There is an urgent need for infrared (IR) detection systems with high-level miniaturization and room-temperature operation capability. The rising star of two-dimensional (2D) semimetals with extraordinary optoelectronic properties can fulfill these criteria. However, the formidable challenges with regard to large-scale patterning and substrate-selective requirements limit material deposition options for device fabrication. Here, we report a convenient and straightforward eutectic-tellurization transformation method for the wafer-level synthesis of 2D type-II Weyl semimetal WTe2. The non-cryogenic WTe2/Si Schottky junction device displays an ultrawide detection range covering 10.6 μm with a high detectivity of ∼109 Jones in the mid-infrared (MIR) region and a short response time of 1.3 μs. The detection performance has surpassed most reported IR sensors. On top of that, on-chip device arrays based on Schottky junction display an outstanding MIR imaging capability without cryogenic cooling, and 2D WTe2 Weyl semimetal can serve as a saturable absorber for stable Q-switched and mode-locked laser operation applications. Our work offers a viable route for wafer-scale vdW preparation of 2D semimetals, showcasing their intriguing potential in on-chip integrated MIR detection systems and ultrafast laser photonics.

The novel vertically standing ${\mathrm{PtSe}}_2$ film on transparent quartz was prepared by selenization of platinum film deposited by the magnetron sputtering method, and an $\mathrm{Nd}\text{:}{\mathrm{LuVO}}_4$ passively mode-locked solid-state laser was realized by using the fabricated ${\mathrm{PtSe}}_2$ film as a saturable absorber. The X-ray diffraction pattern and Raman spectrum of the film indicate its good crystallinity with a layered structure. The thickness of ${\mathrm{PtSe}}_2$ film is measured to be 24 nm according to the cross-section height profile of the atomic force microscope image. High-resolution transmission electron microscopy images clearly demonstrate its vertically standing structure with an interlayer distance of 0.54 nm along the $c$-axis direction. The modulation depth ($\mathrm{\Delta }T$) and saturation fluence (${\mathit{\varphi }}_s$) of ${\mathrm{PtSe}}_2$ film are measured to be 12.6% and $17.1\mathrm{\mu J}/{\mathrm{cm}}^2$, respectively. The obtained mode-locked laser spectrum has a central wavelength of 1066.573 nm, with a 3 dB bandwidth of 0.106 nm. The transform limited pulse width of the mode-locked laser was calculated to be 15.8 ps. A maximum average output power of 180 mW with a working repetition rate of 61.3 MHz is obtained. To the best of our knowledge, this is the first report of the generation of ultrafast mode-locked laser pulses by using layered ${\mathrm{PtSe}}_2$ as a saturable absorber.

We have synthesized high-quality 2D, quasi-2D and 3D (PEA)₂(CsPbBr₃)_n−1PbBr₄ perovskites. Stable mode-locked ultrashort pulses are generated based on these three saturable absorbers.

We report a 166 W burst mode pulse fiber amplifier seeded by a Q-switched mode-locked all-fiber laser at 1064 nm based on a fiber-coupled semiconductor saturable absorber mirror. With a pump power of 230 W at 976 nm, the output corresponds to a power conversion efficiency of 74%. The repetition rate of the burst pulse is 20 kHz, the burst energy is 8.3 mJ, and the burst duration is ∼ 20 μ s, which including about 800 mode-locked pulses at a repetition rate of 40 MHz and the width of the individual mode-locked pulse is measured to be 112 ps at the maximum output power. To avoid optical damage to the fiber, the initial mode-locked pulses were stretched to 72 ps by a bandwidth-limited fiber bragg grating. After a two-stage preamplifier, the pulse width was further stretched to 112 ps, which is a result of self-phase modulation of the pulse burst during the amplification.