JP3260300B2 - Optical fiber probe and method for manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber probe used as an optical probe for detecting or irradiating evanescent light in, for example, a near-field optical microscope which is one of probe scanning microscopes, and a method of manufacturing the same.

[0002]

2. Description of the Related Art The resolution of an image obtained by an ordinary optical microscope is limited by the wavelength of light used (diffraction limit).

On the other hand, in a near-field optical microscope equipped with a probe having a structure that is smaller than the wavelength of light, that is, a nanometer-sized structure, an optical image can be obtained with a resolution exceeding the wavelength of light. Therefore, by utilizing this near-field optical microscope technology, it is possible to measure the shape and spectroscopic measurement of an object such as a biological sample, a semiconductor sample, an optical memory material, a photosensitive material, and the like with a resolution of the order of nanometers, and further, perform a memory operation ( Write / read / erase), optical processing, and the like.

An example of a near-field optical microscope is shown in FIG.
Shown in This microscope is a near-field optical microscope called a collection mode, which measures the shape of an object by detecting evanescent light localized in an extremely close area where the distance from the object surface is smaller than the wavelength of light. Things.

[0005] Specifically, evanescent light 15 generated by irradiating an object with laser light under total reflection conditions.
0 is scattered by the tip of the sharpened portion 151 having a nanometer size of the probe 152. In the microscope shown in this figure, the probe is formed of an optical fiber, and the light scattered by the sharpened portion 151 of the probe 152 is guided to the core of the optical fiber through the sharpened portion. Then, the light guided into the core is emitted from the other end (emission end) of the optical fiber, and is detected by the detector. Then, at this time, a two-dimensional image of the detection light can be obtained by scanning the probe on the object.

As the optical fiber probe 52 used in this near-field optical microscope, as shown in FIG. 45, a tip 151a of a sharpened portion 151 formed in a conical shape having a nanometer size (a so-called tip probe) is used. In addition, as shown in FIG. 46, a material in which a light-shielding coating layer 154 made of metal or the like is formed except for the tip of the sharp portion 151 (a so-called aperture probe ) can also be used. This opening
In the probe , the transmission of the scattered light is blocked at the portion where the light-shielding coating layer 154 is formed, and the scattered light is selectively transmitted from the tip where the light-shielding coating layer 154 is not formed. That is, the tip where the light-shielding coating layer 155 is not formed becomes the scattered light opening 154a, and the opening 154a is used as the above-described optical fiber probe in a size of nanometer.

The near-field optical microscope described above collects evanescent light generated on an object by a probe, and is called a collection mode.

In addition, the near-field optical microscope includes an illumination mode in which an object is locally illuminated by evanescent light generated at the tip of the probe to obtain an optical image, and an object evanescent light generated at the tip of the probe. There is known an illumination correction mode in which light is locally illuminated and light scattered by the tip of the probe is detected through the probe.

Incidentally, the phenomenon of energy transfer between an object and a probe in such a near-field optical microscope is as follows.
It is understood as a short-range interaction between their polarizations. The conditions under which an effective interaction between the object and the probe occurs include, first, the size of the object and the probe are close,
The distance between the object and the probe is smaller than the size of the probe. Here, the size of the probe means a tip diameter in the case of a tip probe and an opening diameter in the case of an open probe. Therefore, in order to obtain high resolution in the near-field optical microscope, the tip diameter and the aperture diameter of these probes are very important.

In the case of a tip probe, the sharpened portion 151 is formed by immersing one end of an optical fiber in a chemical etching solution and sharpening the one end in a conical shape from the outer periphery to the center.

At this time, in order to obtain a probe with a small tip diameter and high resolution, it is necessary to make the sharp angle θ of the sharp portion 151 as small as possible and to form a sharp shape. However, as the acute angle θ decreases, the loss of light at the sharp portion 151 increases, and the transmission efficiency decreases. For this reason, the sharp angle θ cannot be reduced indiscriminately, and there is a limit in improving the resolution.

On the other hand, the aperture probe is formed by forming a conical sharpened portion 151 at one end of an optical fiber and then forming a light-shielding coating layer 154 except for the tip of the sharpened portion 151 by, for example, a vacuum evaporation method. A portion 154a is formed.

In such an aperture probe, light is emitted in a region where the cross-sectional diameter of the sharp portion 151 is equal to or less than the wavelength (hereinafter, the dimension from the tip to the position where the cross-sectional diameter becomes equal to the wavelength is referred to as a chip length L). Is remarkably absorbed by the metal, and the transmission efficiency decreases. For this reason, in order to secure transmission efficiency, it is necessary to increase the acute angle θ of the sharp portion 151 to shorten the chip length L. However, when the acute angle θ is increased, the thickness of the light-shielding coating layer near the opening of the light-shielding coating layer 155 decreases. Since the light is not sufficiently shielded at the thin portion, the substantial aperture diameter becomes large, causing a problem that the resolution is reduced.

[0014]

As described above, the tip probe and the aperture probe sharpened by the conventional methods are difficult to achieve both transmission efficiency and resolution.

Therefore, the present invention has been proposed in view of such a conventional situation, and an object of the present invention is to provide an optical fiber probe having high transmission efficiency and high resolution, and a method of manufacturing the same.

[0016]

In order to achieve the above-mentioned object, a method for manufacturing an optical fiber probe according to the present invention is directed to an optical fiber in which a clad is provided around a core. A first sharpening step of projecting one end of the core from the clad by etching and sharpening the one end in a conical shape, and a conical sharpening process. One end of the core is sharpened such that the inclination angle of the core is changed in two stages by etching so that the inclination angle of the tapered surface on the tip side is smaller than the inclination angle of the next tapered surface, and the rear end of the next tapered surface Side cross section diameter
Be longer than the wavelength of light, and cut off the rear end of the tapered surface on the front end.
A second sharpening step of forming a sharpened portion having a surface diameter equal to or smaller than the wavelength of light .

Further, in the method of manufacturing an optical fiber probe according to the present invention, the one end of the first clad of the optical fiber having the first clad and the second clad provided around the core is inclined from the outer periphery to the inner periphery. A step of forming a slant portion to be formed, a first sharpening step of projecting one end of the core from the first clad by etching and sharpening the one end in a conical shape, and a conical sharpening process. One end of the core is sharpened by etching so that the inclination angle is changed in two stages so that the inclination angle of the tapered surface on the tip side is smaller than the inclination angle of the next tapered surface. The diameter of the end section is the wavelength of light.
And the diameter of the cross section on the rear end side of the tapered surface on the front end side
And a second sharpening step of forming a sharpened portion having a wavelength equal to or less than the wavelength of light .

Further, in the method of manufacturing an optical fiber probe according to the present invention, there is provided an optical fiber having a second core and a clad provided around a first core. A step of forming a portion, and one end of the first core and the second core are made to protrude from the clad by etching, and the inclination angle is changed in two steps so that the inclination angle of the tapered surface on the tip side becomes It is sharpened so as to be smaller than the inclination angle of the tapered surface, and the diameter of the cross section on the rear end side of the next tapered surface is changed to light.
And a section at the rear end side of the tapered surface on the front end side.
And a sharpening step of forming a sharpened portion having a diameter equal to or less than the wavelength of light . Further, the optical fiber probe according to the present invention comprises an optical fiber in which a clad is provided around a core made of pure quartz (SiO ₂ ) , and one end of the core sharpened in a conical shape is inclined.
By changing the angle of inclination in two steps, the inclination angle of the tapered surface on the tip
Sharpened so that it is smaller than the inclination angle of the next tapered surface
The diameter of the cross section on the rear end side of the next tapered surface is the wavelength of light.
And the straight section of the rear end side of the tapered surface on the front end side.
It has a sharp portion whose diameter is equal to or less than the wavelength of light, a light-shielding coating layer is formed except for the tip of the sharp portion, and the tip of the sharp portion has an opening exposed from the light-shielding coating layer. Features.

In the optical fiber probe manufactured by the above-described steps, a sharpened portion is formed at three inclination angles. In an optical fiber probe having a sharpened portion sharpened at these three inclination angles, an effective angle is obtained by setting the inclination angle of the first stage from the tip side of the sharpened portion, that is, the inclination angle of the foremost portion to a small angle. The aperture diameter is reduced and the resolution is improved. Further, by setting the inclination angle of the second stage from the tip side to a large angle, the light transmission efficiency can be sufficiently ensured. Therefore, in this optical fiber probe,
High resolution can be obtained while sufficiently obtaining light transmission efficiency.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

An optical fiber manufactured by the manufacturing method of the present invention.
The inverted probe has a sharpened portion 1 as shown in FIG. 1 formed at one end of an optical fiber, and detects or irradiates light from the tip 1a of the sharpened portion 1, or a so-called tip probe, or FIGS. A so-called aperture probe in which a light-shielding coating layer 5 is formed in a portion excluding the tip of the sharpened portion 1 and light is detected or irradiated from the opening at the tip where the light-shielding coating layer 5 is not formed as shown in FIG. It is.

In the optical fiber probe manufactured by the present invention, in particular, as shown in FIG. 1, the sharpened portion 1 is sharpened by changing the inclination angle in three stages. Hereinafter, the three surfaces having the respective inclination angles of the sharp portion are respectively referred to as the first surfaces from the distal end side.
, The second tapered surface 3 and the third tapered surface 4 of the optical fiber, and the angle of each of the tapered surfaces 2, 3, 4 and the inclined portion with respect to the central axis of the optical fiber is an inclination angle. Twice is called the acute angle. In addition, this optical fiber probe
The diameter d ₁ of the cross section on the rear end side of the first tapered surface 2 is desirably equal to or smaller than the wavelength λ of the light to be propagated, and the diameter d ₂ of the cross section on the rear end side of the second tapered surface 3 is transmitted. The wavelength is preferably equal to or longer than the wavelength λ of the light.

Hereinafter, a method for manufacturing such an optical fiber probe will be described.

First, the tip probe comprises a cladding inclining step of forming an inclined portion which is inclined from the outer circumference to the inner circumference at one end of the fiber cladding, and one end of the core is made to project from the cladding by etching and this end is made conical. A first sharpening step for sharpening, and one end of the conical sharpened core is etched to reduce the inclination angle to 2 degrees.
It is manufactured by a second sharpening step in which sharpening is performed by changing the stages.

The specific manufacturing method will be described below.

First Manufacturing Example In this first manufacturing example, an optical fiber probe is manufactured from an optical fiber 10 having a clad 12 provided around a core 11 as shown in FIG.

First, an inclined portion 13 as shown in FIG. 6 is formed on the cladding 12 of the optical fiber by using a meniscus of an etching solution.

In order to form the inclined portion 13, a floating layer is floated by dropping a liquid having a lower specific gravity than the etching solution into the etching solution, and the optical fiber 10 is placed therein.
Insert The floating layer is for preventing the evaporation of the etching solution, and for example, an organic solution such as low-viscosity dimethyl silicone oil is used.

When the optical fiber 10 is inserted into the etching solution in which the floating layer is floated, a meniscus of the etching solution having a height around the optical fiber 10 is formed.

The diameter of the optical fiber 10 thus inserted into the etching solution is reduced by the etching of the clad 12 in contact with the etching solution. At this time, the height of the meniscus of the etchant formed around the optical fiber 10 becomes lower as the diameter of the optical fiber 10 decreases, so that the position corresponding to the initial height of the meniscus is in contact with the etchant. Is shorter, and the lower the time, the longer the time of contact with the etching solution. Therefore, as shown in FIG. 6, below the position corresponding to the initial height S of the meniscus, the diameter decreases as it goes down, and an inclined portion 13 that is inclined from the outer periphery toward the inner periphery is formed. Since the inclination angle ω _{1/2 of the} inclined portion 13 with respect to the fiber central axis depends on the type of liquid used for the floating layer, the inclination angle ω _1/2 can be controlled by selecting the liquid. For example, the inclination angle omega _1/2 in the case of using the low viscosity dimethylsilicone oil floating layer 2
0 °.

After the inclined portion 13 is formed in the clad in this manner, one end of the core 11 is projected from the clad 12 and the one end is sharpened conically as shown in FIG. .

In the first sharpening step, the etching is performed under the etching conditions such that R ₁₂ <R ₂₂ when the etching rate of the core is R ₁₂ and the etching rate of the clad is R ₂₂ .

When one end of the optical fiber having the inclined portion 13 formed in the clad 12 in the previous step is immersed in an etching solution having such an etching rate, the optical fiber 10
In the tip side since the etching rate R ₂₂ of the cladding 12 is greater than the etching rate R ₁₂ of the core 11, toward the cladding 12 is etched before the core 11, the core 1
1 protrudes from the cladding 12.

On the outer peripheral surface side of the optical fiber 10, the clad 12 exposed on the outer peripheral surface is etched, and by the etching of the clad 12, the outer peripheral surface of the core 11 starts to be exposed from the distal end side. The core 11 exposed on the outer peripheral surface is also etched. At this time, since the outer peripheral surface of the core 11 is exposed from the front end side, the etching amount increases toward the front end side, and the diameter decreases. Therefore, by continuing this etching for a certain period of time, a conical sharp portion 14 protruding from the clad 12 is formed at one end of the core 11 as shown in FIG. The sharp angle ψ ₁ of the sharp portion 14 is determined by the etching speeds R ₁₂ and R ₂₂ and the inclination angle ω _1/2 of the inclined portion of the clad.
And is represented by the following equation:

[0035] _{sin (ψ 1/2) =} R 12 / R 22 · sin (ω 1/2) Next, the core 11 is sharpened conically in this way
Is sharpened by changing the inclination angle in two stages in a second sharpening step as shown in FIG.

In the second sharpening step, the etching is performed under the etching conditions such that R ₁₃ > R ₂₃ when the etching rate of the core is R ₁₃ and the etching rate of the clad is R ₂₃ .

In the etching solution having such an etching rate, the conical sharp portion 14 is formed on the core 11 in the previous step.
When one end of the optical fiber 10 on which the optical fiber 10 is formed is immersed, since the etching rate of the core 11 is higher than the etching rate of the clad 12 on the distal end side of the optical fiber 10, the length of the distal end of the core 11 protruding from the clad 12 gradually increases. It becomes shorter. Further, on the outer peripheral surface side of the optical fiber 10, the core 11 already exposed on the outer peripheral surface is etched, and the outer peripheral surface of the core 11 is newly exposed and etched by etching the clad 12.
Even in the process of newly exposing the outer peripheral surface of the core 11, the outer peripheral surface of the core is exposed from the front end side. However, since the etching conditions in the second sharpening step are different from the etching conditions in the first sharpening step, the portion of the core 11 where the outer peripheral surface is already exposed and the outer peripheral surface are newly added in this step. The exposed portion has a different inclination angle. Therefore, as shown in FIG. 8, a first tapered surface 15 and a second tapered surface 16 having different inclination angles are formed on the core 11,
Also, a third tapered surface 17 is formed on the clad, and a sharpened optical fiber probe is manufactured by changing the inclination angle in three stages.

The acute angle α of the first tapered surface 15
And the diameter d ₁ of the cross section on the rear end side are the sharp angle ψ ₁ of the sharp portion 14 in the first sharpening step and the core 11 in the second sharpening step.
Determined by the etching rate R ₁₃ and etching time.

The acute angle β of the second tapered surface 16 can be obtained by the following equation.

[0040] sin (β / 2) = R 13 / R 23 · sin (ω 1/2) Further, the diameter d ₂ of the rear end side of the cross section of the second tapered surface 16
Is equal to the core diameter, and the inclination angle γ / 2 of the third tapered surface 17 is
Corresponds to the inclination angle ω _1/2 in the cladding inclination step.

As described above, in this manufacturing example, an optical fiber probe is manufactured from an optical fiber having a clad provided around a core. As the optical fiber, for example, one having the following material configuration is used.

Core: germanium dioxide-added quartz Clad: pure quartz In the case of an optical fiber having such a material composition, the following is suitable as an etchant used in each step.

Cladding inclination step: HF acid First sharpening step (R ₁₂ <R ₂₂ ): 40% by weight NH ₄ F
Aqueous solution: 50% by weight HF acid: H ₂ O (volume ratio) is 10:
1: 1 buffered hydrogen fluoride solution Second sharpening step (R ₁₃ > R ₂₃ ): 40 wt% NH ₄ F
Aqueous solution: 50% by weight HF acid: H ₂ O (volume ratio) is 10:
1: Y (however, Y> 30) or 1.7: 1: Y (however, Y> 1) buffered hydrogen fluoride solution Second Production Example In this second production example, as shown in FIG. An optical fiber probe is manufactured from a double clad optical fiber 20 in which a first clad 22 is provided around a core 21 and a second clad 23 is further provided therearound.

First, an inclined portion 24 as shown in FIG. 10 is formed in the first clad 22 by selective chemical etching of the first clad 22 and the second clad 23.

To form the inclined portion 24, the etching rate of the core 21 is R ₁₁ , the etching rate of the first cladding 22 is R ₂₁ , and the etching rate of the second cladding 23 is R 11.
Performing etching under the etching condition such that R ₁₁ = R ₂₁ <R ₃₁ is taken as _31.

When one end of the optical fiber is immersed in an etching solution having such an etching rate, the etching rate R ₃₁ of the second clad 23 is made larger than the etching rates R ₁₁ and R _{21 of the} core 21 and the first clad 22. Is larger than the first cladding 22 on the distal end side of the optical fiber 20.
The second clad 23 is etched before the core 21 and the core 21 and recedes from the base end face.

On the outer peripheral surface side of the optical fiber 20, the second clad 23 exposed on the outer peripheral surface is etched, and the second clad 23 is etched so that the outer peripheral surface of the first clad 22 is etched. The surface starts to be exposed from the front end side, and the first clad 22 exposed on the outer peripheral surface is also etched. At this time, since the outer peripheral surface of the first clad 22 is exposed from the front end side, the amount of etching increases toward the front end side, and the diameter decreases. Therefore, as shown in FIG. 10, the first clad 22 has an inclined portion 2 inclined from the outer peripheral portion to the inner peripheral portion.
4 are formed.

[0048] The inclination angle omega _2/2 of the inclined portion is determined by the etching rate R _21, R _31, is expressed by the following equation.

[0049] _{sin (ω 2/2) =} R 21 / R 31 after the formation of the inclined portion 24 to the first cladding 22 in this manner, the core 21 by a first sharpening process as shown in FIG. 11 One end is made to protrude from the first cladding 22 and this end is sharpened conically.

In the first sharpening step, the etching rate of the core 21 is R ₁₂ , the etching rate of the first clad 22 is R ₂₂ , and the etching rate of the second clad 23 is R 12.
When the ₃₂ etched in the etching conditions such that _{R 12 <R 22 <R 32} .

In the etching solution having such an etching rate, the inclined portion 2
4 is dipped one end of the optical fiber having a, the tip end of the optical fiber 20 is greater than the etching rate R ₂₂ of the etch rate R ₃₂ of the second cladding 23 is first clad 22, the first cladding 22 since the etching rate R ₂₂ greater than the etching rate R ₁₂ of the core 21, the second
Is etched before the first cladding 22 is formed. Then, the first cladding 22 is etched before the core 21, and the core 21 is
It protrudes from 2.

Further, on the outer peripheral surface side of the optical fiber 20, the outer peripheral surface of the first clad 22 is exposed from the distal end side by etching the second clad 23, and the first clad 22 is etched in the same process as described above. Is etched in an inclined manner. Then, as the first clad 22 is etched, the outer peripheral surface of the core 21 starts to be exposed from the tip side, and the core 21 exposed on the outer peripheral surface is also etched. At this time, since the outer peripheral surface of the core 21 is exposed from the front end side, the etching amount increases toward the front end side, and the diameter decreases. Therefore, by continuing this etching for a certain period of time, a conical sharp portion 25 protruding from the clad 22 is formed at one end of the core 21 as shown in FIG. In addition, the sharp angle ψ of the sharp portion 25
₂ is determined by the etching rate R _12, R ₂₂ and the inclination angle omega _2/2 of the inclined portion of the cladding is expressed by the following equation.

[0053] _{sin (ψ 2/2) =} R 12 / R 22 · sin (ω 2/2) or _{sin (ψ 2/2) =} R 12 / R 32 also of the inclined portion 24 of the first cladding 21 Tilt angle ω ₂ /
Relation 2 and the etching rate R _{2 2,} R ₃₂ is represented by the following formula.

[0054] sin (ω _2/2) = then R ₂₂ / R _32, the one end of the core 21 which is sharpened conically in this way, the inclination by the second sharpening step as shown in FIG. 12 Change the corner in two steps to sharpen it.

In the second sharpening step, the etching speed of the core 21 is R ₁₃ , the etching speed of the first cladding 22 is R ₂₃ , and the etching speed of the second cladding 23 is R ₁₃ .
R _13> R ₂₃ is taken as ₃₃ <etched with etching conditions such that R _33.

In the etching solution having such an etching rate, a conical sharp portion 25 is formed on the core 21 in the previous step.
When immersing the one end of the optical fiber 20 formed with, at the tip end of the optical fiber 20 is greater than the etching measure R ₂₃ of the etch rate R ₃₃ of the second cladding 23 is first clad 22, the first cladding 22 Etching rate R ₂₃
Is smaller than the etching rate R ₁₃ of the core 21, so that the distal end face of the second clad 23 further retreats with respect to the distal end face of the first clad 22. And the first cladding 2
The length of the sharpened portion of the core 20 protruding from 2 gradually decreases.

Further, on the outer peripheral surface side of the optical fiber, the outer peripheral surface of the first clad 22 is exposed from the distal end side by etching the second clad 23, and the first clad 22 is formed in the same process as described above. Etching is performed in an inclined manner.
Then, by etching the first cladding 22, the outer peripheral surface of the core 21 is newly exposed and etched. Even in the process of newly exposing the outer peripheral surface of the core 21, the outer peripheral surface of the core 21 is exposed from the front end side, so that the etching amount increases toward the front end side, and the shape becomes inclined. However, since the etching conditions in the second sharpening step are different from the etching conditions in the first sharpening step, the portion of the core 21 where the outer peripheral surface is already exposed and the outer peripheral surface are newly added in this step. The exposed portion has a different inclination angle. Therefore, as shown in FIG. 12, the core 21 has the first tapered surface 26 and the second tapered surface 2 having different inclination angles.
7 is formed, and the third tapered surface 2 is formed on the cladding 22.
8 is formed, and a sharpened optical fiber probe is manufactured by changing the inclination angle in three stages.

The acute angle α of the first tapered surface 26
And the diameter d ₁ of the section on the rear end side are the sharp angle ψ ₂ of the sharp portion 25 in the first sharpening step and the core 21 in the second sharpening step.
Determined by the etching rate R ₁₃ and etching time.

The acute angle β of the second tapered surface is obtained by the following equation.

[0060] sin (β / 2) = R 13 / R 23 · sin (ω 2/2) or sin (β / 2) = R 13 / R 33 In addition, the rear end side of the cross section of the second tapered surface 27 Diameter d ₂
Is equal to the core diameter, and the inclination angle γ / 2 of the third tapered surface 28 is
Corresponds to the tilt angle omega _2/2 in the clad inclined step. The relationship between the etching rate R _23, R ₃₃ at the tilt angle omega _2/2 third etching process is expressed by the following formula.

[0061] sin (ω _2/2) = In this production example R ₂₃ / R ₃₃ Thus, for manufacturing an optical fiber probe from the first clad and the second clad optical fiber which is provided around the core . As the optical fiber probe, for example, one having the following material configuration is used.

Core: Quartz doped with germanium dioxide First clad: Pure quartz Second clad: Quartz doped with fluorine In the case of an optical fiber having such a material composition, the following etchant is appropriate as an etchant used in each step. It is.

Clad tilting step (R ₁₁ = R ₂₁ <R ₃₁ ):
40 wt% NH ₄ F aqueous solution: 50 wt% HF acid: H ₂ O
A buffered hydrogen fluoride solution having a (volume ratio) of 1.7: 1: 1 First sharpening step (R ₁₂ <R ₂₂ <R ₃₂ ): 40% by weight N
H ₄ F aqueous solution: 50% by weight HF acid: H ₂ O (volume ratio) is 1
0: 1: 1 buffered hydrogen fluoride solution Second sharpening step (R ₁₃ > R ₂₃ <R ₃₃ ): 40% by weight
NH ₄ F aqueous solution: 50% by weight HF acid: H ₂ O (volume ratio) is 10: 1: Y (where Y> 30) or 1.7: 1:
Buffered hydrogen fluoride solution of Y (where Y> 1) Note that in this manufacturing example, the remaining state of the second clad can be controlled by the etching time in the clad tilting step. For example, if the etching time is set relatively short, an optical fiber probe in which the second clad remains can be obtained. Such an optical fiber probe in which the second cladding remains has a single mode in which light of a single wavelength mode propagates in the core and light of a plurality of waveguide modes propagates in the first cladding. -Can be used as a multimode fiber. Third Manufacturing Example In this third manufacturing example, an optical fiber probe is manufactured from an optical fiber in which a clad 32 is provided around a core 31 as shown in FIG.

First, an inclined portion is formed in the clad 32 by melt-drawing the optical fiber.

To form the inclined portion, as shown in FIG. 14, a part of the optical fiber 30 is melted by heating, and as shown in FIG. 15, both sides of the melted portion are pulled left and right. Stretch. Then, by further pulling the optical fiber 30, the optical fiber 30 is split into two as shown in FIG. The separated optical fiber 30 is
As shown in FIG. 17, an inclined portion 33 is formed in the clad 32 at one end portion that has been melt-drawn, and a shape is obtained in which a thread having a sharp angle is drawn on the tip end side of the inclined portion 33. In addition, the core 31 has a reduced diameter at the distal end portion due to being stretched, and has a shape in which the distal end surface is buried in the clad. It should be noted that the shape of the clad tip portion as if a thread had been drawn is removed by etching in the next step.

After the optical fiber is melt-drawn in this manner, one end of the core 31 is made to protrude from the clad 32 by a first sharpening step, and this one end is sharpened conically as shown in FIG.

In the first sharpening step, the etching is performed under the etching conditions such that R ₁₂ <R ₂₂ when the etching rate of the core 31 is R ₁₂ and the etching rate of the clad 32 is R ₂₂ .

When one end of the melt-stretched optical fiber 30 is immersed in an etching solution having such an etching rate, the clad 32 is etched on the distal end side of the optical fiber 30 and the distal end surface of the core 31 is exposed. come. After the tip surface of the core 31 is exposed, the cladding 3
Etching rate R 2 of the etching rate R ₂₂ is a core 31
_Since it is larger than ₁₂ , the cladding 32 is etched before the core 31, and the core 31 projects from the cladding 32.

On the outer peripheral surface side of the optical fiber 30, the clad 32 exposed on the outer peripheral surface is first etched. Then, the core 3 is etched by the cladding 32.
The outer peripheral surface of 1 starts to be exposed from the front end side, and the core 31 exposed on this outer peripheral surface is also etched. At this time, since the outer peripheral surface of the core 31 is exposed from the front end side, the amount of etching increases toward the front end side, and the diameter decreases. Therefore, by continuing this etching for a certain period of time, a conical sharpened portion 34 protruding from the clad is formed at one end of the core 31 as shown in FIG. The sharp angle ψ ₃ of the sharp portion 34 is determined by the etching rate R
_12, determined by the inclination angle omega _3/2 of the inclined portion of the R ₂₂ and the cladding is expressed by the following equation.

[0070] _{sin (ψ 3/2) =} R 12 / R 22 · sin (ω 3/2) Since the inclined portion 33 formed in the cladding 32 by melt-drawing the inclination angle enough to go upward becomes small, ω _3/2 with etching time is reduced. Therefore,
Also decreases with etch time earlier acute [psi ₃ of sharpened tip.

Next, one end of the core 31 sharpened conically in this manner is further sharpened by changing the inclination angle in two stages by a second sharpening step as shown in FIG.

In the second sharpening step, etching is performed under the etching conditions such that R ₁₃ > R ₂₃ when the etching rate of the core 31 is R ₁₃ and the etching rate of the clad 32 is R ₂₃ .

In the etching solution having such an etching rate, the conical sharp portion 34 is formed on the core 31 in the previous step.
When one end of the optical fiber 30 on which is formed is immersed, since the etching rate R ₁₃ of the core 31 is higher than the etching rate R _{23 of the} clad 32 on the tip side of the optical fiber 30,
The length of the core 31 protruding from the clad 32 gradually decreases. In addition, on the outer peripheral surface side of the optical fiber 30, the core 31 already exposed on the outer peripheral surface is etched, and the outer peripheral surface of the core 31 is newly exposed and etched by etching the clad 32.
However, in this etching, the portion where the outer peripheral surface is already exposed has a different inclination angle from the portion where the outer peripheral surface is newly exposed in this step.
1 has a first tapered surface 35 and a second tapered surface 36 having different inclination angles, and a clad 32 has a third tapered surface 37 formed therein. The manufactured optical fiber probe is manufactured.

The sharp angle α of the first tapered surface 35
And the diameter d ₁ of the cross section on the rear end side is determined by the acute angle ψ ₃ of the sharp portion 34 in the first sharpening step, the core etching rate R _{13 in} the second sharpening step, and the etching time.

The acute angle β of the second tapered surface 36 is obtained by the following equation.

[0076] sin (β / 2) = R 13 / R 23 · sin (ω 3/2) Further, the diameter d ₂ of the rear end side of the cross section of the second tapered surface 36 is reduced by the core diameter (melt drawing core diameter) and match after the inclination angle gamma / 2 of the third taper surface 37 corresponds to the inclination angle omega _3/2 in the clad inclined step.

As described above, in this manufacturing example, an optical fiber probe is manufactured from an optical fiber having a clad provided around a core. As the optical fiber, for example, one having the following material configuration is used.

Core: germanium dioxide-added quartz Clad: pure quartz In the case of an optical fiber having such a material composition, the following is suitable as an etching solution used in each step.

First sharpening step (R ₁₂ <R ₂₂ ): 40 wt% NH ₄ F aqueous solution: 50 wt% HF acid: H ₂ O (volume ratio) 10: 1: 1 buffered hydrogen fluoride solution Second sharpening step (R ₁₃ > R ₂₃ ): 40% by weight NH ₄ F
Aqueous solution: 50% by weight HF acid: H ₂ O (volume ratio) is 10:
1: Y (however, Y> 30) or 1.7: 1: Y (however, Y> 1) buffered hydrogen fluoride solution Fourth Production Example In this fourth production example, as shown in FIG. A double core optical fiber 4 in which a second core 42 is provided around a first core 41 and a cladding 43 is further provided therearound.
From 0, an optical fiber probe is manufactured.

First, as in the third manufacturing example, the optical fiber 4
0 is melt-stretched. The melt-drawn optical fiber 40 is
As shown in FIG. 21, an inclined portion 44 is formed in the clad 43 at one end portion, and a shape in which a tip end side of the inclined portion 44 has a sharp angle is drawn. Also,
The first core 41 and the second core 42 are reduced in diameter at the distal end portion by being extended, and have a shape in which the distal end surface is buried in the clad. It should be noted that the shape of the clad 43, such as a thread at the tip, is removed by etching in the next step.

After the optical fiber is melt-drawn in this manner, one end of the first core 41 is made to protrude from the clad and sharpened in a conical shape by a sharpening step as shown in FIG.

In this sharpening step, when the etching rate of the first core 41 is R ₁₂ , the etching rate of the second core 42 is R ₂₂ , and the etching rate of the cladding 43 is R ₃₂ , R ₁₂ <R ₂₂ <etched with etching conditions such that R _32.

When one end of the melt-stretched optical fiber 40 is immersed in an etching solution having such an etching rate, the clad 43 is etched at the tip side of the optical fiber 40, and the first core 41 and the second core 41 are etched. The tip end surface of the core 42 is exposed. After the tip surfaces of the cores 41 and 42 are exposed, the etching rate R _{32 of the} clad 43 is increased.
There greater than the etching rate R ₂₂ of the second core 42,
The etch rate R ₂₂ of the second core 42 is first core 41
Because of greater than the etching rate R _12, cladding 43
Are etched prior to the second core 42. Then, the second core 42 is etched before the first core 41, and the first core 41 projects from the second core 42.

On the outer peripheral surface side of the optical fiber, the clad 43 exposed on the outer peripheral surface is first etched.
Then, the outer peripheral surface of the second core 42 starts to be exposed from the front end side by the etching of the clad 43, and the second core 42 exposed on this outer peripheral surface is also etched. At this time, since the outer peripheral surface of the second core 42 is exposed from the front end side, the etching amount increases toward the front end side, and the diameter decreases. Therefore, an inclined portion that is inclined from the outer peripheral portion to the inner peripheral portion is formed in the second core 42. Further, by etching the second core 42, the outer peripheral surface of the first core 41 starts to be exposed from the front end side and is subsequently etched. At this time, since the outer peripheral surface of the first core 41 is exposed from the front end side, the etching amount increases toward the front end side, and the diameter decreases. Accordingly, by continuing this etching for a certain period of time, a conical sharp portion protruding from the second core 42 is formed at one end of the first core 41. As a result, as shown in FIG.
Is formed, a second tapered surface 46 is formed on the second core 42, and a third tapered surface 47 is formed on the cladding 43, thereby manufacturing an optical fiber probe.

[0085] In this first previously acute [psi ₄₁ of sharpened tip of the core 41 formed by sharpening process, previously acute [psi ₄₂ of the second core 42, the inclination angle omega ₄ of the cladding in the cladding inclined step
/ 2 and the etching rates R ₂₁ , R ₂₂ , R in the sharpening process
_It is determined by ₃₂ and is expressed by the following equation.

[0086] _{sin (ψ 41/2) =} R 12 / R 32 · sin (ω 4/2) sin (ψ 42/2) = R 22 / R 32 · sin (ω 4/2) In addition, the melt drawing Inclined part 4 formed in clad
Since the inclination angle of the sample No. ₄ becomes smaller toward the upper side, ω 4/2 decreases with the etching time. Therefore, the first
The core tilt angle [psi _41/2, the inclination angle [psi _42/2 of the second core
Also decreases with the etching time.

The acute angle α of the first tapered surface 45 matches the acute angle ψ ₄₁ of the first core 41 in the sharpening step, and the acute angle β of the second tapered surface 46 in the sharpening step. consistent with previous acute [psi ₄₂ of the second core 42 of the. The acute angle γ of the third tapered surface 47 matches the acute angle ω ₄ of the inclined portion formed on the clad. Also, the diameter d ₁ of the cross section on the rear end side of the first tapered surface 45 matches the core diameter of the first core 41 (core diameter reduced by melt drawing), and The diameter d ₂ of the cross section on the end side matches the core diameter of the second core 42 (the core diameter after being reduced by melt drawing).

As described above, in this manufacturing example, the optical fiber probe is manufactured in the above two steps. Thereafter, etching is further performed so as to reduce the length of the sharp portion as shown in FIG. You may.

In the subsequent sharpening step, the first core 41
When the etching rate of R ₁₃ is R ₁₃ , the etching rate of the second core 42 is R ₂₃ , and the etching rate of the cladding 43 is R ₃₃ , the etching is performed under the etching conditions such that R ₁₃ > R ₂₃ <R _33. .

When one end of the optical fiber having the conical sharpened portion formed in the core 41 in the previous step is immersed in an etching solution having such an etching rate, the etching rate R of the clad 43 on the tip side of the optical fiber is reduced. ₃₃ is greater than the etching rate R ₂₃ of the second core 42, the etching rate R ₂₃ of the second core 42 is smaller than the etching rate R ₁₃ of the first core 41, the distal end surface of the clad 43 second With respect to the tip end surface of the core 42 of FIG. Then, the length of the first core 41 projecting from the second core 42 gradually decreases.

On the other hand, on the outer peripheral surface side of the optical fiber 40, the cladding 43 is etched so that the second core 4
2 is newly exposed and subsequently etched.
Further, by etching the second core 42, the outer peripheral surface of the first core 41 is newly exposed and etched. In this etching, the portion where the outer peripheral surface is already exposed has a different inclination angle from the portion where the outer peripheral surface is newly exposed in this step. Therefore, as shown in FIG. The first tapered surface 48 and the second
, A third tapered surface 49a and a fourth tapered surface 49b are formed on the second core 42, and a fifth tapered surface 50 is formed on the cladding 43.
By changing the inclination angle in five stages, a sharpened optical fiber probe is manufactured.

Note that the acute angle α of the first tapered surface 48 is
And the diameter d ₁ of the cross section on the rear end side are determined by the sharp angle ψ ₄₁ of the sharp portion 46 formed in the sharpening step, the etching rate R ₁₃ and the etching time.

The acute angle β of the second tapered surface 49 can be obtained by the following equation.

[0094] sin (β / 2) = R 13 / R 23 · sin (ψ 42/2) Further, the diameter d ₂ of the rear end side of the cross section of the second tapered surface by a first core diameter (melt drawing consistent with decreased core diameter after), consistent with the third inclined angle [psi _42/2 of the inclined portion formed on the second core the inclination angle gamma / 2 of the tapered surface at the sharpening process.

As described above, in this manufacturing example, an optical fiber probe is manufactured from an optical fiber in which the second core and the clad are provided around the first core. As the optical fiber, for example, one having the following material configuration is used.

First core: germanium dioxide high-concentration doped quartz Second core: germanium dioxide low-concentration doped quartz Clad: pure quartz In the case of an optical fiber having such a material composition, the following etchant is used in each step. Something like that is appropriate.

First sharpening step (R ₁₂ <R ₂₂ <R ₃₂ ):
40 wt% NH ₄ F aqueous solution: 50 wt% HF acid: H ₂ O
(Volume ratio) of 10: 1: 1 buffered hydrogen fluoride solution second sharpening step _{(R 13> R 23 <R} 33)): 40 wt%
NH ₄ F aqueous solution: 50% by weight HF acid: H ₂ O (volume ratio) is 10: 1: Y (where Y> 30) or 1.7: 1:
Buffered hydrogen fluoride solution of Y (where Y> 1) Above, four examples of the method of manufacturing the optical fiber probe are described,
Although the optimum material configuration and etching conditions of the optical fiber probe have been exemplified, the material configuration and the etching conditions are not limited thereto.

For example, regarding the etching conditions, since the etching rate ratio of germanium dioxide-added quartz to pure quartz can be quantitatively controlled by the concentration of the buffered hydrogen fluoride solution, a predetermined etching rate is determined based on the relationship between the rate ratio and the concentration. What is necessary is just to determine so as to satisfy the speed condition.

That is, the buffered hydrogen fluoride solution is composed of a 40% by weight aqueous solution of NH ₄ F, 50% by weight of HF acid and H ₂ O, and its concentration is determined by the volume ratio X of the NH ₄ F aqueous solution or the volume ratio Y of H ₂ O. Is controlled by

Here, when the volume ratio X of the aqueous NH ₄ F solution is increased from 0 when the volume ratio of HF acid is 1 and the volume ratio Y of H ₂ O is 1, the pureness of the germanium dioxide-added quartz is increased. The etching rate ratio R _Ge / R _{0 with} respect to quartz decreases as the volume ratio X increases.
It becomes the minimum when. When the volume ratio X of the NH ₄ F aqueous solution exceeds 30, the etching rate ratio R _Ge / R ₀ of germanium dioxide-added quartz to pure quartz increases with an increase in the volume ratio X. When the volume ratio X of the aqueous NH ₄ F solution is 1.7, the etching rate ratio R _Ge / R ₀ of germanium dioxide-added quartz to pure quartz is 1. On the other hand, when the volume ratio X of the NH ₄ F aqueous solution is fixed at 10 and the volume ratio Y of H ₂ O is increased, the etching rate ratio R _{Ge of} germanium dioxide-added quartz to pure quartz is increased.
/ R ₀ increases as the volume ratio Y increases. In addition, H ₂ O
Is 30, the etching rate ratio R _Ge / R ₀ of germanium dioxide-added quartz to pure quartz is 1
become.

Therefore, when etching an optical fiber formed by providing a clad made of pure quartz around a core made of germanium dioxide-doped quartz,
In order to satisfy (etching rate of core) <(etching rate of clad), NH ₄ F aqueous solution: HF acid: H ₂ O
Are X: 1: 1 (X> 1.7) or 10: 1: Y (Y <3
0) etc., and in order to satisfy (core etching rate)> (cladding etching rate),
NH ₄ F aqueous solution: HF acid: H ₂ O is X: 1: 1 (X <1.
7), 1.7: 1: Y (Y> 1), 10: 1: Y (Y>
30) or the like.

The optical fiber may be one using B ₂ O ₃ -doped quartz. B ₂ O ₃ added quartz is B ₂ O ₃
Since the refractive index decreases with an increase in the amount of addition of, it is used as a cladding material in an optical fiber. B ₂
When O ₃ is used as the cladding material, it is appropriate to use pure quartz having high transmittance in the ultraviolet region as the core material.

When an optical fiber probe is manufactured from the optical fiber using the B ₂ O ₃ -doped quartz as a cladding material according to the first to fourth manufacturing examples, specifically, the following material constitution is used. Optical fibers can be used.

First production example: core; pure quartz / cladding; B ₂ O ₃ added quartz Second production example: core; pure quartz / first cladding; B ₂
O ₃ doped silica / second cladding; fluorine doped quartz third manufacturing example: core; pure silica / cladding; B ₂ O ₃ doped quartz fourth Preparation: first core; pure silica / second core B
₂ O ₃ -added quartz / cladding; B ₂ O ₃ -low-concentration added quartz / pure quartz When an optical fiber using B ₂ O ₃ -added quartz as a cladding material is etched with a buffered hydrogen fluoride solution, (the etching rate of the core) ) <(Clad etching rate)
In order to obtain the following, NH ₄ F aqueous solution: HF acid: H ₂ O is converted into X:
1: 1 (X <1.7), 1.7: 1: Y (Y> 1), 1
A volume ratio such as 0: 1: Y (Y> 30) may be used. Further, in order to satisfy (etching rate of core)> (etching rate of clad), NH ₄ F aqueous solution: HF acid: H ₂ O
X: 1: 1 (X> 1.7), 10: 1: Y (Y <3
A volume ratio such as 0) may be used.

As described above, the sharpened portion of the optical fiber probe sharpened at the three inclination angles has a small effective aperture diameter by reducing the acute angle α of the first tapered surface, thereby reducing the resolution. Is improved. At this time, when the sharp portion is sharpened in a conical shape at a constant inclination angle, the smaller the inclination angle, the greater the light loss and the lower the transmission efficiency. On the other hand, in the case where the sharp portion is sharpened at three levels of inclination angles, the inclination angle β / 2 of the second tapered surface is set even if the acute angle α of the first tapered surface is made small. The transmission efficiency of light can be increased by increasing. That is, with this optical fiber probe, high resolution can be obtained while sufficiently obtaining light transmission efficiency.

An optical fiber probe having a sharpened portion is manufactured as described above. This optical fiber probe is further provided with a sharpened portion and a tip serving as an opening as shown in FIGS. Alternatively, the light-shielding coating layer 5 may be formed. 2 and 3 show the light-shielding coating layer 5 formed on the sharp portion shown in FIG.
The light-shielding coating layer 5 has a sharp angle α of 50 ° or less, a sharp angle β of 180 °, a sectional diameter d ₁ of less than the wavelength of light λ, and a sectional diameter d ₂ of the same size as the wavelength of light λ. Is formed.

When the light-shielding coating layer 5 is formed, light is blocked at the portion where the light-shielding coating layer 5 is formed, and light is selectively taken in only through the minute aperture, so that the resolution is improved. , S / N ratio is improved. Hereinafter, a method for forming the light-shielding coating layer 5 will be described.

Example of forming light-shielding coating layer The light-shielding coating layer 5 is formed by forming a light-shielding metal film on a sharp portion by a vacuum evaporation method, a sputtering method, or an electroless plating method, and excluding a tip portion thereon. It is formed by forming an etching mask and then performing etching to remove the metal film at the tip.

However, in order to obtain a sufficient light-shielding property by the light-shielding coating layer 5, a dimension L (hereinafter, referred to as a chip length L) from the tip 1a of the sharp portion to a position where the cross-sectional diameter of the sharp portion becomes equal to the wavelength. ) Is important, and the chip length L is the skin depth of the metal forming the light-shielding coating layer 5.
It is desirable that the thickness be at least about 5 to 10 times, and more than th. In addition, skin dept
h means that the light intensity is 1 / e when light is transmitted through the metal.
² (where e is a natural constant) is the thickness of the metal, and the smaller the value of the metal, the greater the light absorption coefficient. The skin depth of this metal is
Usually, it is 20 to 30 nm. Therefore, it is preferable that the chip length is specifically selected to be about 100 to 200 nm.

First, such a light-shielding coating layer is formed as shown in FIG.
A method of forming a sharp portion 53 of an optical fiber in which a clad 52 is provided around a core 51 as shown in FIG.

In order to form the light-shielding coating layer, specifically, the optical fiber is rotated around its central axis in a vacuum using a vacuum evaporation apparatus, and metal vapor is supplied from the side surface of the sharp portion 53. To deposit. As a result, a light-shielding coating layer 54 is formed on the sharp portion 53 as shown in FIG.

The coating layer 54 has a high light-shielding property,
Materials of high conductivity are used, aluminum,
Gold, silver, platinum or the like can be used. Among them, aluminum is preferred.

Next, as shown in FIG.
An etching mask 55 is formed on the portion of the substrate 4 excluding the tip. The etching mask 55 is formed by rotating the optical fiber around its central axis in a vacuum using a vacuum deposition apparatus, and supplying vapor from a corrosion-resistant material to perform vapor deposition.

In vacuum vapor deposition, since the straightness of the metal vapor is high, when the metal vapor is supplied from behind to the sharp portion, the metal vapor does not flow to the tip of the coating layer, and the etching mask 55 is formed only in the region excluding the tip. Can be formed.
For example, when the metal vapor is incident from the rear side such that the incident direction of the metal vapor forms an angle of 50 ° with the central axis of the optical fiber, an etching mask 55 is formed in a region as shown in FIG.

The etching mask 55 and the material may be any as long as they exhibit corrosion resistance to the etchant in the etching of the coating layer 54 in the next step. For example, chromium is appropriate. Considering the combination with the coating layer, silver, platinum or the like can also be used.

After forming the etching mask 55 in this manner, etching is performed by immersing the tip of the optical fiber on which the coating layer 54 and the etching mask 55 are formed in an etching solution.

When the tip of the optical fiber is immersed in an etching solution, only the coating layer 54 at the tip where the etching mask 55 is not formed is selectively etched, and as shown in FIG. 27, an opening 54a is formed at the tip. The light-shielding coating layer 54 is formed. The etching solution is NaOH
A strong alkaline aqueous solution such as an aqueous solution is used.

Then, as shown in FIG. 28, the etching mask 55 is removed by subjecting the optical fiber to a treatment with an etching solution that dissolves the etching mask and does not dissolve the light-shielding coating layer. Is manufactured.

Next, as shown in FIG. 29, an optical fiber in which a first clad 57 is provided around a core 56 and a second clad 58 is provided therearound, wherein a single wavelength A method of forming a light-shielding coating layer on the sharpened portion 59 of a single-mode / multi-mode fiber in which light of a mode propagates and light of a plurality of guided modes propagates in the first clad will be described.

In such a single-mode / multi-mode fiber, two coating layers of a first light-shielding coating layer and a second light-shielding coating layer are formed, and the first light-shielding coating layer forms the first light-shielding coating layer. An opening corresponding to the clad 57 is formed, and an opening corresponding to the core 56 is formed by the second light-shielding coating layer.

First, in order to form a first light-shielding coating layer, a first coating layer 60 made of gold or the like is formed by sputtering or the like as shown in FIG.

As the first coating layer 60, a material having a high light-shielding property and a high conductivity is used as shown in the method of forming the light-shielding coating layer. In addition to gold, aluminum, silver, and the like are used. , Platinum or the like can be used.

Next, as shown in FIG. 31, a first etching mask 61 is formed except for the tip of the first coating layer 60. In order to form the first etching mask 61, first, the optical fiber on which the first coating layer 60 has been formed is immersed in a resin solution in which a synthetic resin is dissolved in a solvent, and then pulled up from the resin solution.

When the optical fiber is pulled out of the resin solution,
The resin solution attached to the tip is drawn upward by surface tension, and the first coating layer 60 at the tip is exposed from the resin solution. Then, when the solvent in the resin solution evaporates, the synthetic resin remains only in the portion where the resin solution has adhered, and the first etching mask 61 made of the synthetic resin is formed excluding the tip.

Here, the resin solution may be any resin solution having such a small viscosity that the tip can be exposed from the solvent by surface tension. The synthetic resin dissolved in the solvent is
Any material that does not dissolve in the etchant during the etching performed in the next step may be used. Specifically, an acrylic resin or the like is used.

The size of the tip exposed from the resin solution is controlled by the kinematic viscosity of the resin solution and the speed of pulling up the optical fiber from the solvent.

Thus, the first etching mask 6
After forming 1, the optical fiber on which the first coating layer 60 and the first etching mask 61 are formed is etched by immersing it in an etching solution.

When the optical fiber is immersed in the etching solution, the first
Only the first coating layer 60 at the tip end where the etching mask 61 is not formed is selectively etched, and FIG.
As shown in (1), a first light-shielding coating layer 60 having an opening 60a at the tip is formed.

Here, the etchant may be any as long as it can etch the light-shielding coating layer and does not etch the etching mask. Aqueous potassium iodide (KI-I ₂ ) solution, potassium cyanide solution, aqua regia A halogen solution such as iodine or bromine is used. For example, when the light-shielding coating layer 60 is made of gold and the etching mask 61 is made of an acrylic resin, KI-
It is preferable to use an aqueous solution of I ₂ for the etching solution.

After forming the first light-shielding coating layer 60 in this manner, as shown in FIG. 33, the etching mask 61 is peeled off and removed with an organic solvent such as acetone, and then the second light-shielding coating layer 60 is removed. Form a coating layer.

In order to form the second light-shielding coating layer, the optical fiber is rotated around its central axis in a vacuum using a vacuum evaporation apparatus, and metal vapor is supplied from the side of the sharp portion to perform evaporation. . As a result, as shown in FIG.
A light-shielding second coating layer 62 is formed on the substrate.

As the second coating layer 62, any of the materials exemplified as the material of the first light-shielding coating layer 60 can be used, and aluminum is particularly preferable.

Next, as shown in FIG. 35, the second etching mask 63 is removed except for the tip of the second coating layer 62.
To form The second etching mask 63 is formed by rotating the optical fiber about its central axis in a vacuum using a vacuum deposition apparatus, and supplying vapor from a corrosion-resistant material from the side of the sharp portion to perform vapor deposition. I do.

The second etching mask 63 and the material may be any as long as they exhibit corrosion resistance to the etchant in the etching of the coating layer performed in the next step. For example, chromium is appropriate. Considering the combination with other coating layers, silver, platinum or the like can also be used.

Thus, the second etching mask 6
After forming 3, the tip of the optical fiber on which the second coating layer 62 and the second etching mask 63 are formed is etched by immersing it in an etching solution.

When the tip of the optical fiber is immersed in an etching solution, only the light-shielding coating layer at the tip where the second etching mask 63 is not formed is selectively etched,
As shown in FIG. 36, a second light-shielding coating layer 62 having an opening 62a formed at the tip is formed. Note that a strong alkaline aqueous solution such as an aqueous NaOH solution is used as the etching solution. For example, when the light-shielding coating layer is made of aluminum and the etching mask is made of chromium, it is desirable to use an aqueous NaOH solution as an etching solution.

Thereafter, the first to the optical fiber
By performing a process using an etching solution that dissolves the etching mask 63 and does not dissolve the second light-shielding coating layer 62, the etching mask 63 is removed as shown in FIG. 37, and the aperture probe is manufactured.

Next, as shown in FIG. 38, a first cladding 65 is provided around a core 64 and a second cladding 66 is provided therearound. A method for forming the coating layer and the second light-shielding coating layer will be described. In this method, the first light-shielding coating layer is formed by an electroless plating method.

In order to form the first light-shielding coating layer by electroless plating, first, a catalytic metal nucleus such as palladium is deposited on the surface of the sharpened portion 67 and an activation process is performed.

Specifically, the optical fiber is made of tin dichloride (S
Tin is deposited on the fiber surface by immersion in an nCl ₂ ) solution, and then the optical fiber is immersed in a palladium dichloride (PdCl ₂ ) solution. When the optical fiber thus coated with tin is immersed in a palladium dichloride solution, tin is replaced by palladium, and a catalytic metal nucleus of palladium precipitates on the fiber surface.

The activation treatment may be performed by depositing palladium directly on the surface of the sharp portion by a thin film forming technique such as sputtering.

Then, a plated film of nickel or the like is formed on the surface of the sharpened portion of the optical fiber that has been subjected to the activation treatment using an electroless plating solution. Since the plating film is unlikely to be deposited on a pointed surface such as a needle, such as a tip of the sharp portion 67, a plating film of a sufficient thickness is deposited except for the tip of the sharp portion 67, In addition, by stopping the plating at the stage where the plating film is not deposited at the tip of the sharpened portion 67, the first light-shielding coating layer 68 has the opening 68a at the tip as shown in FIG. It is formed.

Next, a second light-shielding coating layer is formed on the first light-shielding coating layer 68.

To form the second light-shielding coating layer, the optical fiber is rotated about its central axis in a vacuum using a vacuum deposition apparatus, and metal vapor is supplied from the side surface of the sharp portion 87 to form a vapor deposition. I do. Thus, a light-shielding second covering layer 69 is formed as shown in FIG.

As the second coating layer 69, a material having high light-shielding properties and high conductivity is used, and aluminum, gold, silver, platinum or the like can be used. Among them, aluminum is preferred.

Next, as shown in FIG. 41, an etching mask 70 is formed except for the tip of the second coating layer 69. The etching mask 70 rotates the optical fiber around its central axis in a vacuum using a vacuum deposition apparatus,
It is formed by supplying vapor from a corrosion-resistant material to the sharpened portion from the side and vapor deposition.

As the etching mask 70 and the material, any material may be used as long as it exhibits corrosion resistance to the etchant in the etching of the second coating layer 69 in the next step. For example, chromium is appropriate. Considering the combination with the coating layer, silver, platinum and the like can also be used.

After forming the etching mask in this manner, the second coating layer 69 and the etching mask 70 are formed.
Etching is performed by immersing the tip of the optical fiber on which the is formed in an etchant.

When the tip of the optical fiber is immersed in an etching solution, only the second coating layer 69 at the tip where the etching mask 70 is not formed is selectively etched.
As shown in FIG. 2, a second light-shielding coating layer 69 having an opening 69a formed at the tip is formed. Note that a strong alkaline aqueous solution such as an aqueous NaOH solution is used as the etching solution.

Thereafter, the etching mask 70 is dissolved in the optical fiber and the second light-shielding coating layer 69 is dissolved.
By performing a process using an etchant that does not dissolve the resist, the etching mask is removed as shown in FIG. 43, and the aperture probe is manufactured.

Although the example of forming the light-shielding coating layer has been described above, in the case of the aperture probe having the light-shielding coating layer formed on the sharpened portion sharpened at the three inclination angles, the first taper is used. Even if the acute angle α of the surface is made small, the chip length L can be reduced by increasing the inclination angle β / 2 of the second tapered surface.

Therefore, in the aperture probe, there is a problem in that the light loss is large in a region below the wavelength, and when the inclination angle of the first tapered surface is large, the light shielding near the aperture becomes insufficient. However, these problems can be avoided, and high transmission efficiency and high resolution can be obtained.

Although the inclination angle γ / 2 of the third tapered surface does not directly affect the resolution and the transmission efficiency, for example, when the light-shielding coating layer is formed by vacuum evaporation, the inclination angle γ / 2 should be as small as possible. It is desirable to make it smaller.

[0154]

EXAMPLES Hereinafter, specific examples of the present invention will be described based on experimental results.

Example 1 First, a double clad optical fiber having the following material composition was prepared.

Material composition of optical fiber Core: relative refractive index difference with respect to germanium dioxide-doped quartz and pure quartz; 1.2%, outer diameter: 1.2
μm First clad: pure quartz Relative refractive index difference to pure quartz; 0%, outer diameter; 27 μm Second clad: fluorine-doped quartz Relative refractive index difference: -0.7%, outer diameter; 125 μm And this light A sharpened portion was formed at one end of the fiber by performing the following first to third sharpening steps.

[0157] (1) one end of the clad inclined step optical fiber, R ₁₁ when the etching rate of the core and R _11, the etching rate of the first cladding R _21, the etching rate of the second cladding and R ₃₁ = R ₂₁ <R ₃₁
Etching was performed under such etching conditions as follows. Etching solution is 40 wt% NH ₄ F aqueous solution: 50 wt% H
It is a buffered hydrogen fluoride solution having a composition of F acid: H ₂ O = 1.7: 1: 1 (volume ratio), and the etching time is 40 minutes.

(2) First Sharpening Step Next, one end of this optical fiber was subjected to a core etching rate of R ₁₂ , a first cladding etching rate of R ₂₂ , and a second
When the etching rate of the cladding of R is ₃₂ , R ₁₂ <
The etching was performed under the etching condition such that R ₂₂ <R ₃₂ . Etching solution is 40 wt% NH ₄ F aqueous solution: 5
This is a buffered hydrogen fluoride solution having a composition of 0% by weight HF acid: H ₂ O = 10: 1: 1 (volume ratio), and the etching time is 2 hours.
0 minutes.

(3) Second Sharpening Step Subsequently, one end of the core of the optical fiber is set to have an etching rate of the core of R ₁₃ and an etching rate of the first cladding of R ₁₃ .
₂₃ , etching was performed under the etching conditions such that R ₁₃ > R ₂₃ <R ₃₃ when the etching rate of the second clad was R ₃₃ . The etching solution is a buffered hydrogen fluoride solution having a composition of 40 wt% NH ₄ F aqueous solution: 50 wt% HF acid: H ₂ O = 1.7: 1: 5 (volume ratio), and the etching time is 1 minute 30 seconds. It is.

As a result, at one end of the optical fiber, a sharp portion including a first tapered surface, a second tapered surface, and a third tapered surface was formed. The sharp angle, cross-sectional diameter and tip length of each tapered surface of the sharp portion are as follows. Further, the second clad was all removed by etching.

The acute angle α of the first taper surface: 20 ° The acute angle β of the second taper surface: 105 ° The acute angle γ of the third taper surface: 60 ° Cross section of the rear end side of the first taper surface Diameter d ₁ : 0.5μ
m The diameter d ₂ of the section on the rear end side of the second tapered surface: 1.2 μm
m Tip length L: 1 μm Tip diameter of the first tapered surface: several nm or less Example 2 In the second sharpening step, 40 wt% NH ₄ F aqueous solution: 50 wt% HF: H ₂ O = 0.1: The sharpening of the optical fiber was performed in the same manner as in Example 1 except that a buffered hydrogen fluoride solution having a composition of 1: 2.5 (volume ratio) was used and the etching time was 1 minute and 10 seconds.

As a result, at one end of the optical fiber, a sharp portion including the first tapered surface, the second tapered surface, and the third tapered surface was formed. The sharp angle, cross-sectional diameter and tip length of each tapered surface of the sharp portion are as follows. Further, the second clad was all removed by etching.

The acute angle α of the first tapered surface: 70 ° The acute angle β of the second tapered surface: 117 ° The acute angle γ of the third tapered surface: 60 ° Cross section of the rear end side of the first tapered surface Diameter d _{1 of} 0.2 μ
m The diameter d ₂ of the section on the rear end side of the second tapered surface: 1.2 μm
m Chip length L: 1 μm Tip diameter of the first tapered surface: several nm or less Example 3 In the clad tilting step, the optical fiber was sharpened in the same manner as in Example 1 except that the etching time was 30 minutes. Was.

As a result, at one end of the optical fiber, a sharp portion including the first tapered surface, the second tapered surface, and the third tapered surface was formed. The sharp angle, cross-sectional diameter and tip length of each tapered surface of the sharp portion are as follows. In this case, a part of the second cladding remained at the end of the third sharpening step.

The acute angle α of the first taper surface: 20 ° The acute angle β of the second taper surface: 105 ° The acute angle γ of the third taper surface: 60 ° Cross section of the rear end side of the first taper surface Diameter d ₁ : 0.5μ
m The diameter d ₂ of the section on the rear end side of the second tapered surface: 1.2 μm
m Chip length L: 1 μm Tip diameter of first tapered surface: several nm or less Example 4 First, an optical fiber having the following material composition was prepared.

Material composition of optical fiber Core: relative refractive index difference to germanium dioxide-doped quartz, pure quartz; 1.2%, outer diameter; 2 μm Cladding: pure quartz, relative refractive index difference to pure quartz; 0%, outer diameter; Then, a sharpened portion was formed at one end of the optical fiber by performing the following melt drawing step, first sharpening step, and second sharpening step.

(1) Cladding tilting step Micro pipette puller (trade name P manufactured by Sutter)
-2000), a portion of the optical fiber was melted by heating, and the fiber was separated into two by pulling both sides of the melted portion.

(2) First Sharpening Step When one end of one of the separated optical fibers is set to have a core etching rate of R ₁₂ and a cladding etching rate of R ₂₂ , R ₁₂ <R _22. Etching was performed under the proper etching conditions. The etching solution is a buffered hydrogen fluoride solution having a composition of 40% by weight NH ₄ F aqueous solution: 50% by weight HF acid: H ₂ O = 10: 1: 1 (volume ratio), and the etching time is 30 minutes.

(3) Second Sharpening Step When one end of the optical fiber is made to have a core etching rate of R ₁₃ and a cladding etching rate of R ₂₃ , R ₁₃ > R _23.
Etching was performed under such etching conditions as follows. Etching solution is 40% by weight NH ₄ F aqueous solution: 50% by weight H
This is a buffered hydrogen fluoride solution having a composition of F acid: H ₂ O = 1.7: 1: 5 (volume ratio), and the etching time is 9 seconds.

As a result, at one end of the optical fiber, a sharp portion including the first tapered surface, the second tapered surface, and the third tapered surface was formed. The sharp angle, cross-sectional diameter and tip length of each tapered surface of the sharp portion are as follows.

The acute angle α of the first tapered surface: 20 ° The acute angle β of the second tapered surface: 105 ° The acute angle γ of the third tapered surface: 60 ° Cross section of the rear end side of the first tapered surface Diameter d _{1 of} 0.1 μ
m Diameter d ₂ of the cross section on the rear end side of the second tapered surface: 0.2 μm
m Chip length L: 0.3 μm Tip diameter of first tapered surface: several nm or less Example 5 A double-core optical fiber having the following material composition was prepared.

Material composition of optical fiber First core: relative refractive index difference with respect to germanium dioxide-doped quartz and pure quartz; 1.5%, outer diameter; 4 μm Second core: relative refractive index with respect to germanium dioxide-doped quartz pure quartz Difference: 0.2%, outer diameter: 12 microns Cladding: pure quartz Specific refractive index difference with respect to pure quartz: 0%, outer diameter: 125 μm Then, one end of this optical fiber is subjected to the following melt drawing step and the first step. The sharpened portion was formed by performing the sharpening step and the second sharpening step.

(1) Cladding tilting step Micro pipette puller (trade name P manufactured by Sutter)
-2000), a portion of the optical fiber was melted by heating, and the fiber was separated into two by pulling both sides of the melted portion.

(2) First Sharpening Step One end of one of the separated optical fibers is set to have an etching rate of the first core of R ₁₂ and an etching rate of the second core of R ₁₂ .
₂₂ , when the etching rate of the clad is R ₃₂ , R ₁₂
Etching was performed under the etching conditions such that <R ₂₂ <R ₃₂ . The etching solution is a 40 wt% NH ₄ F aqueous solution:
This is a buffered hydrogen fluoride solution having a composition of 50% by weight HF acid: H ₂ O = 10: 1: 1 (volume ratio), and the etching time is 30 minutes.

(3) Second sharpening step One end of the optical fiber is connected to the first core at an etching rate of R.
₁₃ , when the etching rate of the second core was R ₂₃ and the etching rate of the cladding was R ₃₃ , etching was performed under the etching conditions such that R ₁₃ > R ₂₃ <R ₃₃ . Etching solution is 40 wt% NH ₄ F aqueous solution: 50 wt% HF
It is a buffered hydrogen fluoride solution having a composition of acid: H ₂ O = 1.7: 1: 5 (volume ratio), and the etching time is 18 seconds.

As a result, at one end of the optical fiber, a sharp portion including a first tapered surface, a second tapered surface, and a third tapered surface was formed. The acute angle (twice the tilt angle), cross-sectional diameter and chip length of each tapered surface of this sharp portion are as follows.

The acute angle α of the first tapered surface: 20 ° The acute angle β of the second tapered surface: 150 ° The acute angle γ of the third tapered surface: 60 ° Cross section of the rear end side of the first tapered surface Diameter d _{1 of} 0.2 μ
m Diameter d ₂ of the cross section on the rear end side of the second tapered surface: 0.4 μm
m Chip length L: 0.6 μm Tip diameter of the first tapered surface: several nm or less Example 6 A clad tilting step to a second sharpening step are performed in the same manner as in Example 1 to sharpen one end of the optical fiber. Part was formed.

Then, a light-shielding coating layer was formed on the sharpened portion as follows.

An aluminum coating layer having a thickness of 200 nm was formed by a vacuum deposition method, and an etching mask was formed on the coating layer except for the tip. This etching mask is a deposited film of chromium and has a thickness of 30 n.
m.

Next, the optical fiber having the aluminum coating layer and the etching mask formed thereon was immersed in a 0.2% by weight aqueous sodium hydroxide solution for 60 seconds to remove the light-shielding coating layer at the tip by etching.

Further, this optical fiber was mixed with 17 g of ceric ammonium nitrate, 5 cc of perchloric acid, and 100 g of water.
The etching mask was removed by etching by dipping in a mixed solution of cc for 30 seconds to form a light-shielding coating layer having an opening at the tip.

The root diameter d _F of the protruding portion protruding from the opening of the light-shielding coating layer was 200 nm.

Example 7 A light-shielding coating layer was formed on the sharp portion of an optical fiber in the same manner as in Example 6, except that the etching time of the etching with the aqueous sodium hydroxide solution was 30 seconds.

The tip surface of the light-shielding coating layer is substantially flush with the tip of the sharp portion, and an optical fiber probe of a type in which the sharp portion of the optical fiber does not project from the opening of the light-shielding coating layer can be obtained. Was.

Example 8 A sharpened portion was formed at one end of an optical fiber by performing the clad tilting step to the second sharpening step in the same manner as in Example 3.

[0186] Then, the first point is added to the sharp portion as follows.
And a second light-shielding coating layer were formed.

First, a 150 nm-thick first covering layer made of gold was formed by a magnetron sputtering apparatus.

Next, the optical fiber is immersed in a resin solution, pulled up, and the solvent is evaporated to form a first etching mask made of resin on the light-shielding coating layer except for the tip. did. This resin solution is obtained by dissolving an acrylic resin in thinner and has a viscosity of 1
The density is 1 cP and the density is 0.85 g / cm ³ . The pulling speed of the optical fiber from the resin solution is 5 cm / sec.

Subsequently, the optical fiber on which the first coating layer and the first etching mask were formed was added to an etching solution for 1 hour.
By immersing for 1 minute, the light-shielding coating layer at the tip was removed by etching to form a first light-shielding coating layer. The etching solution was KI: I ₂ : H ₂ O (weight ratio) =
It is a KI-I ₂ aqueous solution having a composition of 20: 1: 400.

Next, after removing the first etching mask with acetone, a second coating layer made of aluminum having a thickness of 200 nm is formed by vacuum evaporation on the sharp portion where the first light-shielding coating layer is formed. Was formed, and a second etching mask was formed on a portion of the second coating layer except for a tip portion. This second etching mask is
It is a deposited film of chromium and has a thickness of 30 nm.

Next, the optical fiber on which the second coating layer made of aluminum and the second etching mask were formed was immersed in a 0.2% aqueous sodium hydroxide solution for 60 seconds to form a light-shielding coating at the tip. The layer was etched away.

Further, this optical fiber was mixed with 17 g of ceric ammonium nitrate, 5 cc of perchloric acid, and 100 g of water.
The etching mask was etched away by immersion in a mixed solution of cc for 30 seconds to form a second light-shielding coating layer having an opening at the tip.

[0193] The root diameter dF of the protrusion protruding from the opening of the light-shielding coating layer was 200 nm.

Example 9 A sharpened portion was formed at one end of an optical fiber by performing the clad tilting step to the second sharpening step in the same manner as in Example 3.

Then, the first portion is added to the sharp portion as follows.
And a second light-shielding coating layer were formed.

First, the optical fiber was immersed in a 0.1 g / l tin dichloride solution for 3 minutes to deposit tin on the surface of the fiber, and then was immersed in a 0.05 g / l palladium dichloride solution for 3 minutes. By immersion, catalytic metal nuclei of palladium were deposited on the surface of the optical fiber.

Then, the optical fiber thus activated was treated with an electroless nickel plating solution to form a first light-shielding coating layer on the portion excluding the tip of the sharp portion. The composition of the electroless plating solution is as follows.

Composition of Electroless Plating Solution NiSO ₄ 0.1 mol / l CH ₃ COONH ₄ 0.4 mol / l NaH ₂ PO ₂ 0.2 mol / l The electroless plating solution was prepared by adding nitrogen gas before plating. The dissolved oxygen was purged by passing through (nitrogen gas bubbling).

Then, an aluminum coating layer having a thickness of 200 nm was formed by a vacuum deposition method on the sharp portion where the first light-shielding coating layer was formed, and an etching mask was formed on the coating layer except for the tip portion. Was formed. This etching mask is a deposited film of chromium and has a thickness of 30 nm.
It is.

Next, the optical fiber having the aluminum coating layer and the etching mask formed thereon was immersed in a 0.2% by weight aqueous sodium hydroxide solution for 60 seconds to remove the light-shielding coating layer at the tip by etching.

Further, this optical fiber was mixed with 17 g of ceric ammonium nitrate, 5 cc of perchloric acid, and 100 g of water.
The etching mask was etched away by immersion in a mixed solution of cc for 30 seconds to form a second light-shielding coating layer having an opening at the tip.

[0202] root diameter d _F of the projection projecting from the opening of the light shielding covering layer was 200 nm.

[0203]

As is clear from the above description, the method of manufacturing an optical fiber probe according to the present invention can manufacture an optical fiber probe having a small aperture diameter and high transmission efficiency. When such an optical fiber probe is used in a near-field optical microscope, it becomes possible to obtain a high-sensitivity optical image with a resolution on the order of nanometers.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a sharpened portion of an optical fiber probe manufactured by a manufacturing method of the present invention.

FIG. 2 is a cross-sectional view illustrating an example of an optical fiber probe having a light-shielding coating layer formed thereon.

FIG. 3 is a cross-sectional view showing another example of an optical fiber probe on which a light-shielding coating layer is formed.

FIG. 4 is a cross-sectional view showing still another example of an optical fiber probe on which a light-shielding coating layer is formed.

FIG. 5 is a cross-sectional view showing a first manufacturing example of the optical fiber probe in the order of steps, and showing the optical fiber before being sharpened.

FIG. 6 is a cross-sectional view showing a clad tilting step in the first manufacturing example.

FIG. 7 is a cross-sectional view showing a first sharpening step in the first manufacturing example.

FIG. 8 is a sectional view showing a second sharpening step in the first manufacturing example.

FIG. 9 is a cross-sectional view illustrating a second manufacturing example of the optical fiber probe in the order of steps and illustrating the optical fiber before being sharpened.

FIG. 10 is a cross-sectional view showing a clad tilting step in a second manufacturing example.

FIG. 11 is a sectional view showing a first sharpening step in a second manufacturing example.

FIG. 12 is a sectional view showing a second sharpening step in the second manufacturing example.

FIG. 13 is a cross-sectional view showing a third manufacturing example of the optical fiber probe in the order of steps and showing the optical fiber before being sharpened.

FIG. 14 is a schematic view showing a state where heat is applied to an optical fiber.

FIG. 15 is a schematic view showing an optical fiber that is melt-drawn.

FIG. 16 is a schematic view showing a separated optical fiber.

FIG. 17 is a cross-sectional view showing the shape of the optical fiber after melt drawing.

FIG. 18 is a cross-sectional view showing a first sharpening step in a third manufacturing example.

FIG. 19 is a sectional view showing a second sharpening step in the third manufacturing example.

FIG. 20 is a cross-sectional view showing the fourth manufacturing example in the order of steps, showing the optical fiber before being sharpened.

FIG. 21 is a cross-sectional view showing a melt drawing step in a fourth manufacturing example.

FIG. 22 is a cross-sectional view showing a first sharpening step in a fourth manufacturing example.

FIG. 23 is a sectional view showing a second sharpening step in the fourth manufacturing example.

FIG. 24 is a cross-sectional view showing a method of forming the light-shielding coating layer in the order of steps, and showing a sharp portion before the formation of the light-shielding coating layer.

FIG. 25 is a sectional view showing a coating layer forming step by a vacuum evaporation method.

FIG. 26 is a sectional view showing an etching mask forming step by a vacuum evaporation method.

FIG. 27 is a cross-sectional view showing a step of etching the coating layer.

FIG. 28 is a cross-sectional view showing an etching mask removing step.

FIG. 29 is a cross-sectional view showing a sharpened portion before a light-shielding coating layer is formed.

FIG. 30 is a sectional view showing a first coating layer forming step by sputtering.

FIG. 31 is a cross-sectional view showing a first etching mask forming step using a resin.

FIG. 32 is a cross-sectional view showing a step of etching the first coating layer.

FIG. 33 is a cross-sectional view showing a first etching mask removing step.

FIG. 34 is a cross-sectional view showing a step of forming a second coating layer by a vacuum evaporation method.

FIG. 35 is a cross-sectional view showing a step of forming a second etching mask by a vacuum evaporation method.

FIG. 36 is a cross-sectional view showing a step of etching the second coating layer.

FIG. 37 is a cross-sectional view showing a second etching mask removing step.

FIG. 38 is a cross-sectional view showing a sharp portion before a light-shielding coating layer is formed.

FIG. 39 is a cross-sectional view showing a first coating layer forming step by electroless plating.

FIG. 40 is a cross-sectional view showing a second coating layer forming step by a vacuum evaporation method.

FIG. 41 is a cross-sectional view showing an etching mask forming step by a vacuum evaporation method.

FIG. 42 is a cross-sectional view showing a step of etching the second coating layer.

FIG. 43 is a cross-sectional view showing an etching mask removing step.

FIG. 44 is a schematic view showing the principle of a near-field optical microscope.

FIG. 45 is a cross-sectional view showing a tip probe manufactured by a conventional manufacturing method.

FIG. 46 is a cross-sectional view showing an aperture probe manufactured by a conventional manufacturing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Sharp part, 2 1st taper surface, 3 2nd taper surface, 4 3rd taper surface, 5 light-shielding coating layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-159847 (JP, A) JP-A-7-151769 (JP, A) JP-A-7-209307 (JP, A) JP-A-7-159 209308 (JP, A) JP-A-6-130302 (JP, A) JP-A-7-146126 (JP, A) JP-A-7-260459 (JP, A) JP-A-7-261039 (JP, A) Tokuhyo Hei 4-507152 (JP, A) International publication 95/33207 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 13/10-13/24 G12B 21/00- 21/24 G01B 11/30 102 G01B 21/30 G02B 6/10 JICST file (JOIS)

Claims (17)

(57) [Claims] 1. An optical fiber having a cladding provided around a core, a cladding inclining step of forming an inclined portion inclined from an outer periphery to an inner periphery at one end of the cladding, and protruding one end of the core from the cladding by etching. A first sharpening step of making the one end conically sharpened, and changing the inclination angle of the one end of the conically sharpened core into two stages by etching to form an inclination angle of the tapered surface on the tip end side. Is sharpened so as to be smaller than the inclination angle of the next tapered surface, and the diameter of the cross section on the rear end side of the next tapered surface is set to
Wavelength or more, and the cross section of the rear end side of the tapered surface on the front end side
A second sharpening step of forming a sharpened portion having a diameter equal to or less than the wavelength of light . 2. In the cladding tilting step, one end of an optical fiber is etched at an interface between an etchant and a liquid having a lower specific gravity than the etchant.
2. The method for manufacturing an optical fiber probe according to claim 1, wherein an inclined portion is formed at one end of the clad. 3. The method for manufacturing an optical fiber probe according to claim 1, wherein in the clad tilting step, an inclined portion is formed at one end of the clad by melt-drawing the optical fiber. 4. In the first sharpening step, the core etching rate is set to R ₁₂ and the cladding etching rate is set to R ₁₂ .
_{2. The} method according to claim 1, wherein the etching is performed under a condition satisfying R ₁₂ <R ₂₂ when ₂₂ is satisfied. 5. In the second sharpening step, the core etching rate is R ₁₃ and the cladding etching rate is R.
When the _23, R _13> The method of manufacturing an optical fiber probe according to claim 1, wherein the etching is performed conditions satisfying R _23. 6. The optical fiber probe according to claim 1, wherein after the second sharpening step, a light-shielding coating layer is formed at one end of the sharpened optical fiber except for the tip of the core. Method. 7. An optical fiber having a first clad and a second clad provided around a core, a cladding inclining step of forming an inclined portion inclined from an outer periphery to an inner periphery at one end of the first clad; A first sharpening step of projecting one end of the core from the first clad by etching and sharpening the one end of the core in a conical manner; The diameter of the cross section of the rear end side of the next tapered surface is changed to two stages by sharpening the inclination angle of the tapered surface on the front end side so as to be smaller than the inclination angle of the next tapered surface.
Wavelength or more, and the cross section of the rear end side of the tapered surface on the front end side
A second sharpening step of forming a sharpened portion having a diameter equal to or less than the wavelength of light . 8. In the cladding tilting step, when the etching rate of the core is R ₁₁ , the etching rate of the first cladding is R ₂₁ , and the etching rate of the second cladding is R ₃₁ , R ₁₁ = R ₂₁ <. the method of manufacturing an optical fiber probe according to claim 7, wherein the etching is performed under conditions satisfying the R _31. 9. In the first sharpening step, when the etching rate of the core is R ₁₂ , the etching rate of the first cladding is R ₂₂ , and the etching rate of the second cladding is R ₃₂ , R ₁₂ < the method of manufacturing an optical fiber probe according to claim 7, wherein the etching is performed under a condition satisfying R _{22 <R 32.} 10. In the second sharpening step, the etching rate of the core is R ₁₃ , the etching rate of the first cladding is R ₂₃ , and the etching rate of the second cladding is R _33.
And when, _{R 13>} R 23 _<method of manufacturing an optical fiber probe according to claim 7, wherein the etching is performed conditions satisfying R _33. 11. The method for manufacturing an optical fiber probe according to claim 7, wherein after the second sharpening step, a light-shielding coating layer is formed on one end of the sharpened optical fiber. 12. A clad tilting step of forming a tilted portion at one end of the clad of an optical fiber having a second core and a clad provided around a first core, the tapered portion being inclined from an outer periphery to an inner periphery. One ends of the first core and the second core are made to protrude from the clad by etching, and the inclination angle is changed in two steps so that the inclination angle of the tapered surface on the tip side becomes smaller than the inclination angle of the next tapered surface. and sharpening, said next of Te
The diameter of the cross section on the rear end side of the
The diameter of the cross section on the rear end side of the tapered surface on the front side should be smaller than the wavelength of light.
And a sharpening step of forming a sharpened portion. 13. The method for manufacturing an optical fiber probe according to claim 12, wherein, in the cladding tilting step, an inclined portion is formed at one end of the clad by melt-drawing the optical fiber. 14. In the sharpening step, when the etching rate of the first core is R ₁₂ , the etching rate of the second core is R ₂₂ , and the etching rate of the clad is R ₃₂ , R ₁₂ <R ₂₂ < the method of manufacturing an optical fiber probe according to claim 12, wherein the etching is performed under conditions satisfying the R _32. 15. After the sharpening step, the first core has an etching rate of R ₁₃ and the second core has an etching rate of R ₁₃ .
_23, the etching rate of the cladding is taken as R _33, R _13> by etching under a condition satisfying _R 23 _{<R 33,} sharpened by changing the end of the first core inclination in two steps And the rear end side of the next tapered surface
The diameter of the cross section of the light should be greater than the wavelength of light
The method for manufacturing an optical fiber probe according to claim 14, wherein a sharp portion is formed in which a diameter of a cross section on a rear end side of the surface is equal to or less than a wavelength of light. 16. The method of manufacturing an optical fiber probe according to claim 12, wherein, after the sharpening step, a light-shielding coating layer is formed on one end of the sharpened optical fiber. 17. An optical fiber having a clad provided around a core made of pure quartz (SiO ₂ ) , and one end of the conical sharpened core has a two-step inclination angle.
Change to the floor and the inclination angle of the tapered surface on the tip side becomes the next taper
Is sharpened so as to be smaller than the inclination angle of the surface.
The diameter of the cross section on the rear end side of the tapered surface of
The diameter of the cross section on the rear end side of the tapered surface on the front end side
An optical fiber having a sharpened portion having a wavelength or less, a light-shielding coating layer is formed except for the tip of the sharpened portion, and an opening exposed from the light-shielding coating layer at the tip of the sharpened portion. probe.