Application of V3+:YAG crystals for Q-switching and mode-locking of 1.3-μm diode-pumped neodymium lasers

High-power passive Q-switching and mode-locking operation regimes of diode end-pumped Nd:YAG, Nd:YVO 4 , and Nd:YAP active media, operating at a 1.34-μm wavelength are investigated with V 3 + :YAG crystal as the saturable absorber. The highest average power of 2.1 W results from a Nd:YVO 4 crystal placed in a 70-mm-long linear cavity. The corresponding pulse peak power and width are 0.1 kW and 133 ns, respectively. Employing a Nd:YAP crystal and 35-mm cavity length, the highest peak power of ∼2.8 kW results when the laser runs at a 6.5-kHz repetition rate for an average power of ∼0.4 W. A record of 79-μJ pulse energy results from a 64-mm-long resonator with Nd:YAG gain media, however, for a decreased average power of 0.24 W and pulses of 40-ns width. The mode-locking operation regime is investigated in a Z-type cavity. The best results, namely, ∼0.5 W average power with mode-locked envelope energy in excess of 30 μJ and mode-locked pulse energy of 0.7 μJ, are obtained from the Nd:YVO 4 media. Trains of 1-μs-wide pulses with improved stability result from a 1.5-m-long designed cavity with KTP crystal applied for passive negative feedback. A numerical modeling that takes into account the short recovery time of V 3 + :YAG saturable absorber (∼5 ns) and excited state absorption effect is used to analyze and obtain general rules for optimizing such lasers.