Linear Dichroism Spectra of Doped Calcium Gallogermanate Crystals

Abstract

This paper presents the investigation of the linear dichroism (LD) (linear dichroism is difference between the principal extinction coefficients of crystals) in chromium and manganese doped Ca3Ga2Ge4O14 (CGG) crystals. It was known that calcium gallogermanate are very attractive materials due to their various optical properties [1–3]. These crystals have the space group P321 and the crystal structure consists of tetrahedron layers, perpendicular to the c-axis, between which there are layers formed by cations in distorted Thomson cubes [4]. In addition, these systems are uniaxial and optically positive (the refractive indices of extraordinary (ne) and ordinary (no) waves are related according to ne > no) and possess a significant optical birefringence (OB), LD and circular dichroism (CD) [4]. A complete study about CD phenomena in CGG crystals in the range of electronic transitions of structure defects was introduced in [5]. At the same time the CD and absorption spectra in the range 240–850 nm of the chromium doped CGG crystals were in detail investigated by authors [5, 6] on samples cut normally to optic axis, therefore the data about LD are unfortunately not present in these researches. As it was shown, serious experimental difficulties usually exist if one measures simultaneously different optical anisotropy parameters: optical activity (OA), LD, CD in optically birefringent crystals [7, 8]. High-accuracy polarimetric methods represent the most precise and convenient techniques for solving the mentioned crystal optical problems. The temperature dependence of LD and OB changes have been already simultaneously measured in