Design of all-normal dispersion with Ge11.5As24Se64.5/Ge20Sb15Se65 chalcogenide PCF pumped at 1300 nm for supercontinuum generation

Abstract

Supercontinuum spectrum generation is a process in which laser beam in femtoseconds and high power (kilowatts) is converted into a broad-spectrum beam of light after passing through a specific environment. Of course, achieving this range comes with many limitations. In this paper, photonic crystal fibers are used as a substrate for input pulse due to the ability to control dispersion and loss, and creating single-mode operating conditions. One of the main factors for the formation of supercontinuum spectra of injection pulses is maintaining the nonlinear performance of this type of fiber by controlling the effective mode area and also using chalcogenides (nonlinear coefficients about 100 times higher than silica) in their structure. In the proposed structure, a photonic crystal fiber with silica base element and air cavities with hexagonal structure with the center of Ge11.5As24Se64.5 chalcogenide element have been used to provide the nonlinear property of the structure. Also, in this structure, a ring of Ge20Sb15Se65 chalcogenide elements has been used to reduce the effective mode region and create a flat dispersion curve at a wavelength of 1300 nm (second telecommunication window). The input pulse power is 10 kW and its width is 50 femtoseconds, which has caused the range of the supercontinuum from 800 nm to 1900 nm. This structure can be used to provide the required wavelengths as a carrier in a wavelength division multiplexing (WDM).

Exact Solution of the Raman Response Function of Chalcogenide Fiber and Its Influence on the Mid-Infrared Supercontinuum

“…This model uses three parameters to provide the correct location and peak value of the dominant peak in the Raman gain spectrum. Because of its simplicity, it has a great fit with the experimental result within 100 fs, and this simple model has been widely adopted by other researchers [35][36][37]. However, the Raman response function in Equation (2) only considers the main peak of the Raman gain spectrum of fused silica and ignores the influence of other small Raman gain peaks; it does not provide a correct quantitative description of Raman-induced phenomena and leads to difficulty in comparing theorical and experimental results.…”