Abstract
In this paper, antimony trisulfide (Sb2S3) was successfully prepared with the liquid phase exfoliation method and embedded into polyvinyl alcohol (PVA) as a saturable absorber (SA) in a passively mode-locked Er-doped fiber laser for the first time. Based on Sb2S3-PVA SA with a modulation depth of 4.0% and a saturable intensity of 1.545 GW/cm2, a maximum average output power of 3.04 mW and maximum peak power of 325.6 W for the stable mode-locked pulses was achieved with slope a efficiency of 0.87% and maximum single pulse energy of 0.81 nJ at a repetition rate of 3.47 MHz under a pump power of 369 mW. A minimum pulse width value of 2.4 ps with a variation range less than 0.1 ps, and a maximum signal to noise ratio (SNR) of 54.3 dB indicated reliable stability of mode-locking, revealing promising potentials of Sb2S3 as a saturable absorber in ultrafast all-fiber lasers.
Highlights
In past decades, ultrafast pulsed all-fiber lasers have been extensively applied in various fields from industrial applications to fundamental research including material processing, optical devices, optical communications, fiber sensors, laser radar, microscopy imaging, medical treatment, etc., [1,2,3,4,5] Q-switching and mode-locking techniques were the most important and most common methods to achieve ultrafast pulses in fiber lasers [6,7]
(2D) materials, such as graphene [8,9], graphene oxide (GO) [10], MXenes [11], single-walled carbon nanotubes (SWCNTs) [12], quantum wells (QWs) [13], black phosphorus (BP) [14], topological insulators (TIs) [15,16,17], transition metal dichalcogenides (TMDCs) [18,19,20,21,22,23,24], and layered metal sulfides (LMSs) [25] were widely used as saturable absorbers in mode-locked fiber lasers due to their outstanding nonlinear saturable absorption properties caused by sub-band gap absorption or the Pauli blocking principle [26]
When pump power was below 200.3 mW, there were unstable mode-locked pulses with constant increases of optical-to-optical conversion efficiency, while the mode-locking was stable under the pump power over 200.3 mW with fairly stable optical-to-optical conversion efficiency of about 0.82%
Summary
Ultrafast pulsed all-fiber lasers have been extensively applied in various fields from industrial applications to fundamental research including material processing, optical devices, optical communications, fiber sensors, laser radar, microscopy imaging, medical treatment, etc., [1,2,3,4,5] Q-switching and mode-locking techniques were the most important and most common methods to achieve ultrafast pulses in fiber lasers [6,7]. Have held certain attention in mode-locked fiber lasers owning to layer-dependent structural, electronic, and optical properties [25]. In 2017, Zhao et al reported a passively Q-switched and mode-locked Er-doped fiber laser based on an ReS2 saturable absorber [30]. Passively mode-locked operations based on SnS2 SA in both Yb-doped and Er-doped fiber lasers were achieved by Zhang et al [32,33]. SA for demonstrating a passively mode-locked Er-doped all-fiber laser It was based on a film-type SA, which was composed of highly crystalline and pure Sb2 S3 nanosheets prepared by the liquid phase exfoliation method and polyvinyl alcohol (PVA) matrix. The signal to noise ratio (SNR) always exceeded 45 dB at any pump power, and there was a minimum pulse width of 2.4 ps with a variation range less than 0.1 ps, revealing fairly stable mode-locked operations in this all-fiber laser
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