Conoscopic figure: a complex consequence of a not so simple phenomenon

Abstract

Observation of conoscopic figures through a special microscope is widely used as an experimental method for determination of optical properties of anisotropic materials. The conoscopic figure appears when a divergent light passes through an anisotropic material sandwiched between crossed polarizers. The complex pattern of bright and dark areas appears due to different polarization states of light. The pattern gives information about optical axes and birefringence of the material and allows for deduction of microscopic structures at the origin of such properties. Due to the complexity of the figure, the method is often used following recipes. This contribution presents a series of experiments that provide students with experiences needed for construction and comprehension of optical phenomena that contribute to the complexity of the conoscopic figure.

The Poincaré-sphere approach to polarization: Formalism and new labs with Poincaré beams

“…[19][20][21] These patterns are widely used in geology for the optical characterization of minerals, 22 but they can easily be reproduced with cellophane, 23 plastics 24 and overhead transparencies. [25][26][27] Along the same lines, liquid crystals also provide a setting for understanding polarization and birefringence. [28][29][30] In this article we propose an experiment that focuses exclusively on the light: the generation and diagnosis of optical beams that have a state of polarization that varies from point to point in the transverse plane of the beam.…”

Propagation of polarised mechanical waves in an anisotropic medium

“…Inside an anisotropic material, a wave propagates as two waves with different phase velocities and mutually perpendicular polarizations. The two polarization directions we call vibration directions, in accordance with [2]. Therefore, the phase difference between the two waves changes with depth, so the polarization state of the actual (superposed) wave also changes with depth.…”