Multimode Bragg diffractions in an ion-exchanged optical waveguide with a sputter-etched periodic surface corrugation

An optical diffraction phenomenon in an ion-exchanged planar optical waveguide with a sputter-etched periodic surface corrugation was experimentally investigated in detail. A single-mode incident beam simultaneously gave rise to several diffracted beams of different mode indices in different directions. This phenomenon was interpreted on the basis of the phase-matching diagram for the multimode Bragg diffraction by using measured wave vectors of the propagation modes and of the surface corrugation.