Sub-wavelength quadratic spatial solitons

Summary from only given. Recently attention has been focused on the investigation of nonparaxial optical beams and sub-wavelength spatial solitons that are not satisfied by using a nonlinear Scrodinger's approach. Such solitons can be used for creation of new optical switching devices. The theory of ultra-narrow spatial solitons can be built on Maxwell's equations in a quadratically nonlinear medium. We have investigated nonparaxial narrow quadratic solitons taking into account the effect of nonlinearly induced diffraction, an effect directly stemming from Maxwell's equations and omitted in the paraxial case of wide beams. We have obtained the simple equations for soliton profile envelopes in the planar case and detected the saturation effect limiting the available soliton width from below. This limit is in the order of the linear wavelength and depends on the type of the nonlinear interaction between first and second harmonic waves. We have also found analytically the exact expressions for the fundamental limit of the soliton width and the auto-model profiles of extremely narrow solitons as well as the numeric solutions.