title: Broadband nonlinear optical response in multi-layer black phosphorus: an emerging infrared and mid-infrared optical material.
abstract: Black phosphorous (BP), the most thermodynamically stable allotrope of phosphorus, is a high-mobility layered semiconductor with direct band-gap determined by the number of layers from 0.3 eV (bulk) to 2.0 eV (single layer). Therefore, BP is considered as a natural candidate for broadband optical applications, particularly in the infrared (IR) and mid-IR part of the spectrum. The strong light-matter interaction, narrow direct band-gap, and wide range of tunable optical response make BP as a promising nonlinear optical material, particularly with great potentials for infrared and mid-infrared opto-electronics. Herein, we experimentally verified its broadband and enhanced saturable absorption of multi-layer BP (with a thickness of ~10 nm) by wide-band Z-scan measurement technique, and anticipated that multi-layer BPs could be developed as another new type of two-dimensional saturable absorber with operation bandwidth ranging from the visible (400 nm) towards mid-IR (at least 1930 nm). Our results might suggest that ultra-thin multi-layer BP films could be potentially developed as broadband ultra-fast photonics devices, such as passive Q-switcher, mode-locker, optical switcher etc.
authors.forename: S B
authors.initials: SB
authors.lastname: Lu
authors.forename: L L
authors.initials: LL
authors.lastname: Miao
authors.forename: Z N
authors.initials: ZN
authors.lastname: Guo
authors.forename: X
authors.initials: X
authors.lastname: Qi
authors.forename: C J
authors.initials: CJ
authors.lastname: Zhao
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.forename: S C
authors.initials: SC
authors.lastname: Wen
authors.forename: D Y
authors.initials: DY
authors.lastname: Tang
authors.forename: D Y
authors.initials: DY
authors.lastname: Fan