JP2001188139A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module reducing man-hours, improving yields and simultaneously improving the utilization factor of the light. SOLUTION: A photonic crystal 9 forming a periodic structure composed of plural media with respectively different refractive indexes is provided. Incident light comprising multiplexed light with plural wavelengths or polarization directions is made incident on the photonic crystal 9 through an optical waveguide 4 and is divided into reflected light reflected with a recessing reflection plane 9a and transmitted light passing through the photonic crystal 9 so as to be taken out from output terminals 5a, 6a of optical waveguides 5, 6 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module such as an optical demultiplexer for demultiplexing an optical signal and an optical multiplexer for demultiplexing an optical signal, which are used for optical communication and optical control.

[0002]

2. Description of the Related Art An optical module used for optical communication and optical control, for example, multiplexes two lights having different wavelengths and reflects an optical signal transmitted by a filter to reflect light of one wavelength and light of another wavelength. Is transmitted and split. FIG. 7 shows a conventional optical module that performs demultiplexing. In the optical module 1, optical waveguides 4, 5, and 6 are formed on a substrate 8. The optical waveguides 4, 5, and 6 are clad 10a, 10
b.

[0003] A slit 10c is formed between the claddings 10a and 10b, and a dielectric multilayer filter 3 in which a dielectric thin film is laminated is disposed in the slit 10c. When the input signal input to the input terminal 4a of the optical waveguide 4 is, for example, light having wavelengths of 1.3 μm and 1.5 μm multiplexed, the dielectric multilayer filter 3 has a wavelength of 1.5 μm.
The light has a reflectance of 100% and a wavelength of 1.5 μm.
The light is designed to have a transmittance of 100% for light of less than m.

Then, an input signal is input from an input terminal 4a, light having a wavelength of 1.3 μm passes through the filter 3 and is extracted from an output terminal 6a, and light having a wavelength of 1.5 μm is reflected by the filter 3. It is taken out from the output terminal 5a.

[0005]

However, according to the conventional optical module 1 described above, the dielectric multilayer filter 3 is formed by laminating several tens of thin films. Therefore, there is a problem that the cost is increased since the mass productivity is poor and the number of steps is increased. In addition, there is a problem that the wavelength at which the reflectance or the transmittance becomes maximum is shifted from a design value due to an error in the film thickness of each laminated film or an error in the film thickness of the entire multilayer film, thereby reducing the yield.

Further, the optical waveguides 4 formed on the substrate 8
It is necessary to arrange the dielectric multilayer filter 3 at a predetermined position with respect to 5 and 6, but the slit 10c having a width of several tens μm is required.
, A dielectric multilayer filter 3 having a thickness of several μm is arranged,
Since the positioning is performed with high precision with respect to the optical waveguides 4 and 5, there is a problem that the number of assembly steps is increased.

If the light emitted from the optical waveguide 4 is directly reflected and transmitted, the light exiting from the optical waveguide has a spread. There is a problem that light use efficiency is reduced.

An object of the present invention is to provide an optical module capable of reducing man-hours and improving the yield and improving the light use efficiency.

[0009]

Means for Solving the Problems To achieve the above object, an invention according to claim 1 comprises a photonic crystal having a periodic structure having a plurality of media having different refractive indexes,
The method is characterized in that incident light incident on the photonic crystal is separated into reflected light reflected by a concave reflecting surface and transmitted light transmitted through the photonic crystal. According to this configuration, the light emitted from the optical waveguide or the optical fiber is incident on the photonic crystal while spreading, and is reflected by the concave reflecting surface so as to narrow the spreading.

According to a second aspect of the present invention, there is provided a photonic crystal having a periodic structure having a plurality of media having different refractive indices, and reflected light reflected on a concave reflecting surface of the photonic crystal. The transmission light transmitted through the photonic crystal is synthesized.

According to a third aspect of the present invention, in the optical module according to the first or second aspect,
The wavelength of light reflected from the photonic crystal and the wavelength of light transmitted therethrough are different. According to this configuration, incident light in which light of a plurality of wavelengths is multiplexed enters the photonic crystal, light of one wavelength is reflected, and light of another wavelength is transmitted. Further, light of one wavelength is reflected by the photonic crystal, and light of another wavelength is transmitted through the photonic crystal and is combined with light of a plurality of wavelengths.

According to a fourth aspect of the present invention, in the optical module according to the first or second aspect,
The light reflected from the photonic crystal and the light transmitted therethrough have different polarization directions. According to this configuration, the incident light incident on the photonic crystal is separated into lights of different polarization directions, and light of one polarization direction is reflected and light of another polarization direction is transmitted. Further, light in one polarization direction is reflected by the photonic crystal, and light in another polarization direction is transmitted through the photonic crystal and is combined with light in a plurality of polarization directions.

According to a fifth aspect of the present invention, in the optical module according to any one of the first to fourth aspects, the photonic crystal is a two-dimensional array in which the medium formed in a columnar shape is arranged. It is characterized by comprising a periodic structure of a shape. According to this configuration, a plurality of media having different refractive indices are formed in a columnar shape and are periodically arranged two-dimensionally to form a photonic crystal.

According to a sixth aspect of the present invention, in the optical module according to any one of the first to fifth aspects, the reflection surface is a toric surface or a cylindrical surface.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. For convenience of description, the same parts as those in FIG. 7 of the conventional example are denoted by the same reference numerals. Figure 1 shows the first
It is a top view showing the optical module of an embodiment. In the optical module 1, optical waveguides 4, 5, and 6 made of alumina or the like covered with clads 10a and 10b are formed on a substrate 8. A slit 10c having a width of several tens of μm is provided between the claddings 10a and 10b, and a photonic crystal 9 is arranged in the slit 10c.

As shown in FIG. 2, the upper and lower surfaces of the photonic crystal 9 are covered with an upper clad 11b and a lower clad 11a, and a two-dimensional medium in which two media 9c and 9d having different refractive indexes are periodically arranged. It has a periodic structure. By appropriately selecting the refractive indexes and the arrangement periods of the media 9c and 9d, light incident on the photonic crystal 9 can be separated into reflected light and transmitted light according to the wavelength or the polarization direction. Further, the transmitted light can be separated by being refracted in different directions according to the wavelength or the polarization direction.

As shown in FIG. 3, the photonic crystal 9 in which the mediums 9c and 9d are composed of holes and alumina is a porous material having periodic cylindrical holes (9c) by anodizing aluminum 9e. Of alumina (9d) is formed. This makes it possible to easily form the photonic crystal 9 integrally with the substrate 8. At this time, different characteristics can be obtained by filling the holes with a medium having another refractive index. Also, silicon or the like is formed on a desired substrate,
After patterning the hole forming portion with an electron beam, a columnar hole can be formed by a method such as etching.

As shown in FIG. 4, when light of wavelengths λ1 and λ2 is multiplexed and input from the input terminal 4a (see FIG. 1) of the optical waveguide 4, the photonic crystal 9 is output from the output end 4b of the optical waveguide 4. It is injected toward. The light of wavelength λ1 of the incident light incident on the photonic crystal 9 is reflected on the reflection surface 9a. The reflected light enters the input end 5b of the optical waveguide 5, and the light having the wavelength λ1 is extracted from the output terminal 5a (see FIG. 1).

Wavelength λ2 incident on photonic crystal 9
Is transmitted through the photonic crystal 9, emitted from the transmission surface 9 b, and enters the optical waveguide 6. And the output terminal 6a
(See FIG. 1), light of wavelength λ2 is extracted. In this manner, the incident light in which the lights of the wavelengths λ1 and λ2 are multiplexed is separated, and the light can be demultiplexed.

Light emitted from the output end 4b of the optical waveguide 4 toward the photonic crystal 9 is emitted from the narrow optical waveguide and spreads as shown by A1. When the reflecting surface 9a of the photonic crystal 9 is made concave, the reflected light is B1.
Therefore, the light is efficiently incident on the optical waveguide 5 and the loss can be reduced.

At this time, the reflection surface 9a of the photonic crystal 9 is formed so that the output end 4b of the optical waveguide 4 and the input end 5b of the optical waveguide 5 have a geometrically conjugate relationship.
The reflected light can be more efficiently introduced into the optical waveguide 5. Since the traveling direction of the transmitted light incident on the photonic crystal 9 is determined depending on the wavelength,
The transmitted light does not diverge regardless of the shape of the reflection surface 9a. Therefore, even if the reflecting surface 9a of the photonic crystal 9 is concave, the transmitted light passing through the optical waveguide 6 is not adversely affected.

As in this embodiment, the photonic crystal 9
When the reflecting surface 9a is formed by a concave surface composed of a cylindrical surface, manufacture is easy. Light emitted from the output end 4b of the optical waveguide 4 also spreads in a direction perpendicular to the plane of the drawing. For this reason, it is preferable to form the reflection surface 9a so as to have a radius of curvature also in a direction perpendicular to the paper surface.

At this time, since the optical waveguide 4 and the optical waveguide 5 are arranged on the same plane, light is incident on the reflecting surface 9a at an angle as shown in FIG. Light enters the reflection surface 9a without being inclined. For this reason, the radius of curvature for optimally converging the reflected light differs between the horizontal plane and the vertical plane. Therefore, the reflecting surface 9a of the photonic crystal 9 is
When a toric surface having different radii of curvature is used in two orthogonal directions as shown in (1), the reflected light can be optimally focused in each direction, so that the efficiency can be further improved.

In FIG. 1, when lights of wavelengths .lambda.1 and .lambda.2 are input from output terminals 5a and 6a of optical waveguides 5 and 6 as indicated by broken arrows, light of wavelength .lambda. The light of wavelength λ2 is transmitted through the photonic crystal 9. As a result, light having wavelengths λ1 and λ2 can be extracted from the input terminal 4a of the optical waveguide 4, and the optical module 1 can be used as an optical multiplexer for combining lights having different wavelengths.

In FIG. 1, the photonic crystal 9
By changing the refractive index, period, and the like of the mediums 9c and 9d, it is possible to separate incident light according to the polarization direction. That is, an optical signal in which the TE mode light and the TM mode having different polarization directions are combined is input from the input terminal 4a, and the output terminals 5a, 6a
, The TE mode light and the TM mode light can be separated and extracted. Further, similarly to the above, it is also possible to combine lights having different polarization directions by reflection and transmission.

FIG. 6 shows an optical module 1 according to a second embodiment.
FIG. The same parts as those in the first embodiment of FIG. 1 are denoted by the same reference numerals. In the present embodiment, the media 9c and 9d (see FIG. 2) of the photonic crystal 9 have a different refractive index and periodic arrangement from those of the first embodiment, and the light transmitted through the photonic crystal 9 further differs depending on the wavelength. It can be emitted in any direction.

From the input terminal 4a of the optical waveguide 4, the wavelength λ1,
When the lights of λ2 and λ3 are multiplexed and input, the optical waveguide 4
From the output end 4b. The light of wavelength λ1 of the incident light incident on the photonic crystal 9 is reflected on the reflection surface 9a. The reflected light enters the optical waveguide 5, and the light having the wavelength λ1 is extracted from the output terminal 5a.

The light of wavelengths .lambda.2 and .lambda.3 incident on the photonic crystal 9 is refracted in different directions and transmits through the photonic crystal 9, and from the transmission surface 9b, the optical waveguides 6, 7 respectively.
Incident on. Then, the wavelength λ is output from the output terminals 6a and 7a.
2. Light of λ3 is extracted respectively. In this manner, the incident light in which the lights of the wavelengths λ1, λ2, and λ3 are multiplexed is separated, and demultiplexing can be performed. By setting the mediums 9c and 9d of the photonic crystal 9 to have different refractive indices and arrangement periods, it is possible to separate transmitted light at still another wavelength.

In the present embodiment, as in the first embodiment, the optical waveguides 5, 6, 7 and
From the output terminals 5a, 6a, 7a of the wavelength λ1, λ2, λ
When the lights of the wavelengths λ1 and λ3 are input, the light of the wavelength λ1 is reflected on the reflection surface 9a of the photonic crystal 9, and the lights of the wavelengths λ2 and λ3 are transmitted through the photonic crystal 9. As a result, it is possible to take out light obtained by combining lights of wavelengths λ1, λ2, λ3 from the input terminal 4a of the optical waveguide 4, and to use the optical module 1 as an optical multiplexer for combining lights having three different wavelengths. Can be.

In the first and second embodiments, the optical waveguides 4, 5, 6, and 7 are formed on the substrate 8 by film formation. However, even if light is guided using an optical fiber instead of the optical waveguide. Good. Further, a triangular lattice or a square lattice can be used as the type of lattice arrangement of the photonic crystal, and another lattice arrangement may be used. Further, a part having a non-uniform period may be provided in a part of the photonic crystal having a uniform periodic arrangement. This makes it possible to change characteristics such as transmission of only a specific wavelength.

[0031]

According to the present invention, by using a photonic crystal for an optical module for splitting and combining light, it is possible to easily separate or separate reflected light and transmitted light having different wavelengths and polarization directions into transmitted light. Transmitted light can be easily synthesized.
In addition, since the photonic crystal does not need to be multi-layered as in the related art, the number of steps can be reduced and the yield can be improved. Further, the photonic crystal can be integrally formed on the substrate, and the number of manufacturing steps can be further reduced without requiring a step of arranging the filter with high accuracy as in the related art.

Further, according to the present invention, since the reflection surface of the light reflecting the photonic crystal is concave, the light emitted from the output end of the narrow optical waveguide or the optical fiber toward the photonic crystal and spreads, When the light is reflected by the reflection surface, the light is converged, efficiently enters the output optical waveguide, and the loss can be reduced. If the reflecting surface is a cylindrical surface, manufacturing becomes easy and man-hours can be reduced. Further, when the reflecting surface is a toric surface, it is possible to focus the incident light on the spread in the two orthogonal directions, and it is possible to further reduce the loss.

[Brief description of the drawings]

FIG. 1 is a plan view showing an optical module according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a photonic crystal of the optical module according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a method for manufacturing a photonic crystal of the optical module according to the first embodiment of the present invention.

FIG. 4 is a main part detailed view showing the optical module according to the first embodiment of the present invention.

FIG. 5 is a perspective view showing a shape of a photonic crystal of the optical module according to the first embodiment of the present invention.

FIG. 6 is a plan view illustrating an optical module according to a second embodiment of the present invention.

FIG. 7 is a perspective view showing a conventional photodetector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical module 4, 5, 6, 7 Optical waveguide 3 Dielectric multilayer film filter 4a Input terminal 5a, 6a, 7a Output terminal 8 Substrate 9 Photonic crystal 9a Reflection surface 9b Transmission surface 9c, 9d Medium 10a, 10b Cladding 10c Slit 11a Lower cladding 11b Upper cladding

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hikaru Yokoyama 2-3-13 Azuchicho, Chuo-ku, Osaka City Inside Osaka International Building Minolta Co., Ltd. (72) Miyuki Teramoto 2-3-3 Azuchicho, Chuo-ku, Osaka-shi 13 Osaka International Building Minolta Co., Ltd. (72) Inventor Kojiro Sekine 2-3-1 Azuchicho, Chuo-ku, Osaka City Osaka International Building Minolta Co., Ltd. F-term (reference) 2H047 KB01 LA18 QA01 TA44

Claims (6)

[Claims] 1. A photonic crystal having a periodic structure having a plurality of media having different refractive indices, wherein the reflected light reflects incident light incident on the photonic crystal on a concave reflecting surface; An optical module, wherein the optical module is separated into transmitted light that transmits light. 2. A photonic crystal having a periodic structure having a plurality of media having different refractive indices, the reflected light being reflected by a concave reflecting surface of the photonic crystal, and the transmitted light being transmitted through the photonic crystal. An optical module characterized by combining the above. 3. The optical module according to claim 1, wherein wavelengths of light reflected by the photonic crystal and light transmitted therethrough are different from each other. 4. The polarization direction of light reflected from the photonic crystal and light transmitted through the photonic crystal are different from each other.
Alternatively, the optical module according to claim 2. 5. The optical module according to claim 1, wherein the photonic crystal has a two-dimensional periodic structure in which the media formed in a columnar shape are arranged. 6. The reflection surface according to claim 1, wherein said reflection surface is a toric surface or a cylindrical surface.
The optical module according to any one of the above.