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Methods and apparatus for producing small, bright nanometric light sources from apertures that are smaller than the wavelength of the emitted light. Light is directed at a surface layer of metal onto a light barrier structure that includes one or more apertures each of which directs a small spot of

Methods and apparatus for producing small, bright nanometric light sources from apertures that are smaller than the wavelength of the emitted light. Light is directed at a surface layer of metal onto a light barrier structure that includes one or more apertures each of which directs a small spot of light onto a target. The incident light excites surface plasmons (electron density fluctuations) in the top metal surface layer and this energy couples through the apertures to the opposing surface where it is emitted as light from the apertures or from the rims of the apertures. Means are employed to prevent or severely limit the extent to which surface plasmons are induced on the surface at the aperture exit, thereby constraining the resulting emissions to small target areas. The resulting small spot illumination may be used to increase the resolution of microscopes and photolithographic processes, and to increase the storage capacity and performance of optical data storage systems.

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1. Apparatus for directing electromagnetic energy onto a target in a small area of illumination, said apparatus comprising, in combination,a source of electromagnetic radiation,a substantially planar light barrier interposed between side source and said target, said light barrier defining a first el

1. Apparatus for directing electromagnetic energy onto a target in a small area of illumination, said apparatus comprising, in combination,a source of electromagnetic radiation,a substantially planar light barrier interposed between side source and said target, said light barrier defining a first electrically conductive surface on the side of said barrier exposed to incident radiation from said source and further defining a second surface on the opposite side of said barrier, said second surface being positioned adjacent to said target, said first electrically conductive surface of said light barrier being formed by a layer of conductive metal having a thickness greater than the skin depth of said metal at the frequency of said electromagnetic radiation, and said light barrier further comprising a barrier material that is opaque to the transmission of said electromagnetic radiation, said barrier material being positioned between said layer of conductive metal and said second surface, said conductive metal and said barrier material having significantly different dielectric properties,one or more apertures through said light barrier, each of said apertures passing from said first surface to said second surface through said layer of conductive metal and through said barrier material, each of said apertures having a width in at least one dimension that is smaller than one wavelength of said electromagnetic radiation,wherein said barrier material confines the extent of the electronic excitation induced in said second surface to the portion of said second surface that is near each of said apertures. 2. Apparatus as set forth in claim 1 wherein said layer of conductive metal extends into the interior side walls of each of said apertures terminating at said second surface in a limited area in the vicinity of each of said apertures. 3. Apparatus as set forth in claim 1 wherein said target is an optical data storage medium. 4. Apparatus as set forth in claim 1 wherein said target is a sample placed between the objective lens of a microscope and said second surface. 5. Apparatus as set forth in claim 1 wherein said target is a photoresist, which is exposed by said electromagnetic radiation in a lithographic process. 6. Apparatus as set forth in claim 1 further including a confined annular conductive area at said second surface surrounding each of said apertures whereby surface excitations at said second surface are confined to the vicinity of each of said apertures. 7. Apparatus as set forth in claim 6 wherein a layer of conductive metal is positioned at said second surface and a groove is formed in said layer of conductive metal surrounding each of said apertures to define said confined conductive area. 8. Apparatus as set forth in claim 1 wherein said barrier material is a dielectric that exhibits a bandgap that is larger than the frequency of said electromagnetic radiation. 9. Apparatus as set forth in claim 8 wherein said electrically conductive surface is constructed of a layer of a first metal and wherein said barrier material is composed of a dielectric and a different metal characterized in that said conductive surface and said barrier material have substantially different resonances. 10. Apparatus as set forth in claim 1 wherein said electrically conductive surface is constructed of a layer of a first metal and wherein said barrier material is a different metal characterized in that said conductive surface and said barrier material have substantially different resonances. 11. Apparatus as set forth in claim 10 wherein said layer of conductive metal extends into the interior side walls of each of said apertures terminating at said second surface in a limited area in the vicinity of each of said apertures. 12. Apparatus as set forth in claim 10 further including a confined annular conductive area at said second surface surrounding each of said apertures whereby surface excitations at said second are surface confined to the vicini ty of each of said apertures. 13. Apparatus as set forth in claim 12 wherein a layer of conductive metal is positioned at said second surface and a groove is formed in said layer of conductive metal surrounding each of said apertures to define said confined conductive area. 14. A device for directing small areas of illumination onto a target comprising, in combination,a source of electromagnetic radiation,a substantially planar dielectric light barrier positioned between said source and said target, said light barrier being opaque to said electromagnetic radiation and defining a first surface facing said source and a second surface facing said target,a layer of metal affixed to said first surface of said light barrier, andan array of one or more apertures passing through said layer of metal and said light barrier, each of said apertures having a width in at least one direction which is shorter than the wavelength of said electromagnetic radiationwhereby the electronic excitation induced in said second surface by electromagnet radiation passing through said apertures is confined to the portion of said second surface that is near each of said apertures. 15. The device set forth in claim 14 wherein light barrier has a thickness on the order of 200 nm. 16. The device set forth in claim 14 wherein said light barrier is selected from a group of dielectric materials including germanium, silicon dioxide, silicon nitride, alumina, and chromia. 17. The device set forth in claim 14 wherein each of said one or more apertures has a width in at least one direction that is between 10 nm and the dimension defined by the Rayleigh criterion for said frequency of electromagnetic radiation. 18. The device set forth in claim 14 wherein said layer of metal has a thickness at least as large as the skin depth of said metal at the frequency of said electromagnetic radiation. 19. The device set forth in claim 14 wherein said metal is selected from a group consisting of gold, silver, aluminum, beryllium, rhenium osmium, potassium, rubidium, cesium, rhenium oxide, tungsten oxide, and copper. 20. The device set forth in claim 14 wherein each of said apertures in said array is a slit having a long dimension and a shorter width dimension, said shorter width dimension being smaller than the wavelength of said radiation. 21. The method of directing electromagnetic radiation from a source to a small area of illumination on a target, which comprises, in combination, the steps of:interposing a radiation barrier between said source and said target, said radiation barrier comprising the combination of a substantially planar dielectric material that is opaque to said electromagnetic radiation defining a first surface closest to said source and an opposing surface closest to said target and a layer of electrically conductive metal covering said first surface, said radiation barrier having an array of apertures therethrough, each of said apertures passing through said layer of electrically conductive metal and through dielectric material to permit radiation to pass from said first surface to said opposing surface to excite only a confined annular area of said opposing surface surrounding each of said apertures,activating said source to direct said radiation from said source onto said layer of electrically conductive metal to induce surface excitations in said layer of metal, andpositioning said aperture adjacent to said target such that electromagnetic energy passing through said aperture induces surface excitations at said opposing surface only in said confined annular area to illuminate said target with said small area of illumination. 22. The method of claim 21 wherein said material that is opaque to said electromagnetic radiation is a dielectric having a bandgap that is larger than the frequency of said electromagnetic radiation. 23. The method of claim 21 wherein said material that is opaque to said electromagnetic radiation is metallic material different from s aid electrically conductive metal and having a substantially different resonance.