A nano-lateral heterojunction of selenium-coated tellurium for infrared-band soliton fiber lasers.

In this work, ultrafast fiber lasers based on 2D selenium-coated tellurium nanosheets in the infrared band are reported. 2D selenium-coated tellurium as a mode locker is shown with broadband saturable absorption and is capable of supporting ultra-stable pulse trains with several hundred-femtosecond pulse widths in the laser cavity. In particular, the as-fabricated 2D selenium-coated tellurium based fiber laser source operating in the communication band (1.5 µm) exhibits the vector pulse property, which supports the study of the vector soliton in ultrafast fiber lasers. The pulse duration of vector solitons is as short as 800 fs. The 2D selenium-coated tellurium is also available for a mode locked fiber laser operating at 1 µm. The laser oscillator has a pulse duration of several picoseconds and the pulse train is ultra-stable after an amplification to 100 mW, which is a promising seed source in the chirped-pulse amplification system in the future.

Lead monoxide: a promising two-dimensional layered material for applications in nonlinear photonics in the infrared band.

Lead monoxide (PbO), a novel few-layer two-dimensional (2D) material, was theoretically predicted to have an excellent optical response. Herein, the nonlinear optical response of PbO in the infrared region was experimentally investigated. The feasibility of PbO nanosheets as an effective optical saturable absorber was experimentally verified for the first time. Based on the excellent nonlinear optical characteristics, 2D PbO was fabricated as a passive mode locker by depositing onto a fiber patch cord and by decorating on a microfiber, both of which were successfully applied in fiber lasers for the passive mode locking operation. The mode locking pulses of the fiber laser were as short as 650 fs at 1.5 µm. A pulse duration of 5.47 ps with a 1 µm fiber laser was also experimentally verified. Finally, a PbO-decorated microfiber was fabricated as an optical thresholder that can enhance the SNR of a 1 GHz signal up to 6 dB. This finding might facilitate the development of nonlinear photonic devices with high stability and their practical applications in the future.