Theoretical Investigation of a Multistage Cascaded Fiber Raman Soliton Frequency Shift System in Mid-Infrared Region

Yiwei Hou,Qi Wu,Francois Ouellette,Hongyu Luo,Xiaodong Wu,Jianfeng Li,Fei Liu

doi:10.1109/jphot.2021.3101508

Yiwei Hou, Qi Wu + Show 5 more

Open Access

https://doi.org/10.1109/jphot.2021.3101508

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Abstract

We demonstrate numerically a novel repeater-based three-stage cascaded soliton self-frequency shift (SSFS) structure including a germania-core fiber, an Er 3+ ZBLAN fiber amplifier, and an indium fluoride (InF 3 ) or TeO 2 -Bi 2 O 3 -ZnO-Na 2 O (TBZN) fiber. Wide wavelength tunability of 2–4.4 μm and 2–5.0 μm was achieved with a 5 m-long InF 3 and a 0.2 m-long TBZN fiber, respectively. Numerical results show that with the same input pulses, stronger SSFS effect with longer wavelength edge occurred in TBZN fiber with shorter fiber length, while Raman solitons with higher energy, conversion efficiency and shorter pulse duration were generated in InF 3 fiber. Compared with the commonly used single frequency shift structure, both the energy and conversion efficiency of Raman solitons in the designed repeater-based three-stage cascaded structure were significantly higher when the same tunable range was achieved. Our work could provide an efficient way to simultaneously improve the tunability, output energy, and conversion efficiency of the existing all-fiber laser sources with a lower operation energy.

Highlights

IN recent years, rapid progress has been made with midinfrared (MIR) laser sources covering the 2-5 μm spectral region, due to the urgent requirements in scientific research, military, and civilian applications
Numerical results show that compared with the single frequency shift structure with InF3 fiber, when the frequency shift from 2 to 4.4 μm was achieved, the repeaterbased three-stage cascaded structure produces soliton pulse with 2.2 nJ higher energy and 32% higher conversion efficiency in InF3 fiber
The simulation of the soliton self-frequency shift (SSFS) effect in thulium-doped fiber amplifier (TDFA) is in high consistency with the experiment

Summary

INTRODUCTION

IN recent years, rapid progress has been made with midinfrared (MIR) laser sources covering the 2-5 μm spectral region, due to the urgent requirements in scientific research, military, and civilian applications. Raman soliton laser, which is realized by the soliton self-frequency shift (SSFS) effect in optical fibers [8], is a most promising candidate for 2-5 μm tunable MIR femtosecond pulse generation It possesses high output beam quality, continuous wavelength tunability, and a compact structure. To achieve a wide tunability, the Raman shifter fiber pumped by high power pulses would inevitably produce higher-order solitons and cause energy separation, resulting in low output energy and conversion efficiency. To achieve high conversion efficiency, low nonlinearity fibers and low operation energy are desirable, which would be beneficial for controlling the soliton order Such behavior would confine the frequency shift effect and cause weak tunability. Numerical results show that compared with the single frequency shift structure with InF3 fiber, when the frequency shift from 2 to 4.4 μm was achieved, the repeaterbased three-stage cascaded structure produces soliton pulse with 2.2 nJ higher energy and 32% higher conversion efficiency in InF3 fiber

NUMERICAL MODELING

Findings

CONCLUSIONS