Elasto-optic properties and internal stress analysis for monoclinic and trigonal crystals

Abstract

We study the elasto-optic behaviour of monoclinic and trigonal crystals. The eigenvalues and eigenvectors of the dielectric impermeability tensor under stress are evaluated by the means of the approximated formulae obtained by Sirotin. The parameters which characterize Bertin's surfaces and fringe patterns in conoscopic observation are determined as functions of either residual or applied stress. Later, the photoelastic constants, and the rotation of the optic plane and optic axes bisector are estimated in order to allow for the evaluation of the residual or applied stress by conoscopic measurements. Finally, we obtain the dependence of the refraction indices on the stress. The knowledge of these crystal properties is mandatory for applications in high physics energy, security, geological prospection and in crystals for photonics and medical applications. The evaluated photoelastic constants allow the development of methodologies for an easy and fast quality control via stress distribution detections by means of conoscopic observation, even for strongly anisotropic crystals. As a case study we apply these results to the cases of monoclinic Lu 2(1−𝑥) Y 2𝑥 SiO 5 (LYSO) and trigonal LiNbO 3 (Lithium Niobate). K: Beam Optics; Detection of defects; Scintillators and scintillating fibres and light guides; Scintillators, scintillation and light emission processes (solid, gas and liquid scintillators) On leave at IMT, Lucca, Italy.

Photoelastic Properties of Trigonal Crystals

“…Comparison of these sums of POC with the analogous ones for principal coefficients π im determined on the direct cut sample makes it possible to confirm the reliability of the POC values as well as piezo-optical identity of the samples cut from the different parts of crystal boule or from different boules. It should be noted that the polarization-optical (see, e.g., [16][17][18][24][25][26][27]) and conoscopic [28][29][30][31][32][33] methods are sometimes used for investigations of crystal photoelasticity. However, in this paper, the photoelasticity of lithium tantalate is solely studied using the interferometric technique.…”

“…It should be noted that the polarization-optical (see, e.g., [16][17][18][24][25][26][27]) and conoscopic [28][29][30][31][32][33] methods are sometimes used for investigations of crystal photoelasticity. However, in this paper, the photoelasticity of lithium tantalate is solely studied using the interferometric technique.…”

Theoretical Basis for the Photoelastic Residual Stress Evaluation in Misaligned Cubic Crystals

“…In more recent times, the photoelastic studies of the anisotropic crystals evolved toward a deeper knowledge of the elasto-optic behavior, a circumstance that allowed for the design of new measurements devices (polariscopes) [20][21][22][23][24]. For instance, the study of the interference fringes in conoscopic observations (i.e., the Cassini-like curves, sections of the Bertin surfaces [25,26]), has improved the knowledge and measurement techniques on complex crystals with low symmetry [27][28][29][30][31][32].…”