JP2002131715A - Optical device and substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical device having a photonic crystal structure in which an optical integrated circuit can be easily formed. SOLUTION: The device is equipped with a first electrode, an electro-optic substrate made of a solid material formed on one surface of the first electrode, a photonic crystal region made of a solid material formed in the electro-optical substrate, a second electrode patterned on the surface of the photonic crystal region opposing to the first electrode, a means to apply a voltage between the first electrode and second electrode, a means to allow light to enter the photonic crystal region under the second electrode, and a means to receive the light guided by the photonic crystal region under the second electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an optical communication system,
Optical device and optical integrated circuit used for optical information system

[0002]

2. Description of the Related Art In recent years, photonic crystals have attracted attention as artificial crystals capable of controlling the wave state of light on the order of wavelength, and many studies have been made.

A photonic crystal is a material obtained by forming a change in the refractive index in a medium transparent to light with a period of about half the light wavelength in the medium.

It is well known that the behavior of a light wave in a photonic crystal can be understood as an analogy of the behavior of an electron wave in a semiconductor crystal. Just as an electron wave in a semiconductor crystal is Bragg-reflected by a periodic crystal structure to form an electron band structure, a light wave in a photonic crystal is scattered by a periodic refractive index change in a medium. Form a photonic band. Photonic crystals have unique optical properties such as a photonic band gap, which is a forbidden band for light, and high dispersibility for light, and are therefore expected to be applied to microminiature optical integrated circuits.

As a method for forming a two-dimensional photonic crystal, a method is known in which holes are periodically formed two-dimensionally in a slab optical waveguide. This method utilizes the fact that the waveguide and the hole have different refractive indexes. Japanese Patent Application Laid-Open No. H11-330619 discloses a method for producing a two-dimensional photonic crystal acting as an optical resonator by this method and realizing an ultra-small ultra-low threshold laser. The proposal in this publication utilizes the fact that light of a wavelength in a photonic band is strongly reflected by a photonic crystal. In addition, Journal of Japan Society of Applied Physics Vol. 68, 1335
Pages 1 to 1345 introduce an L-shaped steeply bent waveguide using a two-dimensional photonic crystal created by the above method. This waveguide uses a photonic crystal as a cladding, utilizing the fact that light of the wavelength in the photonic band is strongly reflected by the photonic crystal, and realizes a steeply bent waveguide, which was impossible in the past. It is assumed that. Japanese Patent Application Laid-Open No. H11-330619 discloses that a two-dimensional photonic crystal is formed by the above method,
We have proposed a method to realize a micro wavelength demultiplexer. This is a proposal utilizing the fact that a photonic crystal exhibits much higher light dispersion than a conventional optical crystal.

As a method of forming a three-dimensional photonic crystal, (a) a method of two-dimensionally periodically opening holes in a semiconductor multilayer film, and (b) a method of two-dimensionally oxidizing a specific layer of the semiconductor multilayer film. And (c) a method of three-dimensionally varying the layer structure of a semiconductor multilayer film is known. Method (a)
It is disclosed in JP-A-11-316154. In this method, two types of semiconductors having different refractive indices are alternately stacked to form a semiconductor multilayer film, and three-dimensional periodic refractive index changes are formed by periodically opening holes in the multilayer film. This is a method of making a photonic crystal. JP-A-11-1
No. 86657 discloses a method for producing a three-dimensional photonic crystal by this method and realizing a microminiature ultra-low threshold laser using the produced crystal as an optical resonator. The method (b) is disclosed in JP-A-2000-31587. In this method, a specific layer constituting a semiconductor multilayer film is oxidized two-dimensionally and periodically to form a photonic crystal. The method (c) is described in Journal of the Japan Society of Applied Physics, Vol. 68, pp. 1335-1345. In this method, two types of semiconductors having different refractive indices are alternately stacked on a substrate having two-dimensional periodic irregularities, and a layer structure having three-dimensional periodic irregularities is reflected by reflecting the irregularities of the substrate in the layer structure. This is a method of forming a three-dimensional photonic crystal by forming.

In addition, Japanese Patent Application Laid-Open No. 10-8305 discloses a method of forming a photonic crystal by opposing a diffraction grating having a metal film formed on the surface thereof and sandwiching an optically functional organic material between the diffraction gratings. Has been proposed.

Further, US Pat. No. 6,064,506 discloses a method of forming a photonic crystal in which a photonic band changes when a voltage is applied, using a nonlinear optical material whose refractive index changes with the application of a voltage. I have.

[0009]

However, in the prior art, it was difficult to form an optical integrated circuit using a photonic crystal. This is because an optical integrated circuit is composed of an optical waveguide having a complicated shape, but a photonic crystal waveguide having a complicated shape cannot be easily formed by the above-described conventional method.

For example, when an L-shaped optical waveguide is formed by two-dimensionally opening holes in a slab type waveguide or a semiconductor multilayer film, a material portion excluding the L-shaped waveguide core is
It is necessary to open holes two-dimensionally at a period of about half the wavelength, but it is difficult to mechanically open holes like this. Therefore, it is difficult to produce an optical integrated circuit having a waveguide having a more complicated shape by this method.

Japanese Patent Application Laid-Open No. HEI 200-200 for producing a photonic crystal by oxidizing a specific layer of a semiconductor multilayer film two-dimensionally and periodically.
The method disclosed in Japanese Patent Publication No. 0-31587 has a disadvantage that the material serving as the base of the photonic crystal is limited.

On the other hand, Japanese Patent Application Laid-Open No. 10-8300 discloses an optical functional organic material sandwiched between diffraction gratings having a metal film formed on the surface.
The method disclosed in Japanese Patent Application Laid-open No. 5-205 has a problem that it is difficult to keep the organic film thickness at a constant value, and is not suitable for producing a uniform photonic crystal.

Also, the above-mentioned US Pat. No. 6,064,506
The method disclosed in U.S. Pat.
Using lithography technology, a columnar structure is created two-dimensionally or three-dimensionally with an interval of about half the light wavelength, and the space formed between the structures is filled with a nonlinear optical material or liquid crystal material. I have. When such a very narrow space is filled with a liquid, voids are inevitably generated, so that it is extremely difficult to obtain an optically uniform photonic crystal.

As described above, in the conventional method, it has been difficult to produce a microminiature optical integrated circuit using a photonic crystal.

An object of the present invention is to provide an optical device having a photonic crystal structure made of a solid material that can easily form an optical integrated circuit.

An object of the present invention is to provide an optical device having a photonic crystal structure in which the photonic band structure and the photonic band gap can be changed.

Another object of the present invention is to provide an optical device having a photonic crystal structure which functions as an optical waveguide.

Another object of the present invention is to provide an optical device having a photonic crystal structure which functions as an electro-optical switch.

Another object of the present invention is to provide a linear type, an L-shaped type, and an S type.
An object of the present invention is to provide an optical device having a photonic crystal structure, which functions as a T-shaped optical waveguide.

Another object of the present invention is to provide an optical device having a photonic crystal structure which functions as an optical integrated circuit comprising an optical waveguide and an electro-optical switch.

Another object of the present invention is to provide an optical device having a photonic crystal structure which functions as a wavelength selection circuit.

Another object of the present invention is to provide an optical device having a photonic crystal structure, which functions as a crossed optical switch.

Another object of the present invention is to provide an optical device having a photonic crystal structure which functions as an optical exchanger.

[0024]

According to the present invention, electrodes are arranged on both surfaces of a photonic crystal made of a solid material formed in an electro-optical substrate made of a solid material, and a voltage is applied to the electrodes. An optical device is realized by changing the refractive index of the substrate in the photonic crystal region between the electrodes.

[0025]

DETAILED DESCRIPTION OF THE INVENTION In the prior art, a photonic crystal having a required photonic band was produced by mechanically or chemically changing the shape of the photonic crystal. Therefore, when an optical integrated circuit including an optical waveguide having a complicated shape is manufactured by the conventional technique, there is a problem that the process becomes complicated.

Incidentally, the photonic band structure also changes depending on the refractive index of the material serving as the base material of the photonic crystal. This can be easily understood from the fact that the refractive index of the material affects the wavelength of light traveling through the material.

Therefore, in the present invention, by arranging electrodes on both surfaces of the photonic crystal and applying a voltage, the refractive index of the substrate in the photonic crystal region is changed by the electro-optic effect. One electrode is provided as a common electrode on the entire surface of the substrate on which the photonic crystal is formed, and the other electrode is formed on the other surface of the substrate on which the photonic crystal is formed as a pattern corresponding to an optical device. Thereby, any optical device can be easily obtained. Hereinafter, the electrodes provided on the entire surface will be referred to as the first electrodes.
And the electrode formed as a pattern corresponding to the optical device will be referred to as a second electrode.

According to the present invention, by applying a voltage between the first electrode and the second electrode, the photonic band structure of the two-dimensional photonic crystal region in which the second electrode is installed is changed to the electro-optic effect. Can be changed.

The second electrode can be patterned into an arbitrary shape by using a photolithography technique used for producing a semiconductor device. Therefore, in the present invention, by appropriately setting the shape of the second electrode, a photonic crystal having a photonic band and a shape required for an optical integrated circuit can be obtained.
It can be formed by the electro-optic effect.

For example, according to the present invention, it is possible to produce an optical device characterized by acting as an optical waveguide. This device utilizes the fact that when a voltage is applied between the first electrode and the second electrode, the photonic band gap of the two-dimensional photonic crystal region where the second electrode is placed changes. This is realized by changing the photonic band gap so that guided light only passes through the portion where the second electrode is provided when a voltage is applied.

In this case, the shape of the optical waveguide is the second electrode shape. Therefore, according to the present invention, an optical waveguide having an arbitrary shape can be formed. For example, when the second electrode shape is linear, L-shaped, S-shaped, and T-shaped, linear, L-shaped, S-shaped, and T-shaped waveguides are formed, respectively. In the optical waveguide according to the present invention, a steeply bent waveguide unique to the photonic crystal waveguide is possible, and the path of the guided light can be bent by 90 degrees.

In the present invention, the second electrode 2 is provided.
To allow light to travel through the two-dimensional photonic crystal, a second
Of the electrode of the wavelength of light guided in the electro-optical substrate 2
1/2 or more.

According to the present invention, an optical device that functions as an electro-optical switch can be manufactured. Since the waveguide device according to the present invention is formed only when a voltage is applied between the first electrode and the second electrode, when the applied voltage is set to 0, the waveguide disappears. As described above, the optical waveguide of the present invention functions as an electro-optical switch that transmits light only when a voltage is applied to the photonic crystal.

Further, according to the present invention, an optical device characterized by acting as an optical integrated circuit comprising an optical waveguide and an electro-optical switch can be produced. This optical device is formed when a plurality of independent second elements are continuously arranged on a single two-dimensional photonic crystal surface on an electrode and a voltage is applied between the first and second electrodes. This is achieved by allowing a portion of the optical waveguide to act as an electro-optic switch.

Further, according to the present invention, it is possible to provide an optical device which functions as a wavelength demultiplexing optical circuit. In this optical device, a plurality of independent second electrodes are continuously arranged on a single two-dimensional photonic crystal surface on a first electrode, and a voltage applied between the electrodes and each pattern electrode is reduced. This is achieved by making them different.

Further, according to the present invention, it is possible to provide an optical device which functions as a cross-type optical switch. This device is realized by forming a cross-type optical circuit by the above-described optical waveguide forming method and enabling the photonic band gap at the crossing portion to be changed.

An optical switch is realized by forming an optical circuit in which a plurality of crossed optical switches are combined in a single two-dimensional photonic crystal.

Although any substrate may be used as the substrate constituting the present invention and exhibiting the electro-optical effect, it is preferable to use an inorganic material from the viewpoint of stability. For example, it has been conventionally used as an optical circuit substrate. Lithium niobate (LiNb
O3) can be used as the substrate.

As described above, according to the present invention, an optical integrated circuit having a photonic crystal structure can be formed electrically from a single two-dimensional photonic crystal in comparison with the prior art which requires complicated steps. Excellent.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, those having the same functions are denoted by the same reference numerals. In the following embodiment, an example using a two-dimensional photonic crystal in which holes are arranged in a square lattice shape will be described, but the present invention is not limited to the hole lattice shape of the two-dimensional photonic crystal. (First Embodiment) FIG. 1 shows the simplest embodiment 1 of the present invention.
FIG. 2 is a schematic diagram showing a perspective view from the top side, and FIG.
FIG. 4 is a cross-sectional view as viewed in the direction of the arrow at the AA position of FIG. FIG. 2 also shows a configuration for applying a voltage between the first electrode and the second electrode. In the figure, 1 is a first electrode, 2 is an electro-optic substrate on the electrode 1, 3 is a hole, 4 is a two-dimensional photonic crystal region formed in the substrate 2, 5 is a second electrode, 6 is Among the photonic crystal regions 4, a modified two-dimensional photonic crystal region 7 whose refractive index changes when a voltage is applied between the electrodes 1 and 5 is used for applying a voltage between the electrodes 1 and 5. A DC power supply 8 is an open / close switch. In the first embodiment, as shown in FIG.
The electrode 1, the electrode 5, and the electro-optical substrate 2 are formed so as to penetrate the electrode 1. The electrode 1, the electro-optical substrate 2, and the electrode 5 are formed in a predetermined shape, and then the holes 3 are formed. This is because it is easier to manufacture, and it is not necessary to form the holes 3 in the electrodes 1 and 5.

The arrangement cycle of the holes 3 is a in both the vertical and horizontal directions. The value of “a” is about の of the wavelength of light guided in the electro-optical substrate 2. For example, when the electro-optical substrate 2 is a photonic crystal for a wavelength band of 1.5 μm used in optical fiber communication, the value of a is about 0.5 μm.

In the first embodiment, when a voltage is applied between the electrodes 1 and 5 by the power supply 7, the portion of the two-dimensional photonic crystal region 4 to which the electric field is applied is a modified two-dimensional photonic crystal. A region 6 is formed, and the refractive index of this region changes due to the electro-optic effect.

The change in refractive index δn due to electro-optics is given by equation (1). δn = zE (1) where z is the electro-optic constant and E is the electric field strength. z
Is a positive or negative value, but it is known that the value of z is positive in many electro-optical materials. In this embodiment,
When an electro-optic material having a positive z is used for the electro-optic substrate 2 and a voltage is applied between the electrodes 1 and 5, the modified two-dimensional photonic crystal region 6 has a refractive index of the portion of the photonic crystal region 4. It was made to be larger than the refractive index.

FIG. 3A is a schematic diagram of the photonic band structure of the two-dimensional photonic crystal region 4. The position of the photonic band gap, which is the forbidden band for light, is indicated by a thick line. Since the modified two-dimensional photonic crystal region 6 is a part of the photonic crystal region 4, if no voltage is applied between the electrodes 1 and 5, that is, if the region is not modified, the photonic crystal region 6 The band structure is also shown in FIG.

When a voltage is applied between the electrodes 1 and 5, the refractive index of the modified two-dimensional photonic crystal region 6 increases due to the electro-optic effect. In general, when the refractive index increases by m times, the wavelength of light guided inside the photonic crystal region 4 in the region where the electrode 5 exists becomes 1 / m, and the wave number k
Becomes m times. On the other hand, since the energy of light does not change before and after the change in the refractive index, the photonic band when a voltage is applied between the electrodes 1 and 5 has a structure in which the scale on the vertical axis is multiplied by 1 / m. In this embodiment, the voltage V is applied between the electrodes 1 and 5.
Was applied, the refractive index of the modified two-dimensional photonic crystal region 6 was set to 1.18 times. Electrode 1,
FIG. 3 shows the photonic band structure of the modified two-dimensional photonic crystal region 6 when a voltage V is applied between the two regions.
(B).

As described above, in the first embodiment, the electrodes 1 and
By applying a voltage between the five, the photonic band structure of the modified two-dimensional photonic crystal region 6 can be changed.

The photonic band gap of FIG. 3B has a larger energy at the upper end and lower end of the band gap and a wider band gap width than that of FIG. 3A. As described above, in this embodiment, the photonic band gap of 6 can be changed by applying a voltage between the electrodes 1 and 5.

As described above, in this embodiment, by applying a voltage between the first electrode and the second electrode, the photonic band structure and the photonic band structure in the photonic crystal region where the pattern electrode is provided are provided. The band gap can be changed. Since the refractive index change δn due to the electro-optic effect increases in proportion to the applied electric field (Equation (1)), in the present embodiment, the photonic band of 6 is changed by changing the applied voltage between the electrodes 1 and 5. It is possible to continuously change the structure and the photonic band gap. FIG. 4 shows that the voltages applied between the electrodes 1 and 5 are 0, 1.
The change in the position of the photonic band gap of the modified two-dimensional photonic crystal region 6 when the voltage is changed to 0 V, 1.2 V, 1.3 V, and 1.5 V is shown. By increasing the applied voltage, the energy at the upper and lower ends of the band gap increases, and the width of the band gap increases.

FIGS. 5, 6 and 7 are sectional views showing the procedure for fabricating the optical device of the first embodiment. First, the electro-optic substrate 2
The electrodes 1 and 5 are formed on both surfaces of. As the electro-optical substrate 2, for example, lithium niobate LiNbO 3 is used, and the electrodes 1 and 5 are formed by depositing a metal such as aluminum on the surface of the electro-optical substrate 2. Subsequently, the electrode 5 is patterned by the photolithography technique used for producing a semiconductor element (FIG. 6). According to the current photolithography technology, a pattern electrode having a line width of about 0.1 μm can be formed. Finally, the holes 3 are formed using electron beam lithography and reactive ion beam etching.
Are formed periodically so as to penetrate the electrode 5, the electro-optical substrate 2, and the electrode 1, thereby obtaining the optical device of the first embodiment (FIG. 7).

When the electrodes 1 and 5 are made of aluminum and the electro-optical substrate 2 is made of lithium niobate, the holes 3
Holes can be selectively etched using optical photolithography technology and plasma etching technology used for manufacturing a semiconductor element. In the plasma etching using CH4 and O2, a chemical reaction shown in the following (Chem. 1) proceeds to generate an active species F.

Under this reaction condition, aluminum is oxidized to aluminum oxide, and can be etched by the active species F under the above reaction conditions. CF4 + O2 → COF2 + F + CO Further, lithium niobate can be etched by the active species F. Therefore, according to the above-mentioned plasma etching, the holes 1 can be formed by etching the electrodes 1 and 5 and the electro-optical substrate 2.

FIGS. 8A and 8B show an example of a method for applying a voltage between the electrodes 1 and 5. FIG. 7A, reference numeral 7 denotes an electric circuit as a voltage source, 8 denotes a metal substrate, 9 denotes an electrode of the voltage source 7, and 10 denotes a metal wire connecting the electrode 5 and the electrode 9. The electrode 1 is arranged so as to be in contact with and electrically connected to a metal substrate 8 connected to another electrode of the voltage source 7. The voltage source 7 generates a predetermined DC voltage between the metal substrate 8 and the electrode 9, and can apply a voltage between the electrodes 1 and 5 by the metal substrate 8 and the metal wires 10. In this way, by combining this embodiment with the electric circuit, a voltage can be applied between the electrodes 1 and 5.

(B), an insulating layer 100 made of, for example, SiO 2 is formed on the upper surface of the electro-optical substrate 2, and a wiring layer 10 ′ instead of the metal wire 10 is formed thereon.
This wiring layer 10 ′ is connected to the electrode 5 via a through hole formed in the insulating layer 100, and the metal wire 1 ′
01 is connected to the electrode 9. When the wiring layer 10 'is formed on the upper surface of the electro-optical substrate 2 as described above,
By providing an insulating layer about three times the thickness of the electro-optical substrate 2,
This wiring layer 10 ′ does not affect the two-dimensional photonic crystal region 4. (Second Embodiment) FIG. 9 is a perspective view of an embodiment of the optical device of the present invention acting as a linear optical waveguide, as viewed from the upper surface side. 1 is a first electrode, 2 is an electro-optical substrate, 3 is a hole,
4 is a two-dimensional photonic crystal region in the electro-optic substrate 2,
5 is a second electrode. In this embodiment, the linear electrode 5
Was used. The width of the electrode 5 was slightly larger than twice the arrangement period a of the holes 3. That is, the wavelength is set to be slightly longer than the wavelength of the light introduced into the waveguide configured in this embodiment. The same applies to the following embodiments. The region covered with the electrode 5 in the two-dimensional photonic crystal region 4 by applying a voltage between the electrodes 1 and 5 becomes a modified two-dimensional photonic crystal region. By applying a voltage between the electrodes 1 and 5, the refractive index of the modified two-dimensional photonic crystal region was increased by the electro-optic effect. Numerals 11 and 12 denote optical fibers, each of which is an end face of the electro-optical substrate 2 and an electrode 5.
Optically connected to the portion of the area covered with.

The arrangement period a of the electrode 1, the electro-optical substrate 2, the holes 3, and the holes 3 is the same as in the first embodiment. This embodiment is different from the first embodiment in that the electrodes 5 and 6 are linear.
This is different from the first embodiment. Therefore, the photonic band structure of the two-dimensional photonic crystal region 4 is as shown in FIG. The photonic band structure of the two-dimensional photonic crystal region modified by applying a voltage between the electrodes 1 and 5 changes according to the applied voltage between the electrodes 1 and 5, and the photonic band structure when the applied voltage is 0 FIG. 3A shows the photonic band structure when the applied voltage is V, and FIG.
(B).

When the light having the light energy A is incident on the end face of the electro-optical substrate 2 in the area covered with the electrode 5 by the optical fiber 11 without applying a voltage between the electrodes 1 and 5, the incident light is changed to the photonic band. Since the light is in the gap (Fig. 3
(See (a)) The light cannot be transmitted through the two-dimensional photonic crystal region 4 and is not output to the optical fiber 12. On the other hand, when a voltage V is applied between the electrodes 1 and 5, the photonic band structure of the modified two-dimensional photonic crystal region is as shown in FIG.
(B), the incident light can pass through the modified two-dimensional photonic crystal region. The photonic band structure of the two-dimensional photonic crystal region 4 excluding the modified two-dimensional photonic crystal region is shown in FIG. 3A regardless of the applied voltage. Therefore, the incident light cannot travel to the two-dimensional photonic crystal region 4 excluding the modified two-dimensional photonic crystal region, and is guided to the inside of the modified two-dimensional photonic crystal region and output to the optical fiber 12. You. As described above, in the present embodiment, when the voltage V is applied between the electrodes 1 and 5, the embodiment functions as a linear optical waveguide.

On the other hand, when no voltage is applied between the electrodes 1 and 5, this embodiment does not function as a waveguide. Therefore, in this embodiment, the transmission state of the light 6 can be controlled by the voltage between the electrodes 1 and 5. That is, when no voltage is applied between the electrodes 1 and 5, the optical fiber 11 and the optical fiber 12 are not optically connected.
When a voltage V is applied between 5, the optical fibers 11 and 12 are optically connected by a modified two-dimensional photonic crystal region. As described above, the present embodiment operates as an electro-optical switch by changing the voltage between the electrodes 1 and 5.

In this embodiment, FIGS. 8 (a) and 8 (b)
Although the same wiring as that described above is provided, the notation is omitted because the figure is only complicated. Also in the following embodiments, the description of the wiring is omitted. (Third Embodiment) FIG. 10 is a perspective view of an embodiment of the present invention acting as an L-shaped optical waveguide as viewed from the top side. 1 is a first electrode, 2 is an electro-optical substrate, 3 is a hole, 4 is a two-dimensional photonic crystal region in the electro-optical substrate 2, and 5 is a second electrode. The third embodiment differs from the second embodiment only in that the electrode 5 has an L-shape, and is otherwise the same. Also in this embodiment, when a voltage is applied to the electrodes 1 and 5, the portion of the two-dimensional photonic crystal region 4 covered by the electrode 5 becomes a modified two-dimensional photonic crystal region, and the second embodiment As in the example, the light incident from the optical fiber 11 is output to the optical fiber 12. As described above, the present embodiment acts as an L-shaped steep waveguide, and enables steeply bent waveguide characteristic of an optical waveguide having a photonic crystal structure.

When no voltage is applied between the electrodes 1 and 5, the third embodiment does not function as an optical waveguide as in the second embodiment. Therefore, in the third embodiment, the optical connection state between the optical fiber 11 and the optical fiber 12 can be changed by changing the voltage between the electrodes 1 and 5, and the device functions as an electro-optical switch. (Fourth Embodiment) FIG. 11 is a perspective view of an embodiment of the present invention acting as an S-shaped optical waveguide as viewed from above. 1 is a first electrode, 2 is an electro-optical substrate, 3 is a hole, 4 is a two-dimensional photonic crystal region in the electro-optical substrate 2, and 5 is a second electrode. The fourth embodiment differs from the second and third embodiments only in that the electrode 5 has an S-shape, and is otherwise the same.

Also in the fourth embodiment, the region covered with the S-shaped electrode 5 becomes a modified two-dimensional photonic crystal region when a voltage is applied between the electrodes 1 and 5. The photonic band structure of the two-dimensional photonic crystal region 4 and the photonic band structure of the two-dimensional photonic crystal region modified by applying a voltage are the same as those in the first embodiment (see FIGS. 3 and 4). .

As in the second and third embodiments, this embodiment functions as an optical waveguide. That is, when a voltage V is applied between the electrodes 1 and 5 and light having an optical energy of A is incident on the optical fiber 11, the incident light is guided to the optical fiber 12 through the modified two-dimensional photonic crystal region. Is output.
As described above, the present embodiment functions as an S-shaped steep waveguide using a steeply bent waveguide characteristic of an optical waveguide having a photonic crystal structure.

On the other hand, when no voltage is applied between the electrodes 1 and 5, this embodiment does not function as a waveguide, as in the second and third embodiments. Therefore, in the fourth embodiment, the optical connection between the optical fiber 11 and the optical fiber 12 can be changed by changing the voltage between the electrodes 1 and 5,
Acts as an electro-optic switch. (Fifth Embodiment) FIG. 12 is a perspective view of an embodiment of the present invention acting as a T-shaped optical waveguide, as viewed from above. 1 is a first electrode, 2 is an electro-optical substrate, 3 is a hole, 4 is a two-dimensional photonic crystal region in the electro-optical substrate 2, and 5 is a second electrode. The fifth embodiment is the same as the second embodiment except that the electrode 5 has a T-shape.

Also in the fifth embodiment, the region covered with the T-shaped electrode 5 becomes a modified two-dimensional photonic crystal region when a voltage is applied between the electrodes 1 and 5. The photonic band structure of the two-dimensional photonic crystal region 4 and the photonic band structure of the two-dimensional photonic crystal region modified by applying a voltage are the same as those in the first embodiment (see FIGS. 3 and 4). .

As in the second to fourth embodiments, this embodiment functions as an optical waveguide. That is, when a voltage V is applied between the electrodes 1 and 5 and light having an optical energy of A is made incident on the optical fiber 11, the incident light is guided through the modified two-dimensional photonic crystal region, and the T-shaped intersection is formed. And output to the optical fibers 12 and 13. As described above, the present embodiment functions as a T-shaped steep waveguide using a steeply bent waveguide characteristic of an optical waveguide having a photonic crystal structure.

On the other hand, when no voltage is applied between the electrodes 1 and 5, this embodiment does not function as a waveguide as in the second to fourth embodiments. Therefore, in the fifth embodiment, the optical connection between the optical fiber 11 and the optical fibers 12 and 13 can be changed by changing the voltage between the electrodes 1 and 5, and the device functions as an electro-optical switch.

As shown in the second to fifth embodiments described above, according to the present invention, an optical waveguide corresponding to the second electrode shape can be formed in the two-dimensional photonic crystal 4, and the formed waveguide is It can operate as an electro-optic switch. According to the present invention, by appropriately changing the shape of the second electrode, a photonic crystal waveguide and an electro-optic switch having an arbitrary shape can be produced, and a complicated optical integrated circuit can be produced. (Sixth Embodiment) FIG. 13 is a perspective view of an embodiment of the present invention acting as an optical integrated circuit comprising an optical waveguide and an electro-optical switch, as viewed from above. 1 is a first electrode, 2
Is an electro-optic substrate, 3 is a hole, 4 is 2 in the electro-optic substrate 2
The two-dimensional photonic crystal regions, 5 and 14 are the second electrodes. In the sixth embodiment, the second electrode is connected to the electrode 5 and the electrode 1
The second embodiment is different from the embodiment 2-5 only in that the first embodiment is divided into four parts and the two parts are arranged with a distance d therebetween. Therefore, when a voltage is applied between the electrodes 1 and 5 and between the electrodes 1 and 14, the electrodes 5 and 1 of the two-dimensional photonic crystal region 4
4 is a modified two-dimensional photonic crystal region 6, and the photonic band structures of the two-dimensional photonic crystal region 4 and the modified two-dimensional photonic crystal region are the same as those in the first embodiment. This is the same as in the example (FIGS. 3 and 4). Here, the distance d between the electrode 5 and the electrode 14 is made smaller than the hole cycle a of the two-dimensional photonic crystal region 4 and the hole 3 for forming the two-dimensional photonic crystal is not included at that position. , So that this region does not scatter or reflect light.

In the sixth embodiment, the optical fibers 11-13
Are provided in the same manner as in the fifth embodiment, but the electrode 5 and the electrode 1
4 and the voltage applied thereto is independently controlled. Therefore, the waveguide between the optical fibers 11 and 13 is guided through the modified two-dimensional photonic crystal region by applying a voltage V between the electrodes 1 and 5, but the gap between the optical fibers 11 and 13 is not limited to this. Since the region corresponding to the electrode 14 is not a modified two-dimensional photonic crystal region, no wave is guided. A voltage V is applied between the electrode 1 and the electrode 5 and between the electrode 1 and the electrode 14, and light with energy A is transmitted by the optical fiber 11.
When incident on the modified two-dimensional photonic crystal region,
The incident light is guided in this region, branched at the T-shaped part of the electrode 5, guided to the optical fiber 12, and also guided to the optical fiber 13.

As described above, in the sixth embodiment, the transmission of the light introduced from the optical fiber 11 is controlled by controlling the voltage applied to the electrode 5 and the electrode 14 independently.
It can function as an optical integrated circuit composed of an electro-optical switch and an optical waveguide that can be controlled by only the optical fiber 12 or both of the optical fibers 12 and 13. (Seventh Embodiment) As described with reference to FIG. 4, the photonic band of the voltage application portion of the two-dimensional photonic crystal region 4 changes depending on the applied voltage. By utilizing this, the above-described sixth embodiment (FIG. 13) can function as a wavelength selection circuit. FIG. 14 shows the photonic band gap of the modified two-dimensional photonic crystal region corresponding to the position of the electrode 14 when the applied voltage between the electrodes 1 and 14 is changed. When the applied voltage is V, this region allows light of energy E to pass but does not transmit light of energy D. When the applied voltage is 1.2 V, this region transmits both light of energy E and light of D. Similarly, the modified 2 corresponding to the position of electrode 5
Also in the case of a two-dimensional photonic crystal region, when the voltage applied between the electrodes 1 and 5 is V, this region transmits light of energy E but does not transmit light of energy D. When the applied voltage is 1.2 V, this region transmits both light of energy E and light of D.

Therefore, a voltage of 1.2 V between the electrodes 1 and 5;
A voltage of V is applied between the electrodes 1 and 14 so that the optical fiber 11
When both the light having energy E and the light having energy D are incident on the modified two-dimensional photonic crystal region, these lights are guided through the modified two-dimensional photonic crystal region corresponding to the electrode 5. Then, the light is branched at the T-shaped portion of the electrode 5, guided to the optical fiber 12, and also guided to the modified two-dimensional photonic crystal region corresponding to the electrode 14. Since a voltage of 1.2 V is applied between the electrodes 1 and 5, the optical fiber 12 can receive both light having energy E and light having energy D.
Since the voltage V is applied between the optical fibers 14, the optical fiber 13 can receive only light having energy E. As described above, the seventh embodiment can function as a wavelength selection circuit by controlling the voltage applied to the electrodes 5 and 14. (Eighth Embodiment) FIG. 15 is a perspective view seen from the top side of an embodiment of the present invention acting as a crossed optical switch.
1 is a first electrode, 2 is an electro-optic substrate, 3 is a hole, 4 is a two-dimensional photonic crystal region in the electro-optic substrate 2, 51,
52 is a second electrode and 18 is a third electrode. In the eighth embodiment, a V-shaped electrode 5 whose bottom is opposed to the second electrode 5
1, 52, and the third electrode 18 is V-shaped electrode 5
Embodiment 2-6 is that the optical fiber for transmitting and receiving light is arranged at the ends of the V-shaped electrodes 51 and 52, and the optical fibers for transmitting and receiving light are arranged at the ends of the V-shaped electrodes 51 and 52. The only difference is that the other is the same. The voltage applied to the electrodes 51 and 52 and the voltage applied to the electrode 18 are controlled independently. Here, the interval d between the electrodes 51 and 52 and the electrode 18 is made smaller than the hole period a of the two-dimensional photonic crystal region 4 and the hole 3 forming the two-dimensional photonic crystal is not included at that position. As in the sixth embodiment, this region does not scatter or reflect light.

Also in the eighth embodiment, when a voltage is applied between the electrodes 1 and 51 and between the electrodes 1 and 52, the area covered with the V-shaped electrode 5 is a modified two-dimensional photonic crystal area. Becomes The photonic band structure of the two-dimensional photonic crystal region 4 and the photonic band structure of the two-dimensional photonic crystal region modified by voltage application are the first.
(See FIGS. 3 and 4). As in Embodiment 2-6, also in this embodiment, the modified two-dimensional photonic crystal region functions as an optical waveguide. That is, when a voltage V is applied between the electrodes 1 and 51 and light having an optical energy of A is incident on the optical fiber 11, the incident light is guided to the optical fiber 12 through the modified two-dimensional photonic crystal region. Is output.

In the eighth embodiment, the third electrodes 18 are arranged at intervals d between the opposed bottoms of the V-shaped electrodes 51 and 52, respectively.
Since the voltage applied to the electrode 52 and the voltage applied to the electrode 18 are controlled independently, the voltage is applied only between the electrodes 1 and 51 and between the electrodes 1 and 52, and the optical energy is Is incident on the optical fiber 12 only. Because no voltage is applied to the electrode 18, the two-dimensional photonic crystal region corresponding to the electrode 18 does not become a modified two-dimensional photonic crystal region and does not function as an optical waveguide. Therefore, even if the two-dimensional photonic crystal region corresponding to the V-shaped electrode 51 becomes a modified two-dimensional photonic crystal region and guides light, the two-dimensional photonic crystal corresponding to the electrode 18 is guided. This is because, in the region, this light is blocked and does not propagate to the modified two-dimensional photonic crystal region corresponding to the V-shaped electrode 52.

On the other hand, when a voltage is applied between the electrodes 1 and 51 and between the electrodes 1 and 52 and a voltage V is also applied between the electrodes 1 and 18, the two-dimensional photo corresponding to the electrodes 51 and 52 is obtained. The nick crystal region becomes a modified two-dimensional photonic crystal region, and a region corresponding to the electrode 18 also becomes a modified two-dimensional photonic crystal region. Therefore, when light having an optical energy of A is incident on the optical fiber 11, the incident light is guided through the region corresponding to the electrode 18 and output to the optical fibers 13 and 17.

This function is reversible.
The same applies to the case where light of light energy A from No. 3 is incident. That is, between the electrodes 1 and 51, the electrodes 1 and 5,
When a voltage is applied only between the electrodes 2, the incident light is propagated only to the optical fiber 17, and between the electrodes 1 and 51 and between the electrodes 1 and 5.
When a voltage V is applied between the electrodes 1 and 18 while a voltage is applied between the two, the incident light is
12 as well.

As described above, in the eighth embodiment, the electrodes 1 and 18
By controlling the voltage applied between them, the output state of light can be changed, and it can function as a cross-type optical switch that can select a bar state or a cross state. (Ninth Embodiment) FIG. 16 is a plan view of an embodiment of the present invention acting as a 4 × 4 optical switch. This embodiment combines four cross-type optical switches of the eighth embodiment with 4 ×
4 constitutes an optical exchanger. This embodiment is shown in a plan view for simplification of the drawing, and the optical fiber is not shown. However, the basic structure is the same as that of the above-described embodiment. 1 is a first electrode, 2 is an electro-optical substrate, 3 is a hole,
4 is a two-dimensional photonic crystal region in the electro-optic substrate 2,
51, 52, 53 and 54 are second electrodes, 181-1
84 is a third electrode. In the ninth embodiment, the second electrodes are the W-shaped electrodes 51-52 whose bottoms face each other and the W-shaped electrodes 53-54 whose bottoms face each other, and the central parts of the electrodes 51 and 53 are integrated. Third electrodes 181-184
Between the opposite bottoms of the W-shaped electrodes 51-52 and W
Between the opposed bottoms of the U-shaped electrodes 53-54 by a distance d (not shown), and W
An optical fiber for transmitting and receiving light is arranged at the end of the U-shaped electrodes 51-54 (however, the illustration is omitted 9), and is different from the embodiments 2-6 and 8 only. Voltage applied to electrodes 51-54 and electrode 181-1
The voltage applied to 84 is independently controlled and selectively performed. Here, the interval d between the electrodes 51 and 52 and the electrode 18 is made smaller than the hole period a of the two-dimensional photonic crystal region 4 and the hole 3 forming the two-dimensional photonic crystal is not included at that position. As in the sixth embodiment, this region does not scatter or reflect light. .

In this embodiment, the second electrodes 51, 52, 5
Two-dimensional photonic crystal regions 4 at both ends of 3 and 54
At the positions corresponding to the incident light S1, S2,
S3 and S4 are added, but the third electrodes 181-184
By selectively applying a voltage between and the electrode 1, the light is switched to one of the output lights S1 ', S2', S3 'and S4'.

For example, a voltage V is applied between the electrode 1 and the electrodes 51, 52, 53 and 54, and the electrode 1 and the electrode 181-
When the incident light S1 to S4 having the energy A is incident in a state in which no voltage is applied to any of
Since only the two-dimensional photonic crystal regions at the positions corresponding to 1, 52, 53 and 54 are only modified two-dimensional photonic crystal regions, the incident light S1-S4 is
As a result of blocking the waveguide at the position corresponding to 81-184,
The light is output as output light S1 ', S2', S3 'and S4', respectively.

On the other hand, while the voltage V is applied between the electrode 1 and the electrodes 51, 52, 53 and 54, and the voltage is applied between the electrode 1 and the electrodes 181-184, the incident light having energy A When S1-S4 enters, the electrodes 51,
Only the two-dimensional photonic crystal regions at the positions corresponding to 52, 53 and 54 are not only the modified two-dimensional photonic crystal regions, but also the two-dimensional photonic crystal regions at the positions corresponding to the electrodes 181-184. The two-dimensional photonic crystal region, the incident light S1-S4
Will be guided at positions corresponding to the electrodes 181-184. As a result, the incident light S1 becomes the output light S4 ', the incident light S2 becomes the output light S2', and the incident light S3 becomes the output light S3 '.
The incident light S4 is output to the output light S1 '. (Other Embodiments) In the above embodiment, the electrode 1 covers the entire surface of the electro-optical substrate 2 forming the two-dimensional photonic crystal region 4, but the modified two-dimensional photonic crystal region 6 In order to form the electrode, it is sufficient that the electrode 1 is provided only in a portion corresponding to the pattern electrode 5. For example, a pattern electrode corresponding to the pattern electrode 5 is formed on an appropriate semiconductor substrate surface by lithography. The electro-optical substrate 2 may be formed thereon.

In the first embodiment, the holes 3 need only be formed periodically, and need not be formed perpendicular to the electro-optical substrate 2 as shown in FIG. This is because regions 4 and 6 interact with the photonic crystal as long as the holes are formed periodically. Second
The same applies to Examples 9 to 9.

[0078]

According to the present invention, an optical waveguide having a photonic crystal structure of an arbitrary shape, an electro-optical switch, an optical integrated circuit comprising them, a wavelength selection circuit, a cross-type optical switch, and an optical switch can be integrated into a single two-dimensional structure. It can be easily formed using a photonic crystal. According to the present invention, it is possible to electrically form a micro optical integrated circuit utilizing the characteristics of a photonic crystal. INDUSTRIAL APPLICABILITY The present invention can be used for an optoelectronic technology in which an optical signal and an electric signal coexist, for example, an optical interconnection technology.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the simplest embodiment 1 of the present invention in the form of a perspective view from the top side.

FIG. 2 is a sectional view taken along the line AA in FIG.

3A is a schematic diagram of a photonic band structure in a two-dimensional photonic crystal region, and FIG. 3B is a schematic diagram of a photonic band structure in a modified photonic crystal region.

FIG. 4 is a diagram showing a change in the position of a photonic band gap in a modified two-dimensional photonic crystal region when a voltage applied between electrodes sandwiching the two-dimensional photonic crystal region is changed.

FIG. 5 is a sectional view showing one of the procedures for producing the optical device of the first embodiment.

FIG. 6 is a cross-sectional view showing a procedure of manufacturing the optical device of the first embodiment following FIG. 5;

FIG. 7 is a cross-sectional view showing a procedure of manufacturing the optical device of the first embodiment following FIG. 6;

FIGS. 8A and 8B are diagrams illustrating an example of a method of applying a voltage between electrodes sandwiching the two-dimensional photonic crystal region according to the first embodiment.

FIG. 9 is a perspective view of Example 2 of the optical device of the present invention acting as a linear optical waveguide, as viewed from above.

FIG. 10 is a perspective view of Embodiment 3 of the present invention acting as an L-shaped optical waveguide, as viewed from above.

FIG. 11 is a perspective view of Example 4 of the present invention acting as an S-shaped optical waveguide, as viewed from above.

FIG. 12 is a perspective view of Embodiment 5 of the present invention acting as a T-shaped optical waveguide, as viewed from above.

FIG. 13 is a perspective view of the sixth embodiment of the present invention, which functions as an optical integrated circuit including an optical waveguide and an electro-optical switch, as viewed from above.

FIG. 14 is a diagram illustrating a photonic band gap of a modified two-dimensional photonic crystal region for causing the electro-optic switch of FIG. 13 to function as the wavelength selection circuit of the seventh embodiment.

FIG. 15 is a perspective view of Embodiment 8 of the present invention acting as a cross-type optical switch as viewed from above.

FIG. 16 is a plan view of Embodiment 9 of the present invention acting as a 4 × 4 optical switch;

[Explanation of symbols]

1: first electrode, 2: electro-optical substrate, 3: hole, 4: 2
Two-dimensional photonic crystal region, 5, 51-54: second electrode, 6: modified two-dimensional photonic crystal region, 7:
Electric circuit, 8: metal substrate, 9: electrode of electric circuit 7, 1
0: metal wire, 11-13, 17: optical fiber,
18, 181-184: third electrode.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H047 KA03 NA02 PA21 RA08 2H079 AA02 AA12 BA01 BA03 CA01 CA05 CA07 DA03 EA03 EA04 EA05 EB12 EB15 KA08 KA20 2K002 AA01 AA02 AB04 AB34 BA06 CA03 DA06 DA07 EA07 EB07 EA07 EB07 EA07 EB09 HA03

Claims (11)

[Claims] A first electrode, an electro-optic substrate made of a solid material formed on one surface of the first electrode, a photonic crystal region made of the solid material formed in the electro-optic substrate, A second pattern formed on the surface of the photonic crystal region facing the first electrode so as to have a width of at least half the wavelength of light guided in the electro-optic substrate.
An electrode, a means for applying a voltage between the first electrode and the second electrode, an irradiator for irradiating light to a photonic crystal region below the second electrode, and a device under the second electrode And a light receiver for receiving light guided by the photonic crystal region. 2. The method according to claim 1, wherein the second electrode is separated into two or more, and the separated electrode is close to about １ ／ of a wavelength of light incident on a photonic crystal region below the second electrode. 2. The optical device according to claim 1, wherein the optical devices are arranged in such a manner that the voltages applied to the respective electrodes are independently controlled. 3. A third independent electrode is placed between the two separated second electrodes so as to be close to about の of the wavelength of light incident on a photonic crystal region below the second electrode. 3. The optical device according to claim 2, wherein the voltage applied to the second electrode and the voltage applied to the third independent electrode are independently controlled. 4. A layer of an insulating material is formed on an upper surface of the electro-optical substrate, and the second or third electrode uses a conductor led out through a through hole formed in the layer of the insulating material. The optical device according to any one of claims 1 to 3, wherein the voltage is applied as the voltage. 5. An electro-optic substrate made of a solid material, a photonic crystal region made of a solid material formed in the electro-optic substrate, and a first pattern formed in the same pattern on both surfaces of the photonic crystal region. And a second electrode, means for applying a voltage between the first electrode and the second electrode, an irradiator for irradiating light to a photonic crystal region below the second electrode, and An optical device comprising: a light receiver that receives light guided by the photonic crystal region below the second electrode. 6. The photonic crystal region corresponding to the pattern of the electrode includes a linear, L-shaped, S-shaped, and T-shaped optical waveguide, an electro-optical switch, a wavelength selection circuit, a crossed optical switch, and light. The optical device according to any one of claims 1 to 5, which functions as an optical integrated circuit including an exchanger, an optical waveguide, and an electro-optical switch. 7. A first electrode, an electro-optic substrate made of a solid material formed on one surface of the first electrode, a photonic crystal region made of the solid material formed in the electro-optic substrate, A second pattern formed on the surface of the photonic crystal region facing the first electrode so as to have a width of at least half the wavelength of light guided in the electro-optic substrate.
And a means for applying a voltage between the first electrode and the second electrode. 8. The second electrode is separated into two or more, and the separated electrode is close to about の of the wavelength of light incident on a photonic crystal region below the second electrode. 8. The substrate for an optical device according to claim 7, wherein the voltage applied to each electrode is independently controlled. 9. A third independent electrode is placed between the two separated second electrodes so as to be close to about 波長 of the wavelength of light incident on a photonic crystal region below the second electrode. 9. The optical device substrate according to claim 8, wherein the voltage applied to the second electrode and the voltage applied to the third independent electrode are independently controlled. 10. A layer of an insulating material is formed on the upper surface of the electro-optical substrate, and the second or third electrode uses a conductor led out through a through hole formed in the layer of the insulating material. 10. A voltage is applied as a result.
The optical device substrate according to any one of the above. 11. An electro-optic substrate made of a solid material, a photonic crystal region made of a solid material formed in the electro-optic substrate, and a first pattern formed in the same pattern on both surfaces of the photonic crystal region. An optical device substrate comprising: a first electrode and a second electrode; and means for applying a voltage between the first electrode and the second electrode.