Generation of tunable ultra-short pulse sequences in a quasi-discrete spectral supercontinuum by dark solitons

Abstract

We explore how to acquire the tunable ultra-short pulse sequences in a quasi-discrete spectral supercontinuum (SC) via the formation of dark solitons in a fiber with two zero dispersion wavelengths (ZDWs). These dark solitons are produced by pumping two pulses in the normal dispersion that are identical but delayed one with respect to the other. Few-cycle pulses with high power as dual pumps experience temporal breakdown, resulting in a nearly-complete conversion of pump energy into two normal dispersion regions to form the ultra-short pulse sequences separated by dark solitons. The spectral interference of these generated ultra-short pulses gives rise to the isolated narrow-band sources, shaping a quasi-discrete spectral SC. Based on the combined effect of group-velocity dispersion and the initial time delay between dual pumps, the spectral width of narrow-band sources behaves in such a similar manner to the temporal width of ultra-short pulses that they are different in two normal dispersion regions. Moreover, they can be regulated considerably by tuning the time delay and pump power. Furthermore, the control of time delay and pump power can bolster the manipulation on the number of ultra-short pulses and narrow-band sources.