Generation of 415 W of p-polarized output power in long pulse operation of Nd:YAG laser using z-fold resonator geometry

• A 415 W p-polarized long pulse Nd:YAG laser demonstrated with higher slope efficiency of 4.3%.
• Design of z-fold resonator has been presented for effective birefringence compensation.
• Optical scheme with concave mirrors, 90° quartz rotator, and a re-entrant feedback mirror has been used.
• This scheme has resulted in an enhancement of 80% of p-polarized power.
• Depolarization losses have also been reduced from 35% to ~1.8% after compensation.

We report on the generation of high average power linearly p-polarized beam in long pulse operation of dual rod Nd:YAG laser. A z-fold resonator configuration has been designed using simple optical scheme to provide effective birefringence compensation, compactness, and reduction of alignment criticality. Using this geometry, a maximum linearly p-polarized average output power of 415 W and a pulse energy of 150 J was achieved with a slope efficiency of 4.3%, which is on higher side for typical lamp pumped long pulse Nd:YAG lasers. For effective birefringence compensation, an intra-cavity concave mirror based imaging system, a 90° quartz rotator, and a re-entrant feedback mirror has been used. This scheme resulted in an enhancement of p-polarized output power of more than 80% as compared to the p-polarized output power without birefringence compensation. Depolarization loss in the resonator has also been reduced significantly from a value of 35% to a value of ~1.8% after birefringence compensation.