中红外室温宽调谐重复频率Fe:ZnSe激光技术研究

Mid-infrared widely tunable repetition frequency Fe:ZnSe laser have attracted much attention due to their wide applications in fields such as eye-safe radar, spectroscopy and infrared counteraction. However, temperature rise of laser crystal caused by heat accumulation at repetition frequency bump and the shortupper level lifetime (370ns) of Fe ion at room temperature wouldcause temperature quenching effects.Now the thermal management has become a core technology in the development of widely tunable repetition frequency Fe:ZnSe laser at room temperature. In this project, from the laser radiation mechanism and thermal management technology, using non-chain DF laser with short pulse width and weak quantum defect as pumping source, two experiment schemes in favor of thermal management are presented respectively, which are double end synchronous pump laser and thin disk laser. The study on Fe:ZnSe laser at room temperature will be performed. By solving the mechanism problems and key technologies, such as radiation properties of Fe:ZnSe crystal, dynamics of Fe:ZnSe laser, thermal management, broadband wavelength tunable, laser mode matching, we aim to obtain stable repetition frequency Fe:ZnSe laser working at room temperature, which wavelength tunable range is 4 to 4.5μm. This research will supply a novel theoretical foundation and technical approach for the development of mid-infrared laser.

中红外宽调谐重复频率掺铁硒化锌（Fe:ZnSe）激光器在人眼安全雷达、光谱学、激光红外对抗等领域具有广泛的应用前景，是中红外激光技术领域的研究热点。重复频率运转的室温Fe:ZnSe激光器严重的热积累及短的上能级寿命（370ns）易引发激光温度淬灭效应，因此高效热管理技术已成为限制室温重复频率Fe:ZnSe激光器发展的瓶颈技术。本项目以Fe:ZnSe激光辐射机理和热管理技术为切入点：采用量子亏损小、脉冲宽度短的氟化氘激光器为泵浦源，设计了双端面交叉同步泵浦和薄片激光器两种有利于热管理的实验方案。拟开展室温Fe:ZnSe激光技术研究，重点解决其中涉及到的Fe:ZnSe晶体辐射特性、激光动力学、热管理、激光宽波段调谐、泵浦光腔模匹配等机理问题和关键技术，实现Fe:ZnSe激光重复频率室温稳定运转，波长调谐范围4～4.5μm，为中红外宽调谐重复频率激光器的发展及应用提供新的理论基础和技术手段。

大能量中红外激光在激光致盲对抗、大气差分吸收雷达、激光与物质相互作用等方面具有广泛的应用前景，是国内外科研工作者关注的热点。Fe:ZnSe激光具有高增益、宽谱调谐的显著优势，是中红外大能量激光的有力竞争者。高增益Fe:ZnSe激光横向自激振荡效应和晶体高效热管理是制约室温大能量Fe:ZnSe激光效率的核心因素。本项目率先从理论层面刨析问题，基于速率方程理论，建立了可描述Fe:ZnSe激光动力学过程的数学模型，理论分析了晶体掺杂浓度、晶体长度和温度等参数对Fe:ZnSe激光性能的影响，揭示了Fe:ZnSe激光辐射机理。进而分析了Fe:ZnSe激光自激振荡阈值条件，发现通过降低抽运光斑尺寸或降低晶体边缘反射率可有效提升寄生振荡阈值，抑制横向寄生振荡的产生。并计算了晶体非通光面涂敷折射率与Fe:ZnSe相近的石墨烯边界条件下出现自激振荡的阈值，发现涂敷石墨烯后可抑制自激振荡的Fe:ZnSe激光晶体利用率由原来的25%提升到37%，为提升重复频率室温大能量Fe:ZnSe激光效率和工作稳定性提供理论指导。在理论分析基础上，基于短脉冲氟化氢激光泵浦源，搭建室温大能量掺铁硒化锌激光实验装置，实验上提出了室温风淋晶体散热和激光晶体非通光面涂敷石墨烯新方法，有效解决重复频率Fe:ZnSe激光晶体散热和横向自激振荡技术难题。采用截面尺寸28 mm×28 mm，长度4 mm，掺杂浓度2×1018 cm-3的体参杂Fe:ZnSe晶体，在泵浦激光脉冲能量1.54J时，实现了脉冲能量502mJ，转换效率32.6%，重复频率50Hz，平均功率22W的激光输出，波长调谐范围4-4.5 μm，开拓了我国在大能量中红外激光技术研究领域新途径。本项目研制的室温大能量Fe:ZnSe激光器技术指标处于国际先进水平。