Black phosphorus Q-switched and mode-locked Er:ZBLAN fiber lasers at 3.5 um

TL;DR

This paper reports the first successful demonstration of passively Q-switched and mode-locked Er:ZBLAN fiber lasers at 3.5 micrometers using black phosphorus as a saturable absorber, advancing mid-infrared pulsed laser technology.

Contribution

It introduces black phosphorus as a novel saturable absorber for 3.5 um fiber lasers, enabling stable Q-switching and mode-locking in this spectral region.

Findings

First demonstration of passively Q-switched Er:ZBLAN fiber laser at 3.5 um.

Black phosphorus saturable absorber enables stable mode-locking.

Advances mid-infrared pulsed laser development.

Abstract

With the proposal of dual-wavelength pumping (DWP) scheme, DWP Er:ZBLAN fiber lasers at 3.5 um have become a fascinating area of research. However, limited by the absence of suitable saturable absorber, passively Q-switched and mode-locked fiber lasers have not been realized in this spectral region. Based on the layer-dependent bandgap and excellent photoelectric characteristics of black phosphorus (BP), BP is a promising candidate for saturable absorber near 3.5 um. Here, we fabricated a 3.5-um saturable absorber mirror (SAM) by transferring liquid-phase exfoliated BP flakes onto a gold-coated mirror. With the as-prepared BP SAM, we realized stable Q-switching and continuous-wave mode-locking operations in the DWP Er:ZBLAN fiber lasers at 3.5 um. To the best of our knowledge, it is the first time to achieve passively Q-switched and mode-locked pulses in 3.5 um spectral region. The research results will not only promote the development of 3.5-um pulsed fiber lasers but also open the photonic application of two-dimensional materials in this spectral region