Tellurium@Selenium core-shell hetero-junction: Facile synthesis, nonlinear optics, and ultrafast photonics applications towards mid-infrared regime

Abstract Tellurium (Te) is a promising material for photonics applications due to its intriguing advantages, such as excellent optical nonlinearity, larger saturable absorption, strong thermo-optic effect, and superior UV–Vis photo-response. However, the limited optical absorption and uncertain stability of Te has greatly limited its applications in mid-infrared and higher band optical regimes. In this contribution, Te@Se core-shell hetero-junction was constructed by epitaxial growth Se on Te nanotubes (NTs), which exhibits strong broadband linear and nonlinear optical response. Compared to pristine Te NTs and current mainstream nanomaterials, Te@Se shows stronger nonlinear absorption and lower saturation intensity at 800 nm. By employing Te@Se as a saturable absorber device of erbium-doped fiber and thulium-doped fiber lasers, the high-power mode-locked pulses with very stable operation in near- and mid- infrared regime can be acquired. These results suggest that Te@Se hetero-junction is a promising material with infinite potential for new generation ultrafast nano-photonics.