Dispersion and anisotropy of thermo-optical properties of Alexandrite laser crystal

Abstract

Dispersion and anisotropy of thermal coefficients of the optical path (TCOP) and thermo-optic coefficients (TOCs) of Alexandrite laser crystal (Cr3+:BeAl2O4) are studied for the three principal light polarizations, E || a, E || b and E || c. Thermo-optic dispersion formulas are presented for the spectral range of 0.4-1.1 µm. All TOCs are positive and show a notable polarization-anisotropy, dna/dT = 5.9, dnb/dT = 6.9 and dnc/dT = 15.2 × 10−6 K−1 at 0.75 µm. Thermal lensing was characterized in a continuous-wave Alexandrite laser pumped at 0.532 µm and operating at 0.7509 µm (for E || b). The measured thermal lens was weak, positive and slightly astigmatic. The sensitivity factors of the thermal lens were found to be Mx = 1.74 and My = 2.38 [m−1/W].