Soliton Coupling Effect: Group-velocity-matching Dispersive Wave Generation and Spectral Tunneling

Concept of spectral soliton coupling is proposed to explain the group-velocity-matching dispersive wave generation and the soliton spectral tunneling effect. Soliton eigen state is found corresponding to a spectral phase profile under which the soliton phase shifts induced by the dispersion and the nonlinearity are instantaneously counterbalanced. A local but non-eigen soliton pulse will shed off energy and form radiations at other wavelengths, during the coupling to the soliton eigen state. Group-velocity-mathing between the local and generated wave is necessary not only as it produces a coupler-like phase profile which supports soliton coupling but also because it physically supports a soliton phase matching condition, which means the generated wave has a soliton state phase matched to the local exciting pulse. Examples in realistic photonic crystal fiber structures are also presented.