Lu Qiao, Ma Jindong, Duan Dian, Lin Xuechun, Mao Qinghe
Opt Express. 2019 Feb 4;27(3):2809-2816. doi: 10.1364/OE.27.002809.
This paper proposes and demonstrates a method to reduce the repetition rate of all- polarization-maintaining (PM) linear-cavity picosecond dissipative soliton passively mode-locked fiber lasers. An optical coupler (OC) is inserted into the cavity to extract pulse energy, and the cavity length is increased using a low-nonlinear coefficient large-mode field fiber at the rear end of the OC, where the propagated pulse has lower energy. This enables the nonlinear phase shift to be within the tolerated value of the single pulse mode-locking even with a considerably increased cavity length; this allows reducing the laser repetition rate considerably without substantially changing the pulse characteristics. Using the proposed method, for a 0.3-nm filter bandwidth, the laser repetition rate is successfully reduced to 1.77 MHz with a nearly Fourier-transform limited pulse duration of 10 ps; it can be further reduced by optimizing the OC split ratio. The proposed method can be applied to reduce the repetition rate for a picosecond dissipative soliton passively mode-locked fiber laser with an arbitrary bandwidth filter.
本文提出并演示了一种降低全保偏（PM）线性腔皮秒耗散孤子被动锁模光纤激光器重复频率的方法。在腔内插入一个光耦合器（OC）以提取脉冲能量，并在OC后端使用低非线性系数大模场光纤增加腔长，在该位置传播的脉冲能量较低。这使得即使腔长显著增加，非线性相位偏移仍能处于单脉冲锁模的容忍值范围内；这使得在基本不改变脉冲特性的情况下大幅降低激光器重复频率成为可能。使用所提出的方法，对于0.3nm的滤波器带宽，激光器重复频率成功降低至1.77MHz，脉冲持续时间接近傅里叶变换极限，为10ps；通过优化OC分光比可进一步降低重复频率。所提出的方法可应用于降低具有任意带宽滤波器的皮秒耗散孤子被动锁模光纤激光器的重复频率。
