JPH0862445A - Manufacture of optical waveguide - Google Patents

Abstract

PURPOSE: To manufacture an optical waveguide in a single time at low cost with a simple method using no photolithography process. CONSTITUTION: A CO2 laser beam is emitted onto a quartz glass base l, the quartz glass base 1 is relatively moved to the CO2 laser beam, whereby a core pattern groove 2 is worked on the quartz glass base 1 upper surface. A core film 3 having a refractive index higher than the quartz glass base 1 is buried in the core pattern groove 2. The whole upper surface of the quartz glass base 1 having the core film 3 with high refractive index buried therein is covered with a clad film 4 having a refractive index lower than the core film 3. Thus, all metal film forming process, photolithography process, metal film patterning process, core layer dry etching process and metal film releasing process which were necessary in the past can be omitted.

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 waveguide in which a core pattern is directly formed on a quartz glass substrate to simplify the process.

[0002]

2. Description of the Related Art Optical signal processing circuits such as an optical demultiplexing / multiplexing circuit, an optical star coupler, and an optical filter are realized with an optical waveguide structure for the purpose of sophistication, multi-functionality, and cost reduction of optical fiber communication. Has become active.

Conventionally, the above optical waveguide has been manufactured by the method shown in FIG. That is, a step 31 of forming a buffer layer having a low refractive index on a Si or glass substrate, a step 32 of forming a core layer having a high refractive index thereon, a step 33 of forming a metal film for a mask on the core layer, Step 34 of applying a photoresist film on the metal film and patterning the photoresist film by photolithography, Step 35 of patterning the metal film by dry etching using the photoresist film pattern as a mask, and masking the metal film pattern Then, a step 36 of etching the core layer by dry etching, a step 37 of removing the metal film, and a step 38 of covering the entire surface of the patterned core layer with a clad layer having a low refractive index are performed.

[0004]

However, the conventional method for manufacturing an optical waveguide has a large number of steps, and it is difficult to reduce the cost. In particular, it is necessary to use a very expensive photomask in the photolithography process, and it is difficult to reduce the cost only by this process. Also, it takes a lot of time to go through many steps until it is completed.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a method for manufacturing an optical waveguide in a simple method at a low cost in a single time.

[0006]

The gist of the present invention is that, in the conventional manufacturing method, a metal film forming step, a photolithography step, a metal film patterning step, a core layer dry etching step, and a metal film peeling step. It is a method of manufacturing an optical waveguide without steps.

Namely, by irradiating a CO ₂ laser beam on a quartz glass substrate by relative movement of the quartz glass substrate with respect to CO ₂ laser beam, a step of processing the core pattern groove in the quartz glass substrate top surface ,
A step of embedding a core film having a higher refractive index than the quartz glass substrate in the core pattern groove, and a step of filling the whole upper surface of the quartz glass substrate having the high refractive index core film with a cladding having a lower refractive index than the core film. And a step of covering with a film.

[0008]

[Operation] A step of forming a conventional metal film by performing the core patterning step with CO ₂ laser beam light,
The photolithography process, the dry etching process of the metal film and the core layer, and the peeling process of the metal film are unnecessary.

In order to realize the optical waveguide of the present invention, a quartz glass substrate is used as a substrate material because the groove can be easily processed by a CO ₂ laser beam and the substrate is cracked during and after processing. This is because it is a very stable material that does not enter or crack.

The core pattern groove can be processed with a CO ₂ laser beam in a very short time and in a clean atmosphere. Moreover, since the inner wall surface of the processed groove is a very smooth surface, an optical waveguide with extremely low light scattering loss can be realized.

The processing time of the groove with the CO ₂ laser is, for example, if the CO ₂ laser power is 70 W,
Since it can be processed at a speed of 1 to 2 mm / sec, it is a very short time (1/10 or less of the conventional one). With respect to the machining dimension accuracy of the core pattern groove, it is possible to obtain a pattern machining accuracy of the order of μm by using an XY drive device using a pulse motor driven numerical control mechanism.

Since the spot diameter of the CO ₂ laser beam is usually about 50 μm, it is very suitable for a method of manufacturing an optical waveguide for multimode transmission.

[0013]

EXAMPLE FIG. 1 shows an example of a method for manufacturing an optical waveguide of the present invention. First, a quartz glass substrate 1 is prepared as shown in (a). Then, as shown in (b), the quartz glass substrate 1
The core pattern groove 2 is formed by irradiating the upper surface of the substrate with a CO ₂ laser beam. Here, the width W of the core pattern groove 2 is preferably in the range of several tens μm to hundreds of tens μm, and the depth T is preferably in the range of several μm to hundreds of tens μm.

The width W is determined by the beam spot diameter of the CO ₂ laser beam. The depth T is the quartz glass substrate 1 when the CO ₂ laser beam is applied to the upper surface of the quartz glass substrate 1.
Of the CO ₂ laser beam and the power P of the CO ₂ laser beam. That is, if the speed V is large, the depth T is small, and if the power P is large, the depth T is large. The opposites show the opposite trend.

Next, as shown in (c), a core film 3 having a high refractive index is formed on the surface where the groove 2 is formed. The core film 3 has a refractive index higher than that of the quartz glass substrate 1, for example, SiO ₂ , Ti, Ge, P, A.
An oxide film containing at least one additive for controlling the refractive index such as 1, Zn, Zr, Ta, Na or K, or a polymer film such as polymethylmethacrylate, polyvinylidene fluoride, polystyrene, polyimide or polycarbonate is used. . Particularly, in the case of a polymer film, a liquid film can be easily obtained, which is advantageous in that it can be uniformly embedded on the surface on which the groove 2 is formed and even in the groove.

In the case of a liquid film, the core film 3 can be formed by heating after application and curing. In the case of an oxide film, it can be formed by a method such as a plasma CVD method, an electron beam evaporation method, a low pressure CVD method, or a flame deposition method.

Next, as shown in (d), the high-refractive-index core film 3 formed on the upper surface of the quartz glass substrate 1 other than the groove 2 is removed by a method such as polishing or etching. Finally, as shown in (e), the cladding film 4 having a low refractive index is formed and completed. Here, this low refractive index clad film 4
As the material, SiO ₂ or SiO ₂ containing at least one kind of refractive index control material such as B or F, or the polymer film described above can be used. Then, the refractive index of the clad film 4 having a low refractive index is equal to that of the core film 3 having a high refractive index.
Use a value lower than that of.

FIG. 2 shows a schematic view of the groove processing apparatus of this embodiment. This is an apparatus for realizing the process of FIG. The quartz glass substrate 1 is fixed on a substrate fixing base 11. The board fixing base 11 is moved by the XY drive unit 9 to X.
It can be moved in the direction 12 and the Y direction 13 by computer numerical control. The XY drive device 9 incorporates a numerical control mechanism driven by a pulse motor, and obtains pattern processing accuracy on the order of μm. A groove 14 is formed in the substrate fixing base 11 so that CO ₂ laser light can penetrate the quartz glass substrate 1. A laser beam 8 from a CO ₂ laser light source 5 is irradiated through a half mirror 6 and a condenser lens 7 so as to focus on the upper surface of the quartz glass substrate 1.

[0019] irradiated with CO ₂ laser beam 8 on the quartz glass substrate 1, move the XY drive device 9, any quartz glass substrate 1 by moving relative to the CO ₂ laser beam 8, a quartz glass substrate 1 top The core pattern groove having the shape of can be processed.

FIG. 3 shows an example of a linear waveguide manufactured by the method for manufacturing an optical waveguide of this embodiment. S
A core pattern groove 2 is formed on the surface of an iO ₂ substrate 1 by CO ₂ laser processing, a high refractive index core film 3 is buried in the groove, and a low refractive index clad film 4 is formed on the core pattern groove 3. The shape of the core pattern groove 2 is a straight line.

FIG. 4 shows an example of the optical waveguide type Y branch circuit manufactured in this embodiment. In this example, a high silicate glass (trade name: Vycor glass, manufactured by Corning Glass, Inc.) substrate 15 containing a small amount of B and Na in SiO ₂ is used as the substrate. The shape of the core pattern groove 2 is Y-shaped. This Y branch circuit 16 has an arrow 20 which is incident on the input section.
Is an optical circuit that equally distributes the optical signal indicated by 2 to the two output sections and outputs the optical signal as indicated by arrows 21 and 22. If the circuits 16 are connected in series, it is possible to realize an optical star coupler having one input and n outputs (n ≧ 4).

FIG. 5 shows an example of the optical waveguide type directional coupling circuit manufactured in this embodiment. In this example, a Si substrate 17 is used as a substrate, and SiO 2 is formed on the Si substrate 17.
_{The two} film 18 is formed, and the core pattern groove 2 is processed in the SiO ₂ film 18. The shape of the core pattern groove 2 is
It is a combination of straight and curved lines. The directional coupling circuit 19 can distribute and merge optical signals, and can have a wavelength selection function.

As other optical waveguides, a ring resonant circuit, a crossing circuit, etc., in which straight and curved groove patterns are combined can be constructed. Further, in order to improve the characteristics of the waveguide, the above B and N are used instead of the quartz glass substrate.
In addition to a, a quartz glass substrate containing at least one kind of refractive index controlling additive such as Ti, Ge, F, P and Al may be used.

[0024]

According to the present invention, C is formed on a quartz glass substrate.
A core pattern groove is formed by irradiating an O ₂ laser beam, a high refractive index core film is embedded in the groove, and finally the entire upper surface of the substrate is covered with a low refractive index film to manufacture an optical waveguide. Therefore, it can be manufactured very easily, in a short time, and at low cost, as compared with the conventional one using photolithography and etching techniques. Also CO
₍₂₎ Grooving with a laser beam can form a very smooth surface in a clean atmosphere, so that an optical waveguide with extremely low light scattering loss can be realized.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of a method for manufacturing an optical waveguide of the present invention.

FIG. 2 is a configuration diagram showing an embodiment of a groove processing device on a quartz glass substrate of the present invention.

FIG. 3 is a side view and a plan view showing an embodiment of an optical waveguide manufactured according to the present invention.

FIG. 4 is a side view and a plan view showing an embodiment of an optical waveguide type Y branch circuit manufactured according to the present invention.

FIG. 5 is a side view and a plan view showing an embodiment of an optical waveguide type directional coupling circuit manufactured according to the present invention.

FIG. 6 is a process drawing of a conventional method for manufacturing an optical waveguide.

[Explanation of symbols]

 1 Quartz glass substrate 2 Core pattern groove 3 Core film with high refractive index 4 Clad film with low refractive index

Claims (4)

[Claims] [Claim 1] was irradiated with CO ₂ laser beam on a quartz glass substrate by relative movement of the quartz glass substrate with respect to CO ₂ laser beam, a step of processing the core pattern groove in the quartz glass substrate top surface A step of embedding a core film having a higher refractive index than the quartz glass substrate in the core pattern groove, and a step of embedding the entire upper surface of the silica glass substrate having the core film having a higher refractive index lower than that of the quartz film. A method of manufacturing an optical waveguide, comprising a step of covering with a clad film. 2. The method of manufacturing an optical waveguide according to claim 1, wherein in the step of processing the core pattern groove, the core pattern groove is composed of a straight line, a curved line, or a combination thereof. A method for manufacturing an optical waveguide, which is a step of processing at least one pattern such as a branch circuit, a ring resonant circuit, and a cross circuit. 3. The optical waveguide according to claim 1, wherein the core film having a high refractive index and the clad film having a low refractive index are oxide films or polymer films. Manufacturing method. 4. The method for manufacturing an optical waveguide according to claim 1, which is for controlling the refractive index of B, Ti, Ge, F, P, Na, Al or the like instead of the quartz glass substrate. A method for manufacturing an optical waveguide using a quartz glass substrate containing at least one kind of additive.