Photonic bandgaps for grating-coupled waveguide modes with a silver tunnel barrier

The optical properties of a periodically modulated photoresist waveguide structure has been explored using the Kretschmann–Raether configuration with a thin silver tunnel barrier. A detailed experimental study of how wavelength-scale periodic texture modifies the dispersion of the guided modes in the visible range for a wide range of azimuthal angles is presented. Fitting the observed in-plane momenta of the modes to predictions from a multilayer, multishape differential grating theory model allows the identities of each of the modes to be confirmed. In addition, the intensities obtained experimentally are compared favourably with those predicted from a theoretical model. Such a waveguide structure can produce not only the photonic bandgaps at the Brillouin zone boundary, but also bandgaps within the Brillouin zone caused by the Bragg scattered guided modes anti-crossing with the unscattered modes. All of these photonic bandgaps have potential applications controlling spontaneous emission in devices.