Few-cycle femtosecond pulses steadily generated in many laboratories attract not only theoretical, but also practical interest as a source of many prospective applications. One of the unique features of few-cycle pulses is that optical media remain intact even at ultrahigh field intensities because of ultrashort pulse duration and, as a consequence, the limited pulse energy. High intensities that cannot be achieved with longer pulses due to immediate breakdown of a material appear to be feasible with few-cycle fields and result in new characteristics of well-known effects. For example, self-phase modulation turns into the generation of spectral supercontinuum, which becomes virtually immanent to intense few-cycle pulses and accompanies other phenomena such as pulse temporal broadening or compression, self-focusing, etc. These effects were extensively studied for single few-cycle pulses. However, interactions of few-cycle pulses were beyond massive investigations. It was shown theoretically and experimentally in Refs. 5, 8, and 9 that the interaction of pulses with different spectral contents in nonlinear media can lead to significant enhancement of spectral ultrabroadening due to cross-phase modulation. In the present study, we demonstrate numerically that the pulse collision can become a source of quasi-discrete supercontinuum visible in the temporal domain as a regular pulse chain with an ultrahigh repetition rate. The opportunity for the generation of a quasi-discrete supercontinuum is confirmed experimentally.
Online access to SPIE eBooks is limited to subscribing institutions.