Photoelastic Properties of Trigonal Crystals

Abstract

All possible experimental geometries of the piezo-optic effect in crystals of trigonal symmetry are studied in detail through the interferometric technique, and the corresponding expressions for the calculation of piezo-optic coefficients (POCs) πim and some sums of πim based on experimental data obtained from the samples of direct and Х/45°-cuts are given. The reliability of the values of POCs is proven by the convergence of πim obtained from different experimental geometries as well as by the convergence of some sums of POCs. Because both the signs and the absolute values of POCs π14 and π41 are defined by the choice of the right crystal-physics coordinate system, we here use the system whereby the condition S14 > 0 is fulfilled (S14 is an elastic compliance coefficient). The absolute value and the sign of S14 are determined by piezo-optic interferometric method from two experimental geometries. The errors of POCs are calculated as mean square values of the errors of the half-wave stresses and the elastic term. All components of the matrix of elasto-optic coefficients pin are calculated based on POCs and elastic stiffness coefficients. The technique is tested on LiTaO3 crystal. The obtained results are compared with the corresponding data for trigonal LiNbO3 and Ca3TaGa3Si2O14 crystals.

Characterization of photoelastic materials by Mach–Zehnder interferometry: Application to trigonal calcium galogermanate (CGG) crystals

“…( 9), the values of the NHW-stress, σ o 24 and σ o 24 (Table II, rows 17 and 18), and the value of S 14 taken with different signs, i.e., (+) and (−), one get considerably different results for POC π 14 , likewise symmetry related POC π 24 (π 24 = −π 14 ), namely, 0.30 ± 0.15 Br and about seven times larger value, 2.07 ± 0.15 Br, respectively. Comparing these magnitudes with the π 14 -value determined in piezooptic geometry independent of the S 14 constant 21,27 (π 14 = 0.23 ± 0.13 Br, see Table II, row 19), one may conclude about a positive sign of the S 14 constant. A similar conclusion can be drawn considering the symmetry related POCs π 41 and π 42 (π 41 = −π 42 ) defined in two different piezooptic geometries (Table II, rows 14 and 22).…”

“…1(c)], appear to be more complicated. For example, POC π 44 is defined using the following relation: 21,27…”

“…9 (Table I) but is opposite in sign. One should be emphasized here that the sign of S 14 turns out to be crucial for a correct determination of π 24 and π 41 POCs since the S 14 constant directly enters into the expressions defining these POCs, 21,27…”

Stimulated Brillouin scattering by surface acoustic waves in lithium niobate waveguides

“…The photoelastic effect (also known as elastooptical effect) is represented by the photoelastic tensor p ijkl [26,47,48]…”

Анизотропия акустооптических свойств кристаллов PbМоО4

“…Согласно теории Поккельса, для нахождения направлений в кристалле, обеспечивающих максимальное значение эффективной фотоупругой постоянной требуется решение системы из 21 нелинейного уравнения 4-го, 3-го и 2-го порядков с тензорами высокого ранга [1,2]. В связи с этим обычно исследуются акустооптические свойства кристаллов для конкретных геометрий акустооптического взаимодействия и для определенных срезов кристалла [3][4][5].…”