Interference between waveguide modes with identical polarization in diffused glass waveguides

An investigation was made of interference of modes with identical polarizations in waveguides formed in glasses by the ion-exchange diffusion method. Such interference was observed in waveguides with a low scattering level if the angular divergence of laser radiation was comparable with the difference between the resonance angles of the excitation of neighboring waveguide modes. The high contrast and independence of the interference pattern of the direction of observation were due to the fact that the interference resulted from the interaction of mode fields in the surface layer of a waveguide.