1.94 um波段Tm:Ho共掺石英基全光纤飞秒脉冲激光技术研究

Femtosecond laser enable to be used for high-quality high-repeatability no-fragment ablation, are of great interest in both military and civil areas. We have studied the absorption characteristics of OH- in the Tm:Ho/ Tm:Ho:Tb co-doped silica fiber within 1.94um wavelength range, and the methods to increasing the pump efficiency of Tm3+,Ho3+ by incorperating cross-relaxation and up-conversion. To improve the characteristic of gain and magneto-optic effect, we will optimize the parameters of high-doping process of Ge, F, Tm3+, Ho3+, and cladding-doping process of Tb3+. Meanwhile, polarization-maintain Tm:Ho/ Tm:Ho:Tb silica fiber perform is fabricated by MCVD, special solution doping technique and side-groove method. Based on Nonlinear polarization rotation (NPR) and precise dispersion management, a stable high-energy (~nJ), high-repetition(~100MHz), narrow-pulse-width(~100fs) femtosecond all-fiber laser operating in the streched- pulse regime at 1.94um will be obtained by pumping at 793nm. It has great potential of the application in high-quality high-repeatability micro-fabrication and surgery.

飞秒激光可以进行高质量、高重复性和无碎屑的烧蚀加工，在军事和民用方面具有广阔的应用前景。本课题研究Tm:Ho/Tm:Ho:Tb共掺石英基光纤在1.94 um波段OH-吸收窗口的辐射特性，利用交叉驰豫及上转换机理提高Tm3+、Ho3+对泵浦光的吸收效率。优化疏松层高掺Ge、F、Tm3+、Ho3+以及包层环形掺Tb3+工艺，提高光纤的增益特性和磁光特性。采用MCVD车床的"湿法"在线掺杂技术和光纤预制棒侧向开槽技术，制作偏振保持Tm:Ho/Tm:Ho:Tb共掺石英基光纤。基于非线性偏振旋转机制并精确控制色散，在793nm激光泵浦下，运转在呼吸锁模状态，形成稳定的高能量(nJ量级)、高重复频率(约100MHz)的飞秒激光脉冲输出(脉宽百fs量级)。为实现利用1.94 um波段飞秒激光对材料进行高质量高重复性的微细加工和外科手术奠定基础。

研制了内包层环形掺Tb3+、纤芯Tm3+、Ho3+共掺石英基光纤。理论研究了1550 nm激光泵浦下Tm3+、Ho3+共掺石英基光纤激光器的输出特性。理论分析了有理数主动锁模掺铥光纤激光器和基于SESAM的锁模掺铥光纤激光器的工作原理。提出了1种基于NALM的被动锁模掺铥光纤激光器。当泵浦光功率为2.98 W时，类噪声脉冲的中心波长为1990.56 nm，光谱的半高宽为14.48 nm，重复频率为9.1 MHz，自相关信号尖峰宽度为518 fs，脉冲能量为26.63 nJ。提出了1种基于NPR的被动锁模掺铥光纤激光器。在激光腔内添加不同长度的单模光纤，调节被动锁模光纤激光器的总色散。当激光腔内总色散为-1.425 ps2时，类噪声脉冲激光输出的中心波长为2003.20 nm，光谱的半高宽为23.20 nm，重复频率为6.32 MHz，自相关信号尖峰宽度为406 fs，脉冲能量可以达到12.342 nJ。提出了1种混合锁模脉冲掺铥光纤激光器。当泵浦光功率为3.52 W。单偏振类噪声脉冲激光输出的中心波长为2007.00 nm，光谱的半高宽为20.00 nm，脉冲的光信噪比大于42 dB，重复频率为2.66 MHz，自相关信号尖峰宽度为258 fs，脉冲能量可以达到42.11 nJ。提出了1种基于保偏光纤光栅和SESAM的可切换单偏振双波长脉冲掺铥光纤激光器。双波长脉冲激光的工作波长为1940.97 nm和1941.73 nm，脉冲激光输出的光信噪比约为57 dB，重复频率为5.73 MHz。单偏振单波长激光脉冲宽度分别为3.78 ps和3.74 ps。在项目研究过程中，发表学术论文40篇，SCI论文29篇，EI论文5篇，核心论文6篇，培养博士生3名，硕士生18名。