High-efficiency resonance coupling effects in zero-order diffractive multilayer structures have applications in fields such as optical filtering and laser technology. These resonance effects arise on phase matching of an incident laser beam to a leaky waveguide made. Then, in theory, complete energy exchange between the input wave and a reflected wave can take place within narrow ranges in wavelength, angle of incidence, index of refraction, or layer thickness. This paper addresses theoretical modeling, experimental realization, and applications of this so-called guided-mode resonance (GMR) effect In particular, the achievable GMR-filter efficiencies, spectral linewidths, sideband levels, and polarization characteristics are treated with a plane-wave model and a Gaussian-beam model, Resonance bandpass filters operating in reflection and transmission are shown to exhibit high efficiencies and extended low sidebands. Genetic algorithms are applied to solve inverse resonance-filter design problems. Applications including GMR laser mirrors, electro-optic modulators, and resonant Brewster filters are presented. Experimental results are shown to agree well with theoretical calculations.