JP2927597B2 - Manufacturing method of glass waveguide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for manufacturing a glass waveguide .

[0002]

2. Description of the Related Art In manufacturing a silica-based glass waveguide, a porous glass layer is deposited on a substrate on which a core is formed by a flame hydrolysis reaction, and then heated to form a transparent glass, thereby forming a clad layer. Techniques for doing so are known. The substrate is made of silica (SiO ₂ ) or silicon (Si), and the heating temperature needs to be 1350 ° C. or lower in order to eliminate the deformation of the substrate at the transparent glass transparentizing temperature. For this reason, P and B dopants are mainly added to lower the transparency temperature. Further, the refractive index of the cladding layer needs to be substantially equal to that of silica in terms of transmission characteristics. This is because, particularly in the case of a directional coupler type multiplexing / demultiplexing glass waveguide, the multiplexing / demultiplexing characteristics greatly change depending on the refractive index.

[0003]

Since the clad layer formed of porous glass is very thin, 40 to 50 μm , B ₂ O ₃ and P ₂ O ₅ are converted to porous glass during vitrification. Volatilizes out of layer. In addition, the diffusion state of B ₂ O ₃ and P ₂ O _{5 in} the porous glass layer is different, and a layer having a large amount of P ₂ O ₅ is formed on the core and the substrate surface, so that the propagation loss and the multiplexing / demultiplexing characteristics are reduced. It changes greatly. For this reason, as described later as a comparative example, there has been a problem that the characteristics are deteriorated due to the generation of abnormal glass.

Therefore, the cladding layer is made of P ₂ O ₅ -B ₂ O ₃
It is necessary to establish a manufacturing method that is SiO ₂ and has a uniform refractive index in the cladding layer.

An object of the present invention is to solve the above-mentioned disadvantages of the prior art and to propose a method of manufacturing a glass waveguide having stable transmission characteristics.

[0006]

SUMMARY OF THE INVENTION The gist of the present invention is that silica
Silicon on glass substrate or silica glass
A core is formed on a substrate, and a porous crack is
After depositing a metal layer,
In the method of manufacturing a glass waveguide having a
First porous material containing B ₂ O ₃ and no P ₂ O ₅
Forming a porous cladding layer and covering the first porous cladding layer
Second porous cladding layer containing P ₂ O ₅ and B ₂ O ₃
Is formed, and then P ₂ O ₅ is diffused by sintering ,
_When the concentration of ₂ O ₅ becomes uniform in the entire cladding layer,
Terminates sintering and forms a glass clad layer with a uniform refractive index
In the method of manufacturing a glass waveguide.

[0007]

At this time, the thickness of the first porous cladding layer is
It is preferable that the thickness is equal to or larger than the second porous cladding layer.

Further, both the first porous clad layer and the second porous clad layer may contain GeO ₂ or TiO ₂ .

[0010]

Examples of EXAMPLES The invention will be described below with reference to FIGS.

An 8 μm thick TiO ₂ —SiO ₂ core glass film was formed on a quartz glass substrate 4 having an outer diameter of 3 inches and a thickness of 1 mm by electron beam evaporation. Quartz glass substrate 4
And the relative refractive index difference Δn was 0.3%. A WSi film having a thickness of 1 μm was formed on the surface of the substrate by a sputtering method. Further, after applying a photoresist, the core pattern was transferred by a mask aligner, and after baking, unnecessary portions were removed. Next, by reactive ion etching (RIE),
After etching only the WSi based on the core pattern of the photoresist, the photoresist is removed. Thereafter, the core glass was etched by RIE to form a core 1 . The substrate was placed on a turntable heated to 450 ° and, using a flame deposition method, first, SiCl ₄ and BCl
₃ to an oxyhydrogen burner, and the first of B ₂ O ₃ —SiO ₂
The porous cladding layer 2 is formed to a thickness of 25 μm. Thereafter, PCl ₃ was added to the burner, and P ₂ O ₅ -B ₂ O ₃ -S
The second porous cladding layer 3 of iO ₂ was formed to a thickness of 20 μm. The substrate is positioned in the quartz glass furnace tube in an electric furnace, the atmosphere was warmed to 1300 ° C. at a heating rate of 5 ° C. / min and He gas, and transparent glass by holding for 1 hour, Fig 2 (c to obtain a glass cladding layer 5 shown in). The thickness of the entire glass clad layer 5 was 20 μm. Further, the relative refractive index difference Δn from the quartz glass substrate 4 is −0.1.
Δn in the thickness direction and in the plane is ± 0.01%
Within the match.

In this embodiment, the directional coupler type multiplexer / demultiplexer shown in FIG. 3 was manufactured. The multiplexing / demultiplexing characteristics shown in FIG. 4 were obtained, and the connection loss with the optical fiber 7 was 0.1 dB / cm. , The isolation of the ports α and β of the glass waveguide containing was -25 dB or less, showing a good demultiplexing characteristic.

Here, as a comparative example, in forming the first porous cladding layer, PCl ₃ was supplied from the beginning and P ₂ was supplied.
After forming only the second porous cladding layer of O ₅ —B ₂ O ₃ —SiO ₂ on the substrate, the glass was formed into a transparent glass to obtain a glass cladding film 5 (see FIG. 2A). As shown in FIG. 2 (b), an extraordinary glass layer 6 made of P ₂ O ₅ having a higher refractive index than that of quartz glass is formed on the core 1 and the quartz glass substrate 4 , and the propagating light also propagates to the above layers. , Loss is 10dB
And the isolation of ports α and β is −
The multiplexing / demultiplexing characteristics were significantly deteriorated to 5 dB or less. As another comparative example, the first porous cladding layer 2 has a thickness of 20 μm.
When the second porous cladding layer 3 had a thickness of 25 μm, a phenomenon similar to the above was observed, and the loss was 3 dB and the isolation was −10 dB.

[0014]

The first porous cladding layer is doped with B ₂ O ₃ , and the second porous cladding layer is doped with P ₂ O ₅ and B ₂ O.
As a result of doping ₃ , the interface with the core
A glass clad layer having a uniform refractive index without an abnormal glass layer having a high P ₂ O ₅ concentration can be formed, and a glass waveguide having good transmission characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which first and second porous cladding layers are formed at an intermediate stage of the manufacturing method of the present invention.

FIGS. 2A and 2B are a cross-sectional view of a glass waveguide of a comparative example and a glass waveguide manufactured according to the present invention, and a diagram showing a refractive index distribution in an ABC cross section. In the case of the comparative example, (c),
(d) shows the case of the present invention.

FIG. 3 is a schematic diagram showing an example of a directional coupler type multiplexer / demultiplexer.

FIG. 4 is a diagram showing the multiplexing / demultiplexing characteristics at a wavelength of 1.3 μm / 1.55 μm of the directional coupler type multiplexer / demultiplexer manufactured by the present invention.

[Explanation of symbols]

 Reference Signs List 1 core 2 first porous clad layer 3 second porous clad layer 4 silica glass substrate 5 glass clad layer 6 abnormal glass layer

Continued on the front page (72) Inventor Toshikazu Kamoshida 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture Within Nippon Electric Cable Co., Ltd. Optro System Research Laboratory (72) Inventor Naoto Uezuka Hidaka-cho, Hitachi City, Ibaraki Prefecture 5-1-1, Nippon Electric Cable Co., Ltd. Optrosystem Research Laboratories (56) References JP-A-5-208836 (JP, A) JP-A-57-139708 (JP, A) JP-A-62-124511 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G02B ^6/ 10-6/22

Claims (2)

(57) [Claims] A core is formed on a silica glass substrate or a silicon substrate on which a silica-based glass is formed, and a layer serving as a cladding of porous glass containing SiO ₂ as a main component is deposited so as to cover the core. In a method of manufacturing a glass waveguide in which a glass clad layer is formed by vitrification, a first porous clad layer containing B ₂ O ₃ and not containing P ₂ O ₅ is formed immediately above a core, (1) A second porous clad layer containing P ₂ O ₅ and B ₂ O ₃ is formed to cover the porous clad layer, and then the P ₂ O ₅ is expanded by sintering.
And the concentration of P ₂ O ₅ becomes uniform over the entire cladding layer.
Sintering is completed at the point of time to form a glass clad layer having a uniform refractive index. 2. A thickness of the first porous cladding layer, the preparation of the glass waveguide of claim 1, wherein the second porous cladding layer equal to or thicker than that.