Optical pulse modulators based on layered vanadium diselenide nanosheets

The transition metal disulfides of VB group elements have gradually come into people's field of vision owing to their two-dimensional structure and unique optical properties. Vanadium diselenide (VSe₂) as a kind of transition metal diselenides, is competent for the applications of nonlinear saturable absorption. The dispersion of few-layer VSe₂is prepared by liquid phase exfoliation method. Clearly, it has an obvious layered structure, and the interlayer spacing is 0.31 nm. The VSe₂nanosheets are inserted into the Erbium-doped fiber laser through tapered deposition method and the measured modulation depth is 1.46%. A 1530.5 nm centered 851-fs pulse is observed with the 3.2 nm 3-dB spectral width. The experimental results show that the pulse is persistent under the power of 334 mW, with signal-to-noise ratio of 41 dB. And an up to 552.4 MHz modulation phenomenon is observed around 1560 nm, so is its frequency tunability. This is the first time that VSe₂is used to realize high frequency modulation in fiber laser. It is proved that VSe₂is expected to be a budding material of ultrafast optical modulation devices and widely used in the field of ultrafast photonics.