JPH03168706A - Manufacture of optical module substrate - Google Patents

Abstract

PURPOSE:To improve the productivity by filling transparent resist in a groove of specific width which cuts an optical waveguide, then irradiating the resist with ultraviolet rays from the end surface of the optical waveguide and performing development processing, and forming a hemispherical projection on each cut surface of the optical waveguide. CONSTITUTION:The optical waveguide 11 is formed in the area of an SiO2 film 10b formed on an Si substrate 10a and the groove 12 is formed intersecting the waveguide to depth large enough to cut the waveguide. Then the UV sensitive transparent resist 13 is filled in the groove 12. The optical waveguide 11 is irradiated with ultraviolet rays like l1 and l2 from both other ends and then the ray are diffused radially in four directions from the cut surface 12a, so that the area of the resist 13 irradiated with the ultraviolet rays changes in quality into a hemispherical convex shape A. Then the development processing is carried out to form the hemispherical projections 11a, i.e. convex lenses on both cut surfaces 12a. Consequently, the optical module is easily constituted which never deteriorates in optical coupling characteristics even if the thickness permissible range of an optical element is expanded.

Description

[Detailed Description of the Invention] [Summary] Regarding the manufacturing method of an optical module substrate, the purpose of this invention is to expand the scope of application of mounted optical elements without degrading optical coupling characteristics and improve productivity. A groove of a predetermined width is formed to cut across an optical waveguide formed on a substrate at least at a depth at which the optical waveguide is cut, and the groove is filled with a transparent resist made of a polymeric material. By irradiating ultraviolet rays from both end faces of the waveguide and developing the resist portion, hemispherical protrusions are formed on each cut surface of the optical waveguide when forming the grooves.

[Industrial application field]

The present invention relates to a process for manufacturing an optical module substrate, and more particularly to a method for manufacturing an optical module substrate that expands the scope of application of mounted optical elements without deteriorating optical coupling characteristics and improves productivity.

In recent years, with the stabilization and miniaturization of optical modules, there has been a demand for greater integration of optical circuits.One way to achieve this is the spatial beam method, in which various optical devices are aligned and arranged between the end faces of optical fibers. In addition, optical waveguide systems in which an optical waveguide is cut midway and various optical elements are inserted between the cut end faces have been put into practical use.

[Conventional technology]

FIG. 3 is a conceptual diagram illustrating the spatial beam system, and FIG. 4 is a conceptual diagram illustrating the optical waveguide system.

In each figure, the structure near the Faraday rotator, which is the main part of the optical isolator, will be explained.

In FIG. 3, reference numeral 1 indicating a flat optical element is, for example, bismuth-substituted garnet [(TbBi)z(FeAIGa)so+
A 45 degree Faraday rotator 1a having a thickness of approximately 300 μm and made of a 45-degree Faraday rotator 1a made of a 45-degree Faraday rotator 1a made of a material made of a polarized light beam and a substrate 1b made of, for example, gadolinium gallium garnet (GGG) on which a dielectric multilayer film as a polarization separation film is deposited are attached and integrated. It has become.

Note that a magnetic field is applied to the optical element 1 by a magnet (not shown).

Further, 2.2' represents an optical fiber, and 3.3' represents an optical lens.

Therefore, the optical devices described above are arranged in alignment with their optical axes aligned, and are arranged near the Faraday rotator of the main part of the optical isolator.

In such a case, the light beam L emitted from the core 2a of the optical fiber 2 becomes parallel light at the optical lens 3 and enters the optical element l as shown by the broken line, and after passing through the optical element l, the light beam L enters the optical element l. It is possible to condense the light and input it into the core of the optical fiber 2'.

In particular, this method has the advantage of being able to construct optical modules with good characteristics without the need for special technology, but since each optical device is arranged spatially, the module becomes large and large. This method has the disadvantage that the optical axis between each optical device must be strictly controlled, which requires a lot of man-hours for adjustment.

Fig. 4 shows the structure of an optical module that takes such drawbacks into consideration. 1 represents the optical element explained in Fig. 3, and like Fig. 3, a magnetic field is applied by a magnet (not shown). It has become.

Reference numeral 4 indicates a waveguide substrate, and 5 indicates an optical waveguide formed on the waveguide substrate 4. The optical waveguide 5 is vertically cut in a part of the waveguide substrate 4 using, for example, a cutting saw. A groove 6 is formed from the upper surface of the waveguide substrate 4, and the width of the groove 6 corresponds to the thickness t of the optical element 1 to be mounted.

Therefore, the optical element 1 is inserted between the grooves 6 at a predetermined position on the optical axis of the optical waveguide 5 and fixed by adhesive or other means to obtain a desired optical module.

In particular, in the case of this method, by setting the width of the groove 6 to correspond to the thickness of the optical element to be inserted, it is possible to eliminate the need for work such as adjusting the optical axis. The optical module can be easily constructed.

However, when the light beam L passing through the optical waveguide 5 exits from the cut end surface 5a, it is diffused by the end surface 5a as shown in the figure L'' and enters the optical element 1, and after passing through the optical element l, There may be a portion, such as the LIF, where the light does not enter the optical waveguide 5, resulting in a decrease in optical coupling characteristics.

In particular, it has been confirmed that the decrease in the optical coupling characteristics greatly affects the thickness t of the optical element 1, and when the thickness t is large, the decrease in the optical coupling characteristics increases. Generally speaking, the thickness L of the optical element 1 is limited to several lOa11.

[Problem to be solved by the invention]

When using conventional optical module substrates, when the thickness of the optical element inserted between the optical waveguides is large, the optical coupling characteristics deteriorate, which places restrictions on the optical elements that can be used. There was a problem.

[Means to solve the problem]

The above problem can be solved by forming a groove of a predetermined width that cuts across an optical waveguide formed on a waveguide substrate at least at a depth that cuts the optical waveguide, and then filling the groove with a transparent resist made of a polymeric material. After filling, the optical waveguide is irradiated with ultraviolet rays from both end surfaces, and the resist portion is developed, thereby forming a hemispherical protrusion on each cut surface of the groove-shaped optical waveguide. The problem is solved by a method of manufacturing a substrate.

[Function] By condensing the diffused light emitted from the cut end surface of the optical waveguide, the light rays in the optical waveguide can efficiently enter the optical element. Furthermore, by condensing the light rays emitted from the optical element, the light rays that pass through the optical element can be effectively made to enter the optical waveguide.

On the other hand, some resists change in quality when irradiated with ultraviolet rays, for example, and in such resists, only the portions altered by the ultraviolet irradiation can be left behind through development processing.

Therefore, when a resist as described above is applied to the cut exposed surface of the optical waveguide and ultraviolet rays are irradiated from the waveguide side, the ultraviolet rays enter the resist while radially diffusing from the cut end surface of the optical waveguide. This means that the resist is transformed into a hemispherical shape from the cut end surface of the optical waveguide, and as a result, a hemispherical protrusion and a convex lens are formed on the cut end surface of the optical waveguide by the development treatment after irradiating the ultraviolet rays. can be shaped.

In the present invention, a hemispherical protrusion, that is, a convex lens is formed by the above method on each of the opposing cut end surfaces formed when the optical waveguide is cut.

Therefore, it is possible to obtain an optical module substrate that allows easy construction of an optical module without degrading the optical coupling characteristics even if the allowable range of the thickness of the optical element is expanded.

[Example] FIG. 1 is a process diagram illustrating a method of manufacturing an optical module substrate according to the present invention, and FIG. 2 is a diagram showing an example of the structure of an optical module.

In FIG. 1(A), a silicon dioxide (Sing) film 10b having a thickness of about 3 μm is formed on a silicon (Si) substrate 10a in the region of the silicon dioxide film tab of the waveguide substrate 10, which has a diameter of about 6 μm. An optical waveguide 11 is formed, and in particular, as shown in FIG.
A groove 12 of approximately Onm is formed from the upper surface of the waveguide substrate IO in a direction perpendicular to the optical waveguide 11.

Note that the groove 12 in this case can be precisely formed by using, for example, a cutting saw as in FIG. 3.

Next, the groove 12 is filled with a transparent resist opening 3 made of a polymeric material such as a commercially available UV-sensitive body resist by coating or other means (C
).

Therefore, when ultraviolet rays are irradiated from both ends of the other end (not shown) of the optical waveguide 11 as shown in FIGS. At this point, the ultraviolet irradiated areas of the resists 1 and 13 change into a convex hemispherical shape.

(D) shows such a state, and A shows a hemispherical altered area.

After that, if a normal development process is carried out using, for example, a commercially available developer, only the altered hemispherical area A will be left and the other parts will be removed, so the hemispherical shape shown in (E) will be removed. A desired optical module substrate 14 including the protrusions 11a can be obtained.

In such an optical module substrate l4, both cut surfaces 1 of the groove 12
The hemispherical protrusion 11a formed on 2a provides the same effect as the optical lenses 3, 3' in FIG. 3, and (B)
Since the width d of the groove 12 can be freely set in accordance with the thickness of the optical device to be inserted, the optical coupling characteristics will not deteriorate even if the thickness of the optical element inserted and mounted in the groove 12 is thicker than before. It is possible to construct an optical module without.

FIG. 2 shows an example of the configuration of an optical module, in which (a) is a diagram of the configuration, and (b) is an enlarged view of an optical coupling section for explaining the optical path.

In FIG. 2(a), the optical module board 15 has the same structure as the optical module board 14 explained in FIG. 1, and 16 represents the optical waveguide formed on the optical module board 15. ing.

l7 is the optical module base Fi. 15 shows a groove provided by the means explained in FIG. 1, and 18 represents an optical element similar to that shown in FIG. 4.

Further, the optical module substrate 15 is processed so that the width D of the groove l7 is wider than the thickness T of the optical element 18 inserted and mounted on the optical module substrate 15, for example, by the diameter of the optical waveguide 16, as shown in FIG. A hemispherical protrusion 16a is formed on the cut surface 17a formed during processing of the groove 17 using the method described in .

In this case, since the distance between the vertices of the hemispherical protrusions 16a is approximately equal to the thickness T of the optical element l8, when the optical element 18 is inserted between the hemispherical protrusions 16a, both sides of the optical element 18 become hemispherical. It can be in contact with or in close proximity to the apex of the protrusion 16a.

Here, the optical path in the vicinity of the hemispherical protrusion 16a will be explained, but in order to make it easier to understand, the optical waveguide l6 is shown in the figure.
The thickness T of the optical element 18 inserted and mounted in the middle of the optical element 18 is assumed to be thicker than several tens of micrometers, which is the limit in the conventional case.

(b) Enlarged portion of the hemispherical protrusion 16a in (a)
For example, let L be the light beam sent through the optical waveguide l6.

In this case, when the hemispherical protrusion 16a is not formed, the light ray L travels along the optical path α→L1'' shown by the broken line as explained in FIG. 4, so that the opposing optical waveguide 16
In some cases, the light does not enter the optical waveguide l6, and the optical coupling characteristics deteriorate by the amount that it protrudes from the optical waveguide l6.

On the other hand, if there is a hemispherical protrusion 16a, the light beam L is condensed at the hemispherical protrusion 16a, and the optical path L2°→L2 is shown by a solid line in the figure.
Since the light beam advances as shown in FIG. 1 and effectively enters the opposing optical waveguide l6, deterioration of the optical coupling characteristics can be suppressed.

According to experimental results, the thickness T of the optical element l8 is approximately 300 mm.
uI1 Faraday rotator (wavelength 1.3μm band) and approx.
It has been confirmed that the optical coupling characteristics do not deteriorate even when a 00 μm Faraday rotator (wavelength 1.55 μm band) is used.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a method for manufacturing an optical module substrate that expands the range of application of optical elements and improves productivity without deteriorating optical coupling characteristics.

[Brief explanation of the drawing]

Figure 1 is a process diagram explaining the method for manufacturing an optical module board according to the present invention, Figure 2 is a diagram showing an example of the structure of an optical module, Figure 3 is a conceptual diagram explaining the spatial beam method, and Figure 4. is a conceptual diagram explaining the optical waveguide method. In the figure, 10 is a waveguide substrate, 10a is a silicon substrate, and 10b
11.16 is a silicon dioxide film, 11.16 is an optical waveguide, and 11a. 1
6a is a hemispherical process; 12. 17 is a groove, 12a and 17a are cut surfaces,
13 represents a resist, 14 and 15 an optical module substrate, l8 an optical element, and ^, respectively. Wooden ax %= tMo5-Explanation of the force-making method Σ of Yule's toe removal 3 process diagram Figure 1 (b)
The Meiji 15th Anniversary Compilation 3 Figure t Jinhaji-no-ana and Explanation 13 The Memorial Park Figure 4

Claims (1)

[Claims] An optical waveguide (11) formed on a waveguide substrate (10),
A groove (12) of a predetermined width is formed to cut across at least the optical waveguide (11) at a depth, and the groove (12)
After filling the optical waveguide (11) with a transparent resist (13) made of a polymeric material, ultraviolet rays are irradiated from both end faces of the optical waveguide (11).
Further, by developing the resist (13) portion, hemispherical protrusions (11a) are formed on each cut surface (12a) when forming the groove (12) of the optical waveguide (11). A method for manufacturing an optical module board.