针对基于半导体可饱和吸收体(Semiconductor Saturable Absorber Mirror, SESAM)被动锁模光纤激光器脉冲底座宽和脉冲能量小的问题展开研究, 设计了一种线型腔结构的双SESAM锁模超短脉冲光纤激光器。首先, 通过增加SESAM个数的方式使得光脉冲在谐振腔中的一个振荡周期内多次经过可饱和吸收体, 有效增加了可饱和吸收体对光脉冲前后沿的吸收, 抑制了因泵浦功率过大而产生的调Q锁模效应, 有助于压缩脉冲宽度、提高单脉冲能量, 摆脱了因SESAM调制深度较低而对压缩脉冲宽度和提高单脉冲能量造成的限制。其次, 通过在系统中引入一段正色散光纤, 降低了因峰值功率过高而引起的非线性效应, 进一步提高了脉冲能量。最后, 在相同调制深度及饱和通量条件下, 与单SESAM锁模相比, 双SESAM锁模光纤激光器输出脉冲宽度由693 fs降低到449 fs, 缩短了35.2%, 脉冲能量由2.92 nJ提高到5.31 nJ, 上升45%。

Aiming at the problem of wide pulse pedestal and lower pulse energy of passively mode-locked fiber laser based on Semiconductor Saturable Absorber Mirror(SESAM), a double SESAM passively mode-locked ultrashort pulse fiber laser based on linear cavity structure was designed. Firstly, through increasing the number of SESAM, the optical pulse would pass through the SESAM repeatedly in one oscillating period in the cavity, the absorption of the absorber was improved to the pulse front and back edge, the Q mode-locked effect due to larger pump power was suppressed, contributed to pulse compression and raised the single pulse energy, the effect of the SESAM lower modulation depth on the pulse width and single pulse energy was eliminated. Secondly, the introduction of positive dispersion in the system could reduce the nonlinear effect caused by the peak power, and further improving the pulse energy. Finally, compared with the single SESAM mode locking under the same modulation depth and saturation flux, the output pulse width of the double SESAM mode-locked fiber laser shorted 35.2%, from 693 fs to 449 fs, and the single pulse energy raised 45%, from 2.92 nJ to 5.31 nJ.