Low Threshold and Robust Ultrafast Pulses from Freestanding‐Growth 2D Quaternary BiCuSeO

Abstract

Saturable absorber is a key component in ultrafast pulsed laser systems, which are pivotal in ultrafast physics, high‐speed communication, etc. 2D materials appear to be superior candidates as saturable absorbers for compact pulsed fiber lasers in recent years due to their wide band response and ease of integration. However, the integration of mode‐locked devices inevitably involves contamination or polymer in the interface between the layered saturable absorber and the fiber, which contributes to a high start‐up threshold for the ultrafast pulsed lasers. This study develops an on‐fiber femtosecond laser with 2D narrow‐gap semiconducting BiCuSeO as a saturable absorber by a fully dry integration process thanks to the controllable growth of freestanding quaternary BiCuSeO nanoflakes. The corresponding thermodynamic growth mechanism is systemically revealed by electron microscopy and bind‐energy calculation. An electrostatic‐force‐assisted transfer method is developed to avoid damage or chemical contamination. The BiCuSeO‐based femtosecond laser shows decent output performance (pulse width, signal‐noise ratio and repetition rate are 395 fs, 61 dB, 17.1 MHz) with an ultra‐low threshold of 30 mW. The strategy of controllable growth of free‐standing 2D material facilitates a clean interface between the saturable absorber and fibers, which is favorable for high‐performance ultrafast photonic devices.

GeS2 Nanosheets as Saturable Absorbers for High Signal-to-Noise Ratio in an L-Band Ultrafast Pulsed Laser

“…Besides, unlike the conventional band (C-band), which is generally used in optical communication systems, the long-wavelength band (L-band, i.e., 1565–1625 nm) pulse performs better in terms of information transmission. , Furthermore, infrared pulsed fiber lasers in the L-band have attracted tremendous research interest in multisoliton dynamic and optical communication systems due to their broad gain bandwidth. , To realize stable L-band ultrafast pulses, it is important to realize a reliable mode-locker. Compared with active pulse generation, passively mode-locked technique is the top choice for generating fiber lasers for its advantages such as low cost, flexible system, and good compactness. − Especially, the saturable absorber (SA) material becomes the key element in the passive technique.…”

2D Free‐Standing GeS1−xSex with Composition‐Tunable Bandgap for Tailored Polarimetric Optoelectronics

“…Besides, the conventional synthesis strategies for 2D GeX, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), predominantly employ an in‐plane growth mode on substrate, which inevitably brings about a substantial contact area between the products and substrate, necessitating high‐demand technologies or corrosive solvents for subsequent transfer and van der Waals heterojunction (vdWH) integration process. [ 21–23 ] If 2D GeS 1−x Se x can be grown on the substrate through out‐of‐plane growth (i.e., free‐standing growth), similar to cases in Bi 2 O 2 Se, Bi 2 SiO 5 , and BiCuSeO, [ 24–26 ] the vulnerable transfer process can be effectively circumvented owing to significantly reduced interaction between 2D GeS 1−x Se x and the substrate. Therefore, direct synthesis of 2D composition‐tailored free‐standing GeS 1−x Se x is deemed to be a more efficient solution to obtain high‐quality products.…”

Emerging Schemes for Advancing 2D Material Photoconductive-Type Photodetectors

“…Two-dimensional layered materials (2DLMs) are denoted as a class of ultra-thin phases in which atomic-scale planar structural units are bonded by weak van der Waals force, while the intralayer atoms are commonly conjugated by strong covalent bonds [22][23][24][25][26][27][28]. In recent years, 2DLMs have attracted widespread attention from researchers worldwide due to their excellent and abundant physical and chemical properties, and these materials have been widely applied in various industries, such as fundamental physics [29][30][31][32][33][34], electronics [35][36][37][38][39][40][41][42], photonics [43][44][45][46][47][48], piezo-phototronics [49], catalysis [50][51][52], batteries [53][54][55][56], energy storage [57], thermal management [58], etc. Due to the high in-plane carrier mobility, self-passivated surface, excellent flexibility, wide availability, good compatibility with the modern microfabrication platform, and thickness/strain-dependent energy band structures, 2DLMs have shown indisputable application prospects in the next generation of photodetection applications [59][60][61][62]…”