JPS58120209A - Optical circuit element of multilayered thin film - Google Patents

Abstract

PURPOSE:To obtain a titled optical circuit element which is designed and manufactured easily and has the less damping, by laminating two thin films formed optical waveguides directly or indirectly and crossing the optical waveguides at a specific angle. CONSTITUTION:A solution in which a copolymer of methyl methacrylate and glycidyl methacrylate, and cinnamic acid (39mol% to glycidyl methacrylate) are dissolved in dioxane, is applied on a glass substrate 1 to form the 1st thin film 2. After irradiating the ultraviolet rays on the film 2 through a mask, the film is subjected to baking to form a waveguide 3. After a thin film 4 is formed directly on the film 2 in the same way as the 1st thin film 2, a waveguide 5 is formed so that the angle assumed by the waveguides 3, 5 is regulated to theta at the crossing part 6. By this way, an optical circuit element in which the coupling degree is made optional by selection of the theta is obtained easily. An intermediate thin film may be disposed between the film 3 and the film 4, and plural waveguides may also be disposed on the 2nd thin film 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical circuit element in which a flat thin film on which an optical waveguide is formed is layered in multiple layers such that the waveguides intersect, and in particular, it relates to a passive circuit made of a polymer thin film. It is related to the element.

The optical coupling part in a conventional directional coupler or coupler is constructed by forming parallel waveguides close to each other in the same thin film, and the degree of coupling C is mainly determined by the length of the parallel waveguides and the spacing between the waveguides. It is expressed by a function such as

Therefore, by changing these, it is possible to manufacture circuit elements with different degrees of coupling, but designing and manufacturing using conventional methods involves various technical difficulties and is inevitably expensive. Rather than providing waveguides in a thin film in parallel and close proximity, the thin films are laminated directly or indirectly, and the waveguides in the thin film are made to intersect at a specific angle, thereby achieving the maximum coupling degree from the original insulating state] 11- It is possible to provide an optical circuit element that is extremely easy to design and manufacture, and has low attenuation.
Therefore, it also facilitates the manufacture of optical ICs. The present invention will be described below with reference to the embodiments shown in the figures.

FIG. 2 is an enlarged cross section at the intersection of a two-layer thin polymer film optical circuit device according to the present invention, in which a first layer thin polymer film (2) is formed on a substrate (1) such as glass, and the thin film A straight or curved waveguide (3) is formed therein. (4) is
In the second layer polymer thin film formed directly on the first layer polymer thin film by the same method, the waveguide (6) (5) is a crossing portion, that is, a coupling portion.

The optical circuit element having the above structure is manufactured, for example, as follows.

A copolymer of methyl methacrylate (MMA) and glycidyl methacrylate (HMA) and cinnamic acid as a dopant (39 mo 1% relative to GMA) were dissolved in 1-4 dioxane and placed on a glass substrate (1) in a nitrogen atmosphere. A first thin film with a thickness of approximately 1 μm is formed on the thin film, a mask is placed on this thin film, the film is irradiated with ultraviolet light for approximately 60 minutes, and then baked at 100°C for 120 minutes to form a waveguide portion, for example, a first waveguide film (2) of 1005 m. form.

As a result, the relative refractive index difference between the exposed part, that is, the waveguide part and the unexposed part! $) is about 1.2 to 2.0%.

Since this first waveguide film (2) has been imparted with solvent resistance by baking, the second waveguide film (4) can be directly formed thereon in the same manner as described above.

Finally, the waveguide (3) of the first waveguide film and the waveguide (5) of the second waveguide film are written so as to intersect (6) at an angle θ.

The relationship between the intersection angle θ and the degree of coupling C was actually measured with respect to the incident power Pi and the exit power vy −P (, and the results are shown in FIG. 4.

As is clear from a certain diagram, when the crossing angle is −=0, the difference is 3 dB.
In other words, it shows a tendency to become %.

Further, when θ=6, Po is substantially 0 and no coupling occurs, so by setting it to 026 or more, it is possible to create a state in which the intersecting waveguides are optically insulated.

Since the crossing angle of the laminated optical waveguides facing each other can be set arbitrarily and easily, the present invention makes it possible to obtain a desired degree of coupling very easily, and the design and manufacture of optical circuit elements becomes very easy. Therefore, if a single laser is used for writing, it is possible to manufacture a waveguide with a line width of about 1 μm that can be used for single mode.

FIG. 5 shows an example of a two-layer star coupler, in which a straight waveguide (3) in the first layer is paired with a crossed waveguide (5a,
5b, 5cm・) are the angles θaw'b and θC, respectively.
It is crossed by...

The light from human hair/Ding port (9) is at each intersection (6) (7
) Ql (1 m
)(1′;!J A mode selector can be easily obtained by selecting .

FIG. 6 is an example of a three-layer star coupler, in which the first layer waveguide (3) is sandwiched from above and below in the thickness direction of the paper to form the second layer special wave a field and the third layer waveguide ae. This is what I did.

When the intersection angles # at each intersection (6), (7), and (8) are equal in both the second layer and the third layer, that is, when they are symmetrical with respect to the input waveguide (3), the light intensity to each output port is In the case of FIG. 5, each number is 2.

The upper side shows the case where the waveguide thin film is directly laminated on the substrate, but even if there is an intermediate thin film (to) between the first thin film and the 21st V film as shown in Figure 7, optical coupling can be obtained in the same way. be able to.

In this case as well, the optical waveguide conditions are the refractive index n of the substrate, the refractive index n2, nl of each thin film, and the refractive index d of the waveguide.

nt as 〉n8, n;)n, and n-1n
;>n8, n, and it is good to select the material of the thin film within a range that satisfies this condition.

Also, the width of each waveguide is Wl,) and the thickness of the thin film is dl, d
2, d, and when the first layer optical waveguide is a multimode optical waveguide, w, ) If w, select the mode to be coupled to the second layer side depending on % and the intersection angle 0. be able to. The degree of coupling in this case is d! It can be changed by

Furthermore, when designing conventional optical circuit elements, nl〉n,
) However, according to the present invention, by constructing an intermediate thin film with a thickness of about 1jIm between the substrate and the waveguide film, the refractive index n of the substrate can be made into an irrelevant factor. This makes it possible to easily manufacture the element.

[Brief explanation of the drawing]

Fig. 1 is a schematic enlarged plan view of the optical circuit element of the present invention; Fig. 2 is a sectional view of the intersection; Fig. 3 is an exploded perspective view; Fig. 4 is a graph showing the relationship between the intersection angle and the degree of coupling; FIG. 5 is a flat WJ diagram of a two-layer star coupler, FIG. 6 is a plan view of a three-layer star coupler, and FIG. 7 is an enlarged cross-sectional view of a crossing portion of another example element. +21 (4)・・・Thin film, (3) (5)・・・
Waveguide, (6) (7) (8)...Cross section. Applicant: Isamu Kato 2
4 Figure 4j (1νm)

Claims (1)

[Claims] A multilayer thin film optical circuit element 0 in which at least two thin films on which optical waveguides are formed are laminated closely or at a predetermined interval so that the waveguides intersect at a predetermined angle.