Theoretical analysis of self-frequency doubling in a high-power longitudinally diode-pumped Nd:YCOB laser

We report a theoretical analysis of a laser-diode-pumped self-frequency-doubling (SFD) Nd:Ca4YO(BO3)(3) (Nd:YCOB) laser for high output power. A SFD model is presented by combining the laser rate equation and second-harmonic generation coupled-wave equations inside the same laser crystal. In this SFD model, the continuous wave end-pumped space-dependent Gaussian beam profile, variation of the pump beam waist, fundamental wave depletion, and thermally induced diffractive losses are taken into account. In order to investigate the dependence of SFD output power on the Nd3+ doping concentration, we implement the measurement of the absorption spectra for different Nd3+ doping Nd: YCOB samples. The comparison of plane wave approximation and the Gaussian beam model with and without thermally induced diffractive losses are presented. Then, we focus on the optimization of a high-power SFD Nd:YCOB laser, including the optimum pump beam waist, the optimum Nd3+ doping concentration, and the optimum Nd:YCOB crystal length. (C) 2016 Optical Society of America