Thermo-optic characterization of Yb:CaGdAlO4 laser crystal

Abstract

Principal thermo-optic coefficients (TOCs), dno/dT and dne/dT, are measured for Yb:CaGdAlO4 crystal, for the first time, to our knowledge. At the wavelength of ~1 μm, they equal –7.6 and –8.6 (Ч10-6 K-1), accordingly. Thermal coefficients of the optical path (TCOP) are determined for this crystal for the principal crystal cuts (a-cut and c-cut) and light polarizations (π or σ). Thermo-optic dispersion formulas are evaluated for both TOC and TCOP coefficients. Optical power of thermal lens is measured for diode-pumped a-cut Yb:CaGdAlO4; it is also calculated on the basis of measured material parameters. Thermal conductivity of CaGdAlO4 crystal is measured versus Yb concentration. The results indicate that a-cut Yb:CaGdAlO4 can provide really "athermal" behavior.