Nonlinear optical properties of arsenic telluride and its use in ultrafast fiber lasers

We report the first investigation results of the nonlinear optical properties of As2Te3. More specifically, the nonlinear optical absorption properties of the prepared alpha -As2Te3 were investigated at wavelengths of 1.56 and 1.9 mu m using the open-aperture (OA) Z-scan technique. Using the OA Z-scan technique, the nonlinear absorption coefficients (beta) of alpha -As2Te3 were estimated in a range from (- 54.8 +/- 3.4)x10(4) cm/GW to (- 4.9 +/- 0.4)x10(4) cm/GW depending on the irradiance of the input beam at 1.56 mu m, whereas the values did from (- 19.8 +/- 0.8)x10(4) cm/GW to (- 3.2 +/- 0.1)x10(4) cm/GW at 1.9 mu m. In particular, the beta value at 1.56 mu m is an order of magnitude larger than the previously reported values of other group-15 sesquichalcogenides such as Bi2Se3, Bi2Te3, and Bi2TeSe2. Furthermore, this is the first time report on beta value of a group-15 sesquichalcogenide at a 1.9-mu m wavelength. The density functional theory (DFT) calculations of the electronic band structures of alpha -As2Te3 were also conducted to obtain a better understanding of their energy band structure. The DFT calculations indicated that alpha -As2Te3 possess sufficient optical absorption in a wide wavelength region, including 1.5 mu m, 1.9 mu m, and beyond (up to 3.7 mu m). Using both the measured nonlinear absorption coefficients and the theoretically obtained refractive indices from the DFT calculations, the imaginary parts of the third-order optical susceptibilities (Im chi ((3))) of As2Te3 were estimated and they were found to vary from (- 39 +/- 2.4)x10(-19) m(2)/V-2 to (- 3.5 +/- 0.3)x10(-19) m(2)/V-2 at 1.56 mu m and (- 16.5 +/- 0.7)x10(-19) m(2)/V-2 to (- 2.7 +/- 0.1)x10(-19) m(2)/V-2 at 1.9 mu m, respectively, depending on the irradiance of the input beam. Finally, the feasibility of using alpha -As2Te3 for SAs was investigated, and the prepared SAs were thus tested by incorporating them into an erbium (Er)-doped fiber cavity and a thulium-holmium (Tm-Ho) co-doped fiber cavity for both 1.5 and 1.9 mu m operation.