Drive laser system for a photocathode at IHEP

The Energy Recovery Linac (ERL) can produce continuous electron bunches with low emittance at high average current. The photocathode electron gun needs high repetition rate, high average power drive laser system. Adopting advanced fiber laser technologies, especially using Yb-doped photonic crystal fiber in the laser system, a high repetition frequency, high average power laser system was set up. By using chirped pulse amplification (CPA) and optimizing the design, a 100 MHz oscillator and a 1.3 GHz oscillator were integrated into one laser system. The structure of the whole laser system can be simplified and easy to operate. The second harmonic generation (SHG) efficiencies of the laser system at two different repetition rates have already reached 50% and 30%, respectively. In addition, more than 5 W green light has been achieved, which meets the needs of test platform of photocathode at IHEP. (authors)