Dispersion engineering of highly nonlinear rib waveguide for mid-infrared super continuum generation

Abstract

A rib waveguide structure with a core of As2Se3, upper cladding of air and lower cladding of MgF2 is proposed for generation of a very broad and flat supercontinuum spectrum. Generation of a flat and broad supercontinuum requires high pumping power, but increasing the power leads to material failure in the waveguide. Here we have designed a structure with a high nonlinear coefficient, which can generate a very broad and flat supercontinuum with a width of more than 11μm by using a pumping power of only 100W. To the extent that we have investigated the literature, there is no report so far on such a supercontinuum with only an input power of 100W in waveguides. The appropriate dispersion profile of the structure has resulted in zero dispersion wavelengths (ZDW) at two wavelengths of 2.1μm and 2.8μm. Therefore, this makes the laser pump suitable for the designed structure to be available commercially. The high refractive index difference between the core and the cladding, as well as the decrease of the pumping wavelength have led to the obtained small effective mode area. As a result, the high nonlinear coefficient of 65.4W−1m−1 is obtained at the central wavelength of 2.4μm. Our numerical simulations and analyses indicate that by applying a laser pump with a pulse duration of 85fs and an input power of 100W to the proposed waveguide having only a length of 1cm, the output supercontinuum is achieved covering the wavelength range of 1.5μm to more than12μm, (at the −30dB level from the peak).