Birefringence, isotropic points, and optical filters based on CuGaxAl1-xSe(S)2 crystals

Alisa Masnic,Veaceslav Ursaki

doi:10.53081/mjps.2021.20-2.04

Abstract

A brief review on birefringence and optical filters based on CuGaxAl1-xS2 and CuGaxAl1-xSe2 crystals is given in this paper. Two types of isotropic points are analyzed; one of them refers to a case when the wavelength at which the ordinary and extraordinary refractive indices are equal is situated near the absorption edge, while in the second case the isotropic wavelength is in the region of crystal transparency. It is shown that both of them can be used for the development of band-pass and band-reject filters. The possibility of adjusting the spectral position of an isotropic point by changing the chemical composition of a solid solution is illustrated, and the applicability of CuGaxAl1-xS2 and CuGaxAl1-xSe2 for adjusting the isotropic point to most of Ar+, Kr+, He–Ne, and He–Cd gas lasers lines, as well as to semiconductor lasers, is revealed

Highlights

AIBIIICVI2 compounds are considered as an extension of AIIBVI materials with a zincblende structure from the point of view of their crystalline structure, they being an alternating packing of two zincblende cells with AI and BIII cations instead of AII cations
The results of this study have shown that analyzing the interference bands in the transmission or reflectance spectra measured in the polarizer–crystal–analyzer configuration is a more sensitive and efficient method for the determination of birefringence in crystals and for the determination of isotropic wavelengths than the measurement of interference separately in E||c and E c polarizations
Two types of isotropic points are inherent in CuGaxAl1 xS2 and CuGaxAl1 xSe2 crystals according to their spectral position

Summary

Introduction

AIBIIICVI2 compounds are considered as an extension of AIIBVI materials with a zincblende structure from the point of view of their crystalline structure, they being an alternating packing of two zincblende cells with AI and BIII cations instead of AII cations. The existence of accidental isotropic points, at which the ordinary (no) and extraordinary (ne) refractive indices have equal values, is a necessary condition for anisotropic crystals to be suitable for fabrication of band-reject or band-pass optical filters. Band-reject optical filters are fairly useful for applications in Raman spectroscopy, because they allow measuring Raman scattering at frequencies extremely close to the excitation laser line. Band-reject filters based on uniaxial optically active AgGaSe2 crystals were proposed for Raman spectroscopy with AlGaAs semiconductor lasers [7–10]. Birefringence and existence of isotropic wavelengths in CuGaxAl1-xS2 and CuGaxAl1-xSe2 crystals are explored for the purpose of developing optical filters

Sample Preparation and Experimental Details

Conclusions