Light transmittance through corrugated film

We have theoretically studied light transmittance through symmetrically corrugated metal and dielectric films at small modulation amplitudes. It is shown that the transmission coefficient significantly changes when surface polariton or guided modes are excited. For "thick" metal film the transmission coefficient run up 1 if the diffracted and absorption losses are neglected. We have found that the resonance line width is essentially decreased when the modulation amplitude is small one. The corrugated dielectric films with small losses can be used as effective optical filters.