Abstract

The power scaling on mid-infrared Raman fibre lasers (RFLs) is in demand for applications in health, environment and security. In this paper, we present the simulated laser behaviours of the tellurite glass RFLs pumped by 300-W Tm-doped fibre lasers (TDFLs) at $2~\unicode[STIX]{x03BC}\text{m}$ for the first time. By combining the advantages of the TDFLs and tellurite fibre, the output power at $2.35~\unicode[STIX]{x03BC}\text{m}$ has reached over hundreds of watts by first-order Raman shift. Moreover, the cascaded RFLs have been demonstrated with a wavelength extension greater than $3~\unicode[STIX]{x03BC}\text{m}$ and output power of tens of watts. To maximize the output power and the slope efficiency of the RFLs, we further analyse the interaction between the Raman gain and cavity loss, which are determined by fibre length and output reflectance of the laser cavity.

Highlights

  • IntroductionSignificant efforts have been made to scale the power of cascaded Raman fibre lasers (RFLs) using typical silicate glass fibre at wavelengths between 1 and 2 μm

  • Laser emissions at the mid-infrared (IR) wavelength ranging from 2 to 5 μm have been widely applied in the fields of medical surgery, spectroscopy, gas detection and security, thanks to the tremendous molecular absorption fingerprints and atmospheric transparency window located within this spectral band[1,2,3,4,5,6]

  • We have demonstrated the numerical simulations on the 2 μm Tm-doped fibre lasers (TDFLs)-pumped tellurite Raman fibre lasers (RFLs) emitting in the mid-IR region for the first time

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Summary

Introduction

Significant efforts have been made to scale the power of cascaded RFLs using typical silicate glass fibre at wavelengths between 1 and 2 μm. The cascaded RFL at 3.77 μm based on chalcogenide fibre was reported as the longest wavelength [17] Both the small Raman shift of 250–350 cm−1 and low thermal damage threshold below 1 GW/cm hinder the employment of chalcogenide fibre to achieve power scaling in mid-IR[18]. In another aspect, the RFL based on the fluoride fibre was reported with a record output power of 3.7 W at 2.23 μm, indicating the feasibility of Downloaded from https://www.cambridge.org/core. Towards power scaling over tens of watts in mid-IR fibre laser, it is necessary to theoretically analyse the TDFL-pumped RFL and cascaded RFL based on tellurite fibres. The influences of the fibre length and output reflectance on laser output performance are investigated, while the optimized parameters are determined for the first-order, second-order and third-order RFL, respectively

Theoretical model
Results and discussion
First-order Raman fibre laser
Second-order Raman fibre laser
Third-order Raman fibre laser
Conclusion

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