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 ( × 10−6 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.
Highlights
Thermal lensing is one of the most important limitations for power scaling capabilities of diode-pumped solid-state lasers
In bulk configuration this time, it was recently demonstrated that Yb:CALGO can provide unique stabilization of laser mode at high pump powers [15], the effect that cannot be completely understood on the basis of reported properties up to now
The method for determination of thermo-optic coefficients, dn/dT or TOCs, is based on the measurement of deflection of a probe beam passed through the studied sample with a linear thermal gradient, see Fig. 1(a)
Summary
Thermal lensing is one of the most important limitations for power scaling capabilities of diode-pumped solid-state lasers. Detailed information about properties of thermal lens, as well as material parameters useful for their calculation, is crucial for laser design. In bulk configuration this time, it was recently demonstrated that Yb:CALGO can provide unique stabilization of laser mode at high pump powers [15], the effect that cannot be completely understood on the basis of reported properties up to now. This special behavior of Yb:CALGO clearly motivates a better and more accurate understanding of the thermal properties of this atypical crystal
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