中红外波段热效应驱动型光学双稳态激光产生机理及调控研究

Optical bistability was on of the most important dynamics in laser physics and it has drawn great attention in the past years. Current optical bistability in mid-infrared wavelength region has rather low output power and the applications in many fields were greatly limited. Heavy thermal effects in Tm:YAG and Er:YAG laser systems have great impact on the laser performance. The thermal-induced laser bistability has high power difference, tunable bistable region and versatile appearance and the application fields are largely expanded. Laser ceramics have similar optical properties with single crystals and is easier to facilitate non-uniform doping. This project will start from further monitor the thermal induced bistability that was currently observed. The influences of laser cavity, pump power, pump beam shape, doping concentration and the material on the laser bistability would be investigated in detail. A comprehensive theoretical model would be built to illustrate this phenomenon and expand the application fields. By manipulation of the heat fields, we can understand the mutual influences between the laser field, the heat field and the thermal effects. Further study in 3μm region in Er:YAG ceramic lasers would also help to expand the application field and finally achieve mature application of thermal-induced laser bistability in mid-infrared wavelength region.

光学双稳态作为激光物理学中最重要的动力学行为之一，一直被人们致以广泛的关注。现有的中红外波段的双稳激光系统受到功率限制，应用领域受到了极大的限制。Tm:YAG系统中和Er:YAG系统中的热效应严重且对激光器性能影响较大。新型热效应诱导性双稳态具有功率识别度高、双稳范围可调、双稳领域较宽等优势，可以极大的拓展激光双稳态的应用领域。新型陶瓷具有可与晶体比拟的光学性质和更为便捷的制备方法。本项目将探索腔型、泵浦功率、泵浦光斑形貌、陶瓷掺杂、陶瓷种类等因素对该种双稳态效应的的影响规律，建立全面的理论框架及模型探究其他类型双稳态存在的可能性及其形成机理，深入理解高阶模下激光场、热场及宏观热效应之间的相互影响和相互作用机理。以新型多功能Er:YAG陶瓷材料为依托，研究热效应诱导型双稳态在Er:YAG激光器中的新型表现。最终实现新型热驱动型双稳态在中红外陶瓷激光器中的中的成熟应用。

本项目面向热效应驱动型2-3μm波段双稳态激光产生机理及调控技术，在新型饱和吸收体应用探索、新型激光陶瓷性能表征及级联非线性光学变频新现象探索方面取得了系列研究成果。通过深入研究与表征LD泵浦掺铥固体激光介质热效应，在Tm:Y2O3陶瓷中获得了7.25 W连续激光及最小脉冲宽度为115 ns的调Q激光输出，基于VBG实现了中心波长2101 nm、最高功率1.1 W的窄线宽连续激光输出，进一步利用金纳米棒作为可饱和吸收体，实现了2101nm的被动调Q运转，最小脉冲宽度为609ns；基于ReSe2、金纳米棒等新型饱和吸收体，研究了2-3μm波段固体激光短脉冲产生特性，利用ReSe2 宽带可饱和吸收体，在LD泵浦Tm:YLF、Tm:Y2O3激光器中实现了1.9-2.1μm被动调Q激光脉冲输出，并在Tm:YLF 激光器中首次实现了纳秒量级的2.3 μm 的被动调 Q 激光输出，最大输出功率为486 mW，脉冲宽度为716 ns，重复频率为5 kHZ；提出了基于腔内多阶次、多过程级联非线性变频的方案，分别获得了3295nm、3469nm双波长、1.6-1.7 μm多波长正交偏振激光输出。以上研究工作可有效拓展中红外波段双稳态激光的产生机理与技术途径，即基于饱和吸收特性的双稳态运转机制以及热效应与饱和吸收效应混合型双稳态激光产生的新现象探索。项目执行期内，团队成员在Opt. Express、Opt. Mater. Express 等期刊上发表论文8篇（标注资助号61605068），培养硕士研究生5名，获得国家自然科学基金委中俄国际合作交流项目1项。

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