A Novel Repetition Rate Adjustable SBS-Based Q-Switched Fiber Laser

Shaodong Hou,Luyun Yang,Nengli Dai,Ping Chen,Jinyan Li,Zhimu Gu,Jinggang Peng,Haiqing Li

doi:10.1109/jphot.2020.2974881

Abstract

We experimentally demonstrated a novel repetition rate adjustable SBS-based Q-switched fiber laser. An inserted Fabry-Perot interferometer formed by two non-contact end faces of two FC/PC fiber connectors was inserted to help the system stabilize the random output of SBS-based Q-switching. By mechanically fine-tuning the length of the inserted Fabry-Perot interferometer, a linear and continuous repetition rate adjustment under a fixed pump power was achieved. This method paves a new way for the indirect control of repetition rate in SBS-based Q-switched fiber lasers. It is also found out that higher pump power allows wider adjustment range. At 600 mW pumping which is highest pump power of the source, the repetition rate almost tripled from 11.22 kHz to 32.06 kHz only by varying the length of FP cavity in less than 3 μm. In the meantime, the variation of pulse width, output power and single pulse energy were recorded and analyzed under different fixed pump powers. Although the adjusting range of repetition rate is not very wide but the tuning of repetition rate due to such a small length changing is unique and valuable. This original repetition rate control technique has great potential in areas like environment sensing and material detections.

Highlights

Q-switched fiber lasers have been of great importance in many fields for their known advantages of simplicity, compactness and low cost over actively Q-switched fiber lasers
While the laser was under 600 mW pump power, the repetition rate could be adjusted from 11.22 kHz to 32.06 kHz
It should be noted that even with the same moving distance, the distances of two end faces of fiber connectors under different pump power were not equal since the initial length of FP cavity varies with different pump power

Summary

Introduction

Q-switched fiber lasers have been of great importance in many fields for their known advantages of simplicity, compactness and low cost over actively Q-switched fiber lasers. Saturable absorbers (SAs) and fiber nonlinearities have been extensively studied for decades for passive Q-switching. Various SAs have been developed in recent years, such as graphene, single-walled carbon nanotube, transition metal dichalcogenides, topological insulators and black phosphorus [1]–[5]. Their complicated fabrication procedure, low thermal damage threshold and long-term instability hinder their practical application and further development. Methods utilizing Kerr effect, including nonlinear amplifying loop mirror, nonlinear polarization evolution and multimode interference, has been studied extensively and proved to be efficient and inexpensive ways to generate stable Q-switched pulses [6]. As a kind of inelastic scattering, stimulated Brillouin scattering (SBS), was found to be able to produce Q-switched pulses [7]

Methods

Results

Conclusion