JPS6321881B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an optical branch circuit in which an optical branch circuit and an optical fiber are integrally formed on a substrate.

Conventional optical branching circuits of this type bundle two or more optical fibers together and twist the fibers.
There is an optical branch circuit that is heated to 1500°C or higher to fuse and then stretch to form a coupler. This optical branching circuit has the advantage of being easily fabricated using fibers, but it is difficult to make the optical branching ratio of each fiber uniform, and since the optical fibers are heated to 1500°C or higher, e.g. , discharge heating is performed, but in this case there are drawbacks such as poor reproducibility in optical branch path fabrication.

There is also a conventional method in which a total reflection mirror or a half mirror is formed in a focusing rod lens, and the focusing rod lens is connected to the end of a fiber to form an optical branch circuit. With this method, it is possible to arbitrarily set the optical power division ratio by changing the reflectance of the mirror, but the process of aligning the optical axis of the converging rod lens with the optical axis of the optical fiber is complicated; Furthermore, there are disadvantages such as changes in branching properties over time due to the use of adhesives to fix the focusing rod lens and the optical fiber.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the various drawbacks mentioned above and provide a method for manufacturing an optical branch circuit in which an optical fiber and an optical branch circuit are integrally formed on a substrate.

In order to achieve such an object, in the present invention, an optical fiber is fixed on a glass substrate, a glass film is further formed on the glass substrate by a vapor phase reaction deposition method, and the glass film is processed to form an optical branch circuit. Then, the optical fiber and the optical branch circuit are integrated on the glass substrate.

The invention will now be explained in detail with reference to the drawings.

FIGS. 1A to 1F show an example of the manufacturing process of the optical branch circuit of the present invention. Here, as shown in FIG. 1A, a glass plate 1 having, for example, dimensions of 50×50 mm and a thickness of 1 mm is prepared as a substrate. Next, as shown in FIG. 1B, grooves 2 and 3 for fixing the fibers are formed on the substrate 1. These grooves 2 and 3 can be formed, for example, by the following process. First, on the surface of the glass substrate 1 whose surface has been made smooth by polishing,
Deposit metals such as Ti and Si. Next, a photoresist is applied to the deposition surface to form a desired pattern by ordinary photolithography, and using the resist pattern as a mask, unnecessary metal films are removed in CF ₄ and CBrF ₃ gas plasma. Next, using this metal film pattern as a mask, the glass substrate is subjected to reactive sputter etching in Freon gas plasma to form grooves of a desired shape. The remaining metal film is CF ₄ ,
Remove with _CBrF3 gas plasma. Groove 2 is a groove for fixing the input fiber, and if the outer diameter of the fiber is 2b and the diameter of the fiber core is 2a, the depth of this groove is preferably ( ^ba ) and the width is ^2√2-2 . Groove 3 is a groove for fixing the output fiber, and has a depth of (ba) and a width of approximately (n-1)2b+ ^2√2-
A ² is desirable. Here, n is the number of output fibers. Further, the groove 2 for fixing the input fiber and the groove 3 for fixing the output fiber are installed at appropriate intervals.

Next, as shown in FIG. 1C, the input fiber 4 is placed in the groove 2, and the output fiber 5 is placed in the groove 3 and fixed. As a fixing method, for example, a method of fusing the optical fibers 4 and 5 and the glass substrate 1 by discharge heating or irradiation with CO ₂ laser light can be used.

The next step is to fabricate a waveguide for splitting the light emitted from the input fiber 4 into the output fiber 5. In forming the core of such a waveguide, a glass material having a higher refractive index than the glass substrate 1 is deposited on the surface of the substrate to which the input and output fibers 4 and 5 are fixed. This step is performed by depositing core-forming glass particles obtained by processing a glass raw material that will become a core on the substrate 1, and converting the glass particles into transparent glass. That is, the substrate 1 having the above-described input and output fibers 4 and 5
is placed in a reaction vessel and heated to a temperature of approximately 600-1100°C. SiCl ₄ , GeCl ₄ , which becomes the core glass raw material,
TiCl ₄ , PCl ₃ , BBr ₃ , etc. are introduced into a reaction vessel together with oxygen, heated to approximately 1000 to 1400°C to react, and form glass particles for core formation, and these glass particles are deposited on the substrate 1. let Next, the substrate 1 on which the glass particles have been deposited is taken out from the reaction vessel, fixed and placed on a substrate table with a smooth surface made of a fire-resistant material such as graphite and zirconia, and the substrate 1 is To prevent generation, heat in He atmosphere. When the heating temperature ranges from about 1300 to 1600℃, the glass particles become transparent vitrified, as shown in Figure 1D.
As shown in , the surface of the substrate 1 is covered with a core glass layer 6'.
covered with

Next, unnecessary core glass formed on the substrate surface other than the core glass 6 of the optical branching waveguide in the core glass layer 6' is treated with Freon gas similar to that described above, as shown in FIG. 1E. Removed by reactive sputter etching in plasma. As this etching mask, a Si crystal substrate anisotropically etched with a KOH solution or the like can be used. The branching waveguide width is approximately (n
−1) 2b+2√ ² − ² is desirable.

Since the upper part of the core glass 6 is exposed, it is necessary to form clad glass on the exposed plane of the core glass 6 in order to form a waveguide. In forming the cladding, glass fine particles forming the cladding are deposited on the surface of the substrate 1 having the exposed core glass 6 described above, and this is made into transparent glass. That is, a glass material having a softening temperature lower than that of the core glass 6 is used on the surface of the substrate 1, and the glass material 7 forming the cladding is formed as shown in FIG. to cover. In this case, in order to lower the refractive index of the clad glass to be formed, suitable dopants such as SiF ₄ , BF ₃ ,
SF ₆ is introduced into the reaction vessel to deposit the glass particles forming the cladding on the substrate 1 in the same manner as in the core formation described above, and the substrate 1 is taken out and heated to approximately 800 to 1200°C to form glass particles. Turn fine particles into transparent glass. In this case, since the glass becomes transparent at a relatively low temperature, the core glass 6 is not deformed. Through the above steps, an optical branch circuit equipped with an optical fiber is formed.

Although the present invention has been described above for the case where there is one input fiber and five output fibers, the optical branching circuit can be manufactured by the same process even when using any desired number of input fibers and output fibers. The number of fibers is not particularly limited when implementing the present invention. Further, by inserting a diffraction grating on the side surface or in the middle of the branching waveguide, the optical branching circuit can add wavelength selectivity to the output characteristics.

As explained above, the method for manufacturing an optical branch circuit according to the present invention has the following advantages.

(1) Since the optical branch circuit is formed on a flat substrate using photolithography technology, manufacturing reproducibility is good and branch circuits with arbitrary characteristics can be manufactured.

(2) Since the optical fiber and optical branching circuit are integrated, there is little change in branching characteristics over time.
Also, optical axis adjustment is not required.

[Brief explanation of the drawing]

FIGS. 1A to 1F are perspective views showing an example of the manufacturing process of the optical branch circuit according to the present invention. DESCRIPTION OF SYMBOLS 1... Glass substrate, 2... Input fiber fixing groove, 3... Output fiber fixing groove, 4... Input fiber, 5... Output fiber, 6, 6'... Core glass, 7... Clad glass.

Claims (1)

[Claims] 1. A first step of digging grooves for fixing the fiber in both ends of a glass substrate by reactive sputter etching, a second step of fixing the fiber in the groove, and a second step of fixing the fiber in the groove. A third step of depositing glass particles to become core glass on the surface of the fixed substrate and making the deposited glass particles transparent to form a core glass layer; and removing unnecessary core glass portions from the core glass layer. a fourth step of forming a core by depositing glass fine particles to become clad glass on the core, and a fifth step of making the deposited glass fine particles transparent to form a clad glass. A method for manufacturing an optical branch circuit.