JPH0422904A - Rib type optical waveguide - Google Patents

Abstract

PURPOSE:To compact a device without restricting the degree of positional freedom of an optical waveguide by forming a core layer by a liquid material to be cured by energy irradiation and forming plural gratings on the prescribed positions of the rib part unitedly with the rib part. CONSTITUTION:The rib type optical waveguide has a base 1 and the core layer 2 formed on the base 1 and having he rib part 3 are the core layer 2 is formed by the liquid material to be curved by energy irradiation. For instance, the core layer 2 has the rib part 3 projected upward and extended in one direction. The gratings 3a constituted of periodically changing the thickness (height) of the rib part 3 are formed on the prescribed positions of the rib part 3 and the rib part 3 and the gratings 3a are formed unitedly with the core layer 2. Consequently, the degree of freedom of shapes formed by the optical waveguide and the gratings 3a can be increased and the device can be made compact.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a rib-shaped optical waveguide which is a type of channel leading waveguide, and more particularly to a rib-shaped optical waveguide provided with a grating.

Prior art and its problems Typical channel leading waveguides include LiNb0. There is a Ti-diffused optical waveguide 31 fabricated by diffusing T1 into a substrate 30. When applying a grating to such an optical waveguide 31, it is difficult or impossible to form the grating only in the optical waveguide portion, and it is necessary to form the grating 32 over a wider range than the width of the optical waveguide 31. I don't get it.

Therefore, it is not possible to bring another guide wavepath without a grating close to the guide waveguide with a grating, which limits the functionality of the device. There is a problem that devices are becoming larger.

In addition, to fabricate such a channel leading waveguide with a grating, a grating fabrication process is required in addition to the optical waveguide fabrication process. This requires a complex and time-consuming process. Therefore, the iiL productivity is poor. Cost increases. There is a problem with poor reproducibility.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a channel leading waveguide without restricting the spatial freedom of the optical waveguide even when a grating is provided, and to make it possible to miniaturize the device.

Structure 1 of the Invention Functions and Effects The channel guiding waveguide according to the present invention is a rib-shaped guiding waveguide, and includes a substrate and a core layer having a rib portion formed on the substrate, and the core layer is heated by energy irradiation. It is formed using a liquid material that hardens, and is characterized in that gratings are formed integrally with the rib portion at predetermined locations on the rib portion.

Gratings can be made by periodically changing the width of the ribs, by periodically changing the thickness (height) of the ribs, or by periodically changing both the width and height of the ribs. This is realized by The grating may be blazed.

The rib-shaped guided waveguide has a core layer formed on a substrate, and a rib portion is formed integrally with the core layer along the propagation direction of light. In the plane perpendicular to the light propagation direction, the propagating light is confined by the refractive index difference between the core layer and air and the refractive index difference between the core layer and the substrate in the thickness direction of the core layer. In the width direction of the part), confinement is achieved by utilizing the phenomenon that the effective refractive index near the rib part increases because the thickness of the rib part is thicker than other parts of the core layer. A buffer layer may be provided between the substrate and the core layer using a material with a refractive index smaller than that of the core layer, or a buffer layer may be provided using a material with a smaller refractive index than the core layer and tightly adhered onto the core layer. The cladding layer may be formed in this manner.

The rib-shaped leading waveguide according to the invention is, for example.

A standber having a groove corresponding to the rib portion and the grating provided at a predetermined location thereof is prepared, and a liquid material that is hardened by energy irradiation is injected between the standber and the substrate, and the liquid material is cured by irradiating energy. By curing, a core layer in which the rib portion with the grating is integrated is formed, and the core layer is then manufactured by removing the stub bar.

Liquid materials that are cured by energy irradiation include photocurable or thermosetting resins, such as ultraviolet (UV) cured resins. Examples of inorganic materials include coating liquids for forming thermosetting films.

Liquid state also includes gel state.

According to this invention, since the core layer in which the rib portion with the grating is integrated is formed using a liquid material that hardens by energy irradiation, it can be manufactured using a standber, and its manufacture is easy. As a result, mass production and reproducibility are excellent, and manufacturing time can be shortened, so that it can be provided at a low cost. The stanbar is manufactured using a rib-shaped leading waveguide master, and since this master can be manufactured by various methods, such as electron beam lithography, it is possible to realize grating structures of various shapes and leading waveguides having rib structures.

Furthermore, according to the present invention, since the grating can be formed only on the rib portion where the portion directly below the grating becomes the leading wavepath, the degree of freedom in the shapes of the leading wavepath and the grating can be increased, and the functions of the device can be expanded, and the device can be made smaller. It has the advantage of being configurable.

It is preferable to provide the above-mentioned cladding layer in close contact with the core layer. It is preferable to make both the core layer and the cladding layer using a liquid material that is cured by the above-mentioned energy irradiation because this can simplify the process, but the core layer and the cladding layer may be made of other materials. For example, a material having a nonlinear optical effect may be used as the material for the core layer.

By providing the cladding layer, the core layer is protected by the cladding layer, so the core layer is not damaged and handling becomes easy. Furthermore, even if the refractive index of the core layer is large, by appropriately selecting the refractive index of the cladding layer, it is possible to increase the thickness of the core layer and the width of the rib portion to achieve single mode propagation. Yes, 2 is easy to manufacture. The ability to increase the thickness of the core layer and the width of the rib portion also has the advantage of facilitating optical coupling for input and output with optical fibers and the like.

More preferably, a buffer layer is provided between the substrate and the core layer. Any material can be used for the core layer and buffer layer.

By providing a buffer layer and combining the core layer material and the buffer layer material with appropriate refractive indexes, it is possible to increase the thickness of the core layer and the width of the rib portion to achieve single mode propagation of light. Not only can this be realized, but also any material can be used for the substrate.

Example FIG. 1 shows a first embodiment of the invention.

The rib-shaped single mode guiding waveguide shown in FIG. 1 is composed of a substrate 1 and a core layer 2 formed thereon. The core layer 2 has, at its center, a rib portion 3 that projects upward and extends in one direction. A grating 3a is provided at a predetermined location of the rib portion 3, and is configured by periodically changing the thickness (height) of the rib portion 3. The rib portion 3 and its grating 3a are integrally formed with the core layer 2.

The front beam LB propagates directly under the rib portion 3 within the core layer 2, as shown by the chain line and hatching. light beam L
B is due to the refractive index difference between the core layer 2 and air and the refractive index difference between the core layer 2 and the substrate 1 in the vertical direction.
Trapped inside.

In the lateral direction, the effective refractive index of the portion directly below the rib portion 3 is higher than that of the surrounding portion, so that it is confined to a position directly below the rib portion 3.

Due to the presence of the grating 3a, which is formed so that the thickness of the rib portion 3 increases periodically, the effective refractive index of the portion immediately below the rib portion 3 increases periodically, so that the waveguide portion of the light beam LB has a A gradient index grating will be formed. This grating has functions such as reflecting or transmitting a light beam LB of a specific wavelength.

For example, a 5 in 2 glass substrate is used as the substrate 1, and its refractive index is l.46. As will be described later in detail, the core layer 2 can be formed using an ultraviolet (UV) curing resin, and the refractive index of the core layer 2 at this time can be set to, for example, 1.47. In this way, it is possible to form the core layer 2 whose refractive index is slightly higher than that of the substrate 1, so that it is possible to form a single mode guided waveguide and also to increase the thickness of the core layer 2 and the width of the rib portion 3. It becomes possible.

Other materials, such as thermosetting materials, can also be used for the core layer 2. Examples of thermosetting inorganic materials include coating liquids for forming thermosetting films. There are many types of coating liquids, but ZrO2, TiO
2, Aj1203, S i02, etc. are preferred.

The cross-sectional shape of the rib portion 3 can be arbitrary, and in addition to the rectangular shape shown in Fig. 1, it can be semicircular, triangular, entirely rectangular with rounded corners, or entirely rectangular with a central part. Examples include those in which small grooves are formed, and those that are rectangular as a whole with a small protrusion formed in the center.

Various shapes of gratings are also used. Second
The figure shows a second embodiment. The grating 3b is constructed by periodically changing the width of the rib portion 3. FIG. 3 shows a third embodiment. The grating 3C is constructed by periodically changing the thickness and width at the same position of the rib portion 3. These gratings 3b and 3c have functions such as reflecting or transmitting a guided light beam of a specific wavelength.

The fourth factor shows the fourth embodiment. grating 3
d is constructed by periodically changing the thickness of the rib portion 3, and is blazed (formed in a triangular shape). This grating 3d emits the guided light beam upward. Alternatively, a plurality of types of gratings with different periods may be provided at a plurality of locations in the O rib portion, which also has the function of allowing light from above to enter the leading waveguide. This allows it to have a light reflecting function over a wide wavelength range. Also.

The wavelength separation function of guided light can also be achieved.

A cladding layer can be formed on and in close contact with the core layer. The material of the cladding layer is selected so that its refractive index is slightly smaller than that of the core layer. For example, when the core layer is made of a UV-cured resin, the cladding layer can be formed of a UV-cured resin having a smaller refractive index than the core layer. The refractive index of UV-curable resins can be changed by changing the fluorine content. If both the core layer and the cladding layer are made of UV-curable resin, the manufacturing method thereof becomes easy.

As the material for the cladding layer, inorganic materials can be used in addition to organic materials such as UV-curable resins. When using an inorganic material, the cladding layer may be formed by a vapor deposition method or the like.

In addition to the above-mentioned UV curing resin and coating liquid for forming a thermosetting film, the core layer also contains MNA (refractive index, S),
PTS (polydiacetylene, refractive index 1.118)
, KDP (KH2PO4), and other nonlinear organic and inorganic optical materials can be used.

In this way, protection of the core layer can be achieved by providing a buffer layer on the core layer.

Furthermore, a buffer layer can be provided between the substrate and the core layer. A material having a slightly lower refractive index than the core layer is used for the buffer layer.

For example, as a substrate, LiNbO5, Si, Ga
An As substrate or the like is used, and SiO is deposited on it. RF glass
A buffer layer is formed by sputtering.

As the core layer, it is possible to use the above-mentioned UV curable resin, coating liquid for forming a thermosetting film, nonlinear organic or inorganic optical material, and the like.

By providing the buffer layer in this manner, a substrate made of any material can be used.

A core layer may be formed on the substrate via a buffer layer, and a cladding layer may be further provided on the two core layers.

FIG. 5 shows an example of the manufacturing process of the rib-shaped single mode guiding waveguide shown in FIG.

A master disk for a single-mode guided waveguide is fabricated by electron beam lithography. By applying an electron beam resist onto a glass substrate, drawing a rib pattern with a grating on the resist using an electron beam, and then developing it,
A master having a residual film resist 12 that will become a rib portion with a grating on a glass substrate 11 is prepared (FIG. 5(A)).
).

The remaining film resist 12 is thick in the portion corresponding to the grating. When it is difficult to form a residual film resist corresponding to the rib portion with a grating with an accurate shape in one electron beam lithography, the process consisting of resist coating, electron beam lithography, and development is repeated multiple times to create multiple layers. It is preferable to form a laminated residual film resist consisting of (see patent u(1), filed simultaneously, by the same applicant, and by the same attorney).

Next, 13A nickel (Ni) was applied onto this master by electroforming.
is deposited (FIG. 5(B)), and the master is released to obtain a nickel stand bar 13 (FIG. 5(C)).

Next, UV curing resin 2, which is the material of the core layer, is placed on the substrate 1.
Drop A and place nickel stambar 13 on top of it.
Pressure is applied between the substrate 1 and the nickel standber 13 so that the distance between the substrate 1 and the nickel standber 13 becomes a predetermined value, and vibration is applied if necessary (FIG. 5(D)).

Ultraviolet rays are irradiated from the back side of the substrate 1 to cure the UV curing resin (FIG. 5(E)).

After the UV curing resin has hardened, remove the stand bar 13 (
Figure 5 (F)). As a result, a core layer 2 made of UV-curable resin is formed on the substrate 1. and.

A rib portion 3 having a grating 3a is integrally formed in the core layer 2.

FIG. 6 shows an example of application of the rib-type optical waveguide according to the present invention, and shows an interferometric displacement sensor using a grating of the rib portion as a reflector. By appropriately selecting the period, the grating provided on the rib portion functions as a reflector, a wavelength filter that transmits or reflects only light of a specific wavelength, or a mode converter that converts the mode of guided light. This application example uses a grating as a reflector.

A core layer 20 is formed on the substrate 10 , and a Y-branched rib consisting of three rib parts 21 , 22 , 23 is formed on this core layer 20 , and a grating 22 is formed on a part of the rib part 22 .
A is provided. A Y-branch leading wave path is configured by the Y-branch type ribs.

The light incident on the optical waveguide directly under the rib portion 21 is divided into leading waveguides directly under the rib portions 22 and 23 at one branch portion. The guided light that travels through the optical waveguide directly under the rib portion 22 passes through the grating 2
reflected by 2a. Further, the guided light traveling through the optical waveguide directly under the rib portion 23 is reflected by an externally provided mirror 24, and is combined with the light reflected by the grating 22a at a branch portion. Mirror 24 is attached to the object whose displacement is to be measured.

The phase difference between these two lights changes in accordance with the displacement of the mirror 24, so by detecting the interference signal emitted from the optical waveguide directly under the rib portion 21, the displacement of the mirror 24 can be measured on the submicron order. can.

When using conventional channel waveguide gratings or end-face reflection mirrors with metal vapor-deposited on the end faces, as shown in Figure 7, the distance between the single branch optical waveguides was several 100 μm, but in this application example, the distance between the ribs distance d between 22 and 23
can be brought close to about 10 μm. Since the branching angle θ is approximately 1 degree, the device length can be significantly shortened from the conventional 15 mm to 51 m.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing a first embodiment of the invention, Fig. 2 shows a second embodiment of the invention, Fig. 3 shows a third embodiment, and Fig. 4 shows a fourth embodiment. It is a perspective view which shows each example. 5(A) to 5(P) show an example of the manufacturing process of the rib-shaped optical waveguide shown in FIG. 1. FIG. 6 is a perspective view showing an interferometric displacement sensor which is an application example of the rib-shaped optical waveguide according to the present invention. FIG. 7 is a perspective view showing a conventional channel waveguide grating. 1... Board. 2. Core layer. 3, 21.22.23... Rib part. 3a, 3b, 3c, 3d. ...Grating. Below

Claims (4)

[Claims] (1) It includes a substrate and a core layer having a rib portion formed on the substrate, the core layer is formed using a liquid material that is hardened by energy irradiation, and a grating is provided at a predetermined location of the rib portion. A rib-shaped optical waveguide that is integrally formed with a rib portion. (2) The rib-shaped optical waveguide according to claim (1), wherein the grating is configured by periodically changing the width of the rib portion. (3) The rib-shaped optical waveguide according to claim (1), wherein the grating is constructed by periodically changing the thickness of the rib portion. (4) Claim in which the grating is blazed (
The rib-shaped optical waveguide described in 1).