A 222 nm all-solid-state far-ultraviolet C (UVC) pulse laser system based on an optical parametric oscillator (OPO) and second-harmonic generation (SHG) using β-Ba2BO4 (BBO) crystals was demonstrated. Pumped by a Nd:Y3Al5O12 laser with a repetition rate of 100 Hz at 355 nm, the maximum signal laser pulse energy of 1.22 mJ at 444 nm wavelength was obtained from the BBO-OPO system, corresponding to a conversion efficiency of 27.9%. The maximum output pulse energy of 164.9 µJ at the 222 nm wavelength was successfully achieved, corresponding to an SHG conversion efficiency of 16.2%. Moreover, the tunable output wavelength of UVC light from 210 nm to 252.5 nm was achieved.

A single-resonant low-threshold type-I β-Ba2BO4 (BBO) optical parametric oscillator (OPO) with tunable output from 410 nm to 630 nm at 5 kHz repetition rate is reported. By taking the noncollinear phase matching method, low-threshold OPO operation could be obtained compared with the configuration of collinear phase matching, and the maximum optical–optical conversion efficiency of 11.8% was achieved at 500 nm wavelength when 0.4 mJ pump pulse energy was applied. When the noncollinearity angle was preset at 1.6°, 4.8°, and 6.3°, a continuously tuning output with a total spectral range of 220 nm was successfully obtained by adjusting the phase matching angle of the BBO crystal.

One fast simulation method using Markov chains was introduced to simulate angular, energy, and temporal characteristics of pulsed laser beam propagation underwater. Angular dispersion of photons with a different number of collisions was calculated based on scattering function and the state transition matrix of Markov chains. Temporal distribution and energy on the receiving plane were obtained, respectively, by use of a novel successive layering model and receiving ratio. The validity of this method was verified by comparing it with the Monte Carlo ray tracing (MCRT) method. The simulation results were close to those obtained by MCRT but were less time consuming and had smoother curves.

An external frequency doubling electro-optically Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) 473 nm blue laser was demonstrated. With absorbed pump energy of 48 mJ at 100 Hz repetition rate, about 2 mJ of 473 nm blue laser pulse energy was achieved by cascade frequency doubling. The second harmonic conversion efficiency was 64.5%, and overall optical-optical efficiency was 4.2%, respectively. The blue laser pulse width was less than 10 ns, and beam quality factor was less than 2.4.

A highly efficient laser system output at the H-β Fraunhofer line of 486.1 nm has been demonstrated. A high pulse energy single-frequency hybrid 1064 nm master oscillator power amplifier was frequency-tripled to achieve 355 nm laser pulses, which acted as the pump source of the beta barium borate nanosecond pulse optical parametric oscillator. With pump energy of 190 mJ, the laser system generated a maximum output of 62 mJ blue laser pulses at 486.1 nm, corresponding to conversion efficiency of 32.6%. The laser spectrum width was measured to be around 0.1 nm, being in conformity with the spectrum width of the solar Fraunhofer line.

The pulse characteristics of a laser diode dual-end-pumped electro-optic Q-switched Nd:LuAG ceramic laser at various repetition rates are presented. The largest output pulse energy of 11 mJ is realized at the repetition rate of 100 Hz with pump energy of 84.3 mJ, and the slope efficiency in respect to pump pulse energy is 18.6%. The single pulse peak power reaches up to 1.57 MW. Using Nd:LuAG ceramic as the amplification medium seeded by an Nd:YAG laser of 5.2 mJ, a 10.3 mJ amplified pulse is obtained with pump pulse energy of 42.8 mJ, corresponding to an extraction efficiency of 11.9%.