semiconductor and optic materials such as ceramic/wafer/polymer/glass are stress-induced birefringence materials, changes in birefringence distribution may, for instance, indicate changes in material uniformity and stress inside the materials. The PS-OCM has the capability to measure the spatial stress-field distribution of a material caused by the residual stress or applied load. Using the high numerical aperture of the objective lens and the broad bandwidth of the light source, the PS-OCM has the 1.5micrometer and 1.6 micrometer resolutions respectively in the lateral direction and longitudinal (or depth) direction.