Theory of photoinduced second harmonic generation in fiber-optic waveguides

A mechanism for photoinduced second harmonic generation in fiber-optic waveguides made of quartz glass is proposed which is based on the formation of an orientation order in a system of defects characterized by second-order local susceptibility. The interaction between the defects considered here is similar, in a certain sense, to the van der Waals interaction between atoms and molecules. The principal difference is the nature of the electromagnetic field that induces the dipole moments: in the present case, it is the pumping wave field, whereas in the case of van der Waals interaction, it is the fluctuation vacuum field.