Two-dimensional tellurium-polymer membrane for ultrafast photonics.

Tellurium (Te) exhibits many intriguing properties including thermoelectricity, photoelectricity, piezoelectricity, and photoconductivity, and is widely used in detectors, sensors, transistors, and energy devices. Herein, ultrathin two-dimensional (2D) Te nanosheets were fabricated using a facile and cost-effective liquid-phase exfoliation method. Mixing the as-prepared 2D Te nanosheets with polyvinylpyrrolidone (PVP) provided a uniform 2D Te/PVP membrane. The 2D Te/PVP membrane exhibited excellent mechanical properties, thermal properties, and stability. The nonlinear optical properties of the membrane were characterized over the spectral range of 800 to 1550 nm using open-aperture Z-scan technology. A large nonlinear absorption coefficient of about 10-1 cm GW-1 over the whole tested wavelength range demonstrated the efficient broadband saturable absorptivity of the 2D Te/PVP membrane. Using the 2D Te/PVP membrane as a saturable absorber (SA), a highly stable femtosecond laser with a pulse duration of 829 fs in the communication band was obtained. This work highlights the promise of 2D Te/PVP membranes in ultrafast photonics and Te as a new 2D material for use in photonic devices such as all-optical modulators, switches, and thresholds.