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.

Solvothermal Synthesis and Ultrafast Photonics of Black Phosphorus Quantum Dots

“…We further performed a comparison experiment on pure NMP solution, which was verifi ed to be absent of nonlinear saturable absorption effect. [ 38 ] These results confi rm that the saturable absorption response indeed originates from the intrinsic optical absorption in BPQDs other than NMP solution. BP possesses bandgap from 0.3 to 1.5 eV with thickness of BP from bulk degrading to monolayer.…”

“…[28][29][30][31] Mechanical and liquid exfoliation methods have been adopted to prepare BP nanosheets with different numbers of layers and sizes. [32][33][34] Due to thickness-dependent bandgap structure of BP which is tunable ranged from 0.3 eV (bulk) to 1.5 eV (monolayer) [ 26,35,36 ] and anomalous anisotropy, [ 37 ] BP nanosheets show nonlinear saturable absorption properties, [ 38 ] and used as the saturable absorber for fi ber lasers. [ 39,40 ] However, the lateral size and thickness of these BP nanosheets is hardly to be controlled by the liquid exfoliation methods, which limits the investigations of the nonlinear optical properties of the BP with special size.…”

Emerging Trends in Phosphorene Fabrication towards Next Generation Devices

“…It was also reported that BP powder was obtained by grinding bulk BP crystal dispersed in different solvents such as IPA, NMP and ethyl alcohol (EA) to obtain 1 mg mL –1 dispersions, and the dispersions were ultrasonicated for 2 h. The dispersions were then allowed to settle for more than 24 h to enable the removal of large‐size sedimentations by centrifugation (at 1500 rpm for 20 min) 12. The interesting fact behind the formation of thin BP nanoflakes in the solution is that the interlayer van der Waals bonding is broken down by the ultrasonic energy 95…”

“…The NMP solvent for obtaining stable, highly concentrated (≈0.4 mg mL –1 ) BP dispersions was used in LPE in most of the reported studies 12, 67, 85, 91, 95, 118, 160, 166, 183, 185, 186, 187. NMP and DMF are well suit for liquid exfoliation owing to their relatively high boiling points and surface tension (≈40 mJ m –2 ) 166, 183, 188.…”

Mode-Locked Erbium-Doped Fiber Lasers Using 45° Tilted Fiber Grating

“…To obtain ultrashort pulses, the laser generally require a saturable absorber to achieve the mode locking mechanism. Various approaches have been developed since the early days of ultrafast lasers including physical light intensity absorbers such as semiconductor saturable absorption mirrors (SESAMs) [6], [7], carbon nanotubes [8], [9], graphene [10], [11], topological insulators [12], [13], black phosphorous [14], [15], and most recently transition-metal dichalcogenides (TMDs) [16], [17]. However, these physical absorbers either have bandwidth limitation or stability issues.…”