Ultrawide spectral broadening and pulse compression in tapered and photonic fibers

Summary form only given. The generation of supercontinuum light with a spectrum more than two octaves broad in a photonic crystal fiber (PCF) has recently attracted much interest, owing to its significance in optical frequency metrology, pulse compression and spectroscopy. A similar ultrabroadband supercontinuum generation was also observed in tapered fibers. In both structures, the large refractive index step between silica and air is responsible for the shift of the zero dispersion frequency to the visible region near the input pulse frequency. For a deeper understanding of supercontinuum generation, we theoretically study pulse propagation in PCFs and tapered fibers. It is shown that the peculiar dispersion properties and degenerate four-photon mixing play a decisive role in the evolution of the ultrabroadband spectral broadening. We also predict that single-cycle pulses can be generated by application of an appropriate broadband modulator as a liquid-crystal spatial light modulator.