In our work, Cr₂Si₂Te₆, a novel two-dimensional (2D)-layered ferromagnetic insulator, was used as a saturable absorber (SA) for demonstrating a pulsed Er-doped fiber laser (EDFL) based on its nonlinear saturable absorption properties. The modulation depth and saturation intensity of the Cr₂Si₂Te₆-based SA are 6.61% and 10.77 MW/cm², respectively. When the pump power is 60.3 mW, the 13th harmonic mode-locked generation is obtained, the 3 dB optical spectrum bandwidth is 1.392 nm and the central wavelength is 1568.032 nm. When the pump power is higher than 170.3 mW, the EDFL works at the fundamental repetition frequency of 1.23 MHz with a signal-to-noise ratio of 25 dB. The experimental results reveal that Cr₂Si₂Te₆ SA has enormous potential in demonstrating ultrafast fiber lasers and provide references for future research based on Cr₂Si₂Te₆ as ultrafast optical modulators.

With the advances in the field of ultrafast photonics occurring so fast, the demand for optical modulation devices with high performance and soliton lasers which can realize the evolution of multiple soliton pulses is gradually increasing. Nevertheless, saturable absorbers (SAs) with appropriate parameters and pulsed fiber lasers which can output abundant mode-locking states still need to be further explored. Due to the special band gap energy values of few-layer indium selenide (InSe) nanosheets, we have prepared a SA based on InSe on a microfiber by optical deposition. In addition, we demonstrate that our prepared SA possesses a modulation depth and saturable absorption intensity about 6.87% and 15.83 MW/cm², respectively. Then, multiple soliton states are obtained by dispersion management techniques, including regular solitons, and second-order harmonic mode-locking solitons. Meanwhile, we have obtained multi-pulse bound state solitons. We also provide theoretical basis for the existence of these solitons. The results of the experiment show that the InSe has the potential to be an excellent optical modulator because of its excellent saturable absorption properties. This work also is important for improving the understanding and knowledge of InSe and the output performance of fiber lasers.

In our work, a new-type, to the best of our knowledge, ferromagnetic insulator and its nonlinear optical absorption characteristics and related ultrafast modulation applications were investigated. C r 2 S i 2 T e 6 saturable absorbers (SAs) with a modulation depth and a saturable intensity of 9.7% and 3.5 M W / c m 2 were fabricated. By adjusting the pump power to 120 mW and optimizing the polarization state, traditional soliton operations were obtained successfully; the corresponding duration of pulse and the fundamental repetition rate were ∼ 1.33 p s and 6.70 MHz, and the signal-to-noise ratio was 50 dB. The experimental results reveal that C r 2 S i 2 T e 6 with excellent saturable absorption characteristics can be used as a SA to obtain ultrafast pulse lasers.

Mid‐infrared (Mid‐IR) photodetection and imaging are pivotal across diverse applications, including remote sensing, communication, and spectral analysis. Among these, single‐pixel imaging technology is distinguished by its exceptional sensitivity, high resolution attainable through the sampling system, and economic efficiency. The quality of single‐pixel imaging primarily depends on the performance of the photodetector and the sampling system. Photodetectors based on black phosphorus (BP) exhibit low dark current, high specific detectivity ( D ^* ), and room‐temperature operability. Artificial intelligence (AI)‐assisted sampling systems feature efficient and intelligent data reconstruction capabilities. In this work, we demonstrate an AI‐driven black phosphorus (BP)/molybdenum disulfide (MoS ₂ )/hexagonal boron nitride (hBN) heterojunction for Mid‐IR photodetection and imaging. By optimizing the thickness of the heterojunction, the quality of the interface, and the AI algorithm, we achieved high‐performance Mid‐IR photodetection and imaging. Specifically, the photodetector has a responsivity of 0.25 A/W at a wavelength of 3,390 nm, an extremely high D ^* of 3.7 × 10 ⁹ Jones, a response speed as low as 7 ms, and after AI optimization, the image contrast ratio has been improved from 0.227 to 0.890. At the same time, the sampling rate requirement can be reduced to 25 %. Our research indicates that the efficient combination of BP heterojunction photodetectors and AI technology is expected to accelerate the development of Mid‐IR photodetectors and imaging systems.

Abundant research findings have proved the value of two-dimensional (2D) materials in the study of nonlinear optics in fiber lasers. However, there remains two problems: how to reduce the start-up threshold, and how to improve the damage threshold, of fiber lasers based on 2D materials. A 15.1 mW low-threshold mode-locked fiber laser, based on a Cr₂Si₂Te₆ saturable absorber (SA) prepared by the liquid-phase exfoliation method, is demonstrated successfully in this work. This provides a useful and economical method to produce SAs with low insertion loss and low saturation intensity. Besides, multiple high-order harmonics, from the fundamental frequency (12.6 MHz) to the 49th-order harmonic (617.6 MHz), mode-locked operations are recorded. The experimental results indicate the excellent potential of Cr₂Si₂Te₆ as an optical modulator in exploring the soliton dynamics, harmonic mode locking, and other nonlinear effects in fiber lasers.