SBIR-STTR Award

This proposal describes the extension of digital spectrometry to the measurement of the anisotropic permittivities of piezoelectric materials. We show that fresnel's equations for anisotropic media, as is the case with isotropic media, also simplify for an incident angle of 45 deg. In digital spectrometry for isotropic media the sample is fixed and the polarization state of the incident beam is rotated from a horizontal to a vertical position. This action leads to a unique equation for the refractive index. Unfortunately, while this can be done for anisotropic media the result is a pair of nonlinear equations which are not readily solved. However, we have discovered that if the optical beam is fixed and the sample "flipped" through 90 deg, then a pair of uncoupled equations for the anisotropic permittivities can be obtained. The experimental configuration is then developed and described in this proposal to measure these permittivities.

This proposal describes a phase ii dod sbir program to continue and expand a novel technique for measuring the refractive indices of uniaxial (piezoelectric) crystals. During phase i we developed and improved this method which we call dual-beam digital refractometry. By following a dual-beam configuration we show that it is possible to overcome 1) the optical source fluctuations, 2) the detector sensitivity over a spectral range and 3) obtain the theoretical limit of accuracy. The proposed experimental configuration in phase ii contains no moving parts. A mathematical analysis of digital refractometry is made along with an analysis of the experimental configuration.