Near-field light-emitting element and optical head

Abstract

A near-field light-emitting element includes a transparent medium having a plane of incidence into which a laser beam enters, and a light-condensing plane on which the laser beam having entered the plane of incidence is concentrated, and a metal body provided on the light-condensing plane of the transparent medium having a first surface contacting the light-condensing plane, a second surface opposing the first surface, and an aperture which is formed to penetrate through the first and second surfaces at a position where the laser beam is concentrated and which emits a near-field light obtained from the laser beam. The metal body is arranged apart from a center of the aperture by a predetermined distance to connect together the first and second surfaces, and has a plasmon reflection plane that reflects toward the aperture a surface plasmon excited on the first and second surfaces by the laser beam concentrated at the aperture.

1 . A near-field light-emitting element comprising:
 a transparent medium having:   a plane of incidence into which a laser beam enters; and a light-condensing plane on which the laser beam having entered the plane of incidence is concentrated; and a metal body provided on the light-condensing plane of the transparent medium having:   a first surface contacting the light-condensing plane;   a second surface opposing the first surface; and   an aperture which is formed to penetrate through the first surface to the second surface at a position where the laser beam is concentrated and which emits a near-field light obtained from the laser beam, wherein   the metal body is arranged apart from a center of the aperture by a predetermined distance to connect together the first surface and the second surface, and has a plasmon reflection plane that reflects toward the aperture a surface plasmon excited on the first and second surfaces by the laser beam concentrated at the aperture.   
     
     
         2 . The near-field light-emitting element according to  claim 1 , wherein
 a distance from the center of the aperture of the metal body to the plasmon reflection plane corresponds to a resonance wavelength, or thereabouts, of the surface plasmon excited by the metal body.   
     
     
         3 . The near-field light-emitting element according to  claim 1 , wherein
 a distance from the center of the aperture of the metal body to the plasmon reflection plane is greater than or equal to a radius of a light spot of the laser beam concentrated at the metal body.   
     
     
         4 . The near-field light-emitting element according to  claim 1 , wherein
 the aperture of the metal body has a size equal to a wavelength of the laser beam or less.   
     
     
         5 . The near-field light-emitting element according to  claim 1 , wherein
 the aperture of the metal body is formed in a shape of a slit from an outer brim of one of the first and second surfaces to an outer brim of the remaining surface.   
     
     
         6 . The near-field light-emitting element according to  claim 1 , wherein
 the metal body assumes a circular outer shape, and an edge surface forming the outer shape is taken as the plasmon reflection plane.   
     
     
         7 . The near-field light-emitting element according to  claim 1 , wherein
 the metal body assumes a rectangular outer shape, and an edge surface forming the outer shape is taken as the plasmon reflection plane.   
     
     
         8 . The near-field light-emitting element according to  claim 1 , wherein
 the metal body assumes an essentially circular or rectangular shape centered on the aperture and has a slit penetrating through the first surface to the second surface, and   an inner wall surface of the slit is taken as the plasmon reflection plane.   
     
     
         9 . The near-field light-emitting element according to  claim 8 , wherein
 a distance from the center of the aperture to the wall surface of the slit corresponds to a resonance wavelength, or thereabouts, of the surface plasmon excited by the metal body.   
     
     
         10 . The near-field light-emitting element according to  claim 1 , wherein
 the metal body assumes an essentially concentric or rectangular shape centered on the aperture and has a plurality of slits penetrating almost through the first and second surfaces, and   inner wall surfaces of the plurality of slits are taken as the plasmon reflection planes.   
     
     
         11 . The near-field light-emitting element according to  claim 10 , wherein
 a distance from the center of the aperture to an inner wall surface of the innermost slit among the plurality of slits corresponds to a resonance wavelength, or thereabouts, of the surface plasmon excited by the metal body.   
     
     
         12 . The near-field light-emitting element according to  claim 1 , wherein
 the plane of incidence has a spherical plane into which the laser beam is concentrated by a light-condensing optical system enters.   
     
     
         13 . The near-field light-emitting element according to  claim 1 , wherein
 the transparent medium has a reflection plane which reflects the laser beam having entered the plane of incidence to converge at the light-condensing plane.   
     
     
         14 . The near-field light-emitting element according to  claim 13 , wherein
 the reflection plane is formed through use of a portion of a spheroid or a paraboloid of revolution.   
     
     
         15 . The near-field light-emitting element according to  claim 1 , wherein
 the metal body has a minute metal body at the center of the aperture, and   a shape of a coaxial-type aperture is formed by the aperture and the minute metal body.   
     
     
         16 . The near-field light-emitting element according to  claim 1 , wherein
 the metal body has a protuberance section projecting into the aperture from a brim thereof.   
     
     
         17 . The near-field light-emitting element according to  claim 1 , wherein the aperture of the metal body assumes a rectangular shape, and
 the laser beam concentrated at the light-condensing plane of the transparent medium is to be polarized perpendicular to a longitudinal direction of the aperture.   
     
     
         18 . The near-field light-emitting element according to  claim 1 , wherein
 a thickness of the metal body is smaller than a wavelength of the laser beam, and is sufficient to block the laser beam.   
     
     
         19 . An optical head comprising:
 a transparent medium having:   a plane of incidence into which a laser beam enters; and   a light-condensing plane on which the laser beam having entered the plane of incidence is concentrated; and   a metal body provided on the light-condensing plane of the transparent medium having:   a first surface contacting the light-condensing plane;   a second surface opposing the first surface; and   an aperture which is formed to penetrate through the first and second surfaces at a position where the laser beam is concentrated and which emits a near-field light obtained from the laser beam, wherein   the metal body is arranged apart from a center of the aperture by a predetermined distance to connect together the first surface and the second surface, and has a plasmon reflection plane that reflects toward the aperture a surface plasmon excited on the first and second surfaces by the laser beam concentrated at the aperture.