Palladium selenide as a broadband saturable absorber for ultra-fast photonics

Abstract Air-stable broadband saturable absorbers (SAs) exhibit a promising application potential, and their preparations are also full of challenges. Palladium selenide (PdSe 2 ), as a novel two-dimensional (2D) layered material, exhibits competitive optical properties including wide tunable bandgap, unique pentagonal atomic structure, excellent air stability, and so on, which are significant in designing air-stable broadband SAs. In our work, theoretical calculation of the electronic band structures and bandgap characteristics of PdSe 2 are studied first. Additionally, PdSe 2 nanosheets are synthesized and used for designing broadband SAs. Based on the PdSe 2 SA, ultrafast mode-locked operations in 1- and 1.5-μm spectral regions are generated successfully. For the mode-locked Er-doped operations, the central wavelength, pulse width, and pulse repetition rate are 1561.77 nm, 323.7 fs, and 20.37 MHz, respectively. Meanwhile, in all normal dispersion regions, mode-locked Yb-doped fiber laser with 767.7-ps pulse width and 15.6-mW maximum average output power is also generated successfully. Our results fully reveal the capacity of PdSe 2 as a broadband SA and provide new opportunities for designing air-stable broadband ultra-fast photonic devices.