New Yb-doped crystal Yb3+∶Lu2SiO5 (Yb∶LSO) lasers pumped by diode-laser at 976 nm with passively Q-switched and multi-wavelength continuous-wave (CW) output were demonstrated. The maximum CW output power was 490 mW with the absorbed pump power of 2.57 W. The slope efficiency and optical-optical conversion efficiency were 22.2% and 14.2% respectively. The threshold was 299 mW, and the laser wavelength was 1084 nm. The wavelength could be tunable from 1034 to1085 nm with a prism. For the Q-switched output, the laser operated at 1058 nm with an InGaAs semiconductor saturable absorber mirror (SESAM). The Q-switched output slope efficiency of 3.0% with the maximum absorbed pump power of 1.73 W was also obtained. The pulse repetition rate was 25～39 kHz and was increased with the pump power increased.

A single resonant intracavity KTP optical parametric oscillator (OPO) is constituted by placing a non-critical phase-matched KTP crystal in a flashlamp pumped and passive Q-switched Nd∶YAG laser with an unstable resonator. The wavelength tuning property of output signal laser is studied and the tunable laser pulses of 1.57～1.60 μm are obtained. The experimental results show that the output energy of signal laser at 1.57 μm decreases, and the pulse duration changes to some extent, with the increase of the cavity length of the optical parametric oscillator. When the pump energy is larger, the energy conversion efficiency goes to saturation with the increasing of pump energy, and then drops gradually. And a reasonable interpretation is given theoretically. When the cavity length is 5 cm and the pulse duration of pump laser at 1.06 μm is 30 ns, the pulse duration and output energy of signal laser at 1.57 μm are 2.5 ns and 21.3 mJ respectively. The pulse duration of signal laser at 1.57 μm is only 1/12 of that of the pump laser at 1.06 μm, and the electro-optical energy conversion efficiency is 0.128%.

An intracavity KTiOAsO4 (KTA) optical parametric oscillator (OPO) pumped by a laser diode array side-pumped, acousto-optically (AO) Q-switched Nd∶YAG laser is investigated. The output performance of KTA-OPO is tested at different repetition rates and transmissions of the output mirror. Through discussion of the threshold formula of the singly resonant OPO, a plane-concave cavity and a short OPO cavity length are employed to decrease the OPO′s pumping threshold. The parameters of output laser have been measured at different repetition rates and transmissions of the output mirror. When the repetition rates of acousto-optic Q-switch and transmission of output mirror are 4 kHz and 30% respectively, the output peak power of 1570 nm wavelength reaches 5.6×104 W with the pulse width of 2.5 ns. The highest average output power of 560.3 mW is obtained. KTA is a kind of ideal material used to make pocket and portable OPO laser.

A 1176 nm Raman laser is obtained by use of self-frequency Raman conversion in a laser diode-pumped actively acousto-optically Q-switched Nd∶YVO4 1064 nm laser. The characteristics including the average output power, pulse width and pulse energy versus incident pump power and pulse repetition rates are measured. The widths of the typical fundamental pulses at 1064 nm and the Raman pulses at 1176 nm are 26.3 ns and 9.0 ns, respectively. At a repetition rate of 20 kHz and an incident pump power of 8.46 W, an average output power of 0.384 W at 1176 nm and an optical-to-optical conversion efficiency of 4.54% are obtained. The rate equations are used to describe the performance of the self-Raman actively Q-switched Nd∶YVO4 laser. Experimentally measured and theoretically calculated pulse energies and pulse widths at 1176 nm for the pulse repetition rates of 10, 20, and 30 kHz are compared, the theoretical results are in agreement with the experimental results on the whole.

First-order quasi-phase-matched intracavity second harmonic generation (ISHG) internal to a 1064-nm-Nd∶YVO4 laser end-pumped by a laser diode (LD) based on MgO-doped stoichiometric periodically poled lithium tantalate (PP-MgO∶SLT) is demonstrated. The PP-MgO∶SLT crystal is 20-mm-long and has a grating period of 7.93 μm (at room temperature), which is periodically poled along the z-axis by using the external electric poling technique. The fundamental and second harmonic waves are of z-polarization to access the largest effective nonlinear coefficient. Using a three-mirror folded cavity design for the Nd∶YVO4 laser, the maximum green light output power of 2.1 W and the conversion efficiency of 19% are achieved at an incident LD pump power of 11 W. The relationship between the conversion efficiency of a single-pass extracavity second harmonic generation (ESHG) in PP-MgO∶SLT and the crystal temperature is theoretically investigated. It is found that the measured acceptance temperature bandwidth of the ISHG is significantly wider than that of the ESHG. In addition, the ISHG curve shows an abrupt decrease in second harmonic power as a function of the crystal temperature, and the corresponding discussion is presented.