Abstract
A miniature, high repetition rate, short pulse width acousto-optically Q-switched Nd:YVO4 laser in fundamental mode is presented. Miniature solid-state lasers have the characteristics of short cavity length and small mode area in the cross section, which, on the one hand, benefits high gain, high repetition rate and short pulse width, on the other hand, makes it difficult to achieve high mode-matching efficiency and causes higher order modes oscillation. The thermal lens in Nd:YVO4 is treated as thick lens under high pump intensity. The mode-matching efficiency is analyzed with the thermal lens being equivalent to a thin lens array. In high repetition rate Q-switching operation, 3.6 ns pulses at 500 kHz repetition rate with 20 mm cavity length and 4.1 kW peak power are achieved, without active control of pump beam quality. The laser beam quality factors were measured to be Mx2 = 2.03, My2 = 2.46. By improving the pump beam quality and utilizing the optimal pump beam waist radius and location, the mode-matching efficiency and laser beam quality are improved. 4.0 ns pulses at 500 kHz with 2.5 kW peak power are produced. The beam quality factors were measured to be Mx2 = 1.31, My2 = 1.43.