Study On LD Pumped Self-Q-Switched Intracavity Frequency Doubling Laser

Diode pumped solid-state laser (DPSSL) is a kind of long-life, stable, compact, efficient all-solid laser. It has considerably replaced the other type of lasers. Diode pumped solid-state Q-switched laser is a good source of pulse laser with high peak power and high repetition rate.Pulses in the nanosecond and subnanosecond regimes with high power and high repetition rate have wide applications in lidar, ranging , remote sensing, microsurgery, micromachining, and so on. Laser-Diode (LD) pumped passive Q-switched laser can supply this kind of pulses and have the advantages of simplicity, compactness, high efficiency and low cost. Particularly, Cr4+-doped crystals as passive Q-switch (saturable absorber ) have got extensive attention, such as Cr4+:YAG,Cr4+:GSGG,Cr4+:Mg2SiO4 and Cr4+:YSO, which have the advantages of wild absorption band, good saturable absorption, long restored time, good photo-chemical stability, no fading, good thermal conductivity and high damage threshold. Among these, some Cr4+-doped crystals have the character of polarized absorb, and can obtain the linear polarized output pulse laser without any polarizer. It's a very good character for intracavity frequency doubling. Recently, Cr4+ and laser ion co-doped self-Q-switched crystals are very attractive.The behavior of self-Q-switched DPSSL has been investigated by numerical simulation according to the rate equations of solid-state lasers. Analytical formulas for the peak power, pulse energy, pulse width, energy extraction efficiency, repetition rate and average output power are derived. For the LD pumped self-Q-switched laser, the peak power, pulse energy, pulse width and energy extraction efficiency, which have been influenced by the loss in the cavity, cavity length and the threshold absorption coefficiency of the absorber, have been calculated. Then we know how to choose the parameters of the self-Q-switched laser for design.A diode pumped Cr4+,Nd3+:YAG crystal self-Q-switched laser is demonstrated with fiber coupled LD and the imaging system. The pulse laser with 1064 nm wavelength is obtained. The maximum average output power is 3.36 W, and the pulse duration is 65 ns, and the repetition rate is 87 kHz, the opto-optical efficiency is 15.3%, the slope efficiency is 23.8%. The single pulse energy is about 38.6 (J, and the peak power is 600 W.The intracavity frequency-doubled self-Q-switched laser is first demonstrated. When the KTP crystal is inserted into the cavity, the 532 nm green pulse laser is obtained. The maximum average output power is 1 W, and the pulse duration is 210 ns, and the repetition rate is 47 kHz, the opto-optical efficiency is 6%, the slope efficiency is 8.6%. The single pulse energy is about 21.3 (J, and the peak power is 100 W.