Determination of the photoelastic coefficients in lithium heptagermanate crystals

Abstract

The photoelastic (piezo-optic) property of the ferroelectric crystals lithium heptagermanate Li₂Ge₇O₁₅ (LGO) were studied in para- and ferro-electric phases for different orientations. The value of stress optical coefficient C_ijk (in Brewsters) along a, b, c-axes were determined at RT (291 K) and 278 K and were compared with some other ferroelectric systems like Rochelle-salt (RS), potassium dihydrogen phosphate (KDP) and ammonium dihydrogen phosphate (ADP). Large photoelastic coefficients and other properties like good mechanical strength, or transition temperature close to RT and stability in ambient environment favour LGO as a potential candidate for photoelastic applications.

Key Words:

• Weak ferroelectric
• Li₂Ge₇O₁₅
• lithium hepta germanate
• photoelastic coefficients
• birefringence