Research On Quasi-phase-matching Based Optical Parametric Oscillator And Its Related Lasers

Optical parametric oscillators (OPOs) have substituted traditional lasers in many fields, thus as national defence, polluter detection, biomedicine etc, because of its wide wavelength tunability. In recent years, with the development of quasi-phase-matching technology, especially with the maturity of fabrication technology of PPLN and PPMgLN wafers, much attention has been attracted by quasi-phase-matching based OPOs and their applications. Now, quasi-phase-matching based OPOs has become a research focus in nonlinear optics field.We emphasized our research on the basis of fabricaion of periodically poled MgO-doped lithium niobate (PPMgLN), optical parametric oscillator based on PPMgLN and its related high-power solid-state lasers. The work integrated a great deal of experimental evidence and corresponding theoretical analysis, and its major contribution is listed as follows:1. The Sellmeier equation of 5mol% MgO-doped lithium niobate at different temperature was systematically studied. Then, Both domain-tuning and temperature-tuning characteristics of PPMgLN OPO were intensively studied by numerical calculation. The theoretical results will be useful in the process of PPMgLN domain period designing.2. lmm thick PPMgLN wafers with different domain periods were sucessfully fabricated by applying external electric fields. After etching in HF solution for a few minutes, the PPMgLN wafers showed a homogenously poling area greater than 52mm×40mm and a good duty cycle of near 1:1. The elements that would influence the quality of reversal domains were aslo carefully studied, which included width of electrode, applied voltage, immerging current etc. After that, fabrication process of PPMgLN wafer with 2mm in thickness was also carried out, and some elementary but exciting results have been obtained.3. A high power A-0 Q switched Nd:GdVO4 laser working at 1063nm was established as a pump source for PPMgLN based OPO. Up to now, a maximun output power of 5.73W was obtained from the OPO at a pump power of 10.9W, with a conversion efficiency of 52.6% and a slope efficiency of 68.2%. The corresponding OPO signal and idler wavelength were 1552nm and 3373.8nm, respectively. By changing the domain period of the PPMgLN wafer, a wide spectral tuning range of the OPO output laser was achieved from 1.4 to 1.68μm for signal and from 2.88 to 4.38μm for idler.4. A high power A-0 Q-switched Tm:YAP laser operating at 1.94μm was also established at the same time. The performance of the Tm:YAP laser in A-0 Q switched mode was investigated in detail for the first time. What's more, the thermal lens effect of Tm:YAP laser crystal at different pump power was intensively examined. This laser system will be used as a pump source for PPMgLN OPO operating at 3-5μm, and we are confident that it will bring in higher output power and optical conversion efficiency in this waveband.In conclusion, the performance of quasi-phase-matching technology based OPO was much better than the traditional angle-phase-matching based OPO, especially on its high conversion efficiency and convenient tunability. And it will have important applications in many fields.