Abstract

We have studied the amplification characteristics of a cryogenically cooled ${\mathrm{Yb}}^{3+}\text{:}\mathrm{YAG}$ total-reflection active-mirror (TRAM) ceramic laser including wavefront distortion, birefringence loss, small signal gain (SSG), and temperature rise for developing high-performance master oscillator power amplifier (MOPA) systems. A 0.6 mm thick ${\mathrm{Yb}}^{3+}\text{:}\mathrm{YAG}$ ceramic sample was used, and maximum pump intensity $\sim 10\mathrm{kW}/{\mathrm{cm}}^2$ was reached. The transmitted wavefront was measured by using a Shack–Hartmann wavefront sensor, and we evaluated the thermal lens focal length and Strehl ratio for different pump conditions. We have also observed a butterfly-like leakage profile of thermally induced birefringence loss at the maximum pump intensity. From SSG measurements, we obtained moderate laser gain of $G=3$ for one bounce with a near aberration-free wavefront. Gain calculations, which included also temperature dependence of the emission cross section and reabsorption of ${\mathrm{Yb}}^{3+}\text{:}\mathrm{YAG}$, were in good agreement with the experiments. These experimental results will be useful as benchmark data for numerical simulations of temperature distribution in TRAM and for designing multikilowatt-class high-performance MOPA systems.

© 2014 Optical Society of America

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