Second harmonic generation by off-axis propagation direction in an anisotropic optical waveguide

In an anisotropic waveguide a leaky wave can propagate in an off-axis propagation direction. For waveguides on the X-of negative crystals, a leaky wave is a wave of hybrid polarization with effective refractive index that is less than the substrate ordinary refractive index. The field of a leaky wave consists of a guided-wave part of extraordinary polarization whose power is concentrated in the waveguide and a radiative part of ordinary polarization that leaks into the substrate. In this work we show how the SHG process is modified if a leaky wave is involved in interaction