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Solitons forming inside optical fibers are perturbed by several higher-order dispersive and nonlinear effects, especially when ultrashort optical pulses are used to excite them. We study, both analytically and numerically, how the radiation emitted by solitons in the form of dispersive waves ͑sometimes called Cherenkov radiation͒ is affected by these higher-order effects. Our results show that a certain minimum amount of third-order dispersion is needed before the amplitude of the dispersive wave becomes large enough for a spectral peak to appear in the output spectrum. This minimum value depends on the soliton order N and decreases with increasing N. The amplitude of the radiation peak increases initially with both the magnitude of the third-order dispersion and the soliton order, but then saturates to a relative power level that is typically below 10% of the launched power. Our results reveal several interesting features that should be of relevance for applications requiring an ultrabroadband optical source.

Dispersive waves (DW) are generated owing to perturbation of solitons by higher-order dispersion (HOD) and nonlinearity during supercontinuum (SC) generation. The frequencies of these waves are governed by a phase-matching condition in the form of a polynomial whose coefficients depend on the numerical values of the properly normalized third- and HOD parameters. Our extensive numerical solutions show that all odd HOD terms generate a single peak on the blue or the red side of the carrier frequency, depending on the sign of the corresponding term. In contrast, positive even HOD terms create conjugate DW peaks, in both the blue and red sides. No radiation is observed for negative values of these parameters. The combination of all even and odd HOD coefficients may generate more than two DW peaks for some specific choice of parameters. The results predicted by the phase-matching condition agree well with extensive numerical simulations revealing interesting facts of SC generation.

We explore the possibility of exciting the so-called quartic solitons in specially designed slot waveguides based on silicon and silica or silicon nanocrystals. This requires the excitation of the structure with quasi-transverse-magnetic polarized pulses-for which the Raman effect is absent-and at a specific infrared wavelength for which only the second- and fourth-order group velocity coefficients are nonvanishing. Pulses launched in these conditions will generate a spectrally localized continuum coming from the spectral interference of many quartic solitons. DOI: 10.1103/PhysRevA.87.02580

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