JP3444352B2 - Optical transmission line manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical transmission line manufactured by using a photocurable resin solution and light.
In particular, a photocurable resin solution is used as a mixed solution of two kinds having different curing start wavelengths and different refractive indexes, and one photocurable resin solution is used to form the core of the transmission line and both photocurable resin solutions to form a clad portion. The present invention relates to a method of manufacturing a transmission line. The present invention also relates to a method of manufacturing an optical transmission line in which an optical fiber is dipped in the above mixed solution and continuously connected to the optical fiber with good linear parallelism. The present invention provides an inexpensive and low-loss optical interconnection in optical communication,
It can be applied to optical demultiplexers or multiplexers.

[0002]

2. Description of the Related Art In recent years, a technique for forming an optical transmission line at the tip of an optical fiber using a photocurable resin solution has been attracting attention. For example, there is a method of manufacturing an optical waveguide disclosed in JP-A-4-165311. Briefly, first
In the step, one end of the optical fiber is dipped in a photocurable resin solution made of, for example, a fluorine-based monomer. Then, light having a wavelength that cures the solution is emitted from the tip of the fiber (second step). For example, when a laser beam having a wavelength close to the ultraviolet region or a short wavelength laser beam is irradiated, the photocurable resin solution at the tip portion is cured by a photopolymerization reaction.
A so-called core portion is formed at the emission end according to the power distribution. When the core portion is formed, the above light is further propagated to form the core portion one after another, and as a result, the optical transmission line is formed.

Then, as a third step, the photocurable resin solution is removed from the photocurable resin solution and the remaining photocurable resin solution is removed by washing or the like. Next, as a fourth step, the translucent resin is coated again. This is for the purpose of coating the core surface and protecting it from dust and scratches. Then, as a final fifth step, the tip end surface of the formed core portion is polished to form the emission surface of the transmission path. In this way, an optical transmission line continuous with the optical fiber was formed in about 5 steps.

[0004]

However, in the above-mentioned conventional example, the optical transmission line is meandering as a result. Meandering means that when the z axis is taken in the optical axis direction, the radius periodically differs with respect to the value of z. This is due to a mismatch in the refractive index between the core of the optical fiber and the photocurable resin solution. As a result, the outgoing spread becomes large and a gradient index optical transmission line is formed.

In the gradient index transmission line, light meanders according to the refractive index. That is, depending on the length of the transmission line,
Its focal length changes. For this reason, in the end face polishing in the final step, it is necessary to determine the polishing amount while measuring the focal length, and there is a drawback that a great manufacturing cost is required. Further, according to the above-mentioned conventional example, the transmission path length of the formed core portion is 8.5 mm. If the end surface treatment is applied, the size will be further reduced. This can be applied as a connector for connecting optical fibers, but it is difficult to insert a branching mirror or the like into the transmission line to form a demultiplexer / multiplexer. There are also reports that a tapered optical transmission line is formed at the tip of an optical fiber. The formation of the tapered optical transmission line is also caused by the mismatch of the above-mentioned refractive indexes. When this tapered optical transmission line is applied to the multiplexer / demultiplexer, there is a drawback that the loss increases due to its spread. Further, in the case of the above method, when the cladding is cured as it is, the refractive index becomes the same as that of the core. Therefore, in order to obtain a step index type optical transmission line, a separate step of replacing the fiber clad with another material is required.
There was a problem of poor productivity.

The present invention has been made to solve the above problems, and an object thereof is to easily produce a core part and a clad part by using a mixed solution of two kinds of photocurable resin solutions. The core part is to provide a linearly extended optical transmission line. Moreover, it is providing the manufacturing method. Another object is to provide an optical transmission line that is linearly extended from the exit regardless of the type of optical fiber by adjusting the refractive index of the photocurable resin solution according to the optical fiber used. Is. In addition, other objectives are assembly costs,
An object of the present invention is to provide an inexpensive optical transmission line manufacturing method in which the component cost is significantly reduced.

[0007]

In order to achieve this object, a method of manufacturing an optical transmission line according to a first aspect of the present invention is directed to introducing a light of a predetermined wavelength into a photocurable resin solution, and A method for manufacturing an optical transmission line, wherein a continuous optical transmission line is produced from an entrance by being cured into a light-curable resin solution, wherein the photocurable resin solution comprises a first photocurable resin solution and a first photocurable resin solution. curing initiation wavelength than the resin solution is rather short, the first photo-curable resin
A mixed solution with a second photo-curable resin solution having a refractive index smaller than that of the solution, and a light beam in a wavelength band that cures only the first photo-curable resin solution is incident on the mixed solution. It is characterized in that an axial optical transmission line is produced.

According to a second aspect of the present invention, there is provided a method of manufacturing an optical transmission line, wherein light having a predetermined wavelength is introduced into a photocurable resin solution and cured in the optical axis direction so that light continuous from an entrance is obtained. A method for manufacturing an optical transmission line for producing a transmission line, comprising:
The photocurable resin solution includes a first photocurable resin solution and a second photocurable resin solution having a curing initiation wavelength shorter than that of the first photocurable resin solution.
Of the photocurable resin solution, wherein a light beam having a wavelength band that cures only the first photocurable resin solution is incident on the mixed solution to form an axial core portion, and then mixed. The cladding is formed around the core by irradiating light in the wavelength band that cures both the first and second photocurable resin solutions from around the solution, and the refractive index of the core is the refractive index of the cladding. It is characterized by forming a larger optical transmission line. Further, according to the optical transmission line manufacturing method of the present invention, the refractive index of the first photocurable resin solution at the time of curing is higher than the refractive index of the mixed solution. To do.

According to the fourth aspect of the present invention, the light of the predetermined wavelength is emitted from the tip of the optical fiber impregnated with the mixed solution, and the optical transmission line is It is characterized in that it is continuously manufactured from the tip of the optical fiber.

According to the fifth aspect of the present invention, the optical fiber is a step index type optical fiber whose refractive index changes stepwise at the boundary between the core and the clad. Yes, the core refractive index is n
_{When the} refractive index of the mixed solution is _{f 1} , the refractive index of the clad portion is n _f2 , the refractive index of the core portion of the optical transmission line is n _A2 , and the refractive index of the mixed solution is n _C1 , the refractive index of the mixed solution is set to satisfy the conditional expression (5). The rate is adjusted.

[Formula 5] (n _f1 ) ² − (n _f2 ) ² ≦ (n _A2 ) ² − (n _C1 ) ² (5)

According to the method of manufacturing an optical transmission line of claim 6 of the present invention, the optical fiber is a graded index type optical fiber having a refractive index gradient with a predetermined function in the radial direction, The maximum refractive index at the center of the core of the optical fiber is n _f1 , the diameter of the core is 2 a _f , the refractive index of the cladding is n _f2 , the refractive index of the core of the optical transmission line is n _A2 , and the refractive index of the mixed solution is n n. when the _C1, p is an integer to satisfy the core portion diameter 2a _w of the optical transmission line to be fabricated with (6) conditional expression, the refractive index of the mixed solution is characterized in that it is adjusted.

[6] _{2a w = 2a f [1 /} (2 △) · (n A2 2 -n C1 2) / n A2 2] 1 / p ^{_{However, △ = (n f1 2 -n}} f2 2) / (2n _f1 ² ) (6)

According to the seventh aspect of the present invention, there is provided a method for manufacturing an optical transmission line, wherein the tip of the optical fiber is dipped in a photo-curable resin solution, and light of a predetermined wavelength is emitted from the tip of the optical fiber. than to cure the photocurable resin solution in the optical axis direction, a manufacturing method of the optical transmission line to produce an optical transmission path which is continuous from the optical fiber tip, the photocurable resin soluble
The liquid is a solution of the first photocurable resin solution and the first photocurable resin solution.
Since the curing start wavelength is shorter than that of the liquid, the first photocurable resin solution
A second photocurable resin solution having a smaller refractive index than the refractive index
A mixed solution, the optical fiber is a step index optical fiber which changes stepwise at the boundary of the cladding portion refractive index core portion, the core portion refractive index n of the
Let _{f1 be} the refractive index of the cladding part, n _f2 , the refractive index of the optical transmission line to be formed be n _A2 , and the refractive index of the photo-curable resin solution be n _C1, and the photo-curing should be performed so as to satisfy the condition of formula (7). wherein the refractive index of sexual resin solution is adjusted.

(7) (n _f1 ) ² − (n _f2 ) ² ≦ (n _A2 ) ² − (n _C1 ) ² (7)

Further, according to the method of manufacturing an optical transmission line according to claim 8 of the present invention, the photocurable resin solution contains the first light
Curing resin solution and the first photocurable resin solution
The starting wavelength is shorter than the refractive index of the first photocurable resin solution.
With a mixed solution with a second photo-curable resin solution with a small refractive index
There, in its optical fiber is a graded index optical fiber having a refractive index gradient in a predetermined function in the radial direction, the maximum refractive index of the core portion center of the optical fiber n _f1, core portion diameter 2a _f, The refractive index of the cladding is n _f2 ,
When the refractive index of the optical transmission line to be formed is n _A2 , the refractive index of the photocurable resin solution is n _C1 , and p is an integer, the diameter 2a _{w of the} optical transmission line to be produced satisfies the condition (8). Then, the refractive index of the photocurable resin solution is adjusted.

2 a _w = 2a _f [1 / (2Δ) · (n _A2 ² −n _C1 ² ) / n _A2 ² ] ^{1 / p} where Δ = (n _f1 ² −n _f2 ² ) / (2n _f1 ² ) (8)

[0014]

FUNCTION AND EFFECT The method for manufacturing an optical transmission line according to the first aspect of the present invention employs a mixed solution in which two kinds of photocurable resin solutions are mixed. It consists of a mixture of a first photocurable resin solution and a second photocurable resin solution having a property that the curing start wavelength is shorter than that of the first photocurable resin solution. Further, the refractive index of the first photocurable resin solution at the time of curing is set to be higher than the refractive index of the mixed solution at the time of curing. This mixed solution is put in, for example, a rectangular parallelepiped transparent container.

Light having a wavelength band λ _w (λ ₂ <λ _w <λ ₁ ) for curing the first photo-curable resin solution is incident on the mixed solution in the form of a beam. Here, the wavelength λ ₁ is the curing start wavelength of the first photocurable resin solution, and the wavelength λ ₂ is that of the second photocurable resin solution. The light in the wavelength band λ _w is a short-wavelength laser light such as He-Cd. As a result, only the first photocurable resin solution in the mixed solution is cured by the photopolymerization reaction to form a linear core portion.
At this time, a mixed solution composed of two kinds of photocurable resin solutions remains on the outer periphery of the core portion. In the method for manufacturing an optical transmission line according to claim 2 of the present invention, next, a wavelength band λ _c for curing both photocurable resin solutions is applied from around the mixed solution.
The light of (λ _c <λ ₂ ) is irradiated from, for example, an ultraviolet lamp to solidify the residual solution by the photopolymerization reaction. As a result, the clad portion is formed around the core portion.
Further, due to the setting of the above-mentioned refractive index, the refractive index of the core portion at this time is higher than that of the cladding portion. That is, a step index type optical transmission line is formed. In this way, a step index type optical transmission line having a core portion and a cladding portion is formed by light irradiation in two steps. Therefore, the manufacturing method of the optical transmission line is extremely efficient.

At this time, the transparent container for the mixed solution may have any shape. As a result, the clad portion has an arbitrary shape and can be manufactured, for example, according to the shape of the product. That is, the clad portion can be directly fixed to the product. Therefore, the optical transmission line is extremely convenient. Further, the optical transmission line is collectively molded by only irradiating the light in the predetermined wavelength bands λ _w and λ _c . Therefore, the manufacturing method has a low assembly cost.

Further, as described in Japanese Patent Application No. 10-152157, an optical element such as a half mirror is inserted into the container and the above steps are followed to form the optical transmission line and the half mirror in close contact with each other. It is also possible to manufacture optical demultiplexers.

It is also known that the phase of the light wave changes when the optical transmission line is distorted. Since the above-mentioned manufacturing method enables an arbitrary clad shape, various physical quantities such as stress, electric field, magnetic field, and ultrasonic wave can be easily applied to the transmission line. This makes it possible to easily apply stress, that is, a phase change in various forms, and to form an optical element such as a phase modulation element. Therefore, the above manufacturing method is a basic technique for forming the basic structure of various optical elements having an optical transmission path.

According to the method for manufacturing an optical transmission line of the present invention, the refractive index of the first photocurable resin solution at the time of curing is adjusted to be higher than the refractive index of the mixed solution. . That is, the first photocurable resin solution cures when irradiated with light in the wavelength band λ ₁ and becomes higher than the refractive index of the mixed solution. That is,
A step index type optical transmission line is formed in the mixed solution. Since it is a step index type, all the incident light is totally reflected, and the optical transmission lines can be sequentially formed efficiently. Therefore, the incident light does not have to be, for example, a laser light having good straightness. It allows the use of, for example, ultraviolet light, which is incident at an angle at which total internal reflection occurs. Therefore, the method of manufacturing the optical transmission line can use various light sources.

According to the manufacturing method of the optical transmission line of the fourth aspect, the tip of the optical fiber is immersed in the mixed solution, and the light of a predetermined wavelength is emitted from the tip. The predetermined wavelength is, for example, short wavelength laser light. The short-wavelength light sequentially causes a photopolymerization reaction with respect to the photocurable resin solution in the optical axis direction. As a result, the core portion of the optical transmission line is in close contact with the core portion of the optical fiber and is continuously formed in a linear shape. Therefore, it is not necessary to align the optical axes of the optical fiber and the optical transmission line. Further, the tip of the optical fiber is firmly fixed in the clad of the optical transmission line by the light irradiation of the wavelength λc. Therefore, the degree of freedom in arranging the optical transmission line is increased, and the handling is simplified. Therefore, the optical transmission line is extremely convenient.

According to the optical transmission line manufacturing method of the present invention, the optical fiber is a step index type optical fiber whose refractive index changes stepwise at the boundary between the core portion and the clad portion, The core refractive index n _f1 , the cladding refractive index n _f2 , the core refractive index n _{A2 of} the optical transmission line, and the refractive index n _C1 of the mixed solution satisfy the condition of the expression (5). This conditional expression is that all the light that has propagated in the step index type optical fiber satisfying the condition of total reflection is refracted at the boundary surface between the core part of the optical fiber and the core part of the optical transmission line, and the refracted light is transmitted again. It is a condition that propagates while satisfying the total reflection condition in the road as well.

The refractive index of the mixed solution is adjusted so as to satisfy the conditional expression (5). Although it is possible to form an optical transmission line even when the conditional expression (5) is not satisfied, there are problems that the shape of the optical transmission line becomes non-uniform and propagation loss due to light leakage increases. By satisfying the conditional expression (5),
All light propagating through the optical fiber is refracted at the boundary,
Similarly, it is propagated to the optical transmission line by total reflection. Total reflection in the optical transmission line means that the optical transmission line is continuously formed. That is, an optical transmission line is formed in which the core of the step index type optical fiber is linearly extended. As a result, a linear optical transmission line directly connected to the tip of the step index type optical fiber can be manufactured.

According to a sixth aspect of the present invention, there is provided a method of manufacturing an optical transmission line, wherein the optical fiber is a gradient index optical fiber having a gradient of a refractive index with a predetermined function in the radial direction, and the core of the optical fiber. Maximum refractive index n _{f1 at} the center of the core, core diameter 2a
_f , clad portion refractive index n _f2 , optical transmission line core portion refractive index n
_A2, a refractive index n _C1 of the mixed solution, the core portion diameter 2a _w of the transmission line to be produced satisfy the above expression (6). However, p is an integer. This equation (6) shows that the diameter 2a _w of the optical transmission line can be controlled by the refractive index n _C1 of the mixed solution. The refractive index n _C1 can be adjusted by the mixing ratio of the above two types of photocurable resin solutions.

The refractive index of the mixed solution is selected so as to satisfy the expression (6). Therefore, the light that has propagated in the vicinity of the optical axis of the optical fiber with good straightness due to refraction is extracted through a smaller aperture. The light thus extracted has a better linearity and similarly forms a step index type optical transmission line in the mixed solution. Therefore, the optical transmission line manufacturing method can be applied to a graded index optical fiber used for high-speed communication.

According to the optical transmission line manufacturing method of the seventh aspect, the tip of the step index type optical fiber is dipped in a photo-curable resin solution, and light of a predetermined wavelength is emitted from the tip of the optical fiber. It The predetermined wavelength is, for example, short wavelength laser light. The short-wavelength light sequentially causes a photopolymerization reaction with respect to the photocurable resin solution in the optical axis direction. As a result, a shaft-shaped optical transmission line (core portion) that is in close contact with the core portion of the optical fiber and is continuously formed is obtained. Therefore, also in this case, it is not necessary to align the optical axis of the optical fiber with the optical axis of the optical transmission line. Incidentally, in claim 2 to claim 6,
The core and the clad of the optical transmission path and spirit to form a light irradiation 2 step, called the core and the clad and the optical transmission path, in the present claims 7 and claim 8 straight linear The purpose is to form an optical transmission line (only the core portion).
Therefore, in claims 7 and 8, the optical transmission line and its core have the same meaning.

Further, according to the above manufacturing method, the refractive index n _f1 of the core of the step index type optical fiber, the refractive index n _{f2 of the} clad, and the refractive index n _{A2 of} the optical transmission line formed in the photo-curable resin solution, The refractive index n _C1 of the photocurable resin solution satisfies the condition of the above formula (7). This conditional expression is that all the light propagating in the step index type optical fiber that satisfies the condition of total reflection is refracted at the boundary surface between the core part of the optical fiber and the optical transmission line, and the refracted light is photocured again. It is a condition that propagates while satisfying the total reflection condition in the optical transmission line in the organic resin solution.

The refractive index of the photocurable resin solution is adjusted so as to satisfy the conditional expression (7). Therefore, all the light propagating through the optical fiber is propagated to the optical transmission line, and the optical transmission line is sequentially formed while being totally reflected. That is, according to the manufacturing method of the present invention, an optical transmission line having good linear parallelism is formed in which the core portion of the step index type optical fiber is linearly extended as it is.

[0028] The refractive index of the photocurable resin solution is higher than the refractive index of the solution by hardening, (7) it is possible implementation if satisfying solution can be selected for expression. Further, as in claim 4, one kind of solution that is selectively photocured when forming a core portion of an optical transmission line with a plurality of kinds of solutions is made higher in refractive index than another kind of solution that is not photocured. so,
It is possible to increase the difference between the refractive index of the core portion after photocuring and the refractive index of the mixed solution, and it is possible to easily select the solution so as to satisfy the condition of the expression (7) . Although around the time the optical transmission path is uncured photocurable resin solution (Liquid), surrounding the optical transmission path at the time of actual use are not particularly limited. Other media, such as gas, other liquids,
It may be solid. It suffices that their refractive index is smaller than that of the optical transmission line. For example, in actual use, it is taken out from the photocurable resin solution, washed, and used. At this time, the circumference of the optical transmission line is air, and its refractive index is higher than that of the surroundings. Therefore, the total reflection condition is maintained, and the optical transmission line is a step index type with little transmission loss. Further, if the surrounding area is a liquid, the optical transmission line has a liquid as a clad, and if it is a solid, a solid as a clad.

Further, the above-mentioned optical transmission line is a highly flexible shaft-shaped optical transmission line. This can be directly arranged on, for example, the emission port of a semiconductor laser element formed on a semiconductor substrate or a light receiving element having a small opening. Therefore, the manufacturing method of the optical transmission line is highly convenient for inputting and outputting light.

According to the method of manufacturing an optical transmission line described in claim 8, the optical fiber immersed in the photocurable resin solution has a gradient index optical fiber having a gradient of refractive index with a predetermined function in the radial direction. The fiber has a maximum refractive index n _{f1 at} the center of the core of the optical fiber, a core diameter 2a _f , and a cladding refractive index n.
_f2, the refractive index n _A2 of the optical transmission path formed, the refractive index n _C1 of the photocurable resin solution, the diameter 2a _w of the optical transmission line to be formed,
The above formula (8) is satisfied. However, p is an integer. The equation (8) shows that the controllable diameter 2a _w of the optical transmission line by the refractive index n _C1 of the mixed solution. Refractive index n _C1
Can be adjusted by the mixing ratio of the above two kinds of photocurable resin solutions.

The refractive index of the photocurable resin solution is selected so as to satisfy the conditional expression (8). Therefore, the light that has propagated in the vicinity of the optical axis of the optical fiber with good straightness due to refraction is extracted through a smaller aperture. The light thus extracted has a better straight traveling property, and similarly forms a step index type optical transmission line in the photocurable resin solution. Therefore, the optical transmission line manufacturing method can be applied to a graded index optical fiber used for high-speed communication .

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on specific embodiments. The present invention is not limited to the examples below. First Embodiment A method of manufacturing an optical transmission line according to the present invention will be described with reference to FIG. The manufacturing method is a so-called movable molding method having no movable part, which uses a photocurable resin which is a liquid monomer and a short wavelength laser which cures the resin. Moreover, the figure is a schematic view of a manufacturing apparatus. The manufacturing method of the present invention includes a mixed liquid 100 in which two kinds of photocurable resin solutions having different curing start wavelengths and different refractive indexes after curing are mixed, a transparent container 110 holding the mixed solution,
And a short wavelength laser 120 that linearly cures one component of the mixed solution, and an ultraviolet lamp 130 that cures the entire mixed solution 100. The optical transmission line is composed of the linear core portion 105 and a clad portion formed around the core portion 105 by curing the entire mixed solution 100.

A feature of the present invention is that two kinds of photocurable resin solutions having different curing start wavelengths and different refractive indexes after curing are mixed, and the mixed solution is used as a photocurable resin solution for stereolithography. . By irradiating light with different wavelength bands in two steps, a so-called step index type optical transmission line in which the refractive index of the core is higher than that of the surroundings is manufactured. Therefore,
First, a method for producing the above mixed solution and then a method for producing an optical transmission line using the same will be described.

The mixed solution is composed of, for example, an epoxy high refractive index photocurable resin solution having a refractive index of 1.49 and an acrylic low refractive index photocurable resin solution having a refractive index of 1.34. The spectral sensitivity characteristics of both are shown in FIG. The horizontal axis represents wavelength and the vertical axis represents relative sensitivity. Curve A is the spectral sensitivity characteristic of the epoxy high refractive index photocurable resin solution, and curve B is the spectral sensitivity characteristic of the acrylic low refractive index photocurable resin solution. As shown in the figure, the photocurable resin solution has a short-wavelength laser 12 whose curing start wavelength is used for curing.
It is selected so as to sandwich the wavelength λ ₁ of zero. Hereinafter, this photocurable resin solution having a high refractive index will be referred to as solution A, and that having a low refractive index will be referred to as solution B.

Generally, when solutions A and B having different refractive indexes are mixed, the refractive index n _c1 of the mixed solution is represented by the equation (9) (Yamaguchi, “Refractive Index” Kyoritsu Shuppan (1981)).

N _C1 = [(2M (C _A ) +1) / (1−M (C _A ))] ^1/2 M (C _A ) = C _A (ρ / ρ _A ) (n _A1 ² −1) ^{_{) / (n A1 2 +2)}} + ( a _{1-C a) (ρ /} ρ B) (n B1 2 -1) / (n B1 2 +2) ··· (9) wherein, [rho: the density of the mixed solution , [rho _a: density of the solution a, ρ _B: density of the solution B, n _A1: refractive index of the solution a n _B1: refractive index of the solution B, C _a: is the weight percent of the solution a. That is, a photocurable resin solution having a high refractive index n _A1 and a low refractive index n _B1
If mixed in a certain ratio, a mixed solution 100 having a refractive index n _C1 with n _B1 <n _C1 <n _A1 is obtained. Then, by selecting the parameters of the Ro～C _A, the mixture refractive index n _C1 of is uniquely determined. Further, the refractive index n _C2 after curing is n _B2 <n _C2 <n _A2 . Here, n _A2 and n _B2 are the refractive indexes of the solutions A and B after curing, respectively.

An optical transmission line is produced by using such a mixed solution 100. The manufacturing process will be described below. First,
A transparent container 110 is filled with this mixed solution 100. next,
Laser light 125 is incident from the short wavelength laser 120. This short wavelength laser 120 has a wavelength λ ₁ = 32, for example.
It is a He-Cd (helium cadmium) laser of 5 nm. This wavelength is shorter than the curing start wavelength of the solution A and longer than that of the solution B as described above. Therefore, only solution A is cured. Further, since it is a laser beam, the beam 125 travels almost straight. Therefore, the linear core portion 105 is formed in the mixed solution 100. At this time, the solution B on the optical axis is pushed to the surroundings.

After the core portion 105 is formed, the ultraviolet lamp 130 uniformly irradiates ultraviolet rays 135 having a wavelength λ ₂ from the surroundings. As shown in FIG. 2, this wavelength is shorter than the curing start wavelength of both solutions A and B. Therefore, both solutions are cured. As a result, around the core portion 105,
That is, the entire mixed solution 100 is cured to form the clad portion. At this time, when the refractive index of the clad portion before curing is n _C1 and that after curing is n _C2 , the refractive index n _{A2 of the} core portion 105 is
Have the following relationships:

N _A2 > n _C2 > n _C1 (10) This is because the core part refractive index n _A2 is the surrounding clad part refractive index n _C2.
This means a higher step index type optical transmission line. Therefore, other laser light introduced into this transmission line or other light introduced at an angle satisfying the condition of total reflection described later propagates while being totally reflected in the core portion 105 of the optical transmission line.

Thus, by mixing two kinds of photocurable resin solutions having different curing start wavelengths and different refractive indexes after curing and irradiating with light having different wavelengths in two steps, it is possible to easily perform step index type optical transmission. A road can be formed. Further, the shape of the container, that is, the clad portion, can be arbitrarily determined depending on, for example, a product to be mounted. Therefore, the manufacturing method of the optical transmission line is extremely convenient. Further, the above-mentioned clad portion shape can be formed in accordance with various actuators such as piezoelectric elements that generate stress. This makes it possible to provide a basic optical element that measures various physical quantities based on the phase difference or a basic optical element that measures a chemical quantity based on the amount of absorbed light. Therefore, the above manufacturing method is a basic technique for manufacturing a useful optical element having an optical transmission path.

(Second Embodiment) FIG. 3 shows a second embodiment formed using a step index type optical fiber. The figure is a manufacturing process diagram. The method of forming the core portion and the clad portion by dividing the light irradiation into two steps is the same. The different point is that the tip of the step index type optical fiber is immersed in the mixed solution to form an optical transmission line integrated with the optical fiber. In addition, the refractive index of the mixed solution is adjusted according to the refractive index of the optical fiber in order to form a linear optical transmission line in close contact with the optical fiber.

In the first step (a) of FIG. 3, the tip of the step index type optical fiber 200 is immersed in the mixed solution 100. At this time, the refractive index n _C1 of the mixed solution is adjusted under a certain condition according to the refractive index of the inserted optical fiber as described later. In the second step (b), the short-wavelength light having the wavelength λ ₁ is introduced into the step index type optical fiber 200, and the core portion 10 is introduced into the emission port by the same mechanism as in the first embodiment.
5 is formed. In the third step (c), light irradiation with the wavelength λ ₁ is continued to allow the core portion 105 to reach the bottom of the transparent container 110. In the fourth step (d), the light irradiation with the wavelength λ ₁ is stopped, and instead, the ultraviolet light with the wavelength λ ₂ is irradiated from an ultraviolet lamp (not shown). Thereby, the core unit 1
The clad portion 106 is formed around 05. At this time, the tip of the optical fiber 200 is fixed in the clad 106. Therefore, an optical transmission line integrated with an optical fiber is formed without the need for optical axis alignment.

FIG. 4 is a horizontal sectional view of the optical transmission line formed in FIG. Centering around the core part 105, the transparent container 11
The clad 106 corresponding to the shape of 0 is formed. Also,
The horizontal axis shows the distance, and the vertical axis shows the refractive index distribution between AA ′ with the refractive index. The refractive index of the core part 105 is constant n _A2 (up to 1.
5), and that of the clad portion 106 is also constant n _C2 (~
1.4). Since n _A2 > n _C2 as described above, the step index type optical transmission line is the same type as the inserted optical fiber 200.

Further, the mixed solution 100 in the step (a)
The index of refraction is strictly adjusted. This is because, depending on the refractive index, the light emitted from the core of the optical fiber 200 is diffused to form a tapered optical transmission line with large propagation loss. Therefore, as shown in FIG. 5, in order to prevent light from diffusing at the interface between the core portion 205 and the core portion 105 of the transmission line, the refractive index n of the mixed solution 100 is adjusted under the conditions described below.
_C1 is adjusted.

The refractive index of the core portion 205 of the optical fiber inserted in the mixed solution 100 is n _f1 , the refractive index of the cladding portion 206 is n _f2 , and the refractive index of the core portion 105 of the optical transmission line to be formed is n _A2. Assuming that the refractive index of the mixed solution 100 is n _C1 , the adjustment condition is the formula (11).

N _C1 ≦ [n _A2 ² −n _f1 ² + n _f2 ² ] ^1/2 (11)

This is because all the light propagating in the optical fiber 200 is mixed with the core portion 105 of the optical transmission line and the mixed solution 10.
It is derived from the condition of total reflection again at the interface with 0. Specifically, the total reflection condition (Equation (12)) at point A in FIG.
It is derived from the refraction condition at the point B (equation (13)) and the total reflection condition at the point C (equation (14)).

(12) sin ⁻¹ (n _f2 / n _f1 ) = θ (12)

[ _Mathematical formula-see original _document ] n _f1 · sin (π / 2−θ) = n _A2 · sin θ _p (13)

Sin ⁻¹ (n _C1 / n _A2 ) ≦ π / 2−θ _p (14) where θ is a propagation angle and θ _p is a refraction angle corresponding to θ (FIG. 5). . If θ and θ _p are eliminated from the above equations (12), (13), and (14), the refractive index n _{C1 of the} mixed solution, the refractive indices n _f1 and n _{f2 of the} inserted optical fiber, and the formed light A relational expression (11) of the refractive index n _A2 of the core portion of the transmission path is derived.

When the refractive index n _C1 of the mixed solution 100 does not satisfy the above equation (11) but the equation (15), that is, the core portion 105 and the cladding portion 106 of the optical transmission line do not satisfy the total reflection condition. There are cases. In such a case, the core part 1
The higher-order mode component leaks from 05 to the clad portion 106, but at a distance of several cm from the optical fiber, a substantially linear core portion 105 is obtained.

[Equation 15] [n _A2 ² −n _f1 ² + n _f2 ² ] ^1/2 <n _C1 <n _A2 (15)

As described above, in this embodiment, the mixed solution 100 is used.
The refractive index of the mixed solution is determined in consideration of the refractive index of the optical fiber 200 inserted in. As a result, the light emitted from the optical fiber goes straight, and the core portion 105 of the formed optical transmission line is not tapered unlike the conventional example. Therefore, according to the method of manufacturing the optical transmission line of the present embodiment, a step index type optical transmission line that is linearly extended from the emission port of the optical fiber along the optical axis can be obtained. Therefore, it is possible to manufacture a highly convenient optical transmission line that can be coupled to other optical elements.

(Third Embodiment) In the second embodiment, the step index type optical fiber 2 is used.
An optical transmission line of the same type was formed at the tip of 00. The third embodiment is characterized in that a graded index type optical fiber having a refractive index distributed in the radial direction is adopted instead of the above optical fiber. The manufacturing process is the same as in the second embodiment. The difference is that the refractive index of the mixed solution is adjusted according to the refractive index of the graded index type optical fiber. According to this, an optical transmission line can be formed at the tip of the graded index type optical fiber.

Since the manufacturing process is the same as that of the second embodiment, the description thereof is omitted. Here, a method of determining the refractive index of the mixed solution will be described. FIG. 6 shows a cross-sectional view of the graded index type optical fiber 300 cut out along the optical axis and its refractive index distribution in the radial direction. The horizontal axis is the distance in the radial direction, and the vertical axis is the refractive index. The graded index optical fiber 300 includes a core portion 305 having a gradient in refractive index and a clad portion 306 that protects the core portion 305. The refractive index n _f (r) of the core portion 305 can be expressed by equation (16), where r is the distance from the center of the core portion 305. This equation (16) is described in, for example, (7.1) and (7.1) on pages 117 to 123 of an introduction to optical fiber communication (Yasuharu Suematsu, Kenichi Iga, Ohmsha Publishing, 1976).
It is widely known as equation (2).

N _f ² (r) = n _f1 ² [1-2 (r / a _f ) ^p · Δ] Δ = (n _f1 ² −n _f2 ² ) / (2n _f1 ² ) (16 ) Where a _f is the radius of the core portion 305 of the graded index optical fiber 300, n _f1 is the maximum refractive index at the center of the core portion 305, n _f2 is the refractive index of the cladding portion 306, p
Is an integer representing the distribution type. For example, p = 2 is used. Δ is called relative refractive index difference. (16) in the case of r = 0 in the case of _{n f (0) = n f1} , r = a f satisfies the _{n f (a f) = n} f2.

Conversely, when the radius r is obtained as a function of the refractive index n _f from the equation (16), the equation (17) is obtained.

## EQU17 ## r (n _f ) = a _f [1 / (2Δ) · (n _f1 ² −n _f ² ) / n _f1 ² ] ^{1 / p} Δ = (n _f1 ² −n _f2 ² ) / ( 2n _f1 ² ) (17) The above formula is the graded index optical fiber 3
It also holds at the interface between 00 and the mixed solution 100. FIG. 7 is an enlarged view of the vicinity of the interface. At this interface, when the radius of the core portion 105 formed as shown in FIG. 7 is a _W ,
The refractive index at that point is n _C1 (boundary condition in the radius r direction). Therefore, r (n _C1 ) = a _w . Therefore, (1
Equation (7) is given as the ratio of the optical fiber having the relative refractive index Δ and the arbitrary refractive index difference (that is, the relative refractive index difference given by n _f1 and n _f ) in this optical fiber. By substituting the relative refractive index difference, the radius a _w of the optical transmission line connected to the optical fiber can be obtained as shown in the equation (18).

## EQU18 ## a _w = a _f [1 / (2Δ) · (n _A2 ² −n _C1 ² ) / n _A2 ² ] ^{1 / p} Δ = (n _f1 ² −n _f2 ² ) / (2n _f1 ² (18) where n _A2 is the refractive index of the formed core portion 105.

From this boundary condition, the radius a of the core portion 105 is
By determining _W , the refractive index n _C1 of the mixed solution 100 can be determined. For example, n _f1 = 1.46, n _f2 = 1.
44, a _W = 24.9 μm, a _f = 50 μm, n _A2 =
When 1.49 and p = 2, the refractive index of the mixed solution is n _C1 = 1.
It becomes 485. This is the refractive index n _A1 , n _B1 of the solutions A and B.
And its weight% are adjusted to prepare. By adjusting in this way, it is possible to extract the light that has gone straight in the vicinity of the optical axis of the core portion 305 of the graded index type optical fiber 300 by further reducing the opening. Therefore, the light emitted from the core portion 305 goes straight better and forms the core portion 105 of the step index type optical fiber in the mixed solution 100.

FIG. 8 shows the outer diameter and the length of the core portion 105 of the optical transmission line manufactured by using the mixed solution 100 adjusted according to the above conditional expression. The horizontal axis represents the transmission path length, and the vertical axis represents the diameter. The transmission path length reached about 40 mm. Also,
A substantially constant diameter is maintained when the transmission path length is 0 mm to 10 mm.

As described above, in this embodiment, the refractive index of the mixed solution is determined in consideration of the refractive index of the graded index type optical fiber used. As a result, the core portion of the optical transmission line does not have a tapered shape, but extends straight from the core portion 305 with good straightness. Therefore, it is a useful optical transmission line manufacturing method applicable to a graded index type optical fiber used for high-speed communication. Further, the optical transmission line can be coupled with other optical elements without loss.

(Fourth Embodiment) In the second and third embodiments, a core of an optical transmission line linearly extended using a mixed solution in which two kinds of photocurable resin solutions are mixed. Although the part was prepared, the linear core part can be formed by one type of photocurable resin solution and one kind of light, and the clad part can be formed by other means.
Alternatively, if an inert gas is used as a medium surrounding the core portion to prolong the life, formation of the clad portion can be omitted. Therefore, the core section and the optical transmission line are used interchangeably herein.

For example, when a step index type optical fiber is used as the optical fiber, one type of photocurable resin solution whose refractive index n _C1 satisfies the above formula (11) is used. The manufacturing process is the same as that of the second embodiment except for the final process of FIG. Since the refractive index n _C1 of the photocurable resin solution is adjusted so as to satisfy the equation (11), the mechanism described in the second embodiment works. As a result, a linear optical transmission line having a diameter substantially equal to that of the core of the step index type optical fiber is formed in the photocurable resin solution.

When a graded index type optical fiber is used as the optical fiber, one type of photocurable resin solution whose refractive index n _C1 satisfies the above formula (18) is used. The manufacturing process is the same as that of the second embodiment except for the final process of FIG. Since the refractive index n _C1 of the photocurable resin solution is adjusted so as to satisfy the expression (18),
The mechanism described in the third embodiment operates. As a result, a linear optical transmission line unit having a diameter smaller than the core diameter of the graded index type optical fiber is formed in the photocurable resin solution. Since these optical transmission lines have small diameters and flexibility, they can be directly arranged in the light emitting portions of LED elements and semiconductor laser elements formed on a semiconductor substrate. Therefore, it is a method of manufacturing an optical transmission line that enables flexible arrangement in other optical elements.

Incidentally, if a solution is selected so that the refractive index after photocuring becomes higher than the refractive index of the solution and the formula (11) or (18) is satisfied, one kind of light is generated as described above. It is also possible to use a curable solution. However, it may be a mixed solution of a photo-curable solution that cures with light of a certain wavelength and another photo-curable solution that has a smaller refractive index than the solution and that does not cure with light of that wavelength. In this case, it is possible to increase the difference between the refractive index of the core portion after curing and the refractive index of the mixed solution,
The refractive index n _C1 of the mixed photocurable solution is expressed by the formula (11), (1
It can be set so as to easily satisfy the expression (8). This makes it possible to easily form a core portion having a high linear parallelism that does not spread in a tapered shape. It is assumed that the optical transmission line has no clad portion, but the clad portion may be formed around the optical transmission line depending on the application. It is formed by the following procedure. For example, a photocurable resin solution having a refractive index n _C1 satisfying the above formula (11) or (18) is selected according to the optical fiber used. Then, it is used as a first photocurable resin solution and is cured to form the linear optical transmission line at the tip of the optical fiber. Then, the first photocurable resin solution is washed and immersed in the second photocurable resin solution. Then, the second photocurable resin solution may be cured. By doing so, a blocked clad portion equivalent to that of the second and third embodiments is formed. Alternatively, the second photocurable resin solution may not be cured, and after it is taken out from the second photocurable resin solution, it may be left on the surface without being washed to be cured. By doing so, a flexible optical transmission line having a small cladding diameter can be formed. Further, the clad portion may not be completely cured. That is, it may be in a gel state or may be in a liquid state. Further, a gas such as air may be used. If the refractive index of the optical transmission line is higher than that of the surrounding medium, the cladding portion can take various forms for various applications.

(Modifications) Although the embodiments representing the present invention have been described above, various modifications can be considered. For example, in the first embodiment, a short wavelength laser is used as a helium cadmium laser (λ = 325 nm).
However, depending on the photocurable resin solution, an argon ion laser (λ = 488 nm), an ultrahigh pressure mercury lamp (λ = 380 nm), or the like can also be applied.

In the first to third embodiments, the mixed solution is an epoxy-based high refractive index photocurable resin solution having a refractive index of 1.49 and an acrylic low-refractive index having a refractive index of 1.34. Although it is composed of a photo-curable resin solution, other material systems may be used as long as the curing start wavelength and the refractive index after curing are different. For example, a fluorine-based monomer or a silicon-based material in which a photoreaction initiator is mixed may be used. It suffices if the above-mentioned spectral sensitivity characteristics and refractive index conditions are satisfied.

Although the step index type optical fiber and the graded index type optical fiber are used in the above embodiment, other fibers may be used. A polarization maintaining fiber, a single mode fiber or the like may be used.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a method for manufacturing an optical transmission line according to a first embodiment.

FIG. 2 is a spectral sensitivity characteristic diagram of the mixed solution according to the first embodiment.

FIG. 3 is a configuration diagram of a method for manufacturing an optical transmission line according to a second embodiment.

FIG. 4 is a cross-sectional view of an optical transmission line according to a second embodiment.

FIG. 5 is an explanatory diagram of propagation conditions in the optical transmission line of the second embodiment.

FIG. 6 is an explanatory diagram of a refractive index distribution related to the optical fiber according to the third embodiment.

FIG. 7 is a relational diagram regarding the core diameter of the optical fiber and the optical transmission line according to the third embodiment.

FIG. 8 is a relationship diagram of a core diameter and a core length of the optical transmission line according to the third example.

[Explanation of symbols]

100 mixed solution 105, 205, 305 core part 106, 206, 306 clad part 110 transparent container 120 short wavelength laser 125 short wavelength laser light 130 ultraviolet lamp 135 ultraviolet light 200 step index type optical fiber 300 graded index type optical fiber

Front Page Continuation (72) Inventor Yasuhiko Takeda 1 in 41, Yokomichi, Nagakute-cho, Aichi-gun, Aichi-gun, Toyota Central Research Institute Co., Ltd. (56) Reference JP 11-326660 (JP, A) JP HEI 7-77637 (JP, A) JP-A-8-320422 (JP, A) JP-A-50-59044 (JP, A) JP-A-57-128301 (JP, A) JP-A-60-173508 (JP, A) JP 60-90312 (JP, A) JP 62-5205 (JP, A) Tanya M. et al. Monro, L .; P oladian, C.I. Martijin de Sterke, Analysi s of self-written waveguides in photo optomers and photo sensitive materials 1, May 1982, PHYSICAL REVIE WE V E., 1998. 1104-1113 Akira Shoji, Satoshi Kawada, Collision and merging of self-forming fibers in photo-curable resin, Autumn 1998 (The 10th) The 59th Annual Meeting of the Japan Society for Applied Physics, 3rd volume, Japan, Japan Society of Applied Physics, September 15, 1998, p. 857, Anthony S, Kewitshch, Amnon Yariv, Self-focusing and self-sampling optoelectronic optics, Optoelectronics, Optoelectronics, Optoelectronics, Optronics, Optoelectronics, Optronics, Optoelectronics, Optoelectronics, Optoelectronics, United States. MERICA, January 1, 1996, Vol. 21 / No. 1, p. 24-26 S.I. J. Frisken, Light-induced optical wave guide uppers, Optics Letters, USA, OPTICAL SOCIETY OF AMERICA, June 15, 1993, Vol. 18 / No. 12, p. 1035-1037 (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 6/13 G02B 6/26 G02B 6/00

Claims (8)

(57) [Claims] 1. A method for producing an optical transmission line, wherein a light having a predetermined wavelength is introduced into a photocurable resin solution and the photocurable resin solution is cured in the optical axis direction to produce a continuous optical transmission line from an entrance. in the method, the photocurable resin solution first curing initiation wavelength than the light-curable resin solution of a photocurable resin solution and the first is rather short, the first
A mixed solution with a second photocurable resin solution having a refractive index smaller than that of the photocurable resin solution, wherein the mixed solution has a wavelength band in which only the first photocurable resin solution is cured. A method for manufacturing an optical transmission line, which comprises making an axial optical transmission line by making a light beam incident. 2. A method for producing an optical transmission line, wherein a light having a predetermined wavelength is introduced into a photocurable resin solution and the photocurable resin solution is cured in the optical axis direction to produce a continuous optical transmission line from an entrance. In the method, the photocurable resin solution is a mixed solution of a first photocurable resin solution and a second photocurable resin solution having a curing initiation wavelength shorter than that of the first photocurable resin solution, A light beam is incident on the mixed solution in a wavelength band that cures only the first photocurable resin solution to form an axial core portion, and the first and second light beams are generated from the periphery of the mixed solution. Light transmission in a wavelength band for curing a curable resin solution to produce a clad part around the core part, wherein the core part has a refractive index higher than that of the clad part. Road manufacturing method. 3. The optical transmission line according to claim 1, wherein the refractive index of the first photocurable resin solution when cured is higher than the refractive index of the mixed solution. Manufacturing method. 4. The light of the predetermined wavelength is emitted from the tip of an optical fiber impregnated with the mixed solution, and the optical transmission line is continuously formed from the tip of the optical fiber. The method for manufacturing an optical transmission line according to claim 1. 5. The optical fiber is a step index type optical fiber whose refractive index changes stepwise at a boundary between a core portion and a cladding portion, wherein the core portion refractive index is n _f1 and the cladding portion refractive index is n _f2. , The refractive index of the core portion of the optical transmission line is n
_A2 , The optical transmission line according to claim 4, wherein the refractive index of the mixed solution is adjusted so that the condition of the expression (1) is satisfied when the refractive index of the mixed solution is n _C1. Manufacturing method. [Equation 1] (n _f1 ) ² − (n _f2 ) ² ≦ (n _A2 ) ² − (n _C1 ) ² (1) 6. The optical fiber is a graded index type optical fiber having a refractive index gradient with a predetermined function in the radial direction, and the maximum refractive index at the center of the core of the optical fiber is n _f1 and the diameter of the core is 2a _f , the refractive index of the cladding is n
_f2, the optical transmission path core part refractive index n _A2 of, when the integer a refractive index n _C1, p of the mixed solution, the core portion diameter 2a _w of the optical transmission line to be fabricated with (2) The method for manufacturing an optical transmission line according to claim 4, wherein the refractive index of the mixed solution is adjusted under the condition that the condition is satisfied. 2 a _w = 2a _f [1 / (2Δ) · (n _A2 ² −n _C1 ² ) / n _A2 ² ] ^{1 / p} where Δ = (n _f1 ² −n _f2 ² ) / (2n _f1 ² ) ・ ・ ・ (2) 7. An optical fiber tip is dipped in a photocurable resin solution, and light of a predetermined wavelength is emitted from the optical fiber tip,
In the method of manufacturing an optical transmission line, in which the optical transmission line is continuous from the tip of the optical fiber by curing the photocurable resin solution in the optical axis direction, the photocurable resin solution is a first photocurable resin. Resin solution and the first
The curing initiation wavelength is shorter than that of the photocurable resin solution of No. 1,
The second refractive index smaller than that of the photocurable resin solution
A mixed solution with a photocurable resin solution, wherein the optical fiber is a step index type optical fiber in which the refractive index changes stepwise at the boundary between the core part and the clad part, and the refractive index of the core part is n _f1. When the refractive index of the cladding portion is n _f2 , the refractive index of the optical transmission line is n _A2 , and the refractive index of the photo-curable resin solution is n _C1 , the photo-curing condition is satisfied so as to satisfy the condition (3). Method for manufacturing an optical transmission line in which the refractive index of a photosensitive resin solution is adjusted. (N 3) (n _f1 ) ² − (n _f2 ) ² ≦ (n _A2 ) ² − (n _C1 ) ² (3) 8. An optical fiber tip is dipped in a photocurable resin solution, and light of a predetermined wavelength is emitted from the optical fiber tip,
In the method of manufacturing an optical transmission line, in which the optical transmission line is continuous from the tip of the optical fiber by curing the photocurable resin solution in the optical axis direction, the photocurable resin solution is a first photocurable resin. Resin solution and the first
The curing initiation wavelength is shorter than that of the photocurable resin solution of No. 1,
The second refractive index smaller than that of the photocurable resin solution
A mixed solution with a photocurable resin solution, wherein the optical fiber is a graded index type optical fiber having a refractive index gradient with a predetermined function in the radial direction, and the maximum refractive index at the center of the core of the optical fiber. _Where n _f1 , the core diameter is 2 a _f , the cladding refractive index is n _f2 , the optical transmission line refractive index is n _A2 , the photocurable resin solution refractive index is n _C1 , and p is an integer, under conditions satisfying the diameter 2a _w of the optical transmission path produced is the (4) equation, the manufacturing method of the optical transmission line, wherein a refractive index of the photocurable resin solution is adjusted. 2 a _w = 2a _f [1 / (2Δ) · (n _A2 ² −n _C1 ² ) / n _A2 ² ] ^{1 / p} where Δ = (n _f1 ² −n _f2 ² ) / (2n _f1 ² ) ・ ・ ・ (4)