Abstract
We demonstrate a new method for measuring the stimulated emission cross-section (σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>s</i></sub> ) of laser crystals for high-power solid-state lasers at working state using the relaxation oscillation frequency (ROF). The method is implemented by measuring the ROF of the laser together with making the relation curve between the ROF and σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>s</i></sub> of the laser. The stimulated emission cross-section of the laser crystal can be obtained when the ROF in the relation curve equals to that of the measured value. Employing the method, the actual σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>s</i></sub> of the Nd:YVO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> crystals with doping concentrations and pumping powers of 0.2 at.% and 51.5 W at 808 nm, 0.8 at.% and 80 W at 888 nm, and 0.8 at.% and 113 W at 888 nm are measured upon considering the influence of concentration quenching and energy transfer upconversion of the lasers. The measured results are 23.34 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-19</sup> , 23.77 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-19</sup> , and 23.42 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-19</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , respectively. The results are further compared and analysed with considering the temperature gradient of the laser crystals. It is found that the anomalous temperature gradient of the laser crystal at working state can induce an inhomogeneous gain spectral broadening, which can severely impact σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>s</i></sub> of the laser crystal.
Published Version
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