Mid-infrared Fe2+:ZnSe semiconductor saturable absorber mirror for passively Q-switched Er3+-doped ZBLAN fiber laser

Shougui Ning,Shouhuan Zhou,Hong Zhang,Lijuan Deng,Guoying Feng,Shenyu Dai,Wei Zhang

doi:10.1063/1.5012847

Abstract

A mid-infrared (mid-IR) semiconductor saturable absorber mirror (SESAM) based on Fe2+:ZnSe for passively Q-switched Er3+-doped ZBLAN fiber laser has been demonstrated. Fe2+:ZnSe SESAM was fabricated by electron beam evaporation method. Fe2+ was innovatively doped into the reflective Bragg stack, in which ZnSe layer served as both doped matrix and high refractive layer during the fabricating process. By using the Fe2+:ZnSe SESAM, stable passively Q-switched pulses with the minimum pulse width of 0.43 μs under a repetition rate of 160.82 kHz were obtained. The recorded maximum average output power of 873 mW with a peak power of 12.59 W and pulse energy of 5.43 μJ were achieved. The results demonstrated a new method for fabricating Fe2+:ZnSe SESAM, which can be used in compact mid-IR Q-switched fiber laser.

Highlights

Mid-IR lasers around 3 μm have attracted increasing interest for their potential applications in medicine, remote sensing, industrial process and longer mid-IR wavelength pump sources
Compared with conventional semiconductor saturable absorber mirror (SESAM) in which the distributed Bragg reflector (DBR) is sandwiched between upper absorber layer and lower substrate, Fe2+ was doped into high refractive layer in our SESAM during the deposition process, the Fe2+:ZnSe layers act as saturable absorber layer as well as high refractive layer
The linear transmission of the Fe2+:ZnSe SESAM was measured by a Fourier transform infrared spectrometer

Summary

INTRODUCTION

Mid-IR lasers around 3 μm have attracted increasing interest for their potential applications in medicine, remote sensing, industrial process and longer mid-IR wavelength pump sources. Fe2+:ZnSe is an important material for 3 μm laser pulse generation owing to their large cross section of absorption and high damage threshold (∼2 J/cm2).[14] The absorption band of Fe2+:ZnSe crystal is from 2.5-4.2 μm, corresponding to the 5E→5T2 vibronic transition of Fe2+, which ensure its application in passive Q-switching in mid-IR lasers.[18,19] Apart from crystal, Fe2+:ZnSe film fabricated by pulse laser deposition (PLD) has been reported for passively Q-switched Er3+-doped ZBLAN fiber laser around 2.78 μm with a pulse energy of 7.89 μJ and pulse duration of 0.742 μs.[20] Compared with either Fe2+:ZnSe crystal or film, conventional SESAM, a kind of reflectance type of SA, is more compact as well as avoiding large insertion loss. SESAM, which is a new device for mid-IR Q-switching fiber lasers

EXPERIMENTAL

RESULTS AND DISCUSSION

CONCLUSION