Maximizing the bandwidth of supercontinuum generation in As₂Se₃ chalcogenide fibers

Abstract

We describe in detail a procedure for maximizing the bandwidth of supercontinuum generation in As₂Se₃ chalcogenide fibers and the physics behind this procedure. First, we determine the key parameters that govern the design. Second, we find the conditions for the fiber to be endlessly single-mode; the fiber should be endlessly single-mode to maintain high nonlinearity and low coupling loss. We find that supercontinuum generation in As₂Se₃ fibers proceeds in two stages — an initial stage that is dominated by four-wave mixing and a later stage that is dominated by the Raman-induced soliton self-frequency shift. Third, we determine the conditions to maximize the Stokes wavelength that is generated by four-wave mixing in the initial stage. Finally, we put all these pieces together to maximize the bandwidth. We show that it is possible to generate an optical bandwidth of more than 4 μm with an input pump wavelength of 2.5 μm using an As₂Se₃ fiber with an air-hole-diameter-to-pitch ratio of 0.4 and a pitch of 3 μm. Obtaining this bandwidth requires a careful choice of the fiber’s waveguide parameters and the pulse’s peak power and duration, which determine respectively the fiber’s dispersion and nonlinearity.