JPH1090549A - Optical multiplexing/demultiplexing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact optical multiplexing/demultiplexing device easy to manufacture by using a diffraction grating of a non-reflection type and making a structure coupling it along a waveguide. SOLUTION: Multiplexed light is made incident on a circular arc channel waveguide 1. Then, this optical waveguide 1 is provided with the diffraction grating 4 distributed along the advance direction of light and diffracting the light in the specified direction, and demultiplexes the light to four kinds of light with different wavelengths such as e.g. wavelengths Aλ1 -λ4 by this diffraction grating 4 to output them. A slab waveguide 2 is provided close to the channel waveguide 1, and it is constituted so as to confine diffracted light from the channel waveguide 1 flatly. That is, this device diffracts the light passing through the channel waveguide 1 without reflecting, and confines the diffracted light as it is flatly by the slab waveguide 2 to converge it to a specified position. Thus, by such a constitution, the optical multiplexing/ demultiplexing device is manufactured easily, and miniaturization becomes possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical multiplexing / demultiplexing apparatus for multiplexing light having different wavelengths and transmitting the multiplexed light through an optical waveguide or, conversely, separating light in the multiplexed optical waveguide by wavelength. .

[0002]

2. Description of the Related Art As a structure of an optical waveguide for multiplexing or separating optical wavelengths, there is a structure using a reflection type diffraction grating or an arrayed waveguide. In a structure using a reflection type diffraction grating, when multiplexed light is applied to this diffraction grating, light separated for each wavelength is reflected and diffracted in different directions or positions, and separated. For multiplexing, if each light path is configured in the reverse manner, a light beam in which all wavelength lights are multiplexed into one can be obtained.

In the structure using the reflection type diffraction grating, diffraction gratings are manufactured at intervals of about 5 times or less of the wavelength of the used light of 1.5 μm to generate unnecessary high-order mode diffracted light. The loss of incident light must be minimized. At the same time, unless the reflection coefficient is made to be 100% as much as possible, loss of incident light occurs. However, it is technically difficult to fabricate a diffraction grating having a reflection structure with a fine resolution and a high reflectance in an optical waveguide.

In particular, in the case of a waveguide using a quartz-based material, it is difficult to perform etching at a depth of about 20 μm or more including the clad layer and the core layer with the above fine resolution in order to produce a reflective structure having a high reflectance. It is. Sie closest to this
In the case of the mens report, the depth is 15 μm and the resolution is
Only the etching of the diffraction grating having the same structure is performed.

Next, in the structure using the array waveguide, first, the multiplexed light propagates through the first slab portion and is distributed and incident on the optical waveguide array. Next, by propagating through the optical waveguides having a unique phase length without being coupled to each other, a phase difference depending on the wavelength is generated between the light in each optical waveguide. Then, the light propagates through the second slab portion and interferes with each other to generate a diffraction effect, and the light separated for each wavelength is separated to different positions.

However, in the structure using this arrayed waveguide, it is necessary to provide a space of at least 25 μm or more in the arrayed waveguide portion so that the waveguides are not coupled, and the design size is larger than that of the diffraction grating type. Become. Further, the design dimensions of the two slab portions also become large due to the necessity of matching with the array waveguide.

The present invention has been made in view of such circumstances, and is easy to manufacture by using a diffraction grating that is not a reflection type and having a structure in which it is coupled along a waveguide. An object of the present invention is to provide a compact optical multiplexing / demultiplexing apparatus.

[0008]

Accordingly, the present invention provides a structure in which a diffraction grating is coupled along a waveguide,
It is possible to use a diffraction grating having a low reflectance. Further, the diffraction grating can be produced by etching simultaneously with the production of the core layer of the waveguide having a thickness of about 6 μm.

That is, the present invention provides a channel type optical waveguide having a diffraction grating distributed along a light traveling direction and diffracting light in a specific direction, and a channel type optical waveguide provided in close proximity to the channel type optical waveguide. An optical multiplexing / demultiplexing device comprising a slab type optical waveguide for confining diffracted light from a wave path in a plane.

According to the present invention, the diffraction grating having the wavelength dispersion function is arranged along the traveling direction of the light propagating in the channel type optical waveguide, and the slab type optical waveguide is provided close to the channel type optical waveguide. A waveguide is provided, and the diffracted light from the channel-type optical waveguide is confined two-dimensionally by the slab-type optical waveguide, so that the light passing through the channel-type optical waveguide is diffracted without being reflected, and the diffracted light Can be confined as it is by the slab type optical waveguide in a planar manner and can be focused on a specific position. Therefore, according to this configuration, the size of the optical multiplexing / demultiplexing apparatus can be reduced, and the manufacturing can be facilitated.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a channel type optical waveguide is an optical waveguide that confine and propagate light in a channel type. Such a channel type optical waveguide is generally used.
The cross-sectional shape is rectangular, and light is confined within this rectangle,
It has the property of propagating light in only one direction. The slab type optical waveguide is an optical waveguide that confine and propagate light in a slab type. Such a slab type optical waveguide usually has a rectangular cross-sectional shape, and has the property of confining light within this rectangle and propagating light two-dimensionally. That is, it has the property of propagating light in a plane.

The waveguide may be made of various materials such as quartz, polymer, semiconductor, etc.
In order to minimize the temperature dependence of the wavelength characteristic, it is desirable to use a quartz-based material.

The diffraction grating according to the present invention is distributed along the traveling direction of light propagating in the channel type optical waveguide,
If it diffracts light of a specific wavelength in a specific direction,
It may be provided in any form. For example, in the optical waveguide, one having a different refractive index of light may be distributed along the traveling direction of the light, or one that refracts light on the side surface of the optical waveguide. May be distributed along.

Further, it is desirable that the diffraction grating in the present invention diffracts light so that the light is condensed at a specific position outside the channel type optical waveguide, and the light is condensed at the specific position. It is desirable that the light has a two-dimensional position distributed for each wavelength. For this purpose, for example, the diffraction grating is manufactured such that the path lengths of the individual refracted lights to the light condensing position have a difference of an integral multiple of the wavelength.

In the present invention, the channel type optical waveguide may be linear, but by forming it into an arcuate shape, the aberration of the condensed light can be improved. In order to improve this aberration, the diffraction grating may be distributed so that the shape changes every cycle, or may be distributed so that the interval changes every cycle.

In order to improve the aberration, any one of the above-mentioned "curved shape", "change in the shape of the diffraction grating", and "change in the interval between the diffraction gratings" can be adopted according to the manufacturing conditions. By improving the aberration, the demultiplexing performance can be improved, and the propagation loss can be reduced. In the channel type optical waveguide of the present invention, the core layer and the diffraction grating of the waveguide can be manufactured by simultaneous etching.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited to this.

FIG. 1 is a structural explanatory view showing the structure of one embodiment of the present invention. In this embodiment, first, a light separating apparatus will be described as an example. In this figure, reference numeral 1 denotes one diffraction-type channel optical waveguide having a channel-type structure (hereinafter, also referred to as a channel waveguide), and 2 denotes a slab-type optical waveguide having a slab-type structure (hereinafter, a slab waveguide). Reference numeral 3 denotes an output channel waveguide connected to the slab waveguide 2.

The channel waveguide 1 for diffraction is an optical waveguide that confine and propagate light in a channel form. The cross-sectional shape of the channel waveguide 1 indicated by the line V-V in the drawing is substantially rectangular, and the light is confined within the rectangle and propagates in only one direction.

The slab waveguide 2 is an optical waveguide in which light is confined and propagated in a slab type. The cross-sectional shape of the slab waveguide 2 indicated by the line VV in the drawing is rectangular, and the light is confined within the rectangle and propagates two-dimensionally. That is, light propagates in a plane.

The slab waveguide 2 is composed of the channel waveguide 1
And diffracted light from the channel waveguide 1 is confined two-dimensionally. An output channel waveguide 3 is formed integrally with the slab waveguide 2. The output channel waveguide 3 has a rectangular cross-section like the channel waveguide 1, and propagates light only in one direction.

The channel waveguide 1 has an arcuate shape in order to improve the aberration. The multiplexed light is multiplexed in the arcuate channel waveguide 1 in a direction indicated by an arrow in the figure. It is incident (shown as input light in the figure). The channel waveguide 1 is provided with a diffraction grating 4 that is distributed along the light traveling direction and diffracts the light in a specific direction. For example, the light is separated into four types of light having different wavelengths, such as wavelengths λ ₁ , λ ₂ , λ ₃ , and λ ₄ (shown as output light in the figure).

FIG. 2 is an explanatory view showing a light convergence state by the diffraction grating of the channel waveguide. As shown in this figure,
In the channel waveguide 1, a diffraction grating 4 coupled to the waveguide is formed along the waveguide. As described above, the diffraction grating is formed on the side surface of the channel waveguide 1, and is formed so that a specific ratio of the guided light is refracted for each peak of the diffraction grating.

That is, as shown in FIG. 3, in order to improve the aberration, a distribution in which the intensity of the refracted light near the center among the plurality of refracted lights is large and the intensity of the refracted light around the center is small is realized. It is a diffraction grating. To achieve this, the intensity of the refracted light can be reduced by flattening the shape of the mountain, and the intensity of the refracted light can be increased by increasing the shape of the mountain. Let me. All the incident light in the channel waveguide 1 is refracted in a direction outside the channel waveguide 1 by the time when the light propagates the entire length of the diffraction grating.

The diffraction grating of the channel waveguide 1 is formed so that each refracted light is all condensed to a specific condensing position by diffraction. For example, as shown in FIG. 2, when the optical path length until each refracted light by the diffraction grating 4 reaches the condensing position is (AB) from the position A to the position B,
The optical path lengths (AB) ₁ , (AB) ₂ , (A
B) The diffraction grating 4 is manufactured so that ₃ ,... Have a difference of an integral multiple of the wavelength between adjacent ones. Further, as shown in FIG. 4, the diffraction gratings 4 are distributed so that the intervals change every one period in order to improve aberration.

Since light has different diffraction properties depending on the wavelength,
With such a diffraction grating 4, light of different wavelengths can be focused on different positions. By making these condensing positions coincide with the incident width of the output channel waveguide 3, light loss can be minimized.

In FIG. 2, the wavelength λ₁Only the light ones
And the diffracted light is, for example, λ₁, Λ _Two, Λ_Three, Λ_FourWaves
Light is collected at different positions B on the same plane for each length. For output
Has a wavelength λ.₁, Λ_Two, Λ_Three, Λ_FourYour
And the incident end is two-dimensionally distributed on the same plane,
As a result, the wavelength-multiplexed incident light is separated into wavelength components.
And output separately.

With respect to the method of manufacturing the diffraction grating 4, a diffraction grating having this structure can be manufactured simultaneously with the channel waveguide 1. For example, in the case of a quartz-based waveguide, a quartz undercladding layer 12 is formed on a silicon (Si) substrate 11 as shown in a cross-sectional view along line VV in FIG. Then, a quartz core layer 13 is also laminated thereon.

Then, the core layer 13 is etched using the mask pattern 14. At this time, as shown in FIG. 2, a channel in which a diffraction grating 4 is formed in a side surface in a curved shape like an arc. A mask pattern of the waveguide 1;
If the slab waveguide 2 with one mask pattern is used, the channel waveguide 1 and the diffraction grating 4 can be produced as they are, and the slab waveguide 2 can be produced at the same time (FIG. 5A). reference).

After the core layer 13 is etched, a quartz overcladding layer 15 is laminated thereon to complete the process (see FIG. 5B). As the material of the waveguide, a polymer or a semiconductor can be used in addition to the quartz-based material.

The light separating apparatus has been described above.
By reversing the direction of the light, this light separation device
It can also be used as an optical multiplexing device that multiplexes light of different wavelengths.

[0032]

According to the present invention, the light passing through the channel-type optical waveguide is diffracted without being reflected, and the diffracted light is confined as it is by the slab-type optical waveguide in a planar manner and condensed at a specific position. Can be done. Therefore, this configuration facilitates the production of the optical multiplexing / demultiplexing apparatus, and enables downsizing.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a light convergence state by a diffraction grating of a channel waveguide according to the present invention.

FIG. 3 is an explanatory view showing an example of a diffraction grating according to the present invention.

FIG. 4 is an explanatory view showing an example of a diffraction grating according to the present invention.

FIG. 5 is an explanatory view showing a method of manufacturing a waveguide according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 channel optical waveguide 2 slab optical waveguide 3 channel waveguide for output 4 diffraction grating 11 substrate 12 undercladding layer 13 core layer 14 mask pattern 15 overcladding layer

Claims (7)

[Claims] 1. A channel-type optical waveguide having a diffraction grating distributed along a traveling direction of light and diffracting light in a specific direction, and diffraction from the channel-type optical waveguide provided in close proximity to the channel-type optical waveguide. An optical multiplexing / demultiplexing device comprising a slab type optical waveguide for confining light in a plane. 2. The diffraction grating of the channel type optical waveguide,
2. The optical multiplexing / demultiplexing apparatus according to claim 1, wherein the light is diffracted so that the light is focused on a specific position outside the channel type optical waveguide. 3. The optical multiplexing / demultiplexing apparatus according to claim 2, wherein the light condensed at the specific position has a two-dimensional position distributed for each wavelength. 4. The optical multiplexing / demultiplexing apparatus according to claim 1, wherein said channel type optical waveguide has a shape curved in an arc shape. 5. The diffraction grating of the channel type optical waveguide,
2. The optical multiplexing / demultiplexing device according to claim 1, wherein the distribution is such that the shape changes in each cycle, and the intensity of the diffracted light changes in accordance with the cycle of the diffraction grating. Device. 6. The diffraction grating of the channel type optical waveguide,
2. The optical multiplexing / demultiplexing apparatus according to claim 1, wherein the distribution is such that the interval changes every period. 7. The optical multiplexing / demultiplexing apparatus according to claim 1, wherein the channel type optical waveguide is formed by simultaneously etching a core layer and a diffraction grating of the waveguide.