Mid-infrared supercontinuum generation based on hexagonal core silica-photonic crystal fiber with low peak power

Abstract

A novel and simple structure of nitrobenzene-filled hexagonal core photonic crystal fibers with supercontinuum spectral broadening in the mid-infrared region is numerically simulated. We can optimize geometrical parameters such as pitch, larger and smaller air hole diameters, hollow core shape to control and design dispersion characteristics, achieving an all-normal near zero flattened dispersion with fluctuation of ± 1.807 ps/nm·km in the 0.431 µm wavelength range and low value of –2.496 ps/nm·km at the 1.55 µm pump wavelength. The two proposed fibers have small effective mode areas leading to high nonlinear coefficients, with values of 8966.877 and 7311.825 W⁻¹.km⁻¹, respectively, at the pump wavelength of 1.55 µm. At 370 W of pump power, a near-infrared supercontinuum spanning from 0.791 to 2.99 µm with a bandwidth at 30 dB of 1.726 µm is obtained using the first fiber with an all-normal dispersion profile. Soliton dynamics govern the expansion of the supercontinuum spectrum into the mid-infrared region when the second fiber is pumped at a wavelength of 1.55 µm in an anomalous dispersion regime, covering from 0.791 to 6.5 µm (bandwidth of 3.49 µm at 30 dB) with a peak power of 500 W. These numerical results can be useful for various purposes such as biomedical, sensors, and optical coherence tomography.