1.06μm结构参数最优化非保偏锁模光纤激光器

Optimization of structural parameters of a 1.06μm non-polarization modelocked fiber laser

采用半导体可饱和吸收镜的锁模光纤激光器是构建皮秒脉冲光纤放大器的热门候选种子光源之一。本文利用非线性薛定谔方程从理论上分析了单模传输光纤和单模增益光纤的模场半径、增益光纤的光纤长度、光纤布拉格光栅的反射率、半导体可饱和吸收镜的调制深度、非饱和损耗和饱和通量对输出脉冲特性的影响。对输出激光的脉冲和光谱特性也进行了理论研究。根据仿真结果,搭建了基于非保偏线型腔和SESAM的掺镱锁模光纤激光器系统。在没有任何腔内色散补偿和外部偏振控制的情况下,获得了中心波长为1.06μm、脉冲宽度小于12.51 ps、光谱宽度为0.32 nm、重复频率为37 MHz、输出功率为2 mW的稳定锁模脉冲激光输出。在我们的实验中,激光脉冲的光谱边缘平滑,光谱分布非常接近高斯线型。最后,通过系统的仿真,近红外锁模光纤激光器的整体结构得到了优化。本文介绍的锁模光纤激光器具有紧凑的非保偏光纤结构、精简的腔内配置和较少的元器件、高质量的输出脉冲相关特性,有望为下一代皮秒脉冲光纤激光器提供性能优异的实用化种子光源。

A mode-locked fiber laser using Semiconductor Saturable Absorber Mirrors(SESAMs)is one of the popular candidate seed light sources for the construction of picosecond pulse fiber amplifier.In this paper,the in⁃fluence of the fiber length of a gain fiber,the reflectance of the Fiber Bragg Grating(FBG),the modulation depth,the unsaturated loss,and the saturation flux of SESAMs,the mode field radii of single-mode transmission fibers and a single-mode gain fiber,on the output pulse characteristics,have been theoretically analyzed using the nonlinear Schrodinger equations.The characteristics of the pulse and the spectrum of an outputted laser have also been investigated theoretically.According to the simulation results,we built an ytterbium-doped mode-locking fi⁃ber laser system based on the non-polarization-maintaining linear cavity and a SESAM.Without any compensa⁃tion for intra-cavity dispersion and external polarization control,a stable mode-locked pulse laser output has been achieved with the center wavelength of 1.06μm,the pulse width of less than 12.51 ps,the spectral width of 0.32 nm,the repetition rate of 37 MHz,and the output power of 2 mW,respectively.The spectral edges of laser pulses appear smooth in our experiment,and the spectral distribution is close to the Gaussian shape.Finally,the overall structure of the near-infrared mode-locked fiber laser has been optimized by the systematic simulation.The mode-locked fiber laser introduced in this paper has a compact non-polarization-maintaining fiber structure,simple intra-cavity configuration with fewer components,high-quality output pulse correlation characteristics,which might provide a practical seed light source with the excellent performance for the next-generation picosec⁃ond pulse fiber lasers.