JPH07146126A - Optical fiber probe and its manufacture - Google Patents

Abstract

PURPOSE:To prevent a cladding part from colliding with a sample and to enhance the efficiency of a detection by a method wherein a detection end part that is the point of a core is installed at the tip of a base end part that is a reduced thickness of the cladding part. CONSTITUTION:One end of an optical fiber 1 in which the diameter of a cladding 2 is at d0 and in which the diameter of a core 4 is at dc is provided with a base end part 3 that is a reduced thickness of the cladding 2 with a diameter of d2, and an optical fiber probe 10 provided with a detection end part 5 in which a point angle of the sharpened core 4 is at theta is constituted at its tip. In addition, the core 4 is formed of quartz doped with GeO2, and the cladding 2 is formed of pure quartz. When the probe 10 is constituted in this manner, the base end part 3 functions as a member by which the length L2 of the detection end part 5 is extended substantially by the portion of its length L1. Consequently, when the probe 10 is used, the peripheral part of the cladding 2 does not collide with a sample, there is no fear that the sample and the probe 10 are damaged, and the cladding 2 can display its function sufficiently.

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 for detecting evanescent light power localized on the surface of an object and a method for manufacturing the same, and is applied to, for example, an optical probe used in a photon scanning microscope.

[0002]

2. Description of the Related Art A photon scanning microscope in which an evanescent light power localized on an object surface is detected by an optical probe is known as an ultra-high resolution optical microscope having a resolution exceeding the diffraction limit of a conventional optical microscope. ing.

That is, as shown in FIG. 8, when the sample surface is illuminated from the back surface of the sample 20 under the condition of total internal reflection, an evanescent field depending on the surface shape is generated on the sample surface side. In the photon scanning microscope, a resolution exceeding the diffraction limit of the conventional optical microscope can be obtained by detecting the evanescent field intensity with the optical probe 22 having the detection end portion 21 having an opening of a wavelength or less. The resolution of the photon scanning microscope is determined by the effective aperture diameter of the optical probe.

Here, since the evanescent field intensity exponentially decreases with the distance from the sample surface, the optical probe becomes an equivalent aperture even if the tip is simply sharpened. Therefore, in the photon scanning microscope, sharpening of the tip of the optical probe is most important.

Conventionally, as a probe manufacturing method, a pipette melt drawing method (DW Pohl, W.denk and M. Lanz: Appl.Phys.Let
t.44 (1984)), a method of sharpening a quartz rod (K. Lieberman,
S.Harush, A.Lewis and R.Kopelman: Science247 (1990) 5
9), Method for etching optical fiber (H. Pagnia, J. Rad
Ojewski and N. Sotnik: Optik 86 (1990) 87)) are known.

In the method of etching an optical fiber, an optical fiber probe is manufactured by sharpening one end of an optical fiber consisting of a core and a clad doped with germanium oxide by etching.

[0007]

By the way, in the conventional optical fiber probe 22 manufactured by sharpening one end of the optical fiber, the cladding diameter D (about 90 μm) is the length L ( 2 to 6 μm), so that the peripheral edge portion 23 of the optical fiber cladding is
May collide with the sample 20 and damage the sample and / or the probe itself. Further, since the power of the evanescent light is extremely small, it is necessary for the optical fiber probe for detecting the power of the evanescent light to avoid the influence of the scattered light and increase the detection efficiency.

Therefore, in view of the actual situation in the conventional optical fiber probe as described above, an object of the present invention is to provide an optical fiber probe in which the cladding portion is less likely to collide with the sample.

Another object of the present invention is to provide an optical fiber probe with high detection efficiency.

Another object of the present invention is to provide a method of manufacturing an optical fiber probe in which the peripheral edge of the clad is less likely to collide with the sample.

Still another object of the present invention is to provide a method of manufacturing an optical fiber probe with high detection efficiency.

[0012]

According to a first aspect of the present invention, there is provided an optical fiber probe in which an optical fiber composed of a core and a clad has a base end portion at one end of the optical fiber and a detection end having the core sharpened. It is characterized by having a part.

An optical fiber probe according to the second invention is
In the optical fiber probe according to the first aspect of the present invention, a gold coating layer is provided on the surface of the detection end, and a minute opening smaller than the wavelength of the detection light is provided at the tip of the detection end. To do.

In the method of manufacturing an optical fiber probe according to the third aspect of the present invention, one end of an optical fiber having a quartz core and a quartz clad added with germanium oxide is etched with an etching solution containing an aqueous solution of ammonium fluoride, hydrofluoric acid and water. By performing the first etching step of reducing the thickness of the quartz clad to form the base end portion, and etching the tip end side of the base end portion with an etching solution consisting of an aqueous solution of ammonium fluoride, hydrofluoric acid and water. A second etching step of sharpening the core to form a detection end portion.

A method of manufacturing an optical fiber probe according to a fourth aspect of the present invention is the method of manufacturing an optical fiber probe according to the third aspect of the present invention, wherein an ammonium fluoride aqueous solution having a concentration of 40% by weight, hydrofluoric acid and water having a concentration of 50% by weight are used. Using an etching solution having a volume ratio of X: 1: 1 consisting of _{1 to} 1.6, etching is performed with an etching solution of X ₁ = 1.6 to 1.8 in the first etching step, and X ₂ ≧ 3 in the second etching step. It is characterized in that etching is performed with an etching solution.

A method of manufacturing an optical fiber probe according to a fifth aspect of the present invention is the method of manufacturing an optical fiber probe according to the third aspect of the present invention, in which the detection end portion is coated with chrome and then gold. It is characterized in that a minute opening smaller than the wavelength of the detection light is formed at the tip of the detection end.

[0017]

In the optical fiber probe according to the first aspect of the present invention, since the optical fiber consisting of the core and the clad has the base end with the thickness of the clad reduced, the base end sharpens the core. It functions as an extension member that substantially extends the length of the detection end.

In the optical fiber probe according to the second invention, the gold coating layer provided on the surface of the detection end of the optical fiber probe according to the first invention functions as a coating layer for blocking scattered light from the sample surface. Then, the detection light is taken only from the minute opening provided at the tip of the detection end.

In the method for manufacturing an optical fiber probe according to the third aspect of the invention, in the first etching step, one end of the optical fiber consisting of the quartz core and the quartz cladding doped with germanium oxide is treated with an aqueous solution of ammonium fluoride, hydrofluoric acid and water. To form a base end portion by reducing the thickness of the quartz clad by etching with an etching solution consisting of
In the second etching step, the tip end side of the base end portion is etched with an etching solution containing hydrofluoric acid, water and ammonium fluoride to sharpen the core to form a detection end portion.

A method for manufacturing an optical fiber probe according to a fourth aspect of the present invention is the same as the method for manufacturing an optical fiber probe according to the third aspect of the present invention, in which an ammonium fluoride aqueous solution having a concentration of 40% by weight, hydrofluoric acid and water having a concentration of 50% by weight are used. Etching solution having a volume ratio of X: 1: 1 consisting of and is etched in the first etching step with an etching solution of X ₁ = 1.5 to 1.8, and in the second etching step X ₂ ≧ 3 Etching is performed with an etching solution.

In the method of manufacturing the optical fiber probe according to the fifth aspect of the present invention, in the method of manufacturing the optical fiber probe according to the third aspect of the invention, the detection end is coated with chrome, and further coated with gold, thereby performing detection. A double coating layer made of chromium and gold is formed at the end portion, and a minute opening smaller than the wavelength of the detection light is formed at the tip of the detection end portion.

[0022]

Embodiments of an optical fiber probe and a method for manufacturing an optical fiber probe according to the present invention will be described below in detail with reference to the drawings.

The optical fiber probe according to the present invention has a cladding diameter d _o and a core diameter d _C as shown in FIG. 1, for example.
Of the optical fiber 1 has a base end portion 3 having a clad diameter d ₂ with a reduced thickness of the clad 2, and a tip end of the base end portion 3 has a sharpened angle of θ with a sharpened angle θ. It has a part 5. The optical fiber 1 is made of germanium oxide GeO.
_It consists of a quartz core 4 containing ₂ and a pure quartz cladding 2.

The optical fiber probe 10 having such a structure
Since the clad 2 has a detection end 5 having a sharpened core 4 at the tip of the base 3 having a reduced thickness, the base 3 has the length L _{1 of the} detection end 5. It functions as an extension member that substantially extends the length L ₂ . This allows
In this optical fiber probe 10, the cladding 2 is used at the time of use.
The peripheral end portion of the probe does not collide with the sample, and the risk of damaging the sample and / or the probe itself is extremely small. The clad diameter d ₂ of the base end portion 3 is d ₂ ≧ 2d.
By setting _C , the function as the cladding of the optical fiber can be sufficiently exerted.

Here, the optical fiber 1 composed of the quartz core 4 doped with germanium oxide GeO ₂ and the pure quartz cladding 2 is composed of an ammonium fluoride aqueous solution having a concentration of 40% by weight, hydrofluoric acid and a water having a concentration of 50% by weight. Volume ratio is X: 1:
When the end surface is kept in contact with the buffered hydrofluoric acid solution of No. 1, SiO ₂ : SiO ₂ + 6HF → H ₂ SiF ₆ + 2H ₂ OH ₂ SiF ₆ + NH ₃ → (NH ₄ ) ₂ SiF ₆ GeO ₂ : GeO ₂ + 6HF → H ₂ GeF ₆ + 2H ₂ OH ₂ GeF ₆ + NH ₃ → (NH ₄ ) ₂ GeF _{6 The} clad 2 and the core 4 are etched by the chemical reaction. A quartz core 4 and a pure quartz clad 2 to which the germanium oxide GeO ₂ is added, which constitutes the optical fiber 1.
Have a difference in dissolution rate with respect to the etching solution, that is, the buffered hydrofluoric acid solution. Therefore, the quartz core 4 and the pure quartz cladding 2 can be selectively chemically etched by using the buffered hydrofluoric acid solution as an etching solution.

The clad diameter d _o is 125 μm, the core diameter d _C is 3.4 μm, and the germanium oxide (G
Samples A to E having different addition rates of eO ₂ ) Sample A: Addition rate of GeO ₂ in the core 3.6 mol% Sample B: Addition rate of GeO ₂ in the core 8.5 mol% Sample C: GeO _{2 in the} core Addition ratio 14 mol% Sample D: GeO ₂ addition ratio in core 23 mol% Sample E: GeO ₂ addition ratio in core 22 mol% Fluoride F addition ratio 2.1 mol% in the clad A sharpening treatment of the core was performed for XX minutes using an etching solution in which the volume ratio X of ammonium NH ₄ F was changed, and the volume ratio X of ammonium fluoride NH ₄ F in the etching solution and the sharpness angle θ of the core were When the relationship was examined, the results shown in FIG. 2 were obtained.

As is apparent from FIG. 2, by using an etching solution of X ≧ 3, the core can be sharpened to form the detection end portion 5 having a sharpness angle θ at the tip of the optical fiber 1. Particularly, in the optical fiber of the sample E, X
When the sharpening treatment of the core was performed for 40 minutes with the etching liquid of = 5, the detection end portion 5 having the sharpness angle θ of 14 degrees could be formed.

Further, the cladding of the optical fiber is preferentially etched by using an etching solution having a low volume ratio X of ammonium fluoride NH ₄ F to reduce the thickness of the cladding 2 at one end of the optical fiber 1. The proximal end 3 can be formed.

If an etching solution having a volume ratio X of ammonium fluoride NH ₄ F smaller than a certain value is used, the tip of the optical fiber is dented, and the etching time is shortened. From the results of the experiment, it is clear that it is optimal to use the etching solution of X = 1.5 to 1.8 to form the portion 3 on one end of the optical fiber 1. Then, by adjusting the etching time, it was possible to form the base end portion 3 having the cladding diameter d ₁ which was reduced to 1/3 of the original cladding diameter d _o .

Therefore, the optical fiber probe 10 is
The optical fiber 1 having a cladding diameter of d ₀ and a core diameter of d _C was used as a starting material, and was manufactured by the processing procedure shown in the flowchart of FIG.

According to the present invention shown in the flow chart of FIG.
In the method of manufacturing the optical fiber probe, the first etching process is used.
In the following, ammonium fluoride NH_FourVolume ratio X of F
Is X ₁= 1.5-1.8 buffered hydrofluoric acid solution as etching solution
Optical fiber 1
The base end portion 3 is formed at one end of the
Ammonium fluoride NH_FourThe volume ratio X of F is X₂≧
Etching using the buffered hydrofluoric acid solution of 3 as an etching solution
Sharpens the core at the tip of the base end 3 by performing
The detected end portion 5 is formed.

That is, in the method for manufacturing an optical fiber probe according to the present invention, in the first etching step,
Using an etching solution of X ₁ = 1.5 to 1.8, as shown in FIG. 4A, the cladding at one end portion is etched with respect to the optical fiber 1 having a cladding diameter d ₀ and a core diameter d _C. The diameter d _{1 is set} to d ₁ = d ₀ , etching is started from the state of d ₁ = d ₀ , and etching is performed until the target value d _g (d ₀ > d _g > 2d _C + δ) in this first etching step is reached. Then, as shown in FIG. 4B, the cladding diameter is d ₁
= D _g to form the base end portion 3 having a length of L ₀ .

Further, in the second etching step, as shown in FIG.
(C), the clad diameter is d ₀ and the core diameter is d _C
For the optical fiber 1 of No. ₂ , using the etching solution of X ₂ ≧ 3, the cladding diameter of the base end portion 3 to be etched is d ₂ = d _g
Then, the etching is started from the state where the clad diameter is d ₂ = d _g , and the target value d in this second etching step is
Etching is carried out until _p (2d _C + δ> d _p > 2d _C ) and the cladding diameter is d ₂ =, as shown in FIG.
A detection end 5 having a length L ₂ and a sharpness angle θ is formed at the tip of the base end 3 of d _p .

Here, δ is a detection end portion 5 having a sharpness angle θ at one end of the optical fiber 1 having a cladding diameter d ₀ and a core diameter d _C by one etching using an etching solution of X ≧ 3. It is the cladding diameter that decreases when the is formed. Based on an experiment in advance, from the sharp angle θ of the detection end portion 5 to the ammonium fluoride N of the etching liquid used in the second etching step.
By determining the volume ratio X ₂ of H ₄ F and the etching time t ₂ ,
The target values d _g and d _p are set by obtaining the above δ, and the volume ratio X ₁ of ammonium fluoride NH ₄ F of the etching solution used in the first etching step and the etching time t ₁ are determined.

Then, with respect to the optical fiber of the sample E in which the GeO ₂ addition rate in the core was 22 mol% and the fluorine F addition rate in the clad was 2.1 mol%, the etching of X ₁ = 1 in the first etching step was performed. By performing etching for 40 minutes with the liquid, and further performing etching for 40 minutes with the etching liquid of X ₂ = 5 in the second etching step, the cladding diameter d ₂ of the proximal end portion 3 from the optical fiber having the cladding diameter d _o of 125 μm can be obtained. The optical fiber probe 10 thinned to 24 μm could be manufactured.

On the other hand, the optical fiber of the sample E was etched with an etching solution of X = 5 for 60 minutes to sharpen the core, and the optical fiber probe manufactured had a cladding diameter d ₂ of 88 μm.

Further, the optical fiber of the sample A having a GeO ₂ addition rate of 3.6 mol% in the core was etched for 60 minutes in the first etching step with an etching solution of X ₁ = 1.7, and further, In the second etching step, etching was performed using an etching solution of X ₂ = 3, 4, ₂₀ and the relationship between the etching time t ₂ and the cladding diameter d ₂ of the base end portion 3 in the second etching step was examined. However, the results shown in FIG. 5 were obtained.

In FIG. 5, a straight line A ₁ shows the result of etching with an etching solution of X = 3 in the second etching step, and a straight line A ₂ shows an etching solution of X ₂ = 4 in the second etching step. The results of etching are shown, and the straight line A ₃ shows the results of etching with an etching solution of X ₂ = 20 in the second etching step.

Further, GeO in the core₂Addition rate is 3.6
Mol% of the optical fiber of Sample A, GeO in the core₂Attendant
In the optical fiber and core of the above sample D with an addition rate of 23 mol%
GeO₂The optical fiber of the sample E with the addition ratio of 3.6 mol% was used.
For iva, using the etchant with the above volume ratio of X,
Sharpness θ when the core is sharpened by one etching ₁
And the same etching solution is used for the second etching step.
Angle θ when the core is sharpened by etching₂When
Difference Δθ = θ₁−θ₂As shown in FIG.
The results were obtained. The numerical values (14 to 12) in FIG.
4) indicates the angle of the sharpness angle θ at each measurement point.

As is apparent from FIGS. 5 and 6, the cladding diameter d of the base end portion 3 is maintained while maintaining the sharpness angle θ of the detection end portion 5.
It could be controlled thinner ₂ to 1/5 of the original clad diameter d _o. In addition, the difference Δθ in sharpness could be maintained at 0.5 degrees or less.

Further, in the optical fiber probe according to the present invention, a gold coating layer is provided on the surface of the detection end portion, and a minute opening smaller than the wavelength of the detection light is provided at the tip of the detection end portion. The influence of scattered light can be avoided and the detection efficiency can be increased.

In this case, in the optical fiber probe manufacturing method according to the present invention, for example, the base end portion 3 and the detection end portion 5 of the optical fiber probe 10 manufactured by the processing procedure shown in the flowchart of FIG. As shown in FIG. 2, a first coating layer 6A made of chromium is formed by coating chromium, and a second coating layer 6 made of gold is further formed by coating gold.
After forming B, a minute aperture 7 smaller than the wavelength of the detection light is formed at the tip of the detection end portion 5.

Here, gold is unlikely to adhere to quartz glass,
Even if the tip of the optical fiber is directly coated, it is difficult to uniformly coat it with a thickness of 10 nm or more.
Also, although it may easily come off,
By forming the coating layer 6A, gold can be uniformly and stably coated with a thickness of 10 nm or more to form the second coating layer 6B. Therefore, a high light-shielding property can be secured by the second coating layer 6B made of gold.

For the chromium and gold coating, a heating boat type air vapor deposition apparatus was used, the optical fiber probe was tilted and fixed, and chromium or gold was vapor deposited while rotating.

Further, as described above, the second coating layer 6B made of gold is used.
If a higher light-shielding property is ensured by the above, the tip of the detection end portion 5 is also shielded and the evanescent light cannot be detected. Therefore, at the tip of the detection end portion 5, a small amount smaller than the wavelength of the detection light is detected. The opening 7 is formed so that the evanescent light is taken in through the minute opening 7.

In the optical fiber probe 15 according to the present invention manufactured as described above, the detection light is taken in only from the minute opening 7 provided at the tip of the detection end portion 5, so that the influence of scattered light is avoided and the detection efficiency is improved. Can be increased, and evanescent light with extremely low power can be reliably detected.

[0047]

In the optical fiber probe according to the first aspect of the present invention, the detection is performed by sharpening the core at the base end portion formed by reducing the thickness of the cladding provided at one end of the optical fiber including the core and the cladding. Since it functions as an extension member that substantially extends the length of the end, the peripheral end of the clad does not collide with the sample, and the risk of damaging the sample and / or the probe itself is extremely small.

Further, in the optical fiber probe according to the second invention, the gold coating layer provided on the surface of the detection end portion in the optical fiber probe according to the first invention shields the scattered light from the sample surface. Functioning as, and detecting light is taken in only from the minute aperture provided at the tip of this detecting end, it is possible to avoid the influence of scattered light, improve detection efficiency, and reliably detect evanescent light with extremely low power. be able to.

In the method of manufacturing an optical fiber probe according to the third aspect of the invention, in the first etching step, one end of the optical fiber consisting of the quartz core and the quartz cladding doped with germanium oxide is treated with an aqueous solution of ammonium fluoride and hydrofluoric acid. By etching with an etchant composed of water and water to form a base end portion by reducing the thickness of the quartz clad, and in the second etching step, the front end side of the base end portion is treated with an ammonium fluoride aqueous solution, hydrofluoric acid, and The optical fiber probe according to the first aspect of the present invention is less likely to collide with the sample at the peripheral edge of the clad by forming the detection edge formed by sharpening the core by etching with an etchant composed of water. can do.

Further, in the method for manufacturing an optical fiber probe according to the fourth invention, in the method for manufacturing an optical fiber probe according to the third invention, ammonium fluoride having a concentration of 40% by weight and hydrofluoric acid having a concentration of 50% by weight are used. Etching is performed with an etching solution of X = 1.5 to 1.8 in the first etching step using an etching solution containing water and having a volume ratio of X: 1: 1, and etching of X ≧ 3 in the second etching step. By performing the etching with the liquid, the optical fiber probe according to the first aspect of the present invention, in which the peripheral edge portion of the clad is less likely to collide with the sample, can be stably manufactured with high accuracy.

In the method of manufacturing the optical fiber probe according to the fifth invention, in the method of manufacturing the optical fiber probe according to the third invention, the detection end portion is coated with chromium, and further gold is coated, thereby performing detection. By forming a double coating layer of chrome and gold on the end and further forming a minute aperture smaller than the wavelength of the detection light at the tip of this detection end, the influence of scattered light is avoided and detection efficiency is improved. It is possible to manufacture the optical fiber probe according to the second aspect of the present invention, which can be increased in height and can reliably detect evanescent light with extremely low power.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing the structure of an optical fiber probe according to the present invention.

FIG. 2 is a diagram showing the relationship between the volume ratio X of ammonium fluoride NH ₄ F in the etching liquid used for manufacturing the optical fiber probe according to the present invention and the sharpness angle θ of the core of the optical fiber.

FIG. 3 is a flowchart showing a procedure for processing an optical fiber in the method for manufacturing an optical fiber probe according to the present invention.

FIG. 4 is a sectional view of an essential part of an optical fiber in each processing step in the method for manufacturing an optical fiber probe according to the present invention.

FIG. 5 is a diagram showing the relationship between the etching time and the cladding diameter at the base end in the second etching step in the method for manufacturing an optical fiber probe according to the present invention.

FIG. 6 relates to the present invention using the same etching solution as the tip sharpening angle θ ₁ when the core is sharpened by one etching using an etching solution having a volume ratio of ammonium fluoride NH ₄ F of X. FIG. 6 is a diagram showing a difference Δθ = θ ₁ −θ ₂ from the tip sharpening angle θ ₂ when the core is sharpened in the second etching step in the method for manufacturing an optical fiber probe.

FIG. 7 is a cross-sectional view of an essential part showing the structure of the optical fiber probe according to the present invention.

FIG. 8 is a diagram schematically showing the principle of a photon scanning microscope.

[Explanation of symbols]

 1 ... Optical fiber 2 ... Clad 3 ... Base end 4 ... Core 5 ... Detection end 6A ... -First coating layer 6B-Second coating layer 7-Micro aperture 10,15-Optical fiber probe

Claims (5)

[Claims] 1. An optical fiber comprising a core and a clad has at one end a base end portion having a reduced thickness of the clad, and at the tip of the base end portion a detection end portion having the core sharpened. An optical fiber probe characterized by: 2. The gold coating layer is provided on the surface of the detection end portion, and a minute opening smaller than the wavelength of the detection light is provided at the tip of the detection end portion.
The optical fiber probe described. 3. The thickness of the quartz clad is reduced by etching one end of an optical fiber consisting of a quartz core and a quartz clad added with germanium oxide with an etching solution consisting of an aqueous solution of ammonium fluoride, hydrofluoric acid and water. A first etching step for forming a base end portion, and the tip side of the base end portion is etched with an etching solution composed of an aqueous solution of ammonium fluoride, hydrofluoric acid and water to sharpen the core to form a detection end portion. A second etching step, and a method for manufacturing an optical fiber probe. 4. An etching solution comprising an ammonium fluoride aqueous solution having a concentration of 40% by weight, hydrofluoric acid having a concentration of 50% by weight and water and having a volume ratio of X: 1: 1 is used, and X ₁ = 1 in the first etching step. Etching is performed with an etching solution of 0.5 to 1.8, and X is used in the second etching step.
_The method for manufacturing an optical fiber probe according to claim 3, wherein etching is performed with an etching solution of ₂ ≧ 3. 5. The detection end portion is coated with chrome, and further gold is coated, and then a minute aperture smaller than the wavelength of the detection light is formed at the tip of the detection end portion. A method for manufacturing the optical fiber probe described.