Waveguide solution of the Koroteev problem in the nonlinear optics of media with broken mirror symmetry: collinear three- and five-wave mixing schemes in planar waveguides

It is shown that collinear three- and five-wave mixing schemes may operate in an isotropic gyrotropic medium (the Koroteev problem in chiral nonlinear optics) when waveguide propagation of optical waves is employed. The normal modes (eigenmodes) of the waveguide field are characterised by the presence of a longitudinal electric field component, which leads to the appearance of a transverse nonlinear polarisation component and lifts the prohibition of collinear generation of the sum and difference frequencies on the basis of a quadratic nonlinearity, and of a bioCARS signal based on a fourth-order nonlinearity. Expressions are obtained for the amplitudes of signals arising as a result of such nonlinear optical mixing.