Funneling light into subwavelength grooves in metal/dielectric multilayer films.

Light funneling in metal/dielectric multilayer films with subwavelength grooves is numerically and experimentally demonstrated. Incident light at the resonant wavelength can be completely funneled into dielectric layers through a narrow groove that only covers 12.5% of the surface area within one period and absorbed by a resonant cavity composed of metal/dielectric multilayer films. A narrower resonant dip is observed than that produced by bulk metals with the same thickness and grooves. The mechanism and influencing factors of the reflection spectrum, including groove widths, layer numbers, and the profile of the groove side wall are comprehensively analyzed. Coupling between adjacent grooves with different depths are also discussed. Our study can be applied in the applications of biological sensing and infrared detectors.