JPH1010343A - Optical waveguide with filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide provided with a filter easy to form a groove on a wafer collectively, easy to fix a thin film filter and capable of facilitating handling after fixing. SOLUTION: By burying the thin film filter 13 while being in close contact with an inner wall 14 of a V-shaped groove 12, the thin film filter 13 is not tilted more than that, and a stable slope angle is obtained, and an optical characteristic is stabilized. Further, by burying the thin film filter 13 into the groove 12, the matter that the thin film filter 13 is not protruded from an optical waveguide element 10, and the handling is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical waveguide with a filter.

[0002]

2. Description of the Related Art With the development of optical communication technology, various optical components have been used. An optical waveguide with a filter is also one of the optical components. The optical waveguide with filter has a groove formed on the surface of the optical waveguide element so as to cross the waveguide, and a thin film filter is embedded in the groove. Some of the optical waveguides with filters have a groove having a rectangular cross-sectional shape that is inclined by 8 degrees or more with respect to the width direction of the optical waveguide element.

FIG. 8A is a plan view of a conventional optical waveguide with a filter, and FIG. 8B is a cross-sectional view taken along the line AA of FIG. 8A.

[0004] As shown in FIG.
Is inserted into a groove 4 cut on the surface of the optical waveguide element 2 at an angle α with respect to the width direction (Y-axis direction) so as to cross the waveguide 3 and an adhesive 5 so that the upper part is exposed. It is fixed with adhesive.

As shown in FIG. 8B, the groove 4 has a rectangular cross section. The reason that the groove 4 is inclined by the angle α with respect to the width direction of the optical waveguide element 2 is that when the light 6a and 6b propagating through the waveguides 3a and 3b are reflected by the thin film filter 1 as shown in FIG. The reflected light 7a, 7b is
This is to prevent the return to a and 3b, which causes deterioration of the return loss. The thin film filter 1 is designed so that desired optical characteristics can be obtained by inclining it by the angle α. FIG. 9 is an explanatory diagram for explaining the reason why the thin film filter is arranged obliquely with respect to the waveguide.

[0006]

However, the conventional optical waveguide with a filter includes a plurality of optical waveguide elements 2a to 2d.
In order to form grooves 4a to 4d each having an angle α in the width direction (Y-axis direction), as shown in FIG.
The groove 4a is formed in the region where the optical waveguide elements 2a to 2d are formed.
When the grooves 4a to 4d are formed, the grooves 4a to 4d cannot be collectively formed in the optical waveguide elements 2a to 2d by dicing, and the grooves 4a to 4d are not individually formed in the optical waveguide elements 2a to 2d. However, the number of steps increases and the cost increases. FIG. 10 is a diagram showing a region of the optical waveguide element formed on the wafer.

If the grooves 4a to 4d are formed collectively by etching or the like, an enormous amount of time is required for etching and the throughput is deteriorated.

A plurality of optical waveguide elements 2a are formed by dicing.
In order to collectively form the grooves 4a to 4c in the wafers 2b to 2c, as shown in FIG. 11, when the region where the optical waveguide elements 2a to 2c are formed is set on the wafer 8b, the grooves 4a to 4c are formed in the wafer 8b. 4c are collectively formed, but not only does the number of optical waveguide elements 2a to 2c obtained from one wafer 8b decrease, but the optical waveguide elements 2a to 2c must be individually cut out to predetermined dimensions. There is a problem that increases. FIG. 11 is a diagram showing a region of the optical waveguide element formed on the wafer.

Further, in order to obtain desired optical characteristics, the thin film filter must be bonded and fixed vertically (along the Z-axis direction) to the rectangular groove, but it is difficult to bond and fix the thin film filter vertically. There's a problem. When the thin film filter is inclined with respect to the Z axis, the angle formed between the waveguide 3a and the waveguide 3b becomes α
As described above, there is a problem that the loss wavelength dependency of the thin film filter shifts from the wavelength λ1 to the wavelength λ2 as shown in FIG. FIG. 12 is a wavelength loss characteristic diagram of the thin film filter. The horizontal axis indicates the wavelength, and the vertical axis indicates the loss.

Further, the thin-film filter 1 shown in FIG. 8 protrudes above the optical waveguide element 2, so that care must be taken in handling, and there is a problem that workability is remarkably reduced.

An object of the present invention is to provide an optical waveguide with a filter which solves the above-mentioned problems and which can easily form a groove on a wafer and which can easily fix and handle the thin-film filter after fixing. To provide.

[0012]

In order to achieve the above object, the present invention provides a filter having a groove formed on the surface of an optical waveguide element so as to cross the waveguide and a thin film filter embedded in the groove. In the optical waveguide, the groove has a cross-sectional shape of V
It is formed in the shape of a letter, and the thin film filter is buried in the inner wall of the groove while being in close contact with the groove.

In the present invention, in addition to the above configuration, the V-shaped groove preferably has a spread angle of 14 degrees or more.

According to the present invention, in addition to the above structure, the V-shaped groove is formed at a depth such that the thin film filter is embedded therein.
Preferably, the membrane filter is sealed in the groove with an adhesive.

In addition to the above configuration, in the present invention, it is preferable that a V-shaped groove is formed along with the dummy substrate adhered to the surface of the optical waveguide element.

According to the above structure, when dicing the wafer to form a strip-shaped optical waveguide element, dicing is performed in the width direction of the optical waveguide element to form a groove in a plurality of optical waveguide elements at once. it can. In addition, by embedding the thin film filter in the V-shaped groove while keeping the thin film filter in close contact therewith, the thin film filter does not further tilt, and a stable tilt angle is obtained, so that the optical characteristics are stabilized. Further, since the thin-film filter is embedded in the groove, the thin-film filter does not protrude from the optical waveguide element, and handling is easy. Furthermore, when a V-shaped groove is formed together with the dummy substrate after bonding the dummy substrate to the surface of the optical waveguide element, when the dimension of the thin film filter is large, when the optical waveguide element is thin, or when the waveguide is formed. This is advantageous when shortening the length of the transverse groove.

[0017]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1A is a plan view showing an embodiment of an optical waveguide with a filter according to the present invention, and FIG.
It is a BB sectional view taken on the line of (a).

As shown in FIGS. 1A and 1B, a groove 12 is formed on the surface of a strip-shaped optical waveguide element 10 so as to cross the waveguide 11. The groove 12 is formed in the width direction (Y-axis direction) of the optical waveguide element 10, and is formed so that its cross section becomes V-shaped in the depth direction (Z-axis direction). The depth h of the groove 12 is formed to such a depth as to embed the thin film filter 13, and the adhesive 1 is inserted into the groove 12 while the thin film filter 13 is in close contact with one inner wall 14 of the groove 12.
5 embedded. That is, the thin film filter 13
Is not inclined in the Y-axis direction, but the thin-film filter 13 is inclined in the groove 12 by an angle α with respect to the Z-axis.

FIG. 2 is an explanatory diagram for explaining the function of the V-shaped groove shown in FIG.

The inner walls of the two grooves formed in the V-shape in the Z-axis direction of the optical waveguide element 10 are inclined by an angle α with respect to the Z-axis. The spread angle 2α of the V-shaped groove 12 is 14
Degrees or more. For this reason, a part of the light 16a, 16b that has propagated through the waveguides 11a, 11b is reflected in accordance with Snell's law, so that there is no deterioration in the return loss due to the reflected return light 17a, 17b. Further, since the thin film filter 13 is embedded with the adhesive 15 while keeping the thin film filter 13 in close contact with one inner wall 14 of the groove 12, the angle α is maintained without shaking of the thin film filter 13, and desired optical characteristics can be obtained.

As described above, since the groove 12 has a V-shaped cross section, the return loss 17a and 17b from the thin-film filter 13 does not deteriorate the return loss. In addition, it is not necessary to embed and fix the thin film filter 13 vertically in the groove 12, and the embedding of the thin film filter 13 becomes easy. Further, since the thin-film filter 13 is fixed in the groove 12 while being sealed with the adhesive 15, the thin-film filter 13 does not protrude from the surface of the optical waveguide element 10. 10 is easy to handle. Further, as shown in FIG. 3, by forming a groove 12e in the wafer 8c,
The grooves 12a to 12d can be collectively formed in the region where the optical waveguide elements 10a to 10d are formed on c. FIG. 3 is a view showing a region of the optical waveguide element formed on the wafer.

Here, the upper limit value of the angle α will be described.

The upper limit value of the spread angle α of the groove 12 cannot be unconditionally determined because of the relationship with the diffraction loss. As shown in FIG. 4, for example, if the loss is 0.2 dB or less, d
Is approximately 35 μm, and from the relationship of Expression (1), Expression (2)
Is obtained. FIG. 4 is a diagram showing the relationship between the gap of the groove and the loss, with the horizontal axis representing the gap and the vertical axis representing the loss.

D = 2 · h1 · tanα (1) α = tan ⁻¹ (d / 2h1) (2) When d is obtained from the diffraction loss, the upper limit is determined by the depth h1 from the core to the bottom of the groove 12. It is determined.

FIG. 5 is an enlarged sectional view showing a modification of the groove of the optical waveguide with a filter shown in FIG. 1, and FIG. 6 is an enlarged view showing another modification of the groove of the optical waveguide with a filter shown in FIG. It is sectional drawing.

The bottom surface of the groove 12f shown in FIG. 5 is formed flat. In this case, the stress applied to the bottom surface of the groove after dicing is dispersed, so that cracks are less likely to occur.

The bottom surface of the groove 12g shown in FIG. 6 has a curvature. In this case, the stress applied to the bottom surface of the groove after dicing is dispersed, so that cracks are less likely to occur.

FIG. 7A is a plan view showing another embodiment of the optical waveguide with a filter according to the present invention, and FIG. 7B is a cross-sectional view taken along the line CC of FIG. 7A.

For example, a block-shaped dummy substrate 22 is bonded and fixed to the position where the groove 21 is formed on the optical waveguide element 20 with an adhesive 23, and then the dummy substrate 2 is placed on the dummy substrate 22 from above.
The groove 21 is formed by dicing the optical waveguide element 20 together. After the thin film filter 25 is brought into close contact with one inner wall 24 of the groove 21, the thin film filter 25 is sealed and fixed with an adhesive 26. In this manner, when the dimension of the thin film filter 25 is large, when the thickness of the optical waveguide element 20 is small, the length L of the groove crossing the waveguide 27 is L.
This is effective when you want to shorten

According to the present invention, according to the present invention, a groove is formed on the surface of an optical waveguide device so as to cross the waveguide, and a thin film filter is embedded in the groove. The filter is shaped like a letter, and the thin film filter is buried in the inner wall of the groove while keeping it in close contact, so that the groove can be easily formed on the wafer at one time, and the thin film filter can be fixed and handled easily after fixing. The provision of the attached optical waveguide can be realized. In this embodiment, the case where four optical waveguide elements are formed from a wafer has been described, but the present invention is not limited to this.

[0032]

In summary, according to the present invention, the following excellent effects are exhibited.

Since the cross-sectional shape of the groove is formed in a V-shape and the thin-film filter is buried in the inner wall of the groove while being in close contact with the groove, it is easy to form the groove on the wafer at a time, and the thin-film filter is fixed. And an optical waveguide with a filter that is easy to handle after fixing.

[Brief description of the drawings]

FIG. 1A is a plan view showing an embodiment of an optical waveguide with a filter of the present invention, and FIG. 1B is a cross-sectional view taken along the line BB of FIG.

FIG. 2 is an explanatory diagram for explaining a function of a V-shaped groove shown in FIG. 1;

FIG. 3 is a diagram showing a region of an optical waveguide element formed on a wafer.

FIG. 4 is a diagram showing a relationship between a gap of a groove and a loss.

FIG. 5 is an enlarged cross-sectional view showing a modification of the groove of the optical waveguide with a filter shown in FIG.

FIG. 6 is an enlarged sectional view showing another modification of the groove of the optical waveguide with a filter shown in FIG. 1;

FIG. 7A is a plan view showing another embodiment of the optical waveguide with a filter of the present invention, and FIG.
It is a line sectional view.

8A is a plan view of a conventional optical waveguide with a filter, and FIG. 8B is a cross-sectional view taken along line AA of FIG. 8A.

FIG. 9 is an explanatory diagram for explaining the reason why the thin film filter is arranged obliquely with respect to the waveguide.

FIG. 10 is a diagram showing a region of an optical waveguide element formed on a wafer.

FIG. 11 is a diagram showing a region of an optical waveguide element formed on a wafer.

FIG. 12 is a wavelength loss characteristic diagram of a thin film filter.

[Explanation of symbols]

 8c Wafer 10, 10a to 10d Optical waveguide element 11a, 11b Waveguide 12, 12a to 12d Groove 13 Thin film filter 14 Inner wall 15 Adhesive

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshinobu Kurosawa 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture Within the Opto-System Research Laboratory, Hitachi Cable, Ltd. (72) Inventor Ryuta Takahashi Hidaka-cho, Hitachi City, Ibaraki Prefecture 5-1-1, Hitachi Cable, Ltd., Opto-System Research Laboratory (72) Inventor Tatsuo Teraoka 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture, Hitachi Cable, Opto-System Research Laboratory

Claims (4)

[Claims] A groove is formed on a surface of an optical waveguide element so as to cross the waveguide, and a thin film filter is embedded in the groove. In the optical waveguide with a filter, the groove has a V-shaped cross section. An optical waveguide with a filter, characterized in that a thin film filter is embedded in the inner wall of the groove while being in close contact with the groove. 2. The optical waveguide with a filter according to claim 1, wherein the V-shaped groove has a spread angle of 14 degrees or more. 3. The optical waveguide with a filter according to claim 1, wherein the V-shaped groove is formed to a depth such that the thin film filter is embedded, and the thin film filter is sealed in the groove with an adhesive. 4. The optical waveguide with a filter according to claim 1, wherein a dummy substrate is bonded to a surface of the optical waveguide element, and a V-shaped groove is formed for each of the dummy substrates.