报道了一种掺Yb偏振型大模场面积光子晶体光纤(LMA-PCF)飞秒激光器。作为增益介质的光子晶体光纤的单模场面积比传统光纤高一个数量级,有效地降低了非线性系数,使激光器获得高能量输出。激光器基于线形腔结构,利用半导体可饱和吸收镜实现自启动锁模。光纤激光器利用光栅对进行腔内色散补偿,使其运转在呼吸脉冲锁模状态,即在谐振腔的零色散点附近实现锁模。当腔内净色散呈反常色散时,激光器获得了平均功率为400 mW,重复频率为47 MHz(对应于8.5 nJ的单脉冲能量),脉冲宽度为500 fs的稳定的锁模脉冲输出,经腔外色散补偿,脉冲压缩至98 fs。当腔内净色散呈正常色散时,激光器输出的单脉冲能量为10.6 nJ,脉冲宽度为1.76 ps,经腔外色散补偿,脉冲压缩至160 fs。

A femtosecond fiber laser based on Yb-doped single polarization large-mode-area photonic crystal fiber (LMA-PCF) is demonstrated. The photonic crystal fiber acts as laser gain medium. Since the single mode area of the fiber is an order higher than that of conventional fibers, the fiber nonlinearity is effectively scaled down, and much higher energy laser pulse output is achieved. The laser is based on a linear cavity design, and a piece of semiconductor saturable absorber mirror is used to initiate mode-locking operation. A pair of gratings are used as intracavity dispersion compensation, and the fiber laser operates in the stretched-pulse regime where the amount of net cavity dispersion is in the vicinity of zero. For negative net cavity dispersion, the laser generates 500 fs pulses with an average power of 400 mW at a repetition rate of 47 MHz (corresponding to a single pulse energy of 8.5 nJ), and the pulses are dechirped to 98 fs after extracavity dispersion compensation. For positive net cavity dispersion, the laser generates 1.76 ps pulses with a single pulse energy of 10.6 nJ, and the pulses are extracavity dechirped to 160 fs.