SENSITIVE AND SELECTIVE POLARIMETER FOR APPLICATION IN CRYSTAL OPTICS

A polarimeter was constructed that modulates the polarization state of a light wave at the frequencies nu-1 and nu-2. Depending on the property searched for, the frequencies of recorded intensity signals can be selected between nu-1, nu-2, 2-nu-1, 2-nu-2, nu-1 +/- nu-22 and 2(nu-1 +/- nu-2). Optical transfer functions are calculated by use of Jones matrices and experiments are simulated by numerical methods in order to analyze complex problems in polarization optics including propagation of error parameters. Measuring the azimuth and the ellipticity of a light wave with a dynamical analyzer the polarimeter serves for determining the linear and circular anisotropy of a crystal. A sensitivity of 2 x 10(-7) radians is demonstrated. Application of the polarimeter is illustrated by measuring the gyration coefficient g11 of alpha quartz in two different ways. Furthermore, the polarimeter can be used for the measurement of linear and nonlinear electro-optical and piezo-optical effects between 20 and 800 K by subjecting the sample to periodical electric fields and uniaxial mechanical stresses. As an example for this kind of application a new crystal optical effect is investigated. It describes the birefringence originating from the coupling of an electric field and a uniaxial stress.