110 W high stability green laser using type II phase matching KTiOPO4 (KTP) crystal with boundary temperature control

We have developed a diode-pumped high power and high stability green laser. By controlling and stabilizing the boundary temperature of type II phase matching KTP crystal, 110 W high stability green laser output have been achieved. Temperature distribution inside the KTP crystal has been analyzed by solving the thermal conductivity equation. From the temperature distribution inside the KTP crystal, we have calculated the optimal phase matching angles and temperature bandwidth of the type II KTP crystal as a function of temperature. The second harmonic conversion efficiency as a function of temperature has also been calculated. In the experiment, the type II phase matched KTP crystal (optimum phase matching angles are Φ = 24.68°, Θ = 90° under the condition of phase matching temperature 353 K) was used in the intrcavity frequency-doubling resonator. An average output power of 110 W at 532 nm has been achieved with values of 11% and 2% for the optical-to-optical conversion efficiency and the instability, respectively. The optimal boundary temperature of the KTP crystal has been found to be 321.8 K. The experiment results are in good agreement with the theoretical calculation.