Abstract

Surface plasma wave (SPW) dispersion relation in the minigap region, where the unperturbed modes are degenerate, has been recently investigated, both theoretically¹ and experimentally.² Theoretically only energy gaps were predicted in the minigap region, but experimentally it was shown that both momentum and energy gaps exist² although optical excitation resulted only in energy gaps similar to the results obtained by Chen et al.³ Here we present a detailed optical investigation of the (+1, −2) minigap region by varying grating depths and profiles. Momentum gaps observed were critically dependent on grating profiles.

© 1989 Optical Society of America