Preparation of Few-Layer Bismuth Selenide by Liquid-Phase-Exfoliation and Its Optical Absorption Properties

Bismuth selenide (Bi(2)Se(3)), a new topological insulator, has attracted much attention in recent years owing to its relatively simple band structure and large bulk band gap. Compared to bulk, few-layer Bi(2)Se(3) is recently considered as a highly promising material. Here, we use a liquid-phase exfoliation method to prepare few-layer Bi(2)Se(3) in N-methyl-2-pyrrolidone or chitosan acetic solution. The resulted few-layer Bi(2)Se(3) dispersion demonstrates an interesting absorption in the visible light region, which is different from bulk Bi(2)Se(3) without any absorption in this region. The absorption spectrum of few-layer Bi(2)Se(3) depends on its size and layer number. At the same time, the nonlinear and saturable absorption of few-layer Bi(2)Se(3) thin film in near infrared is also characterized well and further exploited to generate laser pulses by a passive Q-switching technique. Stable Q-switched operation is achieved with a lower pump threshold of 9.3 mW at 974 nm, pulse energy of 39.8 nJ and a wide range of pulse-repetition-rate from 6.2 to 40.1 kHz. Therefore, the few-layer Bi(2)Se(3) may excite a potential applications in laser photonics and optoelectronic devices.