Western Illinois University, Physics, Macomb, IL 61455
Conoscopic interference patterns are produced by an optically anisotropic crystal placed between crossed linear polarizer and analyzer and illuminated by a convergent light. The conoscopic interferometric technique is important in studying the optical properties of birefringent materials. For example, the conoscopic interference patterns have been used to identify minerals and to study biological tissues. They are also used to accurately measure the orientation, the refractive indices, the thickness, and the electro-optic effect in crystals. Conoscopic interference patterns are composed by two families of fringes, namely, the isogyre and the isochromatic fringes. The isogyres occur when the two allowed vibration directions of the light in the crystal are close to the transmission axes of the polarizer and the analyzer, so that there is little or no light transmitted through the system. The isochromatic fringes occur when the optical path length difference between the two eigenwaves equals an integer or integer plus half number of wavelengths, so that constructive interference occurs. In this talk, we will present our research on how to calculate the isogyre and the isochromatic fringes of conoscopic interference patterns in a biaxial crystal. These calculated interference patterns are experimentally confirmed by observing the various interference images in a lithium niobate electro-optic crystal under different external electric fields.
[Abstract (DOCX)]