Hello Sir, for your query you can read up two books apart from materials available online.

1. Photonic Crystals: Molding the Flow of Light - Second Edition

2. Photonic crystals: physics and practical modeling

Dear,

I suggest that you focus on the allowed modes for light propagation. Also, for each waveguide, confinement factor depends on different parameters. So, considering the confinement of allowed modes can assist you to find the answer.

Dear sir,

I think the physical mechanism of soliton formation in these waveguides are the same. It should be note the difference of soliton and solition wave. In fact, solition wave is a localized structure which can be found in many nonlinear systems.

So, the most important thing behind the soliton or soliton wave is the balance physical parameter, such as Kerr nonlinearity and GVD for temporal soliton, self focusing (also related to Kerr nonlinearity) and diffraction for spatial soliton, and so on.

I hope I have clearly answered your question.

Best regards

C. Mei

In general, a soliton wave is a nonlinear localized wave possessing a particle-like nature that maintaining its shape during propagation even after an elastic collision with another soliton wave. The possibility of soliton propagation in the anomalous dispersion regime of an optical material was predicted by analyzing theoretically the nonlinear Schrodinger equation (NLSE).

In optics, soliton wave can arise due to the balance between Kerr nonlinear effect and dispersion effect (GVD). Based on confinement in the time or space domain, one can have either temporal or spatial solitons. This induces to an intensity-dependent refractive index of the medium and then leads to temporal self-phase modulation (SPM) and spatial self-focusing. A temporal soliton is formed when the SPM effect compensates the dispersion-induced pulse broadening. In the same way, a spatial soliton is formed when the self-focusing effect counteracts the natural diffraction-induced pulse broadening.