Interferometric measurement of induced birefringence in polycrystalline ZnSe.
The aim of this research project was to assemble an apparatus capable of measuring field-induced birefringence in polycrystalline ZnSe. A Michelson interferometric apparatus was assembled, and care was taken to actively stabilize the interferometer against the effects of environmental noise by using electronic feedback techniques. This greatly enhanced the sensitivity of the interferometric measurements. In addition, the applied electric field was modulated, allowing sophisticated phase-sensitive detection techniques to be used to extract the induced birefringences. Once assembled, the interferometer was tested using electric-field induced birefringence in a perspex sample, since there is Kerr-effect data in the literature against which to compare our measured quadratic electro-optic coefficients. The interferometer was then used to measure the quadratic electrooptic coefficients of polycrystalline ZnSe, these being, to the best of our knowledge, the first such measurements for this species. The theory of electro-optic and photoelastic phenomena is comprehensively reviewed. This has permitted a critical discussion of the measured Kerr coefficients obtained in this project. It is demonstrated how quadratic electro-optic coefficients measured using the traditional technique of static polarimetry might include contributions arising from the linear electro-optic effect, these data being rendered suspect. In addition, suggestions are made as regards to the future possibilities for extending the apparatus to allow for direct measurement of stress-induced birefringences.