Maximizing the bandwidth while minimizing the spectral fluctuations using supercontinuum generation in photonic crystal chalcogenide fibers

Abstract

Recent computational work to optimize the output spectrum of As₂Se₃ and As₂S₃ chalcogenide photonic crystal fibers is summarized. Design procedures for both maximizing the output bandwidth and maximizing the power spectral density in the 3-5 <i>&mu;</i>m range are described. With a 2.5<i>&mu;</i>m pulsed pump source, it is possible to obtain a bandwidth of 4 <i>&mu;</i>m in As₂Se₃ fibers, and, with a 2.0 <i>&mu;</i>m pulsed pump source, it is possible to shift 25% of the input power to the 3-5 <i>&mu;</i>m range in As₂S₃. With a source at 2.8 <i>&mu;</i>m, it is possible to obtain an output power spectral density in As₂S₃ that extends between 2.5 <i>&mu;</i>m and 6.5 <i>&mu;</i>m. The single-shot output power spectral density exhibits rapid 10-20 dB fluctuations as the wavelength varies. Moreover, when the pump pulse duration and peak power vary, there are substantial shot-to-shot fluctuations in both the output bandwidth and spectral power density. With 10% variations of the pump pulse duration and peak power, the output spectrum averaged over 5000 shots exhibits less than 5 dB of variation in the intermediate wavelength range of 2.8-4.6 <i>&mu;</i>m and has a reproducible bandwidth of slightly less than 3 <i>&mu;</i>m. The average over 5000 shots yields the same output spectrum with 10⁶ shots, indicating that the spectrum has converged.