L-Band GHz Femtosecond Passively Harmonic Mode-Locked Er-Doped Fiber Laser Based on Nonlinear Polarization Rotation

Yuanda Ling,Chuanhang Zou,Chang Zhao,Kaiming Zhou,Chengbo Mou,Zhijun Yan,Zhikun Xing,Lin Zhang,Qianqian Huang

doi:10.1109/jphot.2019.2927771

Abstract

Via using an L -band optimized in-fiber polarizing grating device, a GHz L -band femtosecond passively harmonic mode-locked Er-doped fiber laser based on nonlinear polarization rotation is first demonstrated. In total, 4.22 GHz pulses with the duration of 810 fs and super-mode suppression ratio (SMSR) of 32 dB are obtained under the pump power of 712 mW corresponding to 215th harmonic order. The central wavelength of 4.22 GHz pulses is 1581.7 nm with 10.1 nm 3 dB bandwidth. Furthermore, under this fixed pump power, higher harmonic orders can also be attained by rotating the polarization controllers properly. The highest repetition rate we obtained is 7.41 GHz with the SMSR of 20.7 dB.

Highlights

High repetition rate ultrafast L-band fiber lasers have been widely concerned in recent years owing to the expansion requirement of the telecommunications window of the conventional C-band
A single mode fiber (SMF)-based 45°tilted fiber grating (45° TFG) with >30 dB polarization dependent loss (PDL) at L-band region is sandwiched between two polarization controllers (PCs) to realize the nonlinear polarization rotation (NPR) mode locking mechanism
Conclusions we have experimentally demonstrated L-band GHz femtosecond passively HML pulses generated from the NPR-based Er-doped fiber laser

Summary

Introduction

High repetition rate ultrafast L-band fiber lasers have been widely concerned in recent years owing to the expansion requirement of the telecommunications window of the conventional C-band. Passive mode locking has been widely studied to generate ultrashort pulses with high repetition rates, which could be divided into two major ways including short cavity design and PHML. Resulting from the intrinsic energy quantization effect [7, 8], PHML with the all-fiber structure capability is able to achieve high repetition rate ultrashort pulse with reasonable signal-to-noise-ratio (SNR) and resolves the difficulty of the dependency on the specialty gain fiber. [9], utilizing few layers graphene as an effective SA, a passively HML fiber laser operating in L-band has been experimentally demonstrated. Ultrashort pulse with high repetition rate generated through PHML based on NPR have been extensively examined. Sobon et al obtained 10 GHz HML pulses by utilizing double-clad fiber in an Er/Yb co-doped fiber laser based on NPR [14].

Methods

Results

Conclusion