Highly nonlinear As2Se3-based chalcogenide photonic crystal fiber for midinfrared supercontinuum generation

We propose a real, highly nonlinear, As2Se3-based chalcogenide photonic crystal fiber in which a supercontinuum (SC) spanning more than 2 octaves is generated at λ=2.8 μm in the femtosecond regime. The designed PCF is characterized for ultrabroadband midinfrared SC generation in only few millimetres of fiber length. A full modal analysis of the optical properties of the fiber is presented in terms of the effective area, the nonlinearity coefficient, and the chromatic dispersion. A second-order Sellmeier approximation is proposed to estimate the variation of the refractive index of the As2Se3 material as a function of wavelength. The numerical study shows that a SC spanning from 1.9 to 4 μm can be generated in the chalcogenide PCF with an air-hole diameter of 1.26 μm and a pitch of 1.77 μm. We examine the interplay of the nonlinear effects that lead to the construction of the SC as a function of the input power and the fiber length. We find that the dynamics behind the SC generation is mainly ruled by the effects of self phase modulation and stimulated Raman scattering. The intrinsic properties of the chalcogenide glasses and the microstructure provide enhanced optical properties and offer numerous applications in the infrared field. © 2010 SPIE.