JPS6039201B2 - Method for manufacturing integrated optical coupling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an integrated optical coupling device using a thick film.

Integrated optical circuits are necessary for making optical communication devices or optical information processing devices smaller and more robust.

In addition to lasers, optical fibers, and photodetectors, optical communication equipment requires optical control elements such as optical polarization modulators and optical switches, and passive optical elements such as optical branching elements and optical demultiplexers. . In order to realize these light control devices and passive optical devices, an integrated optical system has recently been developed that uses a two-dimensional or three-dimensional light guide made of an optically transparent material with a higher refractive index than its surroundings. has been done. These integrated optical circuits can connect multiple control elements and passive optical elements using the two-dimensional or three-dimensional light guide and incorporate them onto a single substrate, making optical devices more compact and robust. It has the advantage of Furthermore, these integrated optical circuits are primarily based on conventional ICs.
Since it can be manufactured using microfabrication technology and related microfabrication technology, it also has the advantage that batch processing is possible and cost reduction is possible. By the way, when the above-mentioned integrated optical circuit is used in an optical communication device or an optical information processing device, an efficient coupling method with an external optical transmission body such as an optical fiber or an external light source such as a semiconductor laser has been desired.

Conventionally known typical coupling structures between an integrated optical circuit and external light include a grating coupler provided on the light guide surface and a high refractive index glass or single crystal processed into a prism shape. Examples include prism couplers that are used in pressure contact with.

The grating coupler has the advantage of a simple structure because it can be obtained by simply forming uneven grooves on the surface of the light guide. On the other hand, there is a drawback that the coupling efficiency decreases because unnecessary high-order diffracted light appears. Although prism couplers have the advantage of theoretically higher coupling efficiency than grating couplers, they have a complex structure and are not suitable for integration because a separate prism is pressed against the surface of the light guide. There are drawbacks. On the other hand, when external light is efficiently injected into an embedded three-dimensional light guide, a thick film coupler is fabricated from a photopolymerizable material along a part of the upper surface of the light guide. A structure in which light is injected from the sidewall is considered. Atsuwaki coupler
To manufacture by a conventionally known method, a photopolymerizable film is thermocompressed or coated on the upper surface of a three-dimensional light guide prepared in advance, and then a photomask having a desired coupler pattern is closely attached to the film. A known method is to expose the material to light from above, and then process the phenomenon. However, this method not only complicates the process because it is necessary to align the photomask with the light guide pattern, but also has the drawback that the dimensional accuracy during the formation of the thick film coupler is poor.

The object of the present invention is to provide a new method for manufacturing an integrated optical coupling device, which improves the drawbacks of the prior art.

According to the present invention, a step of manufacturing a mask film pattern made of an optically opaque material on the surface of an optically transparent substrate, and a step of forming a light guide part on the substrate using the mask film pattern. , a step of attaching a thick film made of a photopolymerizable substance to the surface of the substrate, and performing optical exposure from the back side of the substrate by providing means for shielding a part of the light guide on the back side of the substrate, There is obtained a method of manufacturing an integrated optical coupling device, characterized in that it includes a step of photoetching the thick film.

Next, details of the present invention will be explained using the drawings.

FIG. 1 is a schematic diagram of the main steps of an embodiment of the present invention.
In FIG. 1A, a mask film 31 made of vapor-deposited gold (Au) is formed by normal photoetching, leaving a light guide region 33 on the surface of a fused silica substrate 11.
Helium ions He132 are irradiated from above the substrate,
Only the light guiding region 33 is implanted. The ion acceleration energy at this time is a single energy of about 160 KeV, and the implantation amount is about 2×15/. As a result, as shown in Figure b', a buried light guide 34 is formed with a central depth of about 0.8 microns and a guide width of about 50 microns. Here, the direction of arrow 50 is the propagation direction of the light guide. Next, in FIG. 1B, a photopolymerizable film 35 mainly composed of acrylic resin and coated on the base film 36 is thermocompression bonded to the surface of the substrate.

Next, as shown in FIG. 3c, a photomask 37 having a dark area 38 is closely attached to the back surface of the substrate so as to partially block the light guide, and the entire back surface is irradiated with parallel light 39 from argon to a laser. Ru. In this case, the laser beam 39 irradiates the back surface of the substrate with an inclination only in the propagation direction 50 of the guide light. In the process of contact optical exposure,
The film 35 is selectively exposed to light by a mask film 31 and a photomask dark area 38 . Through this post-processing process, the thick film pattern 40 of the acrylic resin is formed directly above the embedded light guide as shown in FIG. 4(d). Finally, as shown in FIG. 4E, the unnecessary mask film 31 is removed, and the thick film pattern 40 becomes a desired thick film coupler. At this time, the inclination angle of the end face 41 depends on the inclination angle of the exposure beam 39. FIG. 2 is a structural schematic diagram showing the operating principle of an integrated optical coupling device obtained according to a specific embodiment of the present invention.

In the figure, an embedded optical guide 22 is formed near the surface of a fused silica substrate 21 by the above-described ion implantation method. The light guide 22 has a higher refractive index than its surroundings by ion implantation, and is in close proximity to the thick film coupler 23 obtained by the above method (with a low refractive index layer 28 in between). The thick film coupler 23, the low refractive index layer 28, the light guide 22, the substrate 2
Letting each refractive index of 1 be nc, n6, nW, and ns, the relationship between these is nC>nW>ng~>nS.

Therefore, the external light 25 is transmitted to the end surface 24 of the thick film coupler 23.
When incident light 26 enters the interior through the low refractive index layer 28, it is gradually converted into propagation mode light 27 that propagates through the light guide 22, causing so-called distributed coupling. This is due to the same circumstances as the injection of light guide propagating light using a conventional prism coupler. Therefore, the secondary prism coupler is formed by molding glass or a single crystal into a prism shape, and presses or adheres the prism to the light guide part. Layer 28 corresponded to the air spacing layer or adhesive layer between the prism and the substrate surface. The thickness of the air spacing layer or the adhesive layer varies depending on the prism installation conditions, and is therefore impractical. In contrast, the thick film coupler 23 in the present invention is bonded directly to the substrate by thermocompression, and the thickness of the low refractive index layer 28, which is an important parameter in this coupling device, is determined by the ion implantation conditions described above and can be well controlled. It can be done. As explained above, the manufacturing method of the present invention has several advantages.

The first advantage is that the process of fabricating the thick film coupler directly above the preformed light guide by optical exposure eliminates the need for precise alignment of both the light guide and thick film coupler patterns.

In the conventional method, as shown in FIG. 1c, a photomask having a thick film coupler pattern is brought into close contact with the surface of the base film 36, and exposure is performed from above. In this case, since the thickness of the base film 36 and the photopolymerizable film 35 exceeds several tens of microns, it is difficult to perform the alignment in this step. On the other hand, according to the method of the present invention, the mask film 31 used in producing the light guide is also used as a mask film in producing the thick film coupler. In the present invention, the photomask 37 is required to control the length of the thick film coupler 40;
The thick coupler length does not require precise control. For the above reasons, the present invention does not require precise photomask alignment and can simplify the manufacturing process. A second advantage of the present invention is that the thick film coupler 40 has good dimensional accuracy. As shown in FIG. 1c, in the conventional method, the photopolymerizable film 35 is closely exposed with the base film 36 having a thickness of several microns in between as described above, so that the scattering material that exists on the surface or inside of the base film is increasing. As a result, the light guide during exposure is subjected to scattering, causing dimensional errors in forming a desired pattern. In contrast, in the present invention,
Since the factors that cause dimensional errors have been eliminated, it is possible to achieve high integration that allows formation of fine patterns with high accuracy. As described above, the embedded light guide used in the embodiments of the present invention was one based on the ion implantation method, but the scope of the present invention is not limited to this, and other methods such as ion exchange method, thermal diffusion method, etc. The present invention is also effective for light guides based on the method.

However, when using the thermal diffusion method, the mask film 3 in Figure 1 is used.
As material 1, a metal thin film with a slow diffusion rate is used to the extent that it does not contribute to the formation of a light guide, a diffusion metal film is attached on top of this, thermal diffusion is performed, and then only the diffusion metal film is removed. If a step is added, the present invention will be completely effective from now on. Furthermore, although a photopolymerizable film containing an acrylic resin as a main component was used as the thick film coupler in the above example, other photopolymerizable materials, such as commercially available photoesist materials containing a vinyl cinnamate component as a main component, may be used. The present invention can also be implemented using the following.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the main steps of an embodiment of the present invention, and FIG. 2 is a schematic diagram of the structure of an integrated optical coupling device obtained by the embodiment of the present invention. In the figure, 11 and 21 are fused silica substrates, 22 and 3
4 is an embedded light guide, 23, 4 is a thick film coupler 3
1 is a mask film, 32 is an implanted ion beam, and 39 is a light beam. is 2 diagram O diagram

Claims (1)

[Claims] 1. A method of manufacturing an optical coupling device for coupling external light to a light guide, which includes the steps of manufacturing a mask film pattern made of an optically opaque substance on the surface of an optically transparent substrate; a step of forming a light guide portion on the substrate using a method, a step of attaching a thick film made of a photopolymerizable substance to the surface of the substrate, and a step of forming a thick film made of a photopolymerizable substance on the back surface of the substrate for shielding a part of the light guide. 1. A method of manufacturing an integrated optical coupling device, comprising the steps of: providing a means for optically exposing the substrate from the rear surface side, and photoetching the thick film.