Abstract

A passively mode-locked thulium-doped fiber laser with square-wave pulse generation has been demonstrated using a figure-of-eight configuration with two gain mediums respectively located in the left and right loops. In this laser, mode-locking is achieved based on equivalent saturation absorption of a nonlinear amplifying loop mirror (NALM). The pulse amplitude and width of the square-wave pulse can be continuously extended through controlling pump power of gain mediums in the left and right loops. Moreover, the pulse dynamics and autocorrelation trace reveal the obtained square-wave pulse is a new kind of noise-like pulse, i.e., noise-like square-wave pulse, with capability of supporting higher pulse energy. This find enriches laser pulse dynamics and has important potential applications in laser detection, sensing and other fields.

Highlights

  • In recent years, thulium-doped fiber laser operating in the around 2 μm “eyesafe” spectral region, has become one of research hotspots in the field of laser, due to its important application prospects in medicine, material processing, optical communication, optical fiber sensing, remote sensing and radar technology [1]

  • The pulse dynamics and autocorrelation trace reveal the obtained square-wave pulse is a new kind of noise-like pulse, i.e., noise-like square-wave pulse, with capability of supporting higher pulse energy

  • From a thulium-doped fiber laser based on the nonlinear polarization rotation (NPR) technique, He et al experimentally demonstrated the generation of noise-like pulse (NLP) with pulse energy of 17.3 nJ and spectral bandwidth of 60.2 nm obtaining [28]

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Summary

Introduction

Thulium-doped fiber laser operating in the around 2 μm “eyesafe” spectral region, has become one of research hotspots in the field of laser, due to its important application prospects in medicine, material processing, optical communication, optical fiber sensing, remote sensing and radar technology [1]. From mode-locked thulium-doped fiber lasers using NALM for mode locking, Michalska et al reported NLP generation with spectral width of 32.6 nm [29], while Wang et al obtained square-wave NLPs with pulse width increased from 0.75 to 1.3 ns [30]. We presented the generation of noise-like SWP with adjustable pulse duration and amplitude from a passively mode-locked thulium-doped fiber laser with figure-of-eight configuration. The width and amplitude of the SWP can be independently and continuously extended, while the rectangle profile is maintained This noise-like rectangle pulse free of peak power clamping effect has the potential to support higher pulse energy, which enriches laser pulse dynamics and has important potential applications in the laser detection, sensing and other fields

Experiments and Discusses
Conclusion

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