Fiber optic probe and method of making same

Claim 2

A fiber optic probe adapted for use as a signal collector and illuminator in Near Field Scanning Optical Microscopy (NSOM), Photon Scanning Tunneling Microscopy (PSTM), said probe comprising: (a) an optical fiber of a type characterized by a core and cladding and comprising a tip portion, a tapered portion diverging therefrom and a transmission fiber portion; (b) said tip portion having a radius being sufficiently small to ensure single-mode operation for bare glass fibers or to be below cutoff of a lowest order mode for metal clad fibers; and (c) said transmission fiber portion comprising a multimoded fiber with a V m >10 and an NA>0.13, wherein: V m =mode volume NA=numerical aperture; whereby enhanced resolution and signal-to-noise ratio (SNR) can be achieved by said probe.

Claim 3

A fiber optic probe according to claim 1 wherein said tip radius is defined by equations ρ≦λ/20 and ρ≦λ/5 for bare glass and metal clad fibers, respectively, wherein: ρ=optical fiber core radius λ=source vacuum wavelength.

Claim 4

A fiber optic probe according to claim 1 wherein said tapered portion has an optimum taper angle defined by equation ##EQU12## and by equation ##EQU13## wherein: θ t =optimum fiber taper angle θ c =optimum fiber critical angle.

Claim 5

A fiber optic probe according to claim 1 wherein said optical fiber core comprises silica or doped-silica glass.

Claim 6

A fiber optic probe according to claim 4 wherein a core of the transmission fiber portion of said probe comprises a diameter of less than or equal to 100 microns.

Claim 7

A fiber optic probe according to claim 1 wherein a metal cladding is provided around at least a portion of the tapered portion and the tip portion of said optical fiber.

Claim 8

A fiber optic probe adapted for use as a signal collector and illuminator in Near Field Scanning Optical Microscopy (NSOM), Photon Scanning Tunneling Microscopy (PSTM), said probe comprising: (a) an optical fiber of a type characterized by a silica or doped-silica glass core and a cladding therearound and comprising a tip portion, a tapered portion diverging therefrom and a transmission fiber portion; (b) said tip portion having a radius being sufficiently small to ensure single-mode operation for bare glass fibers or to be below cutoff of a lowest order mode for metal clad fibers; (c) said transmission fiber portion comprising a multimoded fiber with a V m >10 and an NA>0.13, wherein: V m =mode volume NA=numerical aperture; and (d) said tapered portion defining an optimum taper angle defined by an equation ##EQU14## and by an equation ##EQU15## wherein: θ t =optimum fiber taper angle θ c =optimum fiber critical angle; whereby enhanced resolution and signal-to-noise ratio (SNR) can be achieved by said probe.

Claim 9

A fiber optic probe adapted for use as a signal collector and illuminator in Near Field Scanning Optical Microscopy (NSOM), Photon Scanning Tunneling Microscopy (PSTM), said probe comprising: (a) an optical fiber of a type characterized by a silica or doped-silica glass core and a cladding therearound and comprising a tip portion, a tapered portion diverging therefrom and a transmission fiber portion; (b) said tip portion having a radius being sufficiently small to ensure single-mode operation for bare glass fibers or to be below cutoff of a lowest order mode for metal clad fibers; (c) said transmission fiber portion comprising a multimoded fiber with a V m >10 and an NA>0.13, wherein: V m =mode volume NA=numerical aperture; and (d) said tapered portion defining an optimum taper angle defined by an equation ##EQU14## and by an equation ##EQU15## wherein: θ t =optimum fiber taper angle θ c =optimum fiber critical angle; whereby enhanced resolution and signal-to-noise ratio (SNR) can be achieved by said probe.

Claim 10

A fiber optic probe according to claim 1 wherein said tip radius is defined by equations ρ≦λ/20 and ρ≦λ/5 for bare glass and metal clad fibers, respectively, wherein: ρ=optical fiber core radius λ=source vacuum wavelength.

Claim 11

A fiber optic probe according to claim 7 wherein a core of the transmission fiber portion of said probe comprises a diameter of less than or equal to 100 microns.

Claim 12

A fiber optic probe according to claim 7 wherein a metal cladding is provided around at least the tapered portion and the tip portion of said optical fiber.

Claim 15

A method of making a fiber optic probe according to claim 11 further comprising the step of defining said tip radius by the equations ρ≦λ/20 and ρ≦λ/5 for bare glass fiber and metal clad fiber, respectively, wherein: ρ=optical fiber core radius λ=source vacuum wavelength.

Claim 16

A method of making a fiber optic probe according to claim 11 wherein said tapered portion defines an optimum taper angle defined by an equation ##EQU16## and by an equation ##EQU17## wherein: θ t =optimum fiber taper angle θ c =optimum fiber critical angle.

Claim 17

A method of making a fiber optic probe according to claim 13 wherein said optical fiber core comprises silica or doped-silica glass.

Claim 18

A method of making a fiber optic probe according to claim 14 wherein a core of the transmission fiber portion of said probe comprises a diameter of less than or equal to 100 microns.

Claim 19

A method of making a fiber optic probe according to claim 13 wherein a metal cladding is provided around at least a portion of the tapered portion and the tip portion of said optical fiber.