All-polarization-maintaining figure-eight Er-fiber ultrafast laser with a bidirectional output coupler in the loss-imbalanced nonlinear optical loop mirror

• 来源期刊: 中国光学快报（英文版）
• 年，卷（期）: 2018,（12）
• 页码范围: 51-55
• 页数: 5页
• 语种: 英文
• DOI: 10.3788/COL201816.121404

摘要

In this Letter,we report on a novel architecture for a self-starting mode-locked figure-eight erbium-doped fiber laser using a loss-imbalanced nonlinear optical loop mirror (NOLM) with a bidirectional output coupler.An allpolarization-maintaining structure is adopted.A 2 × 2 optical coupler with a splitting ratio of 50:50 is used at the junction to form an NOLM.Another coupler with a splitting ratio of 10:90 is introduced at one end of the fiber loop.The 10:90 coupler plays two roles:power attenuator and bidirectional output coupler.This architecture can achieve both large modulation depth and good self-starting ability simultaneously.With this architecture,the self-starting mode-locking operation is achieved easily with pump power above the threshold.The clockwise and counter-clockwise mode-locked output powers are 10.1 and 10.3 mW,respectively,with the repetition rate of 3.63 MHz.The spectral bandwidths of the clockwise and counter-clockwise mode-locked output pulses are 7.4and 2.9 nm,and the corresponding pulse widths of the direct outputs are 530.6 fs and 1.55 ps,respectively.