Abstract
Dirac-like topological insulators have attracted strong interest in optoelectronic application because of their unusual and startling properties. Here we report for the first time that the pure topological insulator Bi2Te3 exhibited a naturally ultrasensitive nonlinear absorption response to photoexcitation. The Bi2Te3 sheets with lateral size up to a few micrometers showed extremely low saturation absorption intensities of only 1.1 W/cm2 at 1.0 and 1.3 μm, respectively. Benefiting from this sensitive response, a Q-switching pulsed laser was achieved in a 1.0 μm Nd:YVO4 laser where the threshold absorbed pump power was only 31 mW. This is the lowest threshold in Q-switched solid-state bulk lasers to the best of our knowledge. A pulse duration of 97 ns was observed with an average power of 26.1 mW. A Q-switched laser at 1.3 μm was also realized with a pulse duration as short as 93 ns. Moreover, the mode locking operation was demonstrated. These results strongly exhibit that Bi2Te3 is a promising optical device for constructing broadband, miniature and integrated high-energy pulsed laser systems with low power consumption. Our work clearly points out a significantly potential avenue for the development of two-dimensional-material-based broadband ultrasensitive photodetector and other optoelectronic devices.
Highlights
Have the strikingly optical and saturable absorption properties comparable with graphene
Topological insulators in two (2D) and three (3D) dimensions are a focus theme in condensed-matter physics due to their unique phases of quantum matter, which are related closely to the quantum spin Hall effect originating from spin-orbit interactions[23,24,25,26,27,28,29,30,31]
The dispersion was deposited onto a bronze grating substrate and inspected by transmission electron microscopy (TEM)
Summary
Have the strikingly optical and saturable absorption properties comparable with graphene. The simplest topological surface phase, which only consists of a single Dirac cone near the Г point of the surface Brillouin zone, has been recently observed in a class of layered stoichiometric compounds, Bi2Se3, Bi2Te3 and Sb2Te329,33,34 Within these materials, the heavy elements induce strong spin-orbit coupling with energy larger than the bulk bandgap and, the coupling effect can modify the surface state to the metallic phase. We demonstrated the sensitive saturable absorption of large-size Bi2Te3 sheets Taking advantage of these sheets, a low-threshold Q-switched Nd:YVO4 laser was achieved at 1.0 and 1.3 μ m. The Q-switched mode locking operation was obtained These results indicate that the topological insulator Bi2Te3 is a promising saturable absorber for low-threshold pulsed lasers. Such lasers have the potential application of efficiently producing high-energy short pulses in miniature and integrated laser systems without high pump intensity
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