JP2005070683A - Optical fiber tip working method and optical fiber probe manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a cone-shaped tapered surface with various vertex angles irrespective of difference of the mixture amount of germanium and fluorine of a core and a clad. <P>SOLUTION: In order to sharpen the tip 2a of an optical fiber 2, first of all, a cone-shaped tapered surface 7 whose tip is not sharpened is formed by applying laser machining or mechanical grinding to the peripheral surface of the tip of the optical fiber 2 in a rough working process P<SB>1</SB>and thereafter, a sharpened cone-shaped tapered surface 5 is formed at the tip of the optical fiber by applying chemical etching to the tapered surface 7 in a sharpening process P<SB>2</SB>. Then, when an optical fiber probe 1 is formed using the sharpened optical fiber 2, the vertex 5a of the sharpened cone-shaped tapered surface 5 is exposed and also a metal coating 6 which coats at least the part of a core 3 is formed in a coating forming process P<SB>3</SB>which follows the sharpening process P<SB>2</SB>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention irradiates a minute region of an object to be processed with energy light, and uses the energy to perform arbitrary light processing such as light processing, light stimulation and thermal stimulation, and to observe fluorescence, so that the tip of an optical fiber The present invention relates to an optical fiber tip processing method for forming a conical tapered surface and a fiber probe manufacturing method using the same.

In the biological field and the like, optical processing that cuts and binds arbitrary sites of DNA, RNA, and protein biomolecules is performed, and light stimulation and thermal stimulation are applied to arbitrary sites of cells.
In this case, it is usually possible to optically process only an arbitrary part without affecting other parts by squeezing the laser light with a lens and irradiating a minute region. However, due to the diffraction limit of light, the diameter of the light spot is in the micron order, and cannot be reduced to a smaller nanometer order.

  Therefore, when a part of DNA, RNA, or protein is photo-cut and trimmed and only a part having a specific base sequence is taken out as a sample, the diameter of the light spot becomes micron order when using a lens. Therefore, light is irradiated to the periphery of the desired cutting site, and it is extremely difficult to cut the site accurately.

For this reason, an optical fiber probe capable of irradiating light with an irradiation diameter of nanometer order below the diffraction limit has been proposed.
Japanese Patent No. 2792780

  In this optical fiber probe, a metal film is formed on a taper surface excluding its apex by sharpening the core part at least in a conical shape. The light is leaked and irradiated as near-field light in a range of about 10 nm around the periphery.

  Therefore, if the vertex of the optical fiber probe is positioned at an arbitrary position on the object to be processed under the microscope field of view and light is irradiated, the light is irradiated to the range of about 10 nm around the vertex, and the surroundings are affected. Only within that range is light-processed.

By the way, such an optical fiber probe 21 is manufactured through the following processes.
First, when the optical fiber 22 having a flat tip is immersed in buffered hydrofluoric acid as shown in FIG. 7 (a), the optical fiber 22 is selectively selected due to the difference in dissolution rate between the core 23 and the clad 24 as shown in FIG. 7 (b). Etching is performed to form a conical tapered surface 25 having a tip base diameter d = about 20 nm.

  Next, as shown in FIG. 7C, a metal film 26 having a thickness of 150 nm is formed by depositing gold, silver, and aluminum on the periphery thereof, and this is then used as a resin liquid as shown in FIG. When dipped, the paintability in the submicron region is lost, and therefore, the resin film 27 is coated except for the apex 25a of the metal film 26.

  Further, when the metal film 26 is etched as shown in FIG. 7E, the apex 26a portion not coated with the resin 27 is selectively etched to expose the core 23 of the optical fiber 22, and finally, FIG. As shown in f), the optical fiber probe 21 is completed by dipping in a solution and peeling off the resin.

  According to this, the light propagating through the core 23 is leaked as near-field light from the apex 25a where the metal film 26 is not formed to a range of about 10 nm around the vertex 25a, and is irradiated on the workpiece W.

In this case, the tip shape is determined by the difference in dissolution rate between the core 23 and the clad 24, and the difference in dissolution rate depends on the content of germanium or fluorine.
In general, germanium has a lower content in the clad 24 than the core 23, and fluorine has a higher content in the clad 24 than in the core 23. In any case, the clad 24 has a higher dissolution rate than the core 23. The tip of the optical fiber 22 becomes a conical tapered surface 25.

However, recently, an optical fiber probe having an arbitrary apex angle has been demanded in order to investigate the light irradiation characteristics depending on the apex angle or to meet various needs. Therefore, it has been difficult to inexpensively manufacture many types of optical fiber probes with different angles.
In addition, when this optical fiber probe is used for light processing for irradiating a workpiece with ultraviolet rays, germanium contained in the optical fiber reduces the transmittance of the ultraviolet rays.

  Therefore, the present invention has a technical problem to be able to easily form a conical tapered surface at various apex angles regardless of the difference in the mixing amount of germanium or fluorine between the core and the clad.

  An optical fiber tip processing method according to the present invention comprises a roughing step of forming a conical tapered surface whose tip is not sharpened by laser processing or mechanical polishing of the tip peripheral surface of the optical fiber; And a sharpening step of sharpening the apex by etching.

  Further, the method for manufacturing an optical fiber probe according to the present invention includes forming the conical tapered surface with the tip of the optical fiber sharpened by the above processing method, exposing the apex thereof, and at least the core of the conical tapered surface. And a film forming process for forming a metal film covering the portion.

According to the optical fiber tip processing method of the present invention, first, the tip peripheral surface is laser machined or mechanically polished to form a rounded conical tapered surface whose tip is not sharpened.
At this time, the tip is not sharpened yet, but the shoulder portion of the clad is dropped, and the core is exposed in a rounded shape at the tip.
Therefore, if chemical etching is performed in this state, when the optical fiber is not doped with germanium, the core and the clad are polished at substantially the same processing speed, so that the conical tapered surface is maintained in parallel with its apex angle maintained. The tip rounded portion of the tip is polished concentrically, and its radius is gradually reduced and sharpened.

At this time, the apex angle of the sharpened conical tapered surface is maintained as it is when the laser processing is performed in the roughing process, and the angle is maintained regardless of the composition of the optical fiber. Determined by processing.
Therefore, it is possible to process into a conical tapered surface sharpened to various apex angles by changing the apex angle during rough machining.

  In this example, the problem of forming the tip of the optical fiber on a conical tapered surface sharpened at various apex angles was realized regardless of the amount of germanium or fluorine mixed.

  1 is a sectional view showing an optical fiber probe manufactured by the method of the present invention, FIG. 2 is a manufacturing process diagram, FIG. 3 is an explanatory diagram of a roughing process, FIG. 4 is an explanatory diagram of another roughing process, and FIG. Explanatory drawing of a sharpening process, FIG. 6 is explanatory drawing of a film formation process.

  FIG. 1 shows an optical fiber probe 1 manufactured by carrying out the method of the present invention. For example, the tip of an optical fiber 2 having an outer diameter of 5 μm of a core 3 and an outer diameter of 125 μm of a cladding 4 is a sharp conical tapered surface 5 having an apex angle θ. And a metal film 6 is formed except for the apex 5a.

FIG. 2 shows a manufacturing process of such an optical fiber probe 1, and a rough machining process P in which an optical fiber 2 having a flat tip is laser-processed to form a tip of the tip into a rounded conical tapered surface 7 having an apex angle α. ₁ , a sharpening process P ₂ for sharpening the tip, and a film formation process P ₃ for forming a metal film in the vicinity of the apex 5 a of the sharp cone-shaped tapered surface 5.

In rough processing step _{P 1,} if the laser processing optical fiber 2, using a processing method such as that disclosed in JP 2003-33893.
As shown in FIG. 3, the tip of the optical fiber is processed by irradiating the laser beam emitted from the CO ₂ laser 8 from the side surface of the optical fiber 2 and melting and evaporating the irradiated spot. On the optical path L of the laser light from the CO ₂ laser 8 to the optical fiber 2, there is a translucent portion H in which the processing spot shape S corresponding to the tip shape of the optical fiber 2 is enlarged by a predetermined time (for example, 20 times). A mask 10 and a reduction projection optical system 11 for reducing the real image of the light transmitting portion H to the processing spot shape S and forming an image on the optical fiber 2 are interposed, and a laser is interposed between the CO ₂ laser 8 and the mask 10. An expanding collimating lens system 12 that expands the diameter of the light to form a parallel beam is interposed.

If a TEA-CO ₂ laser capable of outputting multimode light having a large peak power and a flat beam profile as a short pulse with a steep rise is used as the CO ₂ laser 8, a large optical pulse energy is obtained. Can be applied to the optical fiber 2 in a short time, and therefore the working efficiency is excellent.
A plurality of masks 10 having triangular light shielding portions 10a having different apex angles are prepared on the light transmitting portion H, and the tip of the optical fiber is arbitrarily set by irradiating laser light while rotating the optical fiber 2. Can be roughly machined into a tapered conical tapered surface 7 having an apex angle of.

Further, as shown in FIG. 4A, the rough machining step P ₁ forms a half angle α / 2 of the apex angle α with respect to the optical axis X while rotating the optical fiber 2 around the optical axis X. A method of irradiating the CO ₂ laser 8 from the direction may be used.
As a result, as shown in FIG. 4B, a rounded conical tapered surface 7 whose tip is not sharpened is formed at the apex angle α.

Next, the sharpening process P _2, as shown in FIG. 5 (a), Sakimaru conical tapered surface 7 by immersing the tip of the optical fiber 2 in a buffer hydrofluoric acid is subjected to chemical etching The tip is sharpened.
When the optical fiber 2 is not doped with germanium, the core 3 and the cladding 4 are polished at substantially the same processing speed as shown in FIG. 5B, so that the conical tapered surface 7 maintains its apex angle α. As it is, it is polished in parallel, and the tip rounded portion 7a is polished concentrically, and its radius is gradually reduced and sharpened.
At this time, the apex angle θ of the pointed conical tapered surface 5, and FIG. 5 (b) and (c), the apex angle of Sakimaru conical tapered surface 7 when the laser processing in the rough processing step P ₁ Since α is maintained as it is, the apex angle θ of the sharp cone-shaped tapered surface 5 is determined by rough machining regardless of the composition of the optical fiber 2.

Further, when the optical fiber 2 is doped with germanium, as shown in FIG. 5D, the processing speed of the cladding 4 is higher than that of the core 3, so that the apex angle α of the conical tapered surface 7 is maintained. While being etched in parallel, the rounded tip portion 7a is etched with a smaller etching amount.
At this time, since the clad 4 is etched first and the peripheral surface of the core 3 is exposed from the tip, the tip side exposed first has a longer processing time and is sharpened to a more acute angle. .
Thus, the core 3 parts apex angle θ of the pointed conical tapered surface 5, FIG. 5 (d) and (e), the Sakimaru conical tapered surface 7 when the laser processing in the rough processing step P ₁ The vertical angle θ is smaller than the vertical angle α, and the relationship of the vertical angle θ <vertical angle α is established, but if the vertical angle α is large, the vertical angle θ is large, and if the vertical angle α is small, the vertical angle θ is small. Regardless of the amount of germanium doped, the apex angle θ can be controlled by the apex angle α.

In the film formation step P _3, to form a metal film 6 which covers at least the core 3 partially to expose the sharpened apex 5a of the conical tapered surface 5.
Specifically, as shown in FIG. 6 (a), a metal film 6 having a thickness of 150 nm is formed by depositing gold, silver, and aluminum on the periphery thereof, as shown in FIG. 6 (b). Is immersed in the resin solution, the resin solution does not have a coating property in the sub-micron region, so that it is coated with the resin 9 except for the vertex 6a of the metal film 6.

  In this state, when the metal film 6 is etched as shown in FIG. 6C, the apex 6a portion that is not coated with the resin 9 is selectively etched, and the tip of the core 3 of the optical fiber 2 is exposed. Finally, as shown in FIG. 6D, the optical fiber probe 1 is completed by dipping in a solution and peeling off the resin.

In the above description, there has been described a case where laser processing the optical fiber 2 in the rough machining step P _1, the present invention is not limited thereto, it may be a case where mechanical polishing.

  As described above, the present invention can form a conical tapered surface at various apex angles regardless of the mixing amount of germanium and fluorine in the core and the cladding, so that the quartz optical fiber for ultraviolet light not doped with germanium, The present invention can be applied to the use of sharpening a quartz optical fiber not doped with fluorine.

Sectional drawing which shows the optical fiber probe manufactured by the method of this invention. The manufacturing process diagram. Explanatory drawing of a rough processing process. Explanatory drawing which shows the other example of a roughing process. Explanatory drawing of a sharpening process. Explanatory drawing of a film formation process. Explanatory drawing which shows the conventional processing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber probe 2 Optical fiber 5 Sharp conical taper surface 5a Vertex 6 Metal film 7 Round conical taper surface P ₁ Roughing process
7a Pointed part P ₂ Sharpening process P ₃ Film formation process
8 CO ₂ laser

Claims (2)

An optical fiber tip processing method for forming the tip of an optical fiber into a conical tapered surface,
A roughing process for forming a conical tapered surface whose tip is not sharpened by laser processing or mechanical polishing of the tip peripheral surface of the optical fiber, and a sharpening for sharpening the apex by performing chemical etching on the tapered surface An optical fiber tip processing method comprising the steps of: A method of manufacturing an optical fiber probe in which the tip of an optical fiber is formed in a conical tapered surface,
A roughing process for forming a conical tapered surface whose tip is not sharpened by laser processing or mechanical polishing of the tip peripheral surface of the optical fiber; And a coating forming step of forming a metal coating that exposes the apex and covers at least a core portion of the conical tapered surface.

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