Abstract
We numerically investigate the use of photonic crystal fiber (PCF) through dispersion engineering of its cladding containing air-holes for supercontinuum (SC) generation in the mid-infrared region using low peak power. A 3.6-cm-long PCF made using Ge11.5As24Se64.5 chalcogenide (ChG) glass with a hexagonal array of air-holes was optimized for obtaining zero-dispersion wavelength through dispersion tailoring around the pump wavelength of 4 μm. We have performed numerical simulations for such dispersion tailored ChG PCF with the peak power range between 0.25 kW and 2 kW. It was found through rigorous numerical simulations that an ultrabroadband mid-infrared SC spectra covering the wavelength range 2-8 μm which is equivalent to 2 octaves could be generated using pump pulses of 320 fs duration at a wavelength of 4 μm with a relatively low peak power of 2 kW by using our proposed ChG PCF design.
Highlights
Supercontinuum (SC) generation is a complex spectral broadening process where a narrow bandwidth pulse undergoes a substantial spectral expansion through the interplay between various linear and nonlinear phenomena that occur during the propagation of the optical signal along the length of the waveguide
The design of a ChG photonic crystal fiber (PCF) for SC generation depends on the accuracy of Group velocity dispersion (GVD) and higher-order dispersion parameters
The GVD curves obtained through finite element (FE) mode-solver were tested by the data fitting method applying Taylor series expansion by which it was observed good matching between the GVD curve obtained through both methods
Summary
Supercontinuum (SC) generation is a complex spectral broadening process where a narrow bandwidth pulse undergoes a substantial spectral expansion through the interplay between various linear and nonlinear phenomena that occur during the propagation of the optical signal along the length of the waveguide. Chalcogenide (ChG) glasses have shown a number of advantages over the other materials mentioned above due to their wider transmission window extending from 2 to 20 μm and higher nonlinearity into the MIR region (Eggleton et al, 2011) Such glasses are attractive for fabricating optical planar waveguides and microstructured based fibers owing to possessing low nonlinear absorption, low TPA, no FCA, and fast response time because of the absence of free-carrier effects. We have shown through rigorous numerical investigations that a 3.6 cm long, dispersion engineered, Ge11.5As24Se64.5 ChG PCF with hexagonal arrays of air-holes in its cladding can be used to generate a broadband SC with sufficient wavelength extension in the MIR regime It was found in many previous experiment based works that for achieving sufficient extension of SC spectrum in the long wavelength region depends on the availability of pump pulses at a suitable wavelength, among other factors, and the pump wavelength needs to be around 4 μm or longer. Our calculated bandwidths are the largest reported so far for SC generated using GeAsSe PCFs pumped at a wavelength of 4 μm with a low peak power of 2000 W
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