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.