High-power near diffraction-limited 1 064-nm Nd:YAG rod laser and second harmonic generation by intracavity-frequency-doubling

Abstract

We present a near diffraction-limited 1 064-nm Nd:YAG rod laser with output power of 82.3 W (M 2 ≈1.38). The power fluctuation over two hours is better than ±1.1%. Pulsed 1 064-nm laser with an average power of 66.6 W and pulse width of 46 ns are achieved when the laser is Q-switched at a repetition rate of 10 kHz. The short pulse duration stems from the short cavity as well as the high-gain laser modules. Using intracavity-frequency-doubling, a 35.0-W near diffraction-limited 532-nm green laser (M 2 ≈1.32) is achieved with a pulse width of 43 ns.OCIS codes: 140.0140, 140.3580, 140.3410, 140.3515. doi: 10.3788/COL201210.071401. Due to their varied applications, high-power green lasers with side-pumped Nd:YAG rod lasers have developed rapidly in the last decade [1−9] . The output power of the green laser exceeds 400 W [7] . However, the reported green lasers [1−9] suffer from low beam quality (M 2 >10), because the side-pumped Nd:YAG rod is influenced by severe thermal effects, such as thermal lensing and thermal birefringence. Moreover, it is very difficult to achieve a good match between the TEM 00 mode and the pumping volume. Few studies have reported high-power green lasers with high beam quality and side-pumped Nd:YAG modules, which are usually obtained by extracavity-frequency-doubling with a complex end-pumped master-oscillator power amplifier (MOPA) system [10−12] or a complex injection seeded system [13] . However, Hirano et al. have reported an output power of 208-W TEM 00 1 064-nm laser with two specially designed side-pumped Nd:YAG modules [14] , which has the potential to obtain high-power high-beamquality second harmonic generation (SHG) with a compact intracavity-frequency-doubling system.In this letter, we report a high-power high-beamquality 1 064-nm Nd:YAG rod laser and SHG by intracavity-frequency-doubling. We used a short symmetrical cavity with two concave mirrors compensating for the thermal focal effect of the Nd:YAG rod. Compared with the complex end-pumped MOPA or injection seeded system, the symmetric cavity is compact and can easily achieve a hundred-watt level near the diffractionlimited laser beam. Moreover, in comparison with the conventional unstable resonators, the plane-parallel cavity has a wider thermal stability region according to the theoretical calculation with the standard ABCD ray propagation matrix. The configuration of the cavity is demonstrated to have a good scheme for high-power TEM 00 1 064-nm laser generation [14] . With two common side-pumped Nd:YAG rod modules in the short cavity, we achieved an 82.3 W near diffraction-limited continuous wave (CW) 1 064-nm laser (M 2 ≈1.38) with a good power stability of ±1.1% for over two hours. The output power and pulse duration with different Q-switched frequencies of 10, 15, and 20 kHz are also studied. A pulsed 1 064-nm laser beam with pulse width of 46 ns is achieved at a Q-switched frequency of 10 kHz and an average output power of 66.6 W. Finally, a 35.2-W pulsed green laser with a pulse width of 43 ns in a near di...