Experimental study on a broad and flat supercontinuum spectrum generated through a system of two PCFs

In this letter, the experimental results on a supercontinuum signal are presented based on a significantly broad and highly flat final spectrum (∼810 nm and less than 3 dB). The supercontinuum was induced by two different microstructures in photonic crystal fibers (PCFs) with solid cores, pumped in the nanosecond regime (large pulses) by a Q-switched Nd:YAG laser. The simultaneous presence of both PCFs allowed an optimized spectrum to be obtained in comparison with the work reported in recent papers. The spectral evolution of a pump pulse propagating into the two PCFs was analyzed experimentally and the dispersion in the PCFs was estimated through numerical simulations. The broadening of the final spectrum was related to nonlinear phenomena such as modulation instability, stimulated Raman scattering, four-wave mixing, self-phase modulation, cross-phase modulation and the formation of higher-order solitons. The proposed scheme may have potential applications for the use of supercontinuum spectra in the areas of sensing, spectroscopy and metrology. (letter)