JPH07261040A - Glass waveguide and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide a glass waveguide in which various elements can be easily added to a light propagation region and which has a small connection loss with an optical fiber, and a manufacturing method thereof. [Structure] After forming a groove 3 which becomes a light propagation region on at least one surface of at least one of the two glass substrates 2a and 2b, both glass substrates 2 are formed with the surface having the groove 3 inside.
Another glass material 1 having a higher refractive index and a lower softening temperature than the glass substrates 2a and 2b is sandwiched between a and 2b, and the glass material 1 is heated and melted while applying pressure from both sides to form the glass substrate 2
The glass material 1 is formed into the groove 3 by bringing the a and 2b into close contact with each other.
Fill the inside to form a light propagation region. On both sides of the groove 3,
By forming another groove 4,5 having a wider width at least at least twice the width of the groove 3, the glass substrates 2a, 2 can be formed.
b It is possible to increase the contact pressure of each other and absorb the excess glass material other than filling the groove 3 which becomes the light propagation region.

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 a glass waveguide suitable for the fields of communication, measurement, and information processing, particularly a functional glass waveguide with optical amplification.

[0002]

In the fields of communication, control and information processing,
In order to use light in a higher degree, researches on optical integrated circuits having various functions are being actively conducted. An optical amplifier is one of the basic elements constituting such an optical integrated circuit. Up to now, the optical amplification effect has been confirmed in a glass waveguide using a phosphate glass doped with 3 wt% of Nd.
(H.Aoki, O.Maruyama, Y.Asahara: Topical meeting on gl
asses for optoelectronics.Extended abstracts, p69,
Dec. 1, (1989)). This manufacturing method is as follows. First, Ti is vapor-deposited on the surface of a phosphate glass substrate doped with 3 wt% of Nd, an optical waveguide mask pattern is provided by using a photolithography method, and Ag that is a diffusion source for controlling the refractive index is vapor-deposited. Next, a voltage is applied for several hours in an electric furnace at about 400 ° C. to diffuse Ag ions through the gap between the Ti films into the glass substrate to form a channel type optical waveguide having a semicircular cross section. The amplification effect has been confirmed by using a laser diode having a wavelength of 802 nm as an excitation light source in this optical waveguide.

[0003]

By the way, in the above-mentioned glass waveguide using the phosphate glass, the Ag ion diffusion region, which is the light propagation region, has a semicircular asymmetrical structure, and therefore the propagation is The intensity distribution of the emitted light becomes distorted, and a large coupling loss occurs when connecting with an optical fiber. Also,
In order to enhance the amplification effect, it is necessary to dope the rare earth element in the light propagation region in a concentrated manner, but in the above-mentioned glass waveguide, the refractive index is controlled for a part of the rare earth element-doped phosphate glass substrate. Since the light propagation region is used, the rare earth element doping concentration in the light propagation region cannot be controlled, and the types of rare earth elements that can be doped are also limited.

Further, in the case where the light propagation region is formed with a bend like a loop-shaped ring laser, in order to suppress an increase in loss due to the provision of the bent portion, the light propagation region, that is, the core and its periphery, is suppressed. It is important to increase the refractive index difference (Δn) from the low refractive index region, that is, the cladding. By increasing Δn, the light is strongly confined in the core, and the bending loss is small even if the optical waveguide is bent with a large locality, and as a result, the element size can be reduced. However, Δn cannot be essentially increased by the manufacturing method in which the refractive index of the core is made larger than that of the peripheral portion by diffusing Ag ions.

An object of the present invention is to solve the above-mentioned problems and to easily add various elements which bring about an amplifying action of light and various elements for controlling the refractive index to a light propagation region, and to provide an optical fiber. It is an object of the present invention to provide a glass waveguide having a small connection loss and a manufacturing method thereof.

[0006]

In order to achieve the above object, the glass waveguide of the present invention is provided with two glass substrates, a groove formed on one surface of at least one of the glass substrates, and this groove. Another glass material with a higher refractive index and a lower softening temperature than the glass substrate is sandwiched between the two glass substrates with the surface facing inside, and the glass materials are heated and melted while pressing the glass material from both sides, It is characterized in that it is constituted by a light propagation region formed by filling the groove with the glass material by closely contacting with each other.

Further, in the glass waveguide of the present invention, another groove having a wider width is formed on both sides of the groove serving as the light propagation region at a distance of at least twice the width of the groove. Is desirable. Further, it is desirable that the outer surface of the glass substrate be covered with a thin film having a softening temperature higher than the softening temperature of the glass material. Further, it is desirable to use phosphate glass containing at least one kind of rare earth element selected from Pr, Nd, Er, Yb, Ho, and Tm as the glass material.

Next, according to the method for manufacturing a glass waveguide of the present invention, after forming a groove serving as a light propagation region on one surface of at least one of the two glass substrates, the surface on which the groove is formed is formed. Another glass material having a higher refractive index and a lower softening temperature than the glass substrate is sandwiched between both glass substrates, and the glass material is heated and melted while pressing it from both sides to bring the glass substrates into close contact with each other. As a result, the glass material is filled in the groove to form a light propagation region.

In the method for manufacturing a glass waveguide according to the present invention, another groove having a wider width is provided on both sides of the groove serving as the light propagation region with a distance of at least twice the width of the groove. After forming, it is desirable to sandwich the glass material between both glass substrates as described above. Further, the outer surface of the glass substrate is coated with a thin film having a softening temperature higher than the softening temperature of the glass material,
It is desirable to heat and melt the glass material at a temperature higher than the softening temperature of the thin film to bring the glass substrates into close contact with each other.

[0010]

According to the glass waveguide of the present invention, the glass material is sandwiched between two glass substrates, and the glass material is heated and melted while being pressed from both sides without depending on diffusion as in the conventional case. By adhering the glass substrates together, the glass material is filled in the groove to form a light propagation region, so that a light propagation region having a symmetrical structure in cross section can be easily formed, and a desired element Since it can be added to the glass material, various elements that bring about a light amplification effect can be added to the light propagation region. Further, since the refractive index of the light propagation region can be easily adjusted by adjusting the concentration of the dopant for controlling the refractive index to be added to the glass material, the light propagation region and its surrounding low refractive index region The refractive index difference (Δn) can be easily adjusted to a desired value.

Next, according to the method for manufacturing a glass waveguide of the present invention, the glass material is sandwiched between two glass substrates, and the glass is pressed from both sides without depending on diffusion as in the conventional case. Since the glass material is filled in the groove to form the light propagation region by heating and melting the material and bringing the glass substrates into close contact with each other, the light propagation region having a symmetrical structure in cross section can be easily formed. it can. Also,
Since a desired element can be added to the above glass material, various elements that bring about a light amplification effect can be added to the light propagation region. Further, a refractive index control dopant added to the above glass material.
Since the refractive index of the light propagation region can be easily adjusted by adjusting the concentration of the punt, the refractive index difference (Δn) between the light propagation region and the surrounding low refractive index region can be easily adjusted to a desired value. it can.

Further, on both sides of the groove serving as the light propagation region, wide grooves which are not involved in light propagation are formed at intervals of at least twice the width of the groove, and then, as described above. If the above glass material is sandwiched between the two glass substrates, the contact pressure between the glass substrates can be increased, and excess glass material other than that filled in the groove serving as the light propagation region can be absorbed. As a result, the glass material remaining between the glass substrates other than the groove serving as the light propagation region can be made extremely thin, and as a result, the guided mode is not excited in this portion. Further, by heating and melting the glass material at a temperature higher than the softening temperature of the glass substrate to bring the glass substrates into close contact with each other, the adhesive force between the glass substrate and the glass material can be enhanced, and the unevenness in the groove can be smoothed. The scattering loss can be reduced. At this time, the outer surfaces of both glass substrates are coated with a thin film having a softening temperature higher than the softening temperature of the glass material, whereby fusion between the glass substrates and the pressing means can be prevented.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a structure and a manufacturing method of a glass waveguide showing an embodiment of the present invention. When manufacturing a glass waveguide, first, a block of phosphate glass is sliced to a thickness of 0.4 mm, and both surfaces thereof are mirror-polished to prepare a glass material 1. This glass material 1 is shown in FIG.
Two glass substrates 2 having a thickness of 1 mm as shown in (a)
It is sandwiched by a and 2b from above and below. Since the glass material 1 is a core layer and the two glass substrates 2a and 2b sandwiching it are clad layers, the refractive index of the glass substrates 2a and 2b must be smaller than that of the glass material 1. The glass material 1 used in this example is composed of 60% by weight of P ₂ O ₅ , and other than that, SiO ₂ , K ₂ O, BaO and the like are contained. SiO ₂ enhances chemical stability, K ₂ O, B
aO serves to widen the vitrification range and lower the softening temperature. Further, this glass material 1 contains 0.2% by weight of Er ₂ O ₃ as an active element which brings about a light amplification effect and 10% by weight of Yb ₂ O ₅ as a sensitizer. The refractive index of this glass material 1 was 1.52 in the wavelength band of 1.5 μm. On the other hand, BK7 glass was used for the glass substrates 2a and 2b to be the cladding layers. Wavelength 1.5
The refractive index of BK7 glass in the μm band is 1.50, which is smaller than the refractive index of the glass material 1 used in this example. A concave groove 3 having a width and a depth of 6 μm is formed by a photolithography method and a dry etching method at the center of one surface of one glass substrate 2b. This groove 3 will become a light propagation region, that is, a core region in a later process. Further, on both sides of this groove 3, another groove 4, 5 wider than the groove 3 is provided.
Are formed. The grooves 4 and 5 on both sides are the central groove 3
At the same time, it was formed by photolithography and dry etching, and its groove width was set to 200 μm, which was sufficiently wider than that of the central groove 3. The distance between the central groove 3 and the grooves 4 and 5 on both sides is set so that the existence of the grooves 4 and 5 on both sides does not affect the light propagation characteristics of the central groove 3.
Is more than twice the width of. In this embodiment, the glass material 1 is sandwiched between the two glass substrates 2a and 2b so that the surfaces on which the grooves 3, 4, and 5 are formed are on the inside, and 620 is applied as a whole while applying pressure from the back of the substrates. The glass substrates 2a and 2b are heated and brought into close contact with each other, and are bonded together. The softening temperature of the phosphate glass constituting the glass material 1 used in this example is about 520 ° C., which is lower than that of the BK7 glass, and the glass material 1 melts in the atmosphere of 620 ° C. and loses its viscosity and loses its backside. Groove 3,4 by pressure from
5 is uniformly filled. This heating temperature is slightly higher than the softening temperature of BK7 glass. Therefore, the fusion force between the glass substrates 2a and 2b and the glass material 1 is strong, and the irregularities in the grooves 3, 4, and 5 are smoothed, and scattering loss is reduced. In this embodiment, the glass substrate 2b is placed on the quartz table 6.
, And a weight is applied from above the glass substrate 2a using a quartz weight 7, and the pressure is about 1 to 3 kg / c.
It was set to m ² . At a temperature of 620 ° C., BK7 glass may also be softened and fused to the table 6 and the weight 7, so that the outer surfaces of the two glass substrates 2a and 2b each have a thickness of about 1 μm.
A thick SiO ₂ thin film 9 is vapor-deposited to prevent fusion with the weight 7. By coating the outer surfaces of the two glass substrates 2a and 2b with the thin film 9 having a softening temperature higher than the heating temperature, even if the glass substrates 2a and 2b are heated at a temperature higher than the softening temperature, a load is applied. The base 6 and the weight 7 are not melt-bonded to the glass substrates 2a and 2b. Groove 3,
Phosphate glass is filled in the grooves 4, 5, and the grooves 3, 4, 5
The phosphate glass in the other parts is removed by pressing.
Since the wide grooves 4 and 5 that do not participate in light propagation are formed on both sides of the light propagation groove 3, the glass substrates 2a and 2b are formed.
It is possible to increase the pressure applied to each other and absorb the excess phosphate glass other than that filled in the light propagation groove 3.
As a result, the adhesive layer of phosphate glass remaining between the glass substrates 2a and 2b other than the grooves 3, 4, and 5 can be made extremely thin, and as a result, the guided mode is not excited in this portion.

In this way, the glass material 1, that is, the phosphate glass is confined in the groove 3 as shown in FIG. 1 (b), and the glass substrates 2a and 2b form a clad, whereby the refractive index from the peripheral portion is increased. A high core region or light guiding region 8 is formed. Finally, the bonded glass substrate 2
The glass waveguide is completed by cutting a and 2b into desired lengths and polishing both end faces into mirror surfaces. Two glass substrates 2a, 2
b serves not only as a clad but also as a protective material when polishing the end face of the waveguide.

In the structure of the present invention, since the light propagation region 8 is completely embedded, even when the end face is polished and connected to the optical fiber, the waveguide end face is chipped or the optical fiber is not properly connected. Never. In the example of FIG. 1, the light propagation region 8 is formed only on one glass substrate 2b, but by forming the light propagation region on the other glass substrate 2a in the same manner, a three-dimensional structure having a higher degree of integration can be obtained. A circuit can be formed. Unlike phosphate glass, which has a three-dimensional network structure like silicate glass, phosphate glass has a chain structure, so that concentration quenching does not easily occur even if it is highly densely doped with an element such as Er that has a light amplifying effect. Therefore, the gain per unit length can be increased as compared with a silica-based Er-doped fiber, and it is a promising material for forming a waveguide type amplifier. In addition, in the present embodiment, Er was added as an element that brings about an amplification effect of light for the purpose of amplifying light in the vicinity of 1.53 μm for application to communication, but other than this, Pr, Nd, Yb,
Even if a rare earth element such as Ho or Tm is doped, good amplification characteristics can be obtained.

[0017]

In summary, according to the present invention, the following excellent effects can be exhibited.

(1) According to the glass waveguide of the present invention,
The glass material is sandwiched between two glass substrates, and the glass material is heated and melted to bring the glass substrates into close contact with each other to fill the glass material in the groove to form a light propagation region. The light propagation region of the structure can be easily formed, and the connection loss with the optical fiber can be suppressed small. Further, since a desired element can be added to the glass material, various elements that bring about a light amplification effect can be added to the light propagation region. Further, since the refractive index of the light propagation region can be easily adjusted by adjusting the concentration of the dopant for controlling the refractive index added to the glass material, the refraction of the light propagation region and the surrounding low refractive index region The rate difference can be easily adjusted to the desired value.

(2) According to the method for manufacturing a glass waveguide of the present invention, a glass material is sandwiched between two glass substrates having a groove formed in at least one of them, the glass material is melted, and the substrates are brought into close contact with each other. It is possible to easily manufacture a glass waveguide including a core having an optical amplification function and a clad that embeds the core. Since no complicated and expensive manufacturing equipment is required, the production cost can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure and a manufacturing method of a glass waveguide showing an embodiment of the present invention. 1 glass material 2a, 2b glass substrate 3, 4, 5 groove

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akifumi Hongo 3550, Kidayo-cho, Tsuchiura-shi, Ibaraki Hitachi Cable Ltd. Advanced Research Center (72) Inventor Seiichi Kashimura 3550, Kidayo-cho, Tsuchiura-shi, Ibaraki Hitachi Cable Shares Company Advance Research Center

Claims (6)

[Claims] 1. Two glass substrates, a groove formed on one surface of at least one of the glass substrates, and a surface having the groove formed inside is provided with a higher refractive index than the glass substrates between the glass substrates. Also, another glass material having a low softening temperature is sandwiched, and the glass material is heated and melted while being pressed from both sides to bring the glass substrates into close contact with each other so that the glass material is filled in the groove to propagate light. A glass waveguide comprising a region and a region. 2. The glass conductor according to claim 1, wherein another groove having a wider width is formed on both sides of the groove serving as the light propagation region at a distance of at least twice the width of the groove. Waveguide. 3. Pr, Nd, E as the glass material
2. A phosphate glass containing at least one kind of rare earth element selected from r, Yb, Ho and Tm.
The described glass waveguide. 4. After forming a groove serving as a light propagation region on at least one surface of at least one of the two glass substrates,
Another glass material having a higher refractive index and a lower softening temperature than the glass substrate is sandwiched between both glass substrates with the surface having the groove formed inside, and the glass material is heated and melted while pressing it from both sides. A method of manufacturing a glass waveguide, wherein the glass material is filled in the groove to form a light propagation region by closely adhering the glass substrates together. 5. Another groove having a wider width is formed on both sides of the groove serving as the light propagation region at an interval of at least twice the width of the groove, and the glass is sandwiched between both glass substrates. The method for manufacturing a glass waveguide according to claim 4, wherein the material is sandwiched. 6. The outer surface of the glass substrate is covered with a thin film having a softening temperature higher than the softening temperature of the glass material, and the glass material is heated and melted at a temperature higher than the softening temperature of the thin film. The method for manufacturing a glass waveguide according to claim 4, wherein the glass substrates are brought into close contact with each other.