Trapping of dispersive waves in solitonic resonators and its role in supercontinuum generation

This work addresses the effect of trapping of quasi-linear dispersive waves between optical solitons propagating in fibers with the high-order dispersion. It is shown that the four-wave mixing between the solitons and the dispersive waves can lead to nearly perfect reflection of the quasi-linear waves from the solitons [1]. Consequently, solitons can play a role of mirrors for the waves, thus forming a Fabry-Perot-like soliton resonator. However, solitons themselves are affected by the strong resonant dispersive waves [2, 3], with a subsequent absorption of energy [4], and an additional frequency shift (acceleration) [2-5]. We demonstrate that the trapped radiation can cause an effective interaction, and, eventually, collision between the solitons, even if the direct inter-soliton interaction is very weak. Two identical solitons were launched with a weak dispersive pulse between them. The field dynamics governed by the generalized Nonlinear Schrödinger equation (GNLS) is demonstrated in Fig. 1(a). An noteworthy feature of the resonator is the modification of the spectrum of the radiation trapped between the solitons (Fig. 1(b)). The observed effect of the radiation-mediated attraction of the solitons can be as a counterpart of the Casimir force. The mechanism of the soliton resonator may strongly manifest itself already at the initial stage of the supercontinuum generation process [6], just after the fission of the injected N-solitons [7]. Figure 1(c) displays such an event in case of a 12-soliton launched into PCF filled by Raman non-active Xenon gas [8].