JP2002267820A - Graded index mirror and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a graded index mirror capable of condensing, diffusing light or the like with a flat surface shape. SOLUTION: In the mirror comprising a reflection layer arranged on a backside of a glass substrate, a layer in parallel with the reflection layer has the refractive index distribution in which the refractive index gradually gets higher towards the terminal parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractive index distribution mirror that can be used for an optical circuit and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art At present, mirrors are widely used as very important components in various fields of optics. For example, in assembling an optical system circuit, a laser beam is reflected on a mirror to irradiate a target portion with light. Also,
A circuit for amplifying light intensity by focusing light rays, for example,
Means such as combining a convex lens and a concave lens and irradiating a target portion with a mirror are employed. When such an optical circuit is integrated, it is preferable that a small number of components be used. For example, in Japanese Patent Application Laid-Open No. 2000-225483, light condensed by a concave lens is reflected by a convex mirror to be converted into a parallel light, and a target portion is formed. There has been proposed a method of irradiating the light.

[0003]

However, in the case of an optical circuit for irradiating a target portion with light by reflecting the laser light to a mirror, the position accuracy is required to be very high, and the If the mirror is displaced due to vibrations from the outside or the like, there is a problem that it becomes impossible to irradiate light to a target portion.
In the case of a method in which light condensed by a concave lens is converted into a parallel ray by reflecting the light on a convex mirror, a glass-based material that is resistant to high-intensity light such as laser light is preferable as the material of the convex mirror. Are extremely difficult to process into a convex mirror, and the cost is very high.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a refractive index distribution mirror capable of condensing light in a planar shape and a method of manufacturing the same. Is what you do.

That is, the refractive index distribution mirror of the present invention is characterized in that, in a mirror provided with a reflection layer on the back surface of a glass substrate, a layer parallel to the reflection layer has a refractive index distribution.

The refractive index distribution mirror according to the present invention is characterized in that the refractive index distribution gradually increases from the center to the side edges of the substrate, and the refractive index distribution further includes a refractive index adjusting component. Characterized by the following:

[0007] The refractive index distribution mirror of the present invention is a glass based mirror.
The plate is made of SiO_TwoSystem, B_TwoO_ThreeSystem, P_TwoO _FiveSystem, TeO_TwoSystem gala
At least one of the glass compositions
Sign.

Further, a method of manufacturing a refractive index distribution mirror according to the present invention is characterized in that the mirror is manufactured by the following steps. (1) a step of producing a porous glass body having communicating pores, (2) a step of impregnating a refractive index adjusting component from a side edge of the porous body, and (3) firing and sintering to produce a glass body (4) a step of forming a glass substrate by slicing and then polishing the glass body, and (5) a step of forming a reflective layer on the back surface of the glass substrate.

Further, a method of manufacturing a refractive index distribution mirror according to the present invention is characterized in that the porous glass body is manufactured by a sol-gel method, and further manufactured by the following steps. (1) a step of obtaining a wet gel by hydrolyzing a metal alkoxide; (2) a step of obtaining a porous gel by subjecting the wet gel to a drying treatment; The solid body is produced by a phase separation method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The refractive index distribution mirror of the present invention is a mirror having a reflection layer provided on the back surface of a glass substrate, wherein a layer parallel to the reflection layer has a refractive index distribution. . This refractive index distribution can gradually increase the refractive index from the center to the side edge of the glass substrate, and they can be freely selected according to the purpose. For example, a case where the refractive index gradually increases from the center to the side edge of the glass substrate will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view of the refractive index distribution mirror 1 of the present invention, and FIG. 2 is an arbitrary plane (AA ′) parallel to the reflection layer 2 of the refractive index distribution mirror 1 of the present invention. The refractive index distribution (refractive index difference) on the cut surface 3 is shown. 1 and 2, the refractive index distribution mirror 1 has a glass substrate 4 having a back surface coated with a reflective layer 2 made of a metal layer such as Ag. The refractive index distribution of the surface 3 of the refractive index distribution mirror 1 cut in a plane parallel to the reflection layer 2 is such that the refractive index 8 gradually increases on a straight line from the center 5 of the glass substrate 4 to the side edges 6 and 7. ing.

Next, the function of light incident on the refractive index distribution mirror 1 will be described. FIG. 3 shows an example in which the emitted light is condensed. The incident light 10 incident in parallel enters the glass substrate 4 and is refracted, then reflected by the reflection layer 2 and transmitted through the glass substrate 2 to the outside. It emerges as outgoing light 11. At this time, the emitted light 11 is condensed 12. FIG. 4 shows an example in which the outgoing light exits as a parallel light beam. The incident light 13 incident non-parallel enters the glass substrate 4 and is refracted. And the outgoing light 14 goes outside as parallel light 15. That is,
If the refractive index at the entrance position is larger than the refractive index at the exit position,
If the emitted light converges in the opposite direction, it becomes divergent.

As described above, the refractive index of the glass substrate 4 is gradually increased from the center 5 to the side edges 6 and 7 on a straight line.
Is larger, the direction of incidence of the incident light can be appropriately selected, so that the emitted light can be condensed or diverged, or can be appropriately selected according to the purpose. That is, if the refractive index at the incident position where the incident light enters the glass substrate 4 is greater than the refractive index at the position where the incident light exits the glass substrate 2 after being reflected by the reflective layer 2, the emitted light converges, and vice versa. If the refractive index at the incident position where the incident light enters the glass substrate 4 is smaller than the refractive index at the position where the incident light exits the glass substrate 2 after being reflected by the reflective layer 2, the emitted light exiting the glass substrate diverges, These can be appropriately selected depending on the conditions. In addition, glass as a substrate used in the present invention,
Since it has high chemical resistance, excellent heat resistance, and is stable for long-term use, it can be widely used in various fields.

Next, a method of manufacturing the refractive index distribution mirror of the present invention will be described. The refractive index distribution mirror of the present invention can be manufactured by the following steps. (1) a step of producing a porous glass body having communicating pores, (2) a step of impregnating a refractive index adjusting component from a side edge of the porous body, and (3) firing and sintering to produce a glass body (4) a step of forming a glass substrate by slicing and then polishing the glass body, and (5) a step of forming a reflective layer on the back surface of the glass substrate.

The porous body having communicating pores can be obtained by, for example, a sol-gel method, a phase separation method, a gas phase method, or the like.

The glass porous body using the sol-gel method can be produced by the following method. (1) a step of obtaining a wet gel by hydrolyzing a metal alkoxide, (2) a step of obtaining a porous gel by drying the wet gel, and a metal alkoxide as a raw material of glass, for example, a silica alkoxide, Tetramethoxysilane, tetraethoxysilane, monomethyltriethoxysilane, monomethyltrimethoxysilane,
Dimethyldiethoxysilane, other tetraalkoxysilane compounds, other alkylalkoxysilane compounds, and the like can be used, and the same metal alkoxide compounds as described above can be used for components other than silica.

For example, taking tetramethoxysilane as an example, first, tetramethoxysilane, which is a metal alkoxide, water and alcohol are mixed at a predetermined ratio, and the mixed solution is cast into a container having a fixed shape (cylindrical shape or the like). Put in. As time passes, tetramethoxysilane reacts with water to form (OH) Si
(OCH ₃ ) ₃ is generated, and the silanol group generated by the reaction is condensed with tetramethoxysilane as a raw material, and (OCH ₃ ) ₃
Dimer of _{Si-O-Si (OCH 3} ) 3 is generated. Furthermore, a polymer reaction occurs one after another from a dimer to a trimer,
After a certain period of time after the mixing, silica particles grow, and the viscosity of the mixed solution sharply increases, causing gelation. The gel thus obtained is a porous gel composed of an aggregate of ultrafine particles of silica glass, and is in a state of being impregnated with a large amount of alcohol or excess water generated by the hydrolysis reaction. Next, the obtained porous gel is dried at a temperature of about 150 ° C. or less.
As the porous gel dries, it shrinks while maintaining a similar shape to the template, and becomes a dry gel in about several days to about one week. The dried gel is also a porous body composed of an aggregate of silica fine particles, similarly to the above-mentioned porous gel. Next, the dried gel is heated to a high temperature and sintered. By firing at about 1000 to 1300 ° C., the dried gel can obtain a transparent silica glass body similar in shape to the mold.

Next, the glass porous material utilizing the phase separation is as follows:
For example, it can be manufactured by the following method. Quartz sand,
Boric acid, soda ash by melting a main raw material Na ₂ O-B ₂ O ₃
After obtaining a SiO ₂ -based borosilicate glass, the glass is formed into a columnar body. Next, the glass columnar body was placed in a range of 500 to 65.
Heat treated at 0 ° C. to separate phases. Due to this phase separation treatment, a SiO ₂ -rich glass phase and a Na ₂ O—B _{2 having} different chemical compositions in the order of several tens of angstroms inside the glass
Entangled separation of the O ₃ -rich glass phase (separation on the order of tens of angstroms) occurs. The size of the microscopically separated glass phase changes depending on the temperature and time of the heat treatment (phase separation heat treatment). Next, when the phase-separated glass is subjected to acid treatment, Na ₂ O is added to the acid solution.
Since only -B ₂ O ₃ phase is readily soluble, while keeping the molded glass of the original type (columnar), porous glass having a communicating pore-rich SiO ₂ ingredient.

The porous glass obtained by the sol-gel method and the phase separation method can be controlled by changing the pore diameter, pore distribution, pore volume, specific surface area and the like according to the purpose. is there. The pore size can be from tens of angstroms to thousands of angstroms depending on the time of heat treatment in the sol-gel method and acid treatment in the phase separation method, etc., and the specific surface area can be controlled from about several m ² / g to several hundred m ² / g. It is. Although the size of the pores of the present invention is not particularly limited, the pore diameter is about several tens of angstroms and the porosity is 2
Those having about 0 to 30% by volume are preferred.

Next, the communicating pores of the glass porous body obtained above are impregnated with a refractive index adjusting component. The impregnation method can be performed by bringing the porous columnar body into contact with a solution or gas containing a refractive index adjusting component. For example,
When impregnating with a solution, it can be impregnated by dipping in a low-viscosity solution or by applying. In this case, a reduced pressure operation is performed to facilitate replacement of the impregnating liquid with air, and a reduced pressure impregnation method (vacuum impregnation method) in which impregnation proceeds or a pressure impregnation method in which compressed air is introduced from the upper part of the impregnation tank and pressurized. Alternatively, it is possible to use an inhalation impregnation method of inhaling under reduced pressure.

The refractive index adjusting components for adjusting the refractive index distribution by impregnating the pores are Ti, Bi,
One of oxides such as Ba, Ca, Zn, Pb, Te, and Ge
More than the ingredients are available. As the raw material sources, alkoxides, acetates, acetyl acetates, nitrates and the like of the components can be used. Further, the refractive index adjusting component,
Impregnated and penetrated from the side edge of the porous body formed into a columnar shape,
It is easy and preferable to have a refractive index distribution in which the refractive index gradually increases from the center to the side edges of the columnar body, but it is not particularly limited thereto.

Next, the porous body impregnated with the refractive index adjusting component is fired and sintered at a high temperature. The sintering temperature for sintering the porous body is 800 ° C. or higher, preferably 1 ° C.
000 ° C. or higher is preferred. By firing at this high temperature,
A sintered, isotropic and homogeneous glass body is obtained. In this case, the refractive index adjusting component impregnated in the porous body contains Ti, Bi, Ba, Ca, Z in the glass.
n, Pb, Te, Ge, etc., remain as oxides, and the concentration distribution of the refractive index adjusting component becomes a refractive index distribution. When the concentration is high, the refractive index is high, and when the concentration is low, the refractive index is low. Becomes

Next, the columnar sintered body obtained above is sliced into slices, and both sides of the sliced cut surface are optically polished to obtain a glass substrate having a mirror-like upper and lower surface and a predetermined thickness. . Note that the cutting method and the optical polishing method are not particularly limited.

Next, the back surface of the substrate is coated with a reflective layer made of a metal layer or the like to obtain a mirror. The reflective layer is preferably a silver layer having a high reflectance, but is not particularly limited to the silver layer.

[0025]

Embodiments of the present invention will be described below. Note that the present invention is not limited to these examples.

[0026]Example Tetramethoxysilane / water / methanol / dimethylphor
Muamide / ammonia in a molar ratio of 1/10 / 2.2 / 1
/0.0004 mixed, hydrolyzed, gelled and porous
After obtaining a porous gel, at 80 ° C. for 120 hours and at 150 ° C.
Dried for 24 hours, SiO_TwoForm the dried gel into pillars
Was. Next, when the weight ratio is Ti (OiC)_ThreeH ₇)_Four: Ekine
(Solvent): H_TwoO = 1: 9: 0.05 Refractive index
Immerse in the mixture of the adjusting components for 10 minutes,
It was impregnated into the communicating pores from the periphery. Then the refractive index
The columnar gel impregnated with the adjusting component is heated from room temperature to 1050 ° C.
2 hours after reaching 1050 ° C
Hold and sinter the dried gel to move from the center to the outside
12mmΦ, length with distribution of high refractive index
A 120 mm non-porous cylindrical glass body was obtained. Then
A 2 mm thick disk is cut out from the cylindrical glass body,
Was optically polished, and then coated on one side with Ag.
Refraction having a refractive index distribution 8 as shown in FIGS. 1 and 2
A rate distribution mirror 1 was obtained. The refractive index of the side edges 6, 7 is 1.8, medium
The refractive index of the core 5 was 1.5. This refractive index distribution mirror 1
In the above, for example, the incident angle 60
° light is emitted so that the reflected light is on the center side.
The angle is 54.1 ° and the light exits at a point with a refractive index of 1.65.
The light becomes 53 °.

By utilizing this property and irradiating light as shown in FIG. 3, the focus of light can be narrowed as when light passes through a convex lens. When the focused light beam is radiated so that the reflected light is away from the center side as shown in FIG. 4, the light beam can be focused and reflected as a parallel light beam. Also, as shown in FIG. 5, the refractive index distribution mirror 1 obtained in the present embodiment and the ordinary mirror 16 are arranged in parallel, and as shown in FIG. 5, the incident light 17 (for example, from a Nd: YAG laser). Light), the light once exiting from the refractive index distribution mirror 1 is reflected by the mirror 16, then enters the glass substrate 4 again, is reflected by the reflection layer 2, and emerges as shown in the figure. 18 light intensity can be increased.

[0028]

According to the present invention, it is possible to condense and diverge light with a planar mirror, so that the number of parts can be reduced and the variation can be expanded when assembling an optical circuit. It has effects such as being able to do.

[Brief description of the drawings]

FIG. 1 is a view showing a longitudinal section of a refractive index distribution mirror of the present invention.

FIG. 2 is a diagram showing a refractive index distribution of a refractive index distribution mirror of the present invention.

FIG. 3 is a diagram showing a case where light rays emitted from the refractive index distribution mirror of the present invention are collected.

FIG. 4 is a view showing a case where a light beam emitted from a refractive index distribution mirror of the present invention is a parallel light beam.

FIG. 5 is a diagram showing a case where a light beam emitted from the refractive index distribution mirror of the present invention is a parallel light beam.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refractive index distribution mirror 2 Reflective layer 3 Cut surface 4 Glass substrate 5 Central part 6, 7 Side edge part 8 Refractive index 10 Incident light 11 Outgoing light 12 Condensing 13 Incident light 14 Outgoing light 15 Parallel light 16 Normal mirror 17 Incident Light 18 Outgoing light

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C03B 32/02 C03B 32/02 C03C 3/16 C03C 3/16 15/00 15/00 G 17/10 17/10 G02B 3/00 G02B 3/00 B F-term (reference) 2H042 DA04 DA12 DB14 DC08 DC09 DE00 4G014 AH02 AH04 AH06 4G015 EA01 4G059 AA17 AB01 AB09 AC05 AC09 BB04 DA01 DB04 4G062 AA04 BB02 BB08 BB09 BB04 NN40

Claims (8)

[Claims] 1. A mirror having a reflective layer provided on the back surface of a glass substrate, wherein a layer parallel to the reflective layer has a refractive index distribution. 2. A refractive index distribution mirror according to claim 1, wherein the refractive index gradually increases from the center to the side edge of the glass substrate. 3. The refractive index distribution mirror according to claim 1, wherein the refractive index distribution is formed by a concentration distribution of a refractive index adjusting component. 4. A glass substrate, SiO ₂ system, B ₂ O ₃ system, P ₂
O ₅ system, the refractive index distribution lens according to any one of claims 1 to 3, characterized in that comprises at least one glass composition of TeO ₂ type glass. 5. A method for manufacturing a refractive index distribution mirror, which is manufactured by the following steps. (1) a step of producing a porous glass body having communicating pores, (2) a step of impregnating a refractive index adjusting component from a side edge of the porous body, and (3) firing and sintering to produce a glass body (4) a step of forming a glass substrate by slicing and then polishing the glass body, and (5) a step of forming a reflective layer on the back surface of the glass substrate. 6. The method for manufacturing a refractive index distribution mirror according to claim 5, wherein the porous glass body is produced by a sol-gel method. 7. The method of manufacturing a refractive index distribution mirror according to claim 6, wherein the method is performed by the following steps. (1) a step of obtaining a wet gel by hydrolyzing a metal alkoxide, (2) a step of obtaining a porous gel by drying the wet gel, 8. The method according to claim 5, wherein the porous glass body is manufactured by a phase separation method.