Photonic modes of metallodielectric periodic waveguides in the midinfrared spectral range

Coupling waveguide modes with localized resonances such as surface plasmons leads to a strong modification of the waveguide properties. We theoretically investigate the case of metallodielectric structures in the midinfrared spectral range and we demonstrate strong coupling between guided modes and surface modes, which is not related to conventional surface plasmons. This can be attributed to surface waves existing even on perfect electric conductors. We predict the existence of a low-loss mode, which interacts strongly with the metal grating. We expect that this result will have a strong impact on midinfrared photonics, such as distributed-feedback lasers or infrared photodetectors.