JP2000228554A - Proximity field light generation element, element array and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a proximity field light generation element and an element array, and a method for manufacturing them, relatively freely shaped to easily manufacture, whose optical axis and focus does not need to be adjusted. SOLUTION: An element array is provided with an incidence surface 11 and a light output surface 12 from which the light incident through the incidence surface 11 and condensed is emitted, and a light-shield film 13 provided on the light output surface 12 has a micro opening 13a generating proximity field light. A lens array main body 10 is pressure-molded in a re-heating method, and on the light exit surface 12 thereof, the light-shield film 13 is formed out of metal material. When the incidence surface 11 is irradiated with the light, it is condensed on the light output surface 12, and the micro opening 13a is formed on the light-shield film 13 by the energy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a near-field light generating element used for a high-density optical memory (recording / reading) and a high-resolution microscope, an element array, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, in the field of optical memory for optically recording / reading information, a larger amount of information can be recorded, that is, recording density is remarkably improved with the increase in speed of computers and development of multimedia. Therefore, a near-field optical recording technique has been proposed. In a conventional optical memory using laser light, the upper limit of the recording density is determined by the diffraction limit of light, and recording / reading can be performed only for a mark of about the wavelength of light (about several 100 nm).

In an optical memory using a near-field light phenomenon proposed in recent years, an optical head is mounted on a recording medium (optical disk) using a probe having a small aperture smaller than the wavelength of light or a solid immersion lens (solid immersion lens). By irradiating recording / reading light with the distance between the recording medium and the recording medium approaching several tens nm, the light exceeds the diffraction limit of the light to several tens nm.
Can be written and read as a signal.

[0004]

2. Description of the Related Art In a conventional optical head for near-field light, it is necessary to combine an element such as a solid immersion lens with a condenser lens, which not only increases the size of the optical head but also adjusts the optical axis. And the focus adjustment is complicated.

On the other hand, in the field of microscopes, Japanese Patent No. 2578
No. 376 discloses a microlens obtained by hardening a transparent resin into a spherical shape on a substrate having a pinhole, together with a method of manufacturing the microlens. Here, light is introduced from the pinhole, and the light is diffused on the pinhole surface of the photocurable transparent resin to cure the region of the light.

[0006] However, in the microlens described in the above-mentioned publication, the shape of the lens is limited to a spherical shape, and the lens material is limited to a photocurable resin. Furthermore, the amount of light required to cure the photo-curable resin is large, and the amount of near-field light leaching from the minute aperture is insufficient. In practice, the resin is cured with the near-field light to obtain a microlens. It is difficult to do this.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a near-field light generating element, an element array, and a method of manufacturing the near-field light generating element which can be easily manufactured in a relatively free shape without the need for optical axis adjustment and focus adjustment. is there.

[0008]

In order to achieve the above objects, a near-field light generating element according to the present invention comprises an incident surface, and an exit surface for emitting condensed light incident from the incident surface. And a minute aperture for generating near-field light in the light-shielding film provided on the emission surface. An element array can be obtained by integrally arranging a plurality of such elements.

If collimated light or divergent light is used as incident light, the incident surface may have a curvature for condensing the incident light on the exit surface or in the vicinity thereof. If the incident surface does not have such a function, the element itself may be provided with a reflecting surface for condensing incident light on the emitting surface or in the vicinity thereof.

According to the near-field light generating element and the element array according to the present invention, a condenser lens is not required, the optical axis adjustment and the focus adjustment can be omitted, and a compact and lightweight optical head can be constructed.

Further, in the manufacturing method according to the present invention, there is provided a process for producing an element main body having a light incident surface and an exit surface for emitting condensed light incident from the incident surface; A step of providing a light-shielding film on a surface; and a step of making light incident on the incident surface and forming a minute opening in the light-shielding film by energy of light condensed on the exit surface or in the vicinity thereof.

According to the manufacturing method, since the minute aperture for generating the near-field light by the energy of the light condensed in the element body is formed, the minute aperture is formed at an accurate position. When assembling the array as an optical head, complicated optical axis adjustment and focus adjustment are not required. Further, the size of the minute aperture can be arbitrarily set by adjusting light energy, irradiation time, and the like.

In particular, if a reheating method in which a material is reheated and pressure-molded is adopted as a process for manufacturing the element body, not only can the element body be mass-produced with high accuracy, but also the material to be used can be made of a general resin or resin. It can be selected from a wide range such as glass.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a near-field light generating element, an element array, and a method of manufacturing the same according to the present invention will be described.
This will be described with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of a method for manufacturing an element array. First, the lens array body 10 is manufactured by a reheating method (FIG. 1A).
reference). Here, a glass material 10 'roughly similar to the lens array body 10 to be obtained by using lanthanum silica glass is prepared, and this glass material 10' is placed in a quartz tube 15 in an upper mold 16 and a lower mold. Pressing was performed at 17.
The facing surface of the upper mold 16 is a flat surface, and the facing surface of the lower mold 17 is a lens shape, and each is precisely finished by mirror polishing silicon carbide.

The molding by the reheating method is performed by heating to 670 ° C. in a nitrogen gas atmosphere and pressurizing for 30 seconds, so that the incidence surface 11 has a radius of curvature of 0.5 mm and a thickness of 0.8 m.
m lens array body 10 was obtained. The focal point of the entrance surface 11 is set on the exit surface 12 formed into a plane.

Next, the emission surface 12 of the lens array body 10
A film of aluminum was formed thereon to a thickness of 1000 angstroms by a vacuum evaporation method, and a light-shielding film 13 was provided (see FIG. 1B).

Thereafter, the entrance surface 1 of the lens array body 10
1 was irradiated with a laser beam having a wavelength of 633 nm at an output of 10 mW for 5 minutes. The laser light is condensed on the incident surface 11 and focused on the emission surface 12, so that a minute opening 13a is formed in the light shielding film 13 (see FIG. 1C).

The size of the formed small opening 13a was 0.5 μm in diameter when observed by an electron microscope.
Further, it was confirmed that near-field light was seeping out from the minute opening 13a. Confirmation of the near-field light is performed by the minute aperture 13a.
The measurement was performed with the output of a photomultiplier (photoelectron amplifier) arranged at a position of 50 nm from.

FIG. 2 shows a second embodiment of a method for manufacturing an element array. First, the lens array body 20 is manufactured by a reheating method (FIG. 2A).
reference). Here, a flat glass material 20 ′ is prepared using lead silica-based flint glass, and this glass material 2 ′ is prepared.
0 ′ was press-formed in a quartz tube 25 with an upper mold 26 and a lower mold 27. The facing surface of the upper mold 26 is a flat surface, and the facing surface of the lower mold 27 is in a lens shape.

Forming by the reheating method is performed by heating to 470 ° C. in an argon gas atmosphere and pressurizing for 22 seconds. The radius of curvature of the entrance surface 21 is 0.3 mm and the thickness is 0.1 mm.
A 4 mm lens array body 20 was obtained. The focal point of the entrance surface 21 is set on the exit surface 22 formed into a plane.

Next, the emission surface 22 of the lens array body 20
On top of this, chromium was deposited to a thickness of 500 angstroms by sputtering, and a light-shielding film 23 was provided (FIG. 2).
(B)).

Thereafter, the entrance surface 2 of the lens array body 20
1, a laser beam having a wavelength of 488 nm is output at 50 mW for 10 minutes.
Irradiated for minutes. The laser light is condensed on the incident surface 21 and is focused on the exit surface 22 to form a minute opening 23a in the light shielding film 23 (see FIG. 2C).

The size of the formed fine opening 23a was 0.3 μm in diameter when observed with an electron microscope.
Further, it was confirmed that near-field light was seeping out from the minute opening 23a. Confirmation of the near-field light is performed by the minute aperture 23a.
The measurement was performed with the output of a photomultiplier (photoelectron amplification tube) arranged at a position of 30 nm from.

FIG. 3 shows a near-field light generating element according to a third embodiment. In this element, an entrance surface 31, an exit surface 32, and an internal reflection surface 33 are formed on a lens body 30 made of a high refractive index substance, a light shielding film 34 is provided on the exit surface 32, and a light reflection film 35 is provided on the internal reflection surface 33. It is provided. The entrance surface 31 and the exit surface 32 are planes, respectively, and the internal reflection surface 33 is a paraboloid of revolution with the tip P as the vertex.

The lens body 30 is made of a titanium-silica glass (SFS57 manufactured by Minolta Co., Ltd.), and is molded under pressure by the same reheating method as in the first and second embodiments. The light-shielding film 34 is formed by sputtering aluminum to a thickness of 500 angstroms. The light reflection film 35 is formed by depositing silver to a thickness of 1000 angstroms by a vacuum evaporation method. The films 34 and 35
May be the same material or may be formed by the same technique.

The light shielding film 34 has a minute opening 34a. The formation method is performed by irradiating the incident surface 31 with laser light, as in the first and second embodiments. The laser beam enters perpendicularly to the incident surface 31, is reflected by the reflecting surface 33 and is focused on the emitting surface 32,
4a will be formed. Near-field light seeps out of the minute opening 34a.

(Use as Optical Head) The above-described element array and element are used as an optical head for recording / reading on a high-density optical recording medium utilizing near-field light. In this case, the incident light for generating the near-field light is the same as or different from the laser light used for forming the minute aperture. Usually, when forming the minute aperture, a laser beam having a higher intensity than the recording / reading light is used. Both may use light having different wavelengths.

It is preferable that the size of the minute aperture is smaller than the wavelength of light used for recording / reading.

The element array shown in each of the above embodiments,
In the element, the minute aperture is formed by the light-condensing action of the element itself, so that light incident upon recording / reading is surely focused on the minute aperture, and a condenser lens is not required.
There is no need to adjust the optical axis or focus with the condenser lens. Therefore, there is an advantage that the optical head can be reduced in size and weight and the assemblability can be improved.

Further, since the emission surfaces 12, 22, 32 are flat, it is easy to mold and is suitable as a slider type (air floating type) optical head.

(Materials and Other Manufacturing Methods) In the manufacturing method of the present invention, a lens body having a predetermined shape is formed from a lens blank, light is condensed using the lens body, and a minute opening is formed in the light shielding film. It is characterized by. Therefore, the material of the lens is not limited to the photocurable resin. For example, acrylic, polycarbonate, vinyl chloride, general transparent resins such as styrene, lead silica-based flint glass, lanthanum silica-based crown glass, titanium silica-based glass,
A glass material such as a boron silica-based glass can be used. That is, a wide range of materials from which the lens can be formed can be selected. In particular, if a reheating method is used for lens molding, mass production can be performed with high accuracy, and an array having a plurality of lenses can be easily molded.

As the light-shielding film, various materials can be used as long as a condition that does not transmit light to be used is satisfied. If light in the visible region is used for forming the minute aperture, a material having a relatively low melting point, such as chromium, aluminum, silver, copper, tin, or lead, is effective, and the film thickness is preferably about 500 to 3,000 angstroms. As the light-shielding film, a light-shielding resin can be used as a material. However, a thin and uniform film can be obtained by using a metal material.
The advantage of using a metal material is that a sufficient light-shielding property can be obtained at a film thickness of about 0.1 to 0.3 μm, and a film can be easily formed to a uniform thickness by a thin film technique such as a vacuum evaporation method or a sputtering method. is there.

The minute aperture is formed in the light-shielding film because light transmitted through the lens is focused on the light-shielding film and the energy dissolves the light-shielding film. This minute aperture clearly coincides with the optical axis of the lens. Therefore, the most concentrated light can be obtained on the minute aperture surface, and the light use efficiency at the time of recording / reading is improved.

It should be noted that the focal point of the lens may be located near the light-shielding film, that is, the focal position may be slightly shifted from the minute aperture surface. In this case, the light amount at the time of forming the minute opening may be increased. However, the size of the minute opening becomes slightly larger.

On the other hand, a light absorbing film may be formed on the exit surface of the lens, and a light shielding film may be formed thereon. The light-absorbing film absorbs light energy, and can form minute openings efficiently. As the light absorbing film, chromium oxide, carbon, a carbon compound, manganese, silicon, or the like can be used, and a black resin can also be used.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a manufacturing method according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of a manufacturing method according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a near-field light generating element according to a third embodiment of the present invention.

[Explanation of symbols]

 10, 20 lens array body 11, 21 entrance surface 12, 22 emission surface 13, 23 light-shielding film 13a, 23a minute aperture 30 lens body 31 incident surface 32 emission surface 33 reflective surface 34 light-shielding Film 34a: minute aperture

Claims (12)

[Claims] 1. A small aperture for generating near-field light in a light-shielding film provided on a light-emitting surface, comprising: a light-incident surface; and an emission surface for emitting condensed light incident from the incident surface. A near-field light generating element. 2. An element array, wherein a plurality of near-field light generating elements according to claim 1 are integrally provided side by side. 3. The near-field light generating element according to claim 1, wherein the incident surface has a curvature for converging the incident collimated light or divergent light on the light exit surface or in the vicinity thereof. Or an element array. 4. The near-field light generating device according to claim 1, further comprising a reflecting surface for reflecting the incident collimated light or divergent light and condensing the light on the light exit surface or in the vicinity thereof. Element or element array. 5. The near-field light generating element or element array according to claim 1, wherein the emission surface is a plane. 6. The near-field light generating element or element array according to claim 1, wherein the light-shielding film is provided on the emission surface via a light absorbing film. 7. The near-field light generating element or element array according to claim 1, wherein the light-shielding film is made of a metal material. 8. The near-field light generating element according to claim 1, wherein the size of the minute aperture is equal to or smaller than a wavelength of light used for recording and / or reading. Element array. 9. A step of fabricating an element body having a light incident surface and an exit surface for emitting condensed light incident from the incident surface; and providing a light shielding film on the exit surface. A step of causing light to enter the incident surface and forming a minute aperture in the light-shielding film by energy of light condensed on the exit surface or in the vicinity thereof. Alternatively, a method for manufacturing an element array. 10. The method according to claim 9, wherein in the step of manufacturing the element body, the material is reheated and pressure-formed. 11. The manufacturing method according to claim 9, wherein a light absorbing film is provided on the emission surface, and the light shielding film is provided on the light absorbing film. 12. The method according to claim 9, wherein the light used in the step of forming the minute aperture is different from the light used for recording and / or reading.
Or the manufacturing method according to claim 11.