Near field scanning optical microscope having a tapered waveguide
First Claim
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1. An optical system, comprising:
- a probe, at least a portion of which is optically transmissive at least at a given wavelength, the probe having a longitudinal axis and a distal end;
an optical aperture defined in the distal end, the aperture having at least one dimension smaller than the given wavelength;
means for optically coupling a light source to the probe such that at least some electromagnetic radiation emitted by the source, at least at the given wavelength, enters or exits the probe through the aperture; and
means for displacing the probe relative to an object,CHARACTERIZED IN THATa) the probe comprises a portion of an optical waveguide having a core and a cladding, the cladding having an outer surface, there being associated with the waveguide at least one guided dielectric mode for radiation of the given wavelength;
b) the waveguide has a taper region that is adiabatically tapered, at least a portion of the taper region being capable of guiding radiation of at least the given wavelength, the taper region having a taper length and a taper angle;
c) the taper region terminates in a substantially flat end face oriented in a plane substantially perpendicular to the longitudinal axis, the aperture being defined in or adjacent the end face;
d) the cladding outer surface in the taper region is substantially smooth;
e) at least a portion of the waveguide in the taper region is coated with an opaque material which has a relatively small penetration depth for electromagnetic radiation of the given wavelength, defining a metallic waveguide portion capable of guiding a metallic mode of radiation of the given wavelength; and
f) the taper angle and taper length are adapted such that radiation propagating in the taper region is substantially interconverted between the dielectric and metallic modes.
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Abstract
An optical system useful, e.g., for near-field scanning optical microscopy is provided. The system incorporates a probe having improved properties. In one embodiment, the probe comprises a tapered and partially metallized portion of a single-mode optical fiber.
130 Citations
15 Claims
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1. An optical system, comprising:
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a probe, at least a portion of which is optically transmissive at least at a given wavelength, the probe having a longitudinal axis and a distal end; an optical aperture defined in the distal end, the aperture having at least one dimension smaller than the given wavelength; means for optically coupling a light source to the probe such that at least some electromagnetic radiation emitted by the source, at least at the given wavelength, enters or exits the probe through the aperture; and means for displacing the probe relative to an object, CHARACTERIZED IN THAT a) the probe comprises a portion of an optical waveguide having a core and a cladding, the cladding having an outer surface, there being associated with the waveguide at least one guided dielectric mode for radiation of the given wavelength; b) the waveguide has a taper region that is adiabatically tapered, at least a portion of the taper region being capable of guiding radiation of at least the given wavelength, the taper region having a taper length and a taper angle; c) the taper region terminates in a substantially flat end face oriented in a plane substantially perpendicular to the longitudinal axis, the aperture being defined in or adjacent the end face; d) the cladding outer surface in the taper region is substantially smooth; e) at least a portion of the waveguide in the taper region is coated with an opaque material which has a relatively small penetration depth for electromagnetic radiation of the given wavelength, defining a metallic waveguide portion capable of guiding a metallic mode of radiation of the given wavelength; and f) the taper angle and taper length are adapted such that radiation propagating in the taper region is substantially interconverted between the dielectric and metallic modes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An optical system, comprising:
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a probe, at least a portion of which is optically transmissive at least at a given wavelength, the probe having a longitudinal axis and a distal end; an optical aperture defined in the distal end, the aperture having at least one dimension smaller than the given wavelength; a source of electromagnetic radiation capable of stimulating an object to emit fluorescent light at least at the given wavelength; means for supporting the object relative to the radiation source and the probe such that at least a portion of the radiation emitted by the source impinges on the object and at least a portion of the fluorescent light emitted by the object enters the probe through the optical aperture; and means for displacing the probe relative to the object, CHARACTERIZED IN THAT a) the probe comprises a portion of an optical waveguide having a core and a cladding, the cladding having an outer surface, there being associated with the waveguide at least one guided dielectric mode for radiation of the given wavelength; b) the waveguide has a taper region that is adiabatically tapered, at least a portion of the taper region being capable of guiding light of at least the given wavelength, the taper region having a taper length and a taper angle; c) the taper region terminates in a substantially flat end face oriented in a plane substantially perpendicular to the longitudinal axis, the aperture being defined in or adjacent the end face; d) the cladding outer surface in the taper region is substantially smooth; e) at least a portion of the waveguide in the taper region is coated with an opaque material which has a relatively small penetration depth for electromagnetic radiation of the given wavelength, defining a metallic waveguide portion capable of guiding a metallic mode of radiation of the given wavelength; and f) the taper angle and taper length are adapted such that radiation propagating in the taper region is substantially interconverted between the dielectric and metallic modes.
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Specification