A high power laser system at 540Â nm with beam coupling by second harmonic generation

We present a novel coupling scheme of two independent amplified beam lines in a Nd:YAP based master oscillator power amplifier (MOPA) system. Second harmonic generation (SHG) with type II phase matching offers the possibility of coupling two perpendicularly polarized beams, which are delivered from a MOPA system with two parallel amplifier chains. To preserve the excellent oscillator beam quality after amplification, the amplifiers are driven in double pass and optical fibres as phase conjugate mirrors (PCM) are used after the first pass. With this method, a single beam with an average power of 124 W is generated in the green spectral range. The laser system operates at an average repetition rate of 2.8 kHz and delivers pulses with a width of 160 ns.