Compact ultra-short pulse visible lasers

开展了1)LiNbO_3波导准相位匹配(QPM)非线性光学波长转换器件、2)稀土掺杂LiNbO_3波导激光器和3)集成光栅大功率半导体激光器的研究工作。研究结果总结如下：1.大阪大学的一名研究人员。参观了斯坦福大学。并得出了这些结果。(1)在LiNbO_3波导QPM器件中，通过将互作用长度增加到5.55 cm，归一化SFG效率达到2800%/W。利用该器件实现了全光开关，并演示了低功率控制光开关。(2)研究了反向质子交换过程对导模的控制。建立了工艺仿真模型并搭建了仿真平台。2.为实现稀土LiNbO_3波导激光器与QPM非线性光学波长转换元件的集成，建立了稀土掺杂LiNbO_3中QPM的磁区倒置光栅制作工艺。研究发现，在稀土扩散掺杂的热处理过程中，SiO_2层的存在抑制了不需要的反转层的形成。通过施加高压脉冲，在稀土掺杂晶体中成功地制作了准相位调制(QPM)光栅。在掺钕LiNbO_3晶体中制作了自倍频波导激光器。在波长为814 nm的激光泵浦下，获得了1084 nm的激光发射和542 nm的腔内二次谐波绿波。

Research work on 1)LiNbO3 waveguide quasi-phase-matching (QPM) nonlinear-optic wavelength conversion devices, 2)rare-earth doped LiNbO3 waveguide lasers, and 3)high-power semiconductor lasers with integrated grating have been performed. Results are summarized as follows :1.A researcher of Osaka Univ. visited Stanford Univ. and obtained these results. (1) Normalized SFG efficiency as high as 2800%/W in LiNbO3 waveguide QPM devices was achieved by increasing the interaction length up to 5.55 cm. The device was used for all-optical switching, and switching by low-power control light was demonstrated. (2) Reverse proton-exchange process was studied to control the guided modes. It is shown that the resultant waveguides provide larger overlap of the interacting guided modes and improve conversion efficiency The process simulation model was built and a simulator was constructed.2.Fabrication technique of domain-inverted grating for QPM in rare-earth doped LiNbO3 was established for integration of rare-earth LiNbO3 waveguide laser and QPM nonlinear optic wavelength conversion elements. It was found that a SiO2 layer suppresses formation of unwanted domain-inverted layer during thermal treatment for rare earth diffusion doping. QPM gratings were successfully fabricated in the resultant rare-earth doped crystal by applying high voltage pulse. A self frequency doubling waveguide laser was fabricated in Nd-diffused LiNbO3. Pumped by a beam at 814 nm wavelength, the laser emission at 1084 nm and the intra-cavity second harmonic green wave at 542 nm was obtained.