In this study, strong two-photon absorption (TPA) in a layered bismuth telluride (Bi2Te3) topological insulator (TI) is observed and investigated by the Z-scan method under excitation with a femtosecond laser pulse at a wavelength of 1056 nm.

Two-dimensional (2D) topological insulators (TIs) have attracted much attention owing to their striking optical nonlinearity. However, the ultra-low saturable intensity (SI) of TIs resulting from the bulk conduction band limits...

The successful demonstration of Q-switched and mode-locked fiber-laser operations using a topological insulator (TI) as saturable absorber (SA) has opened an application window besides TI's originally expected features. However, to date, all-solid-state mode-locked lasers base on TISAs are still unavailable and became a desired goal not only due to their application as light sources, but also because of providing a way for deeper investigation of the nature of ultrafast dynamics present in TISAs. In this paper, the realization of a continuous-wave mode-locked all-solid-state laser with a repetition rate of around 1 GHz is reported using a high-quality TI SA mirror (TI-SAM) with ultralow saturation intensity, fabricated by a spin coating-co-reduction approach. An output power of 180 mW and pulse duration of 8 ps are observed. In addition, a 61 dB pulse-train quality from the radio frequency spectrum of mode-locked operation prove the feasibility of the proposed laser. To the best of our knowledge, this is the first experimental demonstration of a mode-locked solid-state laser based on TIs. In addition, this paper shows that the use of TISAs is a promising option for the realization of scaling solid-state mode-locked lasers with higher repetition rates, reaching order of GHz.

No abstract

In this study, Bi2Te3 cluster was applied as a saturable absorber to investigate the mode-locking behavior of InGaAsP multiple quantum wells (MQWs) whispering gallery mode (WGM). Under optical excitation, the ultralow saturation absorption of Bi2Te3 from bulk state had modulated the intensity inside the microdisk, multi-lasing at different wavelengths with equal spectral spacing was realized. The achieved pulse repetition rate was as high as an estimated 4 THz. Additionally, a clear degenerate breaking was observed with a frequency shift of approximately 1 THz for each lasing mode. To the best of our knowledge, this is the first demonstration of a passively mode-locked WGM laser. These findings may have applications in dual-comb device.