Wide-Spectrum Mid-IR Generation by High-Powe Solid-State Lasers

针对“宽光谱中红外产生系统”，我们对具有非线性波长转换的高平均功率和高峰值功率固体激光器进行了以下研究：(1)二极管泵浦固体激光器的模型：我们将M^2概念应用于固体激光器的优化。在Nd：YVO4激光器中获得了58.6%的最大斜效率。然后对Yb：YAG微芯片和板条激光器的模型进行了修正。(2)高功率激光器的发展：我们开发了一种新的边缘泵浦方案，用于固体激光器的功率调节。斯坦福特大学的拜尔小组已经展示了用于高功率系统的边缘泵浦之字形板条激光器。在板条激光器中，获得了127W的输出功率，斜率效率为57%。而在Yb：YAG晶体中，最大功率限制在40W以下，斜率效率为20%。另一方面，在微芯片方案中对IMS的Taira组进行了研究。采用边缘泵浦的Yb：YAG微片激光器结构，在准连续运转模式下，获得了近100W的输出功率和49%的斜率效率。(3)短脉冲的产生：为了评估Yb：YAG作为超快激光器的潜力，我们测试了它的可调谐性。采用400MYb：μ芯片，获得了最宽的可调谐波长~85 nm，斜率效率高(60%)，输出功率为3W。这一结果表明，用Yb：YAG系统发展~100fs(高达~15fs)的短脉冲激光器是可能的。(3)可广泛调谐的中红外产生：准相位匹配(QPM)方法将开辟波长转换领域的新天地。为了改进新的准相位调制器件的极化方法，我们研制了原位极化系统，并在此基础上获得了一种周期极化的宽带准相位调制芯片：LiNbO_3。此外，我们还与Byer教授和Fejer教授举行了小型会议，讨论了固体激光系统的现有技术和未来的可能性。

Toward "Wide Spectrum Mid-IR Generation System" we have investigated in high average power and high peak power solid-state lasers with nonlinear wavelength conversion as following ; (1) Models for diode-pumped solid-state lasers : We applied M^2 concept to the solid-state laser optimization. The maximum slope efficiency of 58.6% was obtained in Nd : YVO_4 laser. Then we modified our model for Yb : YAG microchip and slab laser. (2) Development of high power lasers : We have developed new edge pumping scheme for power scaling in solid-state lasers. Byer group of Stan ford University has been demonstrated the edge pumped zig-zag slab laser for high-power system. In Nd : YAG slab laser we obtained 127 W output power with 57 % slope efficiency. However, the maximum power was limited below 40 W with 20 % slope efficiency in Yb : YAG slab. On the other hand, Taira group of IMS was investigated in the microchip scheme. Up to near 100 W output power with 49 % slope efficiency have been obtained in quasi-CW operation mode by edge pumped Yb : YAG microchip laser configuration. (3) Short pulse generation : In order to evaluate the potential of Yb : YAG as an ultra fast laser, we examined the tunability. With 400 μm Yb : YAG microchip we achieved the widest tunability, 〜85 nm, in Yb : YAG with high slope efficiency (60 %) and 3 W output power. This result indicates the possibility to develop under 〜100-fs (up to 〜15-fs) short pulse laser with Yb : YAG system. (3) Widely tunable mid-IR generation : The quasi-phase-matching (QPM) methods will open new horizons in the wavelength conversions fields. To improve poling methods for new QPM devices we developed in-situ poling system, then obtained a broad-band-QPM chip in periodically poled MgO : LiNbO_3. Additionally, we have held the small meeting with Prof. Byer and Prof. Fejer to discuss about the current technology and future possibility of the Solid-State Laser Systems.