JPH0756032A - Glass waveguide and its production - Google Patents

Abstract

PURPOSE:To obtain a good propagation characteristic with low loss by preventing the deformation of core waveguides to be generated at the time of sintering porous glass. CONSTITUTION:The core waveguide parts 1a which largely vary in the shrinkage rate of the porous glass at the time of sintering between one side and the other side of the core waveguides 1 are provided with dummy core waveguide parts 6 which prevent the deformation of the core waveguide parts 1a near these parts. The dummy waveguide parts 6 are disposed symmetrically with the core waveguide parts 1a and the positrons and sizes thereof are so considered as not to affect the desired propagation characteristics of the glass waveguides. Even if anisotropic force tends to act on the core waveguide parts 1a, this force is blocked by the dummy core waveguide parts 6 and the influence on the core waveguide parts 1a is shut off. The core waveguide parts 1a are, therefore, not subjected to deformation even at the time of forming clad layers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass waveguide and a method for manufacturing the same, and more particularly to a glass waveguide having no deformation in a core waveguide.

[0002]

2. Description of the Related Art FIG. 4 shows a cross-sectional structure of a conventional glass waveguide. To manufacture this glass waveguide, the glass substrate 3
A core glass film having a refractive index higher than that of the substrate is formed thereon, and after forming the core waveguide 1 by photolithography and reactive ion etching, porous glass is deposited on the substrate 3 and a transparent clad is formed by sintering. The glass layer 2 is formed.
The core waveguide 1 is usually 8 × 8 μm or 6 × 6 μm
Is formed to have a rectangular cross section.

By the way, the core waveguide 1 formed in the glass waveguide is composed of a complicated circuit pattern rather than a linear simple pattern, and a clad glass is formed on the complicated circuit pattern. There are many things that are done. For example, the pattern shown in FIG. 5 is a 1 × 16-branch glass waveguide pattern 4 having a Y-branch structure, and a cladding glass of about 25 μm is formed on this pattern. In order to form a clad glass having this thickness, it is necessary to deposit and sinter porous glass having a thickness of about 250 to 350 μm.

[0004]

However, when the porous glass is deposited and sintered as described above, the thickness of the porous glass is as thick as 250 to 350. And a large amount of shrinkage occurs in the axial direction (thickness direction). At this time, in particular, the core waveguide portion 5 near the root of the Y-branch portion on the line aa 'in FIG. 5 may be deformed as shown in FIG. There is a case where it is inclined by about 1 °. As a result, some of the light leaks from the core to increase the loss, or the light is not evenly distributed, and there is a drawback that the optical output between the ports varies.

This is not limited to the optical branching / coupling device, but also applies to the Mach-Zehnder type and the optical multiplexer / demultiplexer composed of the glass waveguide shown in FIG.
That is, the approaching portion between the core waveguides 1 (on the line bb ')
However, it may be modified as shown in FIG. 6 as in the case of the optical branching / coupling device. As a result of this modification, for example, in the multiplexing / demultiplexing characteristics of the wavelengths of 1.3 μm and 1.55 μm, the center wavelength is
There was a problem that a large deviation of 0 nm occurred and a light of wavelength 1.55 μm greatly leaked to the light emission side of wavelength 1.3 μm.

As described above, since the core waveguide in the portion where the core waveguides are close to each other is deformed during the formation of the clad glass, it is desired to develop a technique in which the core waveguide is not deformed even during the formation of the clad glass. It was

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a glass waveguide having a low loss and good propagation characteristics, and a method for manufacturing the same.

[0008]

The glass waveguide of the present invention is a glass waveguide in which a core waveguide and a cladding layer covering the core waveguide are formed on a substrate, and when the cladding layer is formed in the vicinity of the core waveguide. It has a dummy core waveguide for preventing deformation of the core waveguide.

In this case, it is preferable that the dummy core waveguide is provided symmetrically with respect to the core waveguide, or the substrate is a quartz glass substrate or a silicon substrate having a quartz glass film on the surface.

Further, according to the method of manufacturing a glass waveguide of the present invention, the core waveguide is formed on the substrate, and the dummy core waveguide for preventing the deformation of the core waveguide during the sintering of the porous glass is formed in the vicinity thereof. Then, a porous glass is formed on the substrate on which the core waveguide and the dummy core waveguide are formed,
This is sintered to form a transparent clad layer.

[0011]

After the core waveguide is formed, when the porous glass is deposited on the core waveguide to form the clad layer and the porous glass is sintered and vitrified, the deposition amount of the glass deposited on the substrate is If the one side and the other side of the core waveguide are different, the amount of shrinkage due to vitrification will be different, and the amount of shrinkage on the side of the core waveguide with a large amount of deposition will be larger than that on the side of the core waveguide with a smaller amount of deposition. It is presumed that an anisotropic force acts on the waveguide, which causes deformation of the core waveguide.

In the present invention, since the dummy core waveguide is provided in the vicinity of the core waveguide in the portion where the interval between the core waveguides is narrow such that the amount of shrinkage due to vitrification greatly differs, the core waveguide is anisotropic. Even if any force is exerted, the force is blocked by the dummy core waveguide and the influence on the core waveguide is cut off. Therefore, the core waveguide is not deformed even when the clad layer is formed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a 1 × 16 branch glass waveguide having a Y-branch structure, and FIG. 2 is a sectional view taken along the line cc ′ of FIG. In this glass waveguide, a core waveguide 1 is formed on a quartz glass substrate 3, and a clad layer 2 covering the core waveguide 1 is formed on the core waveguide 1 by glass sintering.

In the core waveguide 1 formed on the substrate 3, the core waveguide portion 1a at the base of the Y branch portion is subjected to the force exerted on the core waveguide portion 1a during the glass sintering of the clad layer to form the core waveguide portion. A dummy core waveguide 6 is provided to prevent the deformation of 1a.

In the illustrated example, the dummy core waveguide 6 is provided symmetrically with respect to the core waveguide portion 1a on both sides of the core waveguide portion 1a of the 1 × 2 branch portion of the input stage. In the 1 × 4 branch section at the subsequent stage, each 1
It is provided on the outside of one of the × 2 branches. It should be noted that the dummy core waveguide 6 provided on one outer side is provided asymmetrically with respect to the core waveguide portion 1a of each 1 × 2 branch portion.
Seen from the entire × 4 branch portion, they are provided symmetrically.

These dummy core waveguides 6 are provided at locations and sizes that do not affect the intended propagation characteristics of the glass waveguide. That is, the installation location of the dummy core waveguide is such that the amount of glass deposited on one side of the core waveguide is greatly different from that on the other side, and the core waveguide portion 1a at the base of the Y-branch portion is susceptible to deformation.
The optimum is near. Also, the size of the dummy core waveguide is 8 × 8 μm or 6 × 6 rectangular cross section of the core waveguide portion 1a.
The size may be the same as μm, but preferably, the width and the height are formed to have a cross section larger than that of the core waveguide portion 1a, so that the core itself can withstand deformation. In particular, the deformation can be almost completely suppressed by setting the width to be 1.5 times or more the width of the core waveguide portion 1a.

FIG. 2 shows a cross section taken along the line cc 'of the Y-branch glass waveguide having the dummy core waveguide 6 as described above. When the dummy core waveguide 6 is provided in the vicinity, even if an anisotropic force acts on the core waveguide portion 1a, the force is blocked by the dummy core waveguide 6 and the influence on the core waveguide 1 is cut off. Therefore, the core waveguide is not deformed even when the cladding layer 2 is formed, and the shape of the core waveguide 1a is maintained even after the cladding 2 layer is formed.

Next, a method of manufacturing the glass waveguide provided with the above-mentioned dummy core waveguide 6 will be specifically described. A TiO ₂ —SiO ₂ core glass film of 8 μm was formed on a quartz glass substrate having a diameter of 3 inches and a thickness of 1 mm by an electron beam evaporation method. 8 × by photolithography and reactive ion etching
A core waveguide pattern having an 8 μm cross section and having 1 × 16 branches as shown in FIG. 1 was formed. At this time, the dummy core waveguide 6 was also formed together. The dummy core waveguide 6 has a 16 × 8 μm cross section, and each core waveguide portion 1a to 20
It was separated by μm. After that, 30 pieces of porous glass is formed by the flame deposition method.
0 μm thick, sintered at 1300 ° C., 24 μm thick P ₂
O ₅ -B ₂ O ₃ to form -SiO ₂ cladding glass,
A 1 × 16-branch glass waveguide was prototyped. For comparison, a glass waveguide without a dummy core waveguide was also manufactured under the same conditions as above.

In both of the prepared 1 × 16 branched glass waveguides, one having a dummy core waveguide had a good transmission loss from 1 input port to 16 output ports of 13.5 dB ± 0.3 dB. On the other hand, the one without the dummy core waveguide had a large loss value and variation of 14.5 dB ± 1.0 dB.

Also, in the bidirectional optical multiplexer / demultiplexer shown in FIG. 3, the core waveguide portion 1a in which the core waveguide 1 is close to the core waveguide portion 1a.
The dummy core waveguides 6 are provided near both sides of the.
By doing so, the core waveguide portion 1a at the approaching portion was not deformed during glass sintering, as in FIG. The center wavelength of this optical multiplexer / demultiplexer was within ± 5 nm, which coincided with the design value. As a result, in the multiplexing / demultiplexing characteristics of the wavelengths of 1.3 μm and 1.55 μm, it was possible to effectively prevent the light of 1.55 μm from leaking to the light emitting side of 1.3 μm.

[0021]

【The invention's effect】

(1) According to the invention described in claim 1 or 3, since the dummy core waveguide is provided in the vicinity of the core waveguide, it is possible to obtain good propagation characteristics with low loss.

(2) According to the invention described in claim 2, since the dummy core waveguides are symmetrically provided, the integrated glass waveguide device can be stabilized.

(3) According to the invention described in claim 4, by forming the dummy core waveguide near the core waveguide, the core waveguide is not deformed even when the cladding layer is formed, and the loss is low. Moreover, it is possible to reproducibly manufacture the glass waveguide that sufficiently satisfies the function of the optical circuit.

[Brief description of drawings]

FIG. 1 is a 1 × 16 showing an embodiment of a glass waveguide of the present invention.
It is a top view of a branch glass waveguide.

FIG. 2 is a sectional view taken along line cc ′ of FIG.

FIG. 3 is a plan view of an optical multiplexing / demultiplexing glass waveguide showing another embodiment of the glass waveguide of the present invention.

FIG. 4 is a cross-sectional view of a glass waveguide in which the core waveguide has no deformation.

FIG. 5 is a plan view of a conventional 1 × 16 branch glass waveguide.

6 is a cross-sectional view taken along the line aa ′ of FIG.

FIG. 7 is a plan view of a conventional multiplexing / demultiplexing glass waveguide.

[Explanation of symbols]

 1 core waveguide 1a core waveguide part 2 clad layer 3 silica glass substrate 4 core waveguide pattern 5 deformed core waveguide part 6 dummy core waveguide

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hideo Otsuki 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture, Hitachi, Ltd., within the Optro System Laboratory, Hitachi Cable, Ltd. (72) Keiichi Higuchi, Hidaka Town, Hitachi City, Ibaraki Prefecture 5-1-1, Hitachi Cable Ltd., Optoro System Laboratories

Claims (4)

[Claims] 1. A glass waveguide in which a core waveguide and a cladding layer covering the core waveguide are formed on a substrate, and a dummy core conductor for preventing deformation of the core waveguide when the cladding layer is formed near the core waveguide. A glass waveguide having a waveguide. 2. The glass waveguide according to claim 1, wherein the dummy core waveguide is provided symmetrically with respect to the core waveguide. 3. The glass waveguide according to claim 1, wherein the substrate is a quartz glass substrate or a silicon substrate having a quartz glass film provided on the surface thereof. 4. A core waveguide is formed on a substrate, a dummy core waveguide for preventing deformation of the core waveguide is formed in the vicinity of the core waveguide, and the core waveguide and the substrate on which the dummy core waveguide is formed are porous. 1. A method for manufacturing a glass waveguide, which comprises forming a high quality glass and sintering the high quality glass to form a transparent clad layer.