高效内腔光泵气体THz激光器动力学模型构建及性能优化研究

High-power optically pumped gas terahertz (THz) laser is of special interest in areas such as THz imaging, THz lidar, environmental monitoring, biomedicine and THz nondestructive evaluation. Intra-cavity pumped gas THz laser has some advantages, such as high efficiency, high power and all-in-one. So far, there are lack of efficient laser technology and theory model for intra-cavity pumped gas THz laser, especially for atmospheric window wavelength output. In order to achieve high efficient, high-power, high beam quality THz laser output, we proposed a novel high-efficient intracavity optically pumped CH3F gas THz laser which is based on the dichroic beam splitter for the first time. Laser kinetics model of intracavity optically pumped CH3F gas THz laser will be established to numerically investigate the output performance of the THz laser. The project’s researches include as follows: experimental study the THz laser kinetics process, determine the transmission parameter and transfer function to establish the laser kinetics model of intra-cavity optically pumped CH3F gas THz laser. Dichroic beam splitter and intra-cavity pumping schemic will be investigated and designed. Experimentally study on THz output characteristics will be carried out by changing the parameters of THz laser. Based on the theoretical analysis and experimental data, we design and optimize the performance of the intra-cavity optically pumped CH3F gas THz laser. This project will provide the theoretical and technical supports for the realization of novel, high efficient, high power, high beam quality and all-in-one optically pumped gas THz laser.

高功率THz激光器在成像、雷达、环境监测、医学及无损检测等领域具有广阔的应用前景。内腔光泵气体THz激光器具有高效率、高功率和一体化等潜在优势。但是，目前缺乏有效的内腔光泵THz激光技术和理论模型，针对大气窗口波长的激光器研究较少。本项目，提出基于二色片的新型高效内腔光泵气体THz激光器，以CH3F为增益气体，建立激光动力学模型，理论结合实验对输出性能进行优化研究，以期获得大气窗口波长的高效率、高功率、一体化的THz激光器。研究内容包括：明确内腔气体THz激光的动力学过程，以实验手段确定传递参量函数，建立内腔THz激光器动力学模型并进行仿真研究；研究内腔泵浦结构，优化谐振腔；研究内腔光泵气体THz激光器的输出特性，获得各参量对THz激光器输出性能的影响规律，并对THz激光器进行优化。本项目将为研制新型、高效、高功率、高光束质量和一体化的气体THz激光器奠定理和技术基础。

高功率THz激光器在成像、雷达、环境监测、医学及无损检测等领域具有广阔的应用前景。光泵气体THz激光器具有高效率、高功率和高光束质量等潜在优势。但是，目前缺乏高效率、高功率的脉冲光泵气体THz激光技术和理论模型，针对大气窗口波长的激光器报道甚少。本项目针对脉冲高能CO2激光泵浦气体THz激光器，开展了理论模型构建、仿真与实验研究。主要研究内容及成果包括：1) 建立了脉冲高功率光泵气体THz激光动力学模型，开展了理论仿真和实验验证。结果表明了该理论模型的准确性和可靠性，工作气压和泵浦能量对输出THz脉冲形状有关键影响，通过调控，可获得三种典型的脉冲。2) 仿真研究了THz功率、泵浦功率、增益系数、泵浦吸收及粒子数密度随时间的演化过程和变化规律。并揭示了导致THz主脉冲分裂的背后物理机制，即双光子增强过程与双光子增强饱和导致的自我猝灭过程引起的增益开关效应。3) 理论结合实验，开展了脉冲光泵气体THz激光的输出性能随各参量的变化和性能优化，理论与实验结果有很好的吻合。4) 以CH3F气体为增益介质，开展了大气窗口波长输出的高性能THz激光器的实验研究和性能优化。获得了大气窗口波长231µm的激光指标是：脉冲能量为31.2 mJ，脉冲宽度为110 ns, 峰值功率约285 kW， M2因子为2.09。大气窗口波长360 µm的大气窗口波长输出指标是：脉冲能量10.3 mJ，峰值功率103 kW，M2因子1.85。依托本项目，项目组共发表SCI 收录论文 4篇（均标注有国家自然科学基金资助号）；授权国家发明专利3项；软件著作权5件；获中国发明协会“发明创业奖创新奖”一等奖1项；培养硕士研究生3名。