Shunbin Lu

Few-layer black phosphorus based saturable absorber mirror for pulsed solid-state lasers.

We experimentally demonstrated that few-layer black phosphorus (BP) could be used as an optical modulator for solid-state lasers to generate short laser pulses. The BP flakes were fabricated by the liquid phase exfoliation method and drop-casted on a high-reflection mirror to form a BP-based saturable absorber mirror (BP-SAM). Stable Q-switched pulses with a pulse width of 620 ns at the wavelength of 1046 nm were obtained in a Yb:CaYAlO(4) (Yb:CYA) laser with the BP-SAM. The generated pulse train has a repetition rate of 113.6 kHz and an average output power of 37 mW. Our results show that the BP-SAMs could have excellent prospective for ultrafast photonics applications.

Broadband third order nonlinear optical responses of bismuth telluride nanosheets

We experimentally observed that a representative two-dimensional layered material, bismuth telluride (Bi2Te3) nanosheets, exhibit obvious broadband nonlinear absorption and large nonlinear refraction investigated by Z-scan technique. Our study may not only verify the giant nonlinear refractive index of Bi2Te3 (~10−8 cm2/W), but also provide some new insights for topological insulator-based photonics, potentially leading to the emergence of several new conceptual optoelectronics devices.

Ultrafast nonlinear absorption and nonlinear refraction in few-layer oxidized black phosphorus

We experimentally investigated the nonlinear optical response in few-layer oxidized black phosphorus (OBP) by the femtosecond Z-scan measurement technique, and found that OBP not only possesses strong ultrafast saturable absorption but also a nonlinear self-defocusing effect that is absent in black phosphorus (BP). The saturable absorption property originates mainly from the direct band structure, which is still maintained in OBP. The emergence of self-defocusing might originate from the combined consequences of the oxygen-induced defects in BP. Our experimental findings might constitute the first experimental evidence on how to dynamically tune its nonlinear property, offering an inroad in tailoring its optical properties through chemical modification (oxidation, introducing defects, etc.). The versatile ultrafast nonlinear optical properties (saturable absorption and self-defocusing) imply a significant potential of the layered OBP in the development of unprecedented optoelectronic devices, such as mode lockers, optical switches, laser beam shapers, and wavelength converters.