Raman competition from ultra-broadband modulation instability gain in the As2Se3 glass photonic crystal fiber filled with argon gas

Abstract

Based on the As2Se3 glass photonic crystal fiber (PCF) filled with Argon gas, pressure- and power-dependent modulation instability(MI) gain properties are studied. Two narrow MI gain bandwidths in the Stokes or anti-Stokes region expand gradually with the increasing light power, and merge into an ultra-broadband gain profile eventually by increasing the pump power from 1 W to 9000 W at a fixed gas pressure. Further increasing pump power will result in the reduction of the gain bandwidth and the formation of a constant narrow-band gain peak, which is a novel phenomenon and observed in our work for the first time. When the argon gas pressure is changed from 1 P0 to 400 P0, a similar gain characteristic is also found. However, their maximum gain bandwidths are reduced from 5065 nm to 3833 nm with the increase of the gas pressure, and their pump power required to generate the narrow-band gain spectrum are reduced from 8450 W to 3060 W. These results indicate that the formation of the ultra-broadband MI gain mainly depends on some nonlinear effects rather than stimulated Raman scattering (SRS) effect, while the single gain peak with a narrow bandwidth mainly results from the SRS effect. And they also show that, it is feasible to control the MI gain characteristic in the mid-infrared region by changing the Argon gas pressure in the As2Se3 PCF, and this scheme can also be used in optical communication and spectral shaping in the future.