Design and Development of Intracavity Optical Parametric Oscillator-based Eye Safe Laser Operating at 20 Hz without Forced Air Cooling

摘要

In this paper we report the design and development of an electro-optically Q-switched diode pumped Nd:YAG laser with intracavity optical parametric oscillator, generating ～ 5 ns laser pulses of ～8 mJ energy at eye safe wavelength of 1534 nm. A Z-shaped laser resonator has been designed with porro prism end reflector in Q-switch arm containing RTP Q-Switch and a suitably oriented waveplate. The gain arm consists of a O3 × 72 mm Nd: YAG laser rod, pumped from one side by 3 × 5 bar laser diode array stack emitting total optical peak power of 740 W at 804 nm at 38 ℃. Thermoelectric coolers (TECs) have been employed to maintain the optimum temperature of laser diode arrays and the combined heat load from the pump chamber and TECs is distributed over the system base plate with embedded heat pipes. Such cooling mechanism has eliminated the requirement of fins and fans in the laser system. Eye safe radiation is out-coupled through intra cavity KTA OPO (5 × 5 × 20 mm~3) placed in the gain arm. Laser was operated at 20 Hz for several duty cycles of 10 min on and 10 min off and output energy remained stable within ±0.5 mJ without any forced air/liquid cooling.