Abstract

The nonreciprocal propagation of surface magnetoplasmon polaritons (SMPP), on doped semiconductors, has been suggested as a mechanism for creating nonreciprocal devices (e.g., isolators) in the IR to near millimeter wave range. Whereas the dispersion relations for such waves have been calculated and measured with prism couplers, the coupling of incident radiation into SMPPs via gratings has not been described theoretically. A nonperturbative theory, based on Rayleigh's method, is presented here and is used to calculate the reflectance for IR radiation incident on doped InSb, in magnetic fields of 10-200 kG. The grating corrugation is adjusted to give the deepest possible reflectance dip, corresponding to the excitation of the SMPP in a given direction. Waves incident from the opposite direction with respect to the surface normal are then not optimally coupled to the SMPP, and yield a shallower reflectance. The difference in reflectance from the two directions (+θ and −θ) is shown to be limited by damping and by a bulk effect associated with the zero-order scattering from the flat surface. Stronger nonreciprocal reflectance is found, using weaker magnetic fields, from a flat surface, via interaction with bulk waves, than from coupling to the surface waves.

© 1989 Optical Society of America