All-solid-state KTA Optical Parametric Oscillation

Due to their advantages such as eye-safe,all-weather operation,pass through smoke and widely applications in the field of military involving photoelectricity counterwork, laser rangefinder,scout,obstacle avoidance and so on,the eye-safe wavelength lasers have been attracted much attention in recent years.The eye-safe wavelength lasers with higher energy and higher pulse repetition rate could be obtained by the technology of optical parametric oscillator(OPO),which has become a central of focus in the fields of lidar systems,range finders and remote sensing etc.In this paper,the results of theoretical and experimental researches on KTA-IOPO at the eye-safe wavelength are presented.The main contents of this dissertation include:1.The development of laser diode-pumped all-solid-state lasers(DPSSL) and the meaning of the eye-safe lasers are reviewed.The main approaches and new results of eye-safe wavelength are summarized.The advantages of optical parametric oscillator at 1.5μm eye-safe wavelength are also introduced.2.The threshold parameters,conversion efficiency and bandwidth of the OPO are theoretically studied by considering the coupling equations of three nonlinear frequencies mixing.The OPO operation conditions and the configuration are summarized.3.The optical,mechenical and chemical properties of the KTA crystal and the Q-switched techenology of the solid-state lasers were described briefly.The design for the most optimum KTA-IOPO was also discussed.4.By using a typeⅡnon-critical phase-matched KTA crystal,the KTA-IOPO was reallized both in a diode end-pumped actively Q-switched Nd:YVO₄ laser with a acousto-optics and in a diode end-pumped passively Q-switched Nd:GdVO₄ laser with a Cr:YAG saturable absorber.In the actively Q-switched operation,When the incident pumping power was 11.3W,1.1W average power with 2.5ns pulse width at the signal (1534nm) wavelength was synchronously obtained at the repetition rate 30kHz.The correspongding peak power and single pulse energy were estimated to be 14.7kW and 36.7μJ.In the passively Q-switched operation,the signal(1534nm) average output power of 109mW was achieved under the incident diode pump power of 8.75W.The correspongding pulse width and repetition rate were 2.94ns and 13KHz respectively.5.With a non-critically phase-matched KTA crystal,the performance of the KTA-IOPO in a diode-side-pumped Nd:YAG lasers in CW was studied.The maximum average output power of 13.6W at the signal wavelength of 1534 nm and 3W at the idler wavelength of 3472.7 nm were obtained with the repetition rate of 18 KHz,giving the optical-optical conversion efficiency of about 5.7%from diode-power at 808 nm to OPO signal output,which was the highest conversion efficiency for intracavity KTA-IOPO with diode-side-pumping configurations to our best knowledge.The signal pulse duration of 5.46 ns was obtained with the highest output power of 13.6 W, corresponding to the single pulse energy of 756μJ and peak power of 138 kW, respectively.At last,the performance of KTA-IOPO and KTP-IOPO were compared at the same configuration.