锁模运转的低阈值掺铥激光器

Tm-doped laser emission band corresponds to the water absorption peak and the atmospheric window band, and has important application in environmental monitoring, medicine, military and spectroscopy. Mode-locked lasers near 2 μm appear particularly useful for time-resolved molecular spectroscopy, as pump sources for synchronously-pumped OPOs operating in 3- 5um, as infrared optical frequency comb, and for generation of the THz pulse. Tm-doped active material's absorption peak corresponds to AlGaAs diode laser emission band, so the doped-Tm laser is very suitable for LD pumping and commercial promotion. This project mainly studies the low threshold and mode-locked operation of doped Tm laser. Theoretically, study the luminescence properties of Tm ion and Tm-Ho co-doped ions, and analyse the effect of the energy level structure, the stimulated emission cross section, the cross relaxation, absorption coefficient and energy transfer up conversion on the pumping threshold. Basing on the analysis of the spectrum of broadband tunability and dispersion characteristic, choose the right mode-locking crystal. The effect of the laser cavity mode, the pump beam and the intracavity power and dispersion on the pump threshold and soliton mode-locked operation is studied. Experimentally, Select suitable crystal for low threshold femtosecond mode-locked operation, design low threshold laser cavity and achieve mode-locked operating of Tm-doped laser by intracavity dispersion compensation.

掺Tm类激光器发射波段处于水的吸收峰和大气窗口波段，在环境监测、医学、军事和光谱学等领域有重要应用。该波段飞秒脉冲在精密时间分辨光谱学，同步泵浦OPO产生3-5um中红外脉冲，红外光学频率梳和THz波产生具有重要价值。掺铥晶体吸收峰正好对应于AlGaAs半导体激光器（LD）的发射波段，十分适合于LD抽运，易于商业化推广。本项目主要针对掺Tm类晶体，研究其低阈值运转以及飞秒锁模脉冲的产生。理论上，研究Tm离子特别是Tm-Ho共掺离子受激发光特性，分析能级结构、受激发射截面、交叉弛豫、FOM值、能级上转换等参数对泵浦阈值的影响；分析其光谱宽带调谐性和色散特征，选择合适的锁模晶体；研究激光腔模、泵浦光斑、腔内色散和腔内功率对泵浦阈值和孤子锁模运转的影响。实验上，选择出适合低阈值飞秒锁模的晶体，设计低阈值运转的激光腔，通过腔内色散补尝实现掺铥激光器的飞秒锁模运转。

掺Tm类激光器发射波段处于水的吸收峰和大气窗口波段，在环境监测、医学、军事和光谱学等领域有重要应用。该波段飞秒脉冲在精密时间分辨光谱学，同步泵浦OPO产生3-5um中红外脉冲，红外光学频率梳和THz波产生具有重要价值。掺铥晶体吸收峰正好对应于AlGaAs半导体激光器（LD）的发射波段，十分适合于LD抽运，易于商业化推广。本项目主要针对掺Tm类晶体，研究其低阈值运转以及锁模脉冲的产生。基于前期理论分析，我们在实验上首次实现了掺铥氟化物Tm：LuLiF4无序介质玻璃基质Tm：ZBLAN晶体的连续锁模运转，并利用低阈值理论，首次实现了以上两类晶体的低阈值运转。同时基于以上研究方案，我们也实现了石榴石类晶体Tm:CaYAlO4和氧化物晶体Tm：LuSCO3的锁模运转，这些晶体表现出在飞秒锁模运转方面很好的性能。项目按计划完成了预定的目标，形成了一整套低阈值掺铥飞秒锁模的技术方案和理论。