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The persistent pursuit of broadband photodetectors derives from their unique properties for promising applications such as optoelectronic devices, imaging sensors, and neuromorphic computing. Here, we fabricated high-performance, ultra-wide spectral response (250–1064 nm) and easy-processing spin-deposition photodetector based on amorphous germanium sulfide (a-GeS) films by using Ti3C2T x transparent electrodes as contacts. In addition, photodetectors based MXenes contacts have larger photocurrent compared with Au contacts because MXenes conductive films have larger photo-responsive active areas and the surface plasmon-assisted hot carriers generated by the laser irradiation on MXenes. As-prepared photodetectors based on MXenes electrodes exhibit a photo-to-dark current ratio of up to 3.91 × 102 under a bias of 8 V, coupled with the response speed of 59 ms, photoresponsivity (166 mA W−1) and high detectivity (4.41 × 1010 Jones). This work combining amorphous materials with highly conductive MXene film has excellent application prospects for ultra-wide spectral response optoelectronic devices.

In-plane anisotropic two-dimensional (2D) materials have gained considerable interest in the field of research, due to having the potential of being used in different device applications. Recently, among these 2D materials, group 10 transition metal dichalcogenides (TMDs) pentagonal Palladium diselenide (PdSe2) is utilized in various sections of researches like nanoelectronics, thermoelectric, spintronics, optoelectronics, and ultrafast photonics, owing to its high air stability and broad absorption spectrum properties. In this paper, it is demonstrated that by utilizing this novel 2D layered PdSe2 material as a saturable absorber (SA) in an EDF laser system, it is possible to obtain switchable laser pulse generation modes. At first, the Q-switching operation mode is attained at a threshold pump power of 56.8 mW at 1564 nm, where the modulation range of pulse duration and repetition rate is 18.5 μs–2.0 μs and 16.4 kHz–57.0 kHz, respectively. Afterward, the laser pulse generation mode is switched to the mode-locked state at a pump power of 63.1 mW (threshold value) by changing the polarization condition inside the laser cavity, and this phenomenon persists until the maximum pump power of 230.4 mW. For this mode-locking operation, the achieved pulse duration is 766 fs, corresponding to the central wavelength and 3 dB bandwidth of 1566 nm and 4.16 nm, respectively. Finally, it is illustrated that PdSe2 exhibits a modulation depth of 7.01%, which substantiates the high nonlinearity of the material. To the best of the authors’ knowledge, this is the first time of switchable modes for laser pulse generation are achieved by using this PdSe2 SA. Therefore, this work will encourage the research community to carry out further studies with this PdSe2 material in the future.

Indium selenide (In2Se3) has attracted tremendous attention due to its favorable electronic features, broad tunable bandgap, high stability and other attractive properties. However, its further applications for nonlinear optics have not yet been fully explored. In this work, we demonstrate that few-layer ?-In2Se3 nanosheets exhibit strong saturable absorption properties over a wide wavelength range covering 800 nm, 1064 nm and 1550 nm. The few-layer ?-In2Se3 nanosheets used for this experiment are fabricated via a simple ultrasonic exfoliation in liquid. Stable ultrafast mode-locking laser pulses are obtained from both ytterbium-doped and erbium-doped fiber laser systems operating at 1064 and 1550 nm, respectively. A pulse duration as short as 215 fs was achieved in the Er-doped fiber laser system. Stable output pulses over 6 hours of operation were obtained in both laser systems. The pulse energy and peak power of the laser output pulses were increased by reducing the In2Se3 thickness. These results indicate that ?-In2Se3 nanosheets with low layer numbers are promising candidates for broad ultrafast photonics devices, such as optical switchers, Q-switchers and mode lockers.