WO2002033478A1

WO2002033478A1 - Optical device and substrate

Info

Publication number: WO2002033478A1
Application number: PCT/JP2001/007212
Authority: WO
Inventors: Tomoyuki Hamada; Toshio Katsuyama; Masayoshi Ishibashi; Masashi Kiguchi
Original assignee: Hitachi, Ltd.
Priority date: 2000-10-19
Filing date: 2001-08-23
Publication date: 2002-04-25
Also published as: JP2002131715A; JP3586635B2

Abstract

An optical device of photonic crystal structure for constituting an optical integrated circuit readily comprising a first electrode, an electro-optical substrate provided on one surface of the first electrode and made of a solid material, a photonic crystal structure region provided in the electro-optical substrate and made of a solid material, a second electrode provided in the photonic crystal region and formed in a pattern on the surface opposed to the one surface, a means for applying a voltage between the first and second electrodes, means for directing a light beam to the photonic crystal region under the second electrode, and means for receiving the light beam guided by the photonic crystal structure region under the second electrode.

Description

Clear ^

Optical devices and substrates Technical field

The present invention relates to an optical communication system, an optical element used in an optical information system, and an optical integrated circuit.

In recent years, photonic crystal structures have attracted attention as a material structure that can control the wave state of light in the order of wavelength, and many studies have been made on them. A photonic crystal structure is a _t- photonic crystal structure that is a material structure obtained by forming a refractive index change with a period of about half the light wavelength in a medium in a medium transparent to light. The behavior of the light wave can be understood as an analogy of the behavior of the electron wave in the 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 structure is subject to a periodic change in refractive index in a medium. It is scattered to form a photonic band. Photonic crystal structures have unique optical properties not found in conventional materials, such as the photonic bandgap, which is a forbidden band for light, and high dispersibility for light. Application is expected.

The photonic crystal structure includes a two-dimensional photonic crystal structure having a two-dimensional periodic refractive index change and a three-dimensional photonic crystal structure having a three-dimensional periodic refractive index change.

As a method of creating a two-dimensional photonic crystal structure, a method of two-dimensionally opening holes in a slab optical waveguide is known. This method utilizes the fact that the waveguide and the hole have different refractive indices. For example, Japanese Patent Application Laid-Open No. H11-313609 discloses a two-dimensional photonic crystal structure acting as an optical co-twist by using this method to realize an ultra-compact ultra-low threshold laser. A method for doing so is disclosed. The proposal in the publication is It utilizes the fact that light of the wavelength in the band is strongly reflected by the photonic crystal structure. In the Journal of the Japan Society of Applied Physics, Vol. 68, pp. 1335, pp. 1 345, an L-shaped steeply bent waveguide using a two-dimensional photonic crystal structure created by the above method is introduced. ing. This waveguide uses a photonic crystal structure as a clad, utilizing the fact that light of a wavelength in the photonic band is strongly reflected by the photonic crystal structure, and is not possible in the past. The above-mentioned Japanese Patent Application Laid-Open No. H11-313609 discloses a two-dimensional photonic crystal structure formed by the above-described method, and furthermore, an ultra-small wavelength A method to realize a wave circuit is also proposed. This is a proposal that utilizes the fact that the photonic crystal structure exhibits much higher light dispersion than conventional optical crystals.

The three-dimensional photonic crystal structure can be prepared by (a) a method of periodically opening holes in a semiconductor multilayer film, or (b) a method of two-dimensionally oxidizing a specific layer of the semiconductor multilayer film. (C) A method of three-dimensionally varying the layer structure of a semiconductor multilayer film is known. The method (a) is disclosed in, for example, Japanese Patent Application Laid-Open No. 11-316154. In this method, two types of semiconductors having different refractive indices are alternately stacked to form a semiconductor multilayer film, and holes are periodically opened in the multilayer film to periodically change the refractive index three-dimensionally. This is a method of forming a three-dimensional photonic crystal structure by forming For example, Japanese Unexamined Patent Publication No. Hei 11-1986657 discloses that a three-dimensional photonic crystal structure is created by this method, and the ultra-small ultra-low threshold laser using the created crystal structure as an optical resonator. Are disclosed. The method (b) is disclosed in, for example, JP-A-2000-31587. In this method, a specific layer constituting a semiconductor multilayer film is oxidized two-dimensionally and periodically to create a three-dimensional photonic crystal structure. The method (c) is described, for example, in the Journal of the Japan Society of Applied Physics, Vol. 68, pp. 135-135. In this method, two types of semiconductors having different refractive indices are alternately laminated on a substrate having two-dimensional periodic irregularities, and three-dimensional periodic irregularities are reflected by reflecting the irregularities of the substrate in the layer structure. This is a method of obtaining a three-dimensional photonic crystal structure by forming a layer structure having the same.

For example, Japanese Patent Application Laid-Open No. 10-83005 discloses that a diffraction grating substrate having a metal film formed on its surface is opposed to an optically functional organic material sandwiched between the diffraction grating substrates. A method for creating a more photonic crystal structure has been proposed.

Further, for example, US Pat. No. 6,064,506 discloses a photonic device in which a photonic band changes when a voltage is applied by using a nonlinear optical material whose refractive index changes according to the voltage applied. A method for constructing a crystal structure is shown. Disclosure of the invention

However, it has been difficult to form an optical integrated circuit with a photonic crystal structure using conventional techniques. The optical integrated circuit is composed of an optical waveguide having a complicated shape, but the conventional method cannot easily produce a waveguide having a photonic crystal structure having a complicated shape.

For example, when an L-shaped optical waveguide is created by two-dimensionally opening holes in a slab waveguide or a semiconductor multilayer film, the material portion excluding the L-shaped waveguide core has a half of the wavelength. It is necessary to make holes two-dimensionally periodically with a small period, but it is difficult to open such holes mechanically. Therefore, with this method, it is difficult to produce an optical integrated circuit having a waveguide having a more complicated shape. Also, the method disclosed in Japanese Patent Application Laid-Open No. 2000-31587, in which a specific layer of a semiconductor multilayer film is oxidized two-dimensionally periodically to form a photonic crystal structure, is disclosed in Japanese Patent Application Laid-Open No. 2000-310587. However, there is a disadvantage that the material used is limited. On the other hand, the method disclosed in Japanese Patent Application Laid-Open No. H10-83005, in which an optically functional organic material is sandwiched between diffraction grating substrates having a metal film formed on the surface, maintains the organic thickness at a constant value. However, it is difficult to create a uniform photonic crystal structure. In the method disclosed in the above-mentioned U.S. Pat. No. 6,064,506, a columnar structure is formed at an interval of about half the light wavelength using a lithographic technique from a material having a high refractive index. Two-dimensional or three-dimensional structures are created, and the space formed between the structures is filled with nonlinear optical material or liquid crystal material. When such a very narrow space is filled with a liquid, voids are inevitably generated, and it is extremely difficult to obtain an optically uniform photonic crystal structure. Thus, it has been difficult with the conventional method to fabricate a microminiature optical integrated circuit using a photonic crystal structure.

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 capable of changing a photonic band structure and a photonic band gap.

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

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

Another object of the present invention is to provide an optical device having a photonic crystal structure acting as a linear, L-shaped, S-shaped, acute-angled, obtuse-angled, arc-shaped, or T-shaped optical waveguide. In the provision of vice.

Another object of the present invention, another object of _t present invention is to provide an optical device of photonic crystal structure, which acts as a light collector product circuit consisting of optical waveguides and electro-optical sweep rate Tutsi includes a wavelength selection circuit It is an object of the present invention to provide an optical device having a photonic crystal structure that acts as a photonic crystal.

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

Another object of the present invention is to provide an optical device having a photonic crystal structure that functions as an optical exchanger. Another object of the present invention is to provide an optical waveguide having a photonic crystal structure in which the optical circuit structure is variable, an electro-optic switch, an optical circuit including the optical waveguide and the electro-optic switch, a wavelength selection circuit, and a crossing. It is to provide an optical device that operates as a type optical switch or optical switch.

Another object of the present invention is to provide a substrate for a device using the above light. According to the present invention, electrodes are arranged on both sides of a photonic crystal structure formed in a solid material formed in an electro-optical substrate made of a solid material, and a voltage is applied to the electrodes, whereby electrodes are formed. An optical device is realized by changing the refractive index of the substrate in the region of the photonic crystal structure in the sandwiched region. BRIEF DESCRIPTION OF THE FIGURES

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 cross-sectional view taken along line AA in FIG.

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

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

FIG. 5 is a cross-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 for manufacturing the optical device of Example 1 following FIG.

FIG. 7 is a cross-sectional view showing a procedure for manufacturing the optical device of Example 1 following FIG.

FIGS. 8 (a) and (b) are diagrams showing an example of a method of applying a voltage between the electrodes sandwiching the two-dimensional photonic crystal region of the first embodiment. FIG. 9 is a sectional view of the second embodiment.

1 0 _t Figure 1 1 is a cross-sectional view showing one step in creating optical devices of Example 2 is a sectional view showing a procedure for creating optical devices in Example 2 which is subsequent to FIG. 1 0.

FIG. 12 is a cross-sectional view showing a procedure for manufacturing the optical device of Example 2 following FIG. 11.

FIG. 13 is a cross-sectional view illustrating a procedure for manufacturing the optical device of Example 2 following FIG.

FIG. 14 is a perspective view of Example 4 of the optical device of the present invention acting as a linear optical waveguide, as viewed from above.

FIG. 15 is a perspective view of Example 4 of the present invention acting as an L-shaped optical waveguide, as viewed from above.

FIG. 16 is a perspective view of Example 4 of the present invention acting as an S-shaped optical waveguide, as viewed from above.

FIG. 17 is a perspective view of Example 4 of the present invention acting as an acute angle optical waveguide, as viewed from above.

FIG. 18 is a perspective view of Example 4 of the present invention acting as an obtuse angle optical waveguide, as viewed from above.

FIG. 19 is a perspective view of Example 4 of the present invention acting as an arc-shaped optical waveguide, as viewed from above.

FIG. 20 is a perspective view of Example 5 of the present invention acting as a T-shaped optical waveguide, as viewed from above.

FIG. 21 is a perspective view of Example 6 of the present invention acting as an optical integrated circuit including an optical waveguide and an electro-optic switch, as viewed from above.

FIG. 22 is a diagram illustrating a photonic band gap of a modified two-dimensional photonic crystal structure region for causing the electro-optic switch of FIG. 13 to function as the wavelength selection circuit of the seventh embodiment.

FIG. 23 shows the top side of the eighth embodiment of the present invention acting as a crossed optical switch. It is the perspective view seen from.

FIG. 24 is a plan view of Embodiment 9 of the present invention acting as a 4 × 4 optical switch.

FIG. 25 is a schematic diagram showing Example 10 of the present invention in the form of a perspective view from above.

FIG. 26 is a perspective view of the optical device of Example 10 acting as an L-shaped or T-shaped optical waveguide, as viewed from the upper surface side.

FIG. 27 is a perspective view of the optical device of Example 10 acting as an intersecting optical switch in a bar state, as viewed from the upper surface side.

FIG. 28 is a perspective view of the optical device of Example 10 acting as a cross-type optical switch in a cross state, as viewed from the upper surface side. BEST MODE FOR CARRYING OUT THE INVENTION

In the prior art, the shape of the photonic crystal structure was mechanically or chemically changed to create a photonic crystal structure having a required photonic band. For this reason, there is a problem that the process becomes complicated when an optical integrated circuit composed of an optical waveguide having a complicated shape is produced by the conventional technology.

By the way, the photonic band structure also changes depending on the refractive index of the material that is the base of the photonic crystal structure. This can be easily understood from the fact that the refractive index of a 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 structure and applying a voltage, the refractive index of the substrate in the photonic crystal structure region is changed by the electro-optic effect. One electrode is provided as a common electrode on the entire surface of the substrate forming the photonic crystal structure, and the other electrode is provided on the other surface of the substrate forming the photonic crystal structure for the optical device. By forming the pattern, any optical device can be easily obtained. Below, electrodes provided on the entire surface Is referred to as a first electrode, and an electrode formed as a pattern corresponding to an optical device is referred to as a second electrode.

-In 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 structure region where the second electrode is installed is electrically controlled. It can be changed by the optical effect. Then, the second electrode can be patterned into an arbitrary shape by using a photolithography technique used for producing a semiconductor element. Therefore, in the present invention, by appropriately setting the shape of the second electrode, a photonic crystal structure having a photonic band and a shape required for an optical integrated circuit can be formed by the electro-optic effect.

For example, according to the present invention, an optical device acting as an optical waveguide can be produced. 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 structure region where the second electrode is installed changes. This is realized by changing the photonic band gap so that the 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, and therefore, according to the present invention, a waveguide having an arbitrary shape can be formed. For example, if the second electrode shape is linear, L-shaped, S-shaped, acute-angled, obtuse-angled, arc-shaped, and T-shaped, respectively, linear, L-shaped, S-shaped, acute-angled, obtuse-angled Shaped, arc-shaped and T-shaped waveguides are formed. In the optical waveguide according to the present invention, a sharply bent waveguide unique to a photonic crystal structure waveguide is possible, and the path of the guided light can be bent by 90 degrees.

In the present invention, the width of the second electrode is set to one of the wavelengths of the light guided in the electro-optical substrate 2 so that the light can travel in the two-dimensional photonic crystal structure on which the second electrode is provided. / 2 or more.

According to the present invention, an optical device that acts as an electro-optic switch is created. it can. 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, the waveguide disappears when the applied voltage is set to zero. Thus, the optical waveguide of the present invention acts as an electro-optic switch that transmits light only when a voltage is applied to the photonic crystal structure.

Further, according to the present invention, it is possible to produce an optical device that functions as an optical integrated circuit including an optical waveguide and an electro-optic switch. This optical device has a plurality of independent second electrodes continuously placed on the surface of a single two-dimensional photonic crystal structure on the electrodes, and a voltage between the first and second electrodes. This is realized by making a part of the optical waveguide formed when the voltage is applied act as an electro-optic switch.

Further, according to the present invention, it is possible to provide an optical device that 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 structure surface on a first electrode, and a space between the electrode and each pattern electrode is provided. This is realized by making the voltage applied to the power supply different.

Further, according to the present invention, it is possible to provide an optical device that operates as a cross-type optical switch. This device is realized by forming an intersecting optical circuit by the above-described optical waveguide forming method, and enabling the photonic band gap at the intersecting 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 structure.

Further, according to the present invention, an optical waveguide having a photonic crystal structure in which the optical circuit structure is variable, an electro-optical switch, an optical circuit including the optical waveguide and the electro-optical switch, a wavelength selection circuit, and a cross-type optical switch are provided. Or an optical device that acts as an optical switch. In this optical device, a plurality of independent second electrodes are successively arranged in a matrix on a single two-dimensional photonic crystal structure surface on a first electrode, and a desired optical circuit structure is formed. 2D photo Achieved by selecting multiple second electrodes to be formed by the electro-optic effect in the nick crystal structure and applying a voltage between the first electrode and the selected second electrode Is done. By making the voltage applied between the first electrode and the selected second electrode different from each other, a wavelength selection circuit, a cross-type optical switch, and an optical switch are realized.

Any material may be used as the substrate exhibiting the electro-optical effect that constitutes the present invention. It is preferable to use an inorganic material from the viewpoint of force stability. For example, niobium conventionally used as an optical circuit substrate lithium acid (L i N b 0 ₃₎ may 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 structure, which is superior to the conventional technology requiring complicated processes. ing.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the figure, components having the same function are denoted by the same reference numerals. Embodiments of the present invention relate to the basic configuration of the invention (Examples 1 and 2), and those in which a single second electrode is provided on the surface of a two-dimensional photonic crystal structure (Examples 3 to 5). A plurality of second electrodes arranged continuously (Examples 6 to 9); and a plurality of second electrodes arranged in matrix (Example 10). are categorized.

In the following embodiments, an example is shown in which a two-dimensional photonic crystal structure in which holes are arranged in a square lattice shape is used. However, the present invention is limited to the hole lattice shape of the two-dimensional photonic crystal structure. Not done.

(First embodiment: embodiment relating to basic configuration)

In this embodiment, a specific example of the most basic configuration of the present invention will be described.

FIG. 1 is a schematic diagram showing the simplest embodiment 1 of the present invention in the form of a perspective view from the upper surface side, and FIG. 2 is a cross-sectional view taken along the line AA in FIG. In Fig. 2, it is also necessary to apply a voltage between the first electrode and the second electrode. Is also shown. 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 structure region formed in the substrate 2, 5 is a second electrode, 6 Is a modified two-dimensional photonic crystal structure region whose refractive index changes when a voltage is applied between the electrodes 1 and 5 in the photonic crystal structure region 4, and 7 is a voltage applied between the electrodes 1 and 5. A DC power supply 8 is an open / close switch. In the first embodiment, as shown in FIG. 2, the holes 3 are formed so as to penetrate the electrode 1, the electrode 5, and the electro-optical substrate 2. Since it is easier to form holes 3 after forming electrodes 5 and electrodes 5 in a predetermined shape, it is not inevitable to form holes 3 in electrodes 1 and 5.

The arrangement period of the holes 3 is a in both the vertical and horizontal directions. The value of “a” is about 1 Z 2 of the wavelength of light guided in the electro-optical substrate 2. For example, when the electro-optical substrate 2 has a photonic crystal structure for a 1.5 m wavelength band used in one optical fiber communication, the value of a is about 0.5 / z m.

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 structure region 4 to which the electric field is applied is a modified two-dimensional photonic crystal. This becomes the structural region 6, where the refractive index changes due to the electro-optic effect.

The change in refractive index δ η due to electro-optics is given by equation (1).

δ η = ζ Ε (1)

Where ζ is the electro-optic constant and Ε is the electric field strength. ζ is a positive or negative value, but it is known that the value of ζ is positive in many electro-optic materials. In this embodiment, an electro-optic material having a positive ζ is used for the electro-optic substrate 2, and when a voltage is applied between the electrodes 1 and 5, the modified two-dimensional photonic crystal region 6 has a modified refractive index. The refractive index was set to be larger than the refractive index of the photonic crystal structure region 4.

FIG. 3A is a schematic diagram of the photonic band structure of the two-dimensional photonic crystal structure region 4. Photonic band, a forbidden zone against light The position of the gap is indicated by a bold line. Since the modified two-dimensional photonic crystal structure 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 band structure is also shown in Fig. 3 (a).

When a voltage is applied between the electrodes 1 and 5, the refractive index of the modified two-dimensional photonic crystal structure region 6 increases due to the electro-optic effect. Generally, 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 Zm, and the wave number k becomes m times. . —On the other hand, since the light energy 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 that is 1 / m times the scale of the vertical axis.

In this embodiment, when a voltage V is applied between the electrodes 1 and 5, the refractive index of the electro-optic substrate constituting the modified two-dimensional photonic crystal structure region 6 is set to 1.18 times. Figure 3 (b) shows the photonic band structure of the modified two-dimensional photonic crystal structure region 6 when a voltage V is applied between the electrodes 1 and 5.

Thus, in the first embodiment, by applying a voltage between the electrodes 1 and 5, the photonic band structure of the modified two-dimensional photonic crystal structure region 6 can be changed.

The photonic band gap in FIG. 3 (b) has larger energy at the upper and lower ends of the band gap and a wider band gap than that in FIG. 3 (a). As described above, in the present embodiment, by applying a voltage between the electrodes 1 and 5, the photonic node gap of the two-dimensional photonic crystal structure region 6 can be changed.

As described above, in the present embodiment, by applying a voltage between the first electrode and the second electrode, the photonic band of the photonic crystal structure region where the pattern electrode is provided is set. The structure and photonic band gap can be varied. The refractive index change δn due to the electro-optic effect is As can be seen from Eq. (1), the voltage increases in proportion to the applied electric field E. In this embodiment, by changing the applied voltage between the electrodes 1 and 5, the photon of the two-dimensional photonic crystal structure region 6 is changed. It is possible to continuously change the tonic band structure and the photonic band gap. Figure 4 shows the modified two-dimensional photonic crystal region 6 when the voltage applied between electrodes 1 and 5 is changed to 0, 1.0 V, 1.2 V, 1.3 V, and 1.5 V. The change in the position of the photonic bandgap 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.

5, 6 and 7 are sectional views showing a procedure for manufacturing the optical device of the first embodiment. First, electrodes 1 and 5 are formed on both sides of the electro-optic substrate 2 (FIG. 5). As the electro-optical substrate 2, for example, lithium niobate LiNbO ₃ is used. 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 optical lithography technique used for semiconductor device fabrication (FIG. 6). According to the current optical lithography technology, a pattern electrode having a line width of about 0.1 ηα can be formed. Finally, by using electron beam lithography and reactive ion beam etching, the holes 3 are periodically formed so as to penetrate through the electrode 5, the electro-optic substrate 2, and the electrode 1, and the present embodiment is performed. The optical device of Example 1 is obtained (Fig. 7).

When the electrodes 1 and 5 are made of aluminum and the electro-optic substrate 2 is made of lithium niobate, the holes 3 are formed by the optical photolithography technology and the plasma etching technology used for fabricating semiconductor devices. It can be formed by selectively etching the holes. In plasma etching using C Η ₄ and C ₂ , the chemical reaction shown below (Fig. 1) proceeds and active species F are generated.

C F ^ + O s—C O F s + F + C O (Ichi 1)

Under this reaction condition, aluminum is oxidized to aluminum oxide, which can be etched by active species F. Also lithium niobate Can be etched by the active species F. Therefore, according to the above-described plasma etching, the holes 1 can be formed by etching the electrodes 1 and 5 and the electro-optical substrate 2.

Figures 8 (a) and (b) show examples of applying a voltage between electrodes 1 and 5.

In (a), 7 is an electric circuit as a voltage source, 8 is a metal substrate, 9 is an electrode of the voltage source 7, and 10 is a metal wire connecting the electrode 5 and the electrode 9. The electrode 1 is arranged so as to be in contact with the metal substrate 8 connected to the other electrodes of the voltage source 7 and to be electrically connected thereto. 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. Thus, by configuring the present embodiment in combination with the electric circuit, a voltage can be applied between the electrodes 1 and 5.

(B) is a top surface of the electro-optical substrate 2, for example, by forming a S i 0 ₂ insulating layer 1 0 0 by, thereon to form a wiring layer 1 0 'in place of the metal Waiya one 1 0, The wiring layer 100 ′ is connected to the electrode 5 through a through hole formed in the insulating layer 100, and is connected to the electrode 9 by a metal wire 101. When the wiring layer 10 ′ is formed on the upper surface of the electro-optical substrate 2 as described above, if the insulating layer having a thickness of about three times the thickness of the electro-optical substrate 2 is provided, the wiring layer 10 ′ becomes a two-dimensional photonic. It does not affect the crystal region 4.

(Embodiment 2 ... Embodiment related to grave book configuration)

In the first embodiment, the holes 3 are formed so as to penetrate the electro-optical substrate 2 as shown in FIG. 2, but such holes are not necessarily required. FIG. 9 is a cross-sectional view of the first embodiment when the holes 3 are not penetrated through the electro-optical substrate 2. In the figure, d is the thickness of the portion of the electro-optic substrate 2 where no holes are formed, and is set to be 以下 or less of the wavelength of light incident on the portion of the photonic crystal structure 4. In general, light cannot enter a region of less than one to two wavelengths. Therefore, the incident light is The holes of the electro-optical substrate 3 cannot enter the portion where the holes are not perforated, and 4 acts as the same photonic crystal structure as in the first embodiment.

The optical device of the present embodiment can be manufactured by using the optical lithography technique and the plasma etching technique as in the first embodiment.

When the material of the electrode 5 is indium oxide.tin (In ₂ O 3 -Sη 0 ₂ ), which is a transparent electrode material, and the material of the electro-optical substrate 2 is lithium niobate, the optical device of this embodiment is used. Can be made using photochemical etching technology. Figures 10, 11, 12, and 13 show the creation procedure. An electro-optical substrate 2 made of iron dopaniobate doped with a small amount (0.2 mo 1%) of iron is formed on an electrode 1, and an electrode 5 of indium tin oxide and a negative resist are formed thereon. Apply 102 (Fig. 10). As a material of the electrode 1, for example, gold is used. The electrode 1 is formed by depositing gold on the electro-optical substrate 2 and the electrode 5 is formed by depositing tin oxide on the electro-optical substrate 2, and the negative resist is formed on the electro-optical substrate 2 and the electrode 5 by a spin coating method. Subsequently, light having a wavelength of 488 rim is applied to the portion of the electro-optic substrate 2 where the holes 3 are to be formed by using a mask 103 by optical lithography (FIG. 11). Since the electrode 5 is a transparent electrode, the irradiation light passes through the electrode 5 and reaches the electro-optical substrate 2. By this light irradiation, the portion 104 of the negative resist 102 irradiated with the light is sensitized and can be removed. As reported by E. Barry et al. In Applied Surface Science, Vol. 144, pp. 328-33, page 1, iron crystals exposed to 488 rim light were used. Since lithium pniobate is easily dissolved in a mixed solution of hydrofluoric acid and nitric acid, the portion 105 of the electro-optical substrate 2 irradiated with light can be etched by this mixed solution. After removing the exposed negative resist 104 (Fig. 12), etching was performed using a 1: 2 mixed solution of hydrofluoric acid and nitric acid, and the electrode 5 of indium oxide and tin and the light- Etching is performed on each portion of the optical substrate 2 to form holes 3 and photonic crystal structure regions 4 (FIG. 13). Since electrode 1 is gold, it is not removed by this mixed solution. light During etching of the portion 105 of the electro-optical substrate 2 irradiated with, the etching speed and time are controlled so that the holes 3 do not penetrate the electro-optical substrate 2 and the thickness d can be left. . The thickness d of the portion of the electro-optic substrate 2 where the holes 3 are not perforated must be set to be equal to or less than 1/2 of the wavelength of light incident on the photonic crystal structure region 4 beforehand. It is exactly the same. The structure of the optical device of this embodiment (FIG. 9) can be obtained by removing the negative resist 102 that has not reacted.

The optical device of this embodiment has an advantage that the mechanical strength is larger than that of the optical device of Embodiment 1 (FIG. 7) since the holes 3 do not penetrate the electro-optical substrate 2 and If the thickness d of the unexposed portion is equal to or less than 1/2 of the wavelength of light incident on the photonic crystal structure region 4, even if the thickness varies, the original function may be impaired. There is no. Therefore, as described in the above-mentioned Barry et al. Document, when lithium iron dopniobate is etched using a 1: 2 mixed solution of hydrofluoric acid and nitric acid at 110 ° C. The etching rate is 0.92 mZ minutes. The etching time can be determined from this data. For example, when a lithium iron dopniobate substrate having a thickness of 100 πα is etched with this mixed solution to make the non-penetrating portions of the pores 0.4, the etching time is 108 minutes 16 Seconds. Obviously, the etching rate can be controlled by changing the concentration and temperature of the etching solution. In this case, the effect of the etching process on the substrate may vary, but it is not necessary to strictly control the thickness d of the non-perforated portion, and there may be a portion that is partially penetrated. It can be simple.

(Third embodiment: an embodiment having a single second electrode)

FIG. 14 is a perspective view of the 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-optic substrate, 3 is a hole, 4 is a two-dimensional photonic crystal structure region in the electro-optic substrate 2, and 5 is a second electrode. In this example, a linear electrode 5 was used. electrode The width of 5 is 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 light introduced into the waveguide configured in the present example. The same applies to the following embodiments. The region covered with the electrode 5 in the two-dimensional photonic crystal structure region 4 by applying a voltage between the electrodes 1 and 5 becomes a modified two-dimensional photonic crystal structure region. By applying a voltage between the electrodes 1 and 5, the refractive index of the modified two-dimensional photonic crystal structure region was increased by the electro-optic effect. Numerals 1 1 and 1 2 are optical fibers, each of which is an end face of the electro-optical substrate 2 and is optically connected to a portion of the area covered with the electrode 5.

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 in shape. Therefore, the photonic band structure of the two-dimensional photonic crystal structure region 4 is shown in FIG. The photonic band structure of the modified two-dimensional photonic crystal structure region by applying a voltage between electrodes 1 and 5 changes according to the applied voltage between electrodes 1 and 5, and when the applied voltage is zero. The photonic band structure is shown in Fig. 3 (a), and the photonic band structure when V is applied is shown in Fig. 3 (b).

When no light is applied between the electrodes 1 and 5 and the optical energy is incident on the end face of the electro-optical substrate 2 in the area covered by the electrode 5 by the optical fiber 111, the incident light Is light in the photonic band gap (see Fig. 3 (a)). Thus, the light cannot pass through the two-dimensional photonic crystal structure region 4 and is not output to the optical fiber 112. 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 structure region is as shown in Fig. 3 (b). It can be transmitted through the crystal structure region. The photonic band structure of the portion of the two-dimensional photonic crystal structure region 4 excluding the modified two-dimensional photonic crystal structure region is shown in Fig. 3 (a) regardless of the applied voltage. For this reason, the incident light is reflected in the two-dimensional photonic region excluding the modified two-dimensional photonic crystal structure region. The light cannot travel to the optical crystal region 4 and is guided to the modified two-dimensional photonic crystal structure region 內 to be output to the optical fibers 12. As described above, in the present embodiment, when the voltage V is applied between the electrodes 1 and 5, it acts as a linear optical waveguide.

On the other hand, when no voltage is applied between the electrodes 1 and 5, the present 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, but when a voltage V is applied between the electrodes 1 and 5, the optical fiber 1 Optical fibers 1 1 and 1 2 are optically connected by a modified two-dimensional photonic crystal structure region. As described above, the present embodiment operates as an electro-optic switch by changing the voltage between the electrodes 1 and 5.

In this embodiment, wiring similar to that described with reference to FIGS. 8 (a) and 8 (b) can be provided, but the notation is omitted because the drawing is complicated. In the following embodiments, the description of the wiring is omitted.

(Fourth embodiment--an embodiment having a single second electrode)

FIGS. 15, 16, 17, 18, and 19 show the L-shaped, S-shaped, acute-angled, obtuse-shaped, and arc-shaped optical waveguides of the present invention, respectively. It is the perspective view seen from the shape side of an example. 1 is a first electrode, 2 is an electro-optic substrate, 3 is a hole, 4 is a two-dimensional photonic crystal structure region in the electro-optic substrate 2, and 5 is a second electrode. The fourth embodiment is the same as the second embodiment except that the shape of the electrode 5 is different. Also in the present 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 structure region, and the second As in the embodiment, the light incident from the optical fiber 11 is output to the optical fiber 12. The waveguides in Figs. 15 to 19 act as steep waveguides, and can provide steeply bent waveguides characteristic of optical waveguides having a photonic crystal structure. When no voltage is applied between the electrodes 1 and 5, the fourth embodiment shown in FIGS. 15 to 19 does not function as an optical waveguide, as in the third embodiment. Therefore, in the fourth embodiment, by changing the voltage between the electrodes 1 and 5, the optical connection state between the optical fibers 11 and 12 can be changed, and the electro-optical switch can be used. This is also the same as in the third embodiment.

(Fifth Embodiment—Embodiment Having Single Second Electrode)

FIG. 20 is a top perspective view of the embodiment of the present invention acting as a T-shaped optical waveguide. 1 is a first electrode, 2 is an electro-optic substrate, 3 is a hole, 4 is a two-dimensional photonic crystal structure region in the electro-optic substrate 2, and 5 is a second electrode. The fifth embodiment differs from the second to fourth embodiments only in that the electrode 5 has a T-shape, and is otherwise the same.

Also in the fifth embodiment, the region covered with the T-shaped electrode 5 becomes a modified two-dimensional photonic crystal structure 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 voltage application are the same as in the first embodiment (FIG. 3, 4). As in the third and fourth embodiments, this embodiment functions as an optical waveguide. That is, when a voltage V is applied between the electrodes 1 and 5 and the optical energy is applied by the optical fiber 11 to the light A, the incident light passes through the modified two-dimensional photonic crystal structure region. The light is guided, branched at the intersection, and output to the optical fibers 112 and 13. As described above, the present embodiment acts 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 third to fifth embodiments. Therefore, in the fifth embodiment, by changing the voltage between the electrodes 1 and 5, the optical connection between the optical fiber 11 and the optical fibers 12 and 13 can be changed. Acts as a switch. As described in Examples 3 to 5 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 structure region 4, and the formed waveguide is an electro-optical switch. It can operate as Although various types of optical integrated circuits are conceivable, the waveguide pattern can be decomposed into the waveguide shapes of the above-described third to fifth embodiments. Therefore, according to the present invention, optical integrated circuits of all shapes can be realized. As described above, 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 formed, and a complicated optical integrated circuit can be formed.

(Sixth embodiment---an embodiment having a plurality of second electrodes)

FIG. 21 is a perspective view of an embodiment of the present invention acting as an optical integrated circuit including an optical waveguide and an electro-optic switch, 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 structure region in the electro-optical substrate 2, and 5 and 14 are second electrodes. The seventh embodiment is different from the second to fifth embodiments only in that the second electrode is divided into an electrode 5 and an electrode 14 and both are arranged at a distance d, and the other is the same. Therefore, when a voltage is applied between electrodes 1 and 5 and between electrodes 1 and 14, the two-dimensional photonic crystal structure in which the regions corresponding to electrodes 5 and 14 of two-dimensional photonic crystal region 4 are modified The region 6 and the photonic band structure of the two-dimensional photonic crystal structure region 4 and the modified two-dimensional photonic crystal structure region are the same as in the first embodiment (FIGS. 3 and 4). ). Here, the distance d between the electrode 5 and the electrode 14 is made smaller than the vacancy period a of the two-dimensional photonic crystal structure region 4 and the vacancy 3 forming the two-dimensional photonic crystal structure at that position. To prevent this area from scattering or reflecting light.

In the sixth embodiment, the optical fibers 11 to 13 are provided in the same manner as in the fifth embodiment, but the electrode 5 and the electrode 14 are separated and the voltage applied thereto is independent. Controlled. Therefore, between the optical fibers 1 1 and 1 2 When a voltage V is applied between the electrodes 1 and 5, the light is guided through the modified two-dimensional photonic crystal structure region. Since the region corresponding to the electrode 14 is not a modified two-dimensional photonic crystal structure region, no wave is guided. When a voltage V is applied between the electrodes 1 and 5 and between the electrodes 1 and 14, light having an optical energy of A is incident on the modified two-dimensional photonic crystal region by the optical fiber 111. The incident light is guided through this region, is branched at the T-shaped portion of the electrode 5, and is guided to the optical fiber 113 as well as to the optical fiber 113.

As described above, in the sixth embodiment, by controlling the voltage applied to the electrode 5 and the electrode 14 independently, the transmission of the light introduced from the optical fiber 11 is restricted to the optical fiber 11 or only to the optical fiber 11. The fiber can function as an optical integrated circuit including an electro-optic switch and an optical waveguide that can be controlled by either of the fibers 112 and 13.

(Seventh embodiment: an embodiment having a plurality of second electrodes)

As described in FIG. 4, the photonic band of the voltage application section of the two-dimensional photonic crystal structure region 4 changes depending on the applied voltage. By utilizing this fact, the sixth embodiment (FIG. 21) described above can function as a wavelength selection circuit. FIG. 22 shows the photonic band gap of the modified two-dimensional photonic crystal structure 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 can pass light with energy E but not light with energy D. When the applied voltage is 1.2 V, this region transmits both light with energy E and light with D. Similarly, also in the case of the modified two-dimensional photonic crystal structure region corresponding to the position of the electrode 5, if the voltage applied between the electrodes 1 and 5 is V, this region will pass light of energy E The energy does not pass through D light. When the applied voltage is 1.2 V, this region passes both light with energy E and light with D. Therefore, a voltage of 1.2 V is applied between the electrodes 1 and 5 and a voltage of V is applied between the electrodes 1 and 14. The optical fiber 111 emits both light having energy E and light having energy D. When the light enters the modified two-dimensional photonic crystal structure region, these lights are guided through the modified two-dimensional photonic crystal structure region corresponding to the electrode 5 and branched at the T-shaped part of the electrode 5. Then, the light is led to the optical fiber 112 and also to the modified two-dimensional photonic crystal structure region corresponding to the electrode 14. Since a voltage of 1.2 V is applied between the electrodes 1 and 5, the optical fiber 112 can receive both the light of energy E and the light of energy D, but the electrodes 1, 1 Since the voltage V is applied between the four, the optical fiber 13 can receive only light having energy E. As described above, the eighth embodiment can function as a wavelength selection circuit by controlling the voltage applied to the electrodes 5 and 14.

(Eighth embodiment-an embodiment having a plurality of second electrodes)

FIG. 23 is a perspective view of the embodiment of the present invention acting as a crossed optical switch, as viewed from above. 1 is a first electrode, 2 is an electro-optic substrate, 3 is a hole, 4 is a two-dimensional photonic crystal structure region in the electro-optic substrate 2, 51 and 52 are second electrodes, and 18 is a third electrode. Electrodes. In the eighth embodiment, the second electrode is divided into V-shaped electrodes 51 and 52 whose bottoms face each other, and the third electrode 18 is divided into the opposed bottoms of the V-shaped electrodes 51 and 52. Only differ from Examples 2 to 6 in that they are separated by a distance d between them and that the optical fibers for transmitting and receiving light are placed at the ends of the V-shaped electrodes 51 and 52. And the others are the same. The voltage applied to the electrodes 51 and 52 and the voltage applied to the electrode 18 are controlled independently. Here, the distance d between the electrodes 51, 52 and the electrode 18 is made smaller than the vacancy period a of the two-dimensional photonic crystal structure region 4 and the vacancy forming the two-dimensional photonic crystal at that position. As in the sixth embodiment, this region is made not to scatter or reflect light so as not to include 3.

Also in Example 8, the area covered by the V-shaped electrode 5 was the electrode 1, 5 When a voltage is applied between the electrodes 1 and between the electrodes 1 and 52, a modified two-dimensional photonic crystal region is formed. The photonic band structure of the two-dimensional photonic crystal structure region 4 and the photonic band structure of the two-dimensional photonic crystal structure region modified by voltage application are the same as in the first embodiment (FIG. 3). , 4). As in Examples 2 to 6, also in this example, 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 made incident on the optical fiber 111, the incident light is guided through the modified two-dimensional photonic crystal region. It is output to the optical fiber 112.

By the way, 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 applied voltage and the voltage applied to the electrode 18 were controlled independently, the voltage was applied only between the electrodes 1 and 51 and between the electrodes 1 and 52 to apply the voltage to the optical fiber 1 1 Therefore, even if the optical energy beam enters the light of A, this light is only guided to the optical fiber 112. Because no voltage is applied to the electrode 18, the two-dimensional photonic crystal structure region corresponding to the electrode 18 does not function as a modified two-dimensional photonic crystal structure region and does not function as an optical waveguide. . Therefore, even if the two-dimensional photonic crystal structure region corresponding to the V-shaped electrode 51 becomes a modified two-dimensional photonic crystal structure region and guides light, it corresponds to the electrode 18. This is because the light is blocked in the two-dimensional photonic crystal structure region and is not propagated to the modified two-dimensional photonic crystal structure region corresponding to the V-shaped electrode 52.

-When a voltage V is applied between electrodes 1 and 5 and between electrodes 1 and 5 and a voltage V is applied between electrodes 1 and 18, it corresponds to electrodes 51 and 52 The two-dimensional photonic crystal structure region becomes a modified two-dimensional photonic crystal structure region, and the region corresponding to the electrode 18 also becomes a modified two-dimensional photonic crystal structure region. Therefore, the optical fiber When the light with the light energy of A is made incident by 1 11, the incident light is guided through the region corresponding to the electrode 18 and outputted to the optical fibers 13 and 17. Here, if the voltage applied between the electrodes 1 and 18 is slightly higher than the voltage V, the change in the refractive index due to the electro-optic effect is proportional to the applied voltage (Equation (1)). The refractive index of the two-dimensional photonic crystal structure is higher than the refractive index of the two-dimensional photonic crystal structure corresponding to the electrodes 51 and 52. Acts as an optical waveguide. In this case, the optical circuit between fibers 12 and 17 and between fibers 11 and 13 can be prevented from crosstalk.

This function is reversible, and the same applies to the case where light having an optical energy of A is incident from the optical fiber 13. That is, when a voltage is applied only between the electrodes 1 and 51 and between the electrodes 1 and 5, the incident light is propagated only to the optical fiber 17, and between the electrodes 1 and 51, the electrodes 1 and 5 2 When a voltage is applied between the electrodes 1 and 18 while a voltage is applied between them, the incident light is also propagated to the optical fibers 11 and 12.

As described above, in the eighth embodiment, it is possible to change the light output state by controlling the voltage application between the electrodes 1 and 18 and to select the bar state or the cross state. It can function as a switch.

(Ninth embodiment: an embodiment having a plurality of second electrodes)

FIG. 24 is a plan view of an embodiment of the present invention acting as a 4 × 4 optical switch. In this embodiment, a four-by-four optical switch is constructed by combining four cross-type optical switches of the eighth embodiment. This embodiment is shown in a plan view for simplification of the drawing, and the optical fiber is not shown, but the basic structure is the same as the above-described embodiment. Where 1 is the first electrode, 2 is the electro-optical substrate, 3 is the hole, 4 is the two-dimensional photonic crystal structure region in the electro-optical substrate 2, 51, 52, 53, and 54 are the second electrodes , 18 ^ to 18 ₄ are third electrodes. In the ninth embodiment, the second electrodes are W-shaped electrodes 51 and 52 whose bottoms face each other and W-shaped electrodes 53 and 54 whose bottoms face each other. The central part of poles 51 and 53 was integrated. The third electrodes 18, to 18 ₄ are spaced d (between the opposed bottoms of the W-shaped electrodes 51, 52 and the opposed bottoms of the W-shaped electrodes 53, 54, respectively. Examples 2 to 5 are arranged in such a manner that they are spaced apart from each other, and that an optical fiber for transmitting and receiving light is arranged at the ends of the W-shaped electrodes 51 to 54 (not shown). Only the difference from 6 and 8 is the same. Both the voltage applied to the voltage electrode 1 8 t~ 1 8 ₄ applied to the electrode 5 1-5 4 is controlled independently, is selectively performed. Here, the distance d between the electrodes 51, 52 and the electrode 18 is made smaller than the vacancy period a of the two-dimensional photonic crystal structure region 4, and the vacancy forming the two-dimensional photonic crystal structure is formed at that position. This is the same as the sixth embodiment in that the region 3 is not included so that this region does not scatter or reflect light.

In this embodiment, the incident light S l, S 2, and the optical fiber 1 are placed at positions corresponding to the two-dimensional photonic crystal structure region 4 at both ends of the second electrodes 51, 52, 53, and 54. S 3 and S 4 are added, but by selectively applying a voltage between the third electrode 18 L to 18 ₄ and electrode 1, the output light 3 1 ′, 3 2 ′, S 3 ′ And S 4 'can be switched.

For example, the electrode 1 and the electrode 5 1, 5 2, 5 3 and 5 to mark pressurizing the voltage V between 4, state shape without applying any voltage also between electrodes 1 and 1 8 • L ^ 1 8 ₄ When incident light S 1 to S 4 having an energy of A is incident, the two-dimensional photonic crystal in which only the two-dimensional photonic crystal structure regions at the positions corresponding to the electrodes 51, 52, 53 and 54 are modified In this case, the incident light S 1 to S 4 is prevented from being guided at the positions corresponding to the electrodes 18 to 18 ₄ , so that the output light S 1 ′, S 2 ′, Output as S 3 'and S 4'.

On the other hand, when 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 18 to 18, the energy A is increased. When the incident light S 1 to S 4 is incident, the electrodes 5 1, 5 2, Only the two-dimensional photonic crystal structure region at the positions corresponding to 53 and 54 becomes a modified two-dimensional photonic crystal structure region, and also corresponds to electrodes 18, ~ 18 The incident light S 1 to S 4 is guided at the position corresponding to the electrodes 18 ^ to 18 4 because the two-dimensional photonic crystal structure region is also a modified two-dimensional photonic crystal structure region It will be. As a result, the incident light S1 becomes the output light S4 ', the incident light S2 becomes the output light S2', the incident light S3 becomes the output light S3 ', and the incident light S4 becomes the output light S1'. , Respectively. By making the voltage applied between electrode 1 and electrode 18 _t to 18 slightly higher than V, the optical circuits S 1 — S 4 ′, S 2 — S 2 ′, S 3 — S 3 ', And S 4-SI' can be prevented from crosstalk as in the eighth embodiment.

In this embodiment, the case where lithium niobate is used for the electro-optical substrate 2 will be considered. Conventionally, a 4 × 4 optical exchanger has been fabricated by diffusing titanium ions into a lithium niobate substrate to form a waveguide core in the substrate. However, in the conventional method, it was necessary to increase the radius of curvature of the waveguide by 4 cm or more. This is because, in the conventional method, the refractive index difference between the waveguide core and the substrate cannot be increased, so if the radius of curvature is not increased, the radiation loss, the light radiation in the waveguide curved section, and the transmission loss will increase. It is. For this reason, the conventional method has a problem that the size of the switch becomes extremely large. For example, if a 4 × 4 optical switch is constructed using lithium niobate according to the conventional technology, the size will be 0.1 × 6.5 cm. (Masahiro Ikeda, “Optical Fiber Communication”, p. Corona, Tokyo, 199 7)). In contrast, the optical exchanger of this example is formed on a photonic crystal structure with a lattice constant a of 0.5 μm and a period of about 35 × 35, and the size is about 18 X 18 μm. Light exchanger of this embodiment, the area compared to conventional optical exchanger is about 1/1 0 ⁸ very small les. Thus, the tenth embodiment operates as a micro optical switch. The conventional optical switch has a length of each waveguide path of about 7 cm and transmission loss. It is about 4.7 dB. In this embodiment, since a waveguide having a photonic crystal structure is used, the loss caused by the waveguide structure is basically extremely small, and the transmission loss is considered to be caused by the lithium niobate used for the electro-optic substrate 2. May be. Assuming that the loss due to lithium niobate is 4.5 dB at 7 cm as described above, since each waveguide path in this embodiment is about 30 `` m, the transmission loss of each path is It is estimated to be 4 XI 0-dB In this way, an extremely low-loss optical exchanger can be realized according to the present embodiment, and the optical anisotropy of lithium niobate is small. The optical switch of the embodiment is characterized in that the guided light is not polarized.

(Embodiment 10-Embodiment having a matrix-shaped second electrode) Fig. 25 shows an optical waveguide, an electro-optic switch, and a wavelength selection circuit whose circuit structure is arbitrarily variable. FIG. 2 is a perspective view seen from the top side of an embodiment of the present invention functioning as an optical circuit including a cross-type optical switch, an optical switch, or an optical waveguide and an electro-optical switch. 1 is a first electrode, 2 is an electro-optical substrate, 3 is a hole, 4 is a photonic crystal structure region in the electro-optical substrate 2, and 5 is a second electrode. In the present embodiment, 96 second electrodes 5 are arranged in a matrix on the electro-optical substrate 2 and the surface of the photonic crystal structure. For simplicity of the figure, 96 second electrodes are denoted by 5, the optical fiber is not shown, and its position is X1 ~; X8, XI '~ X8', Y1 ~ Y 8, Υ 1 'to Υ 8'. Here, the distance d between the adjacent second electrodes 5 is set to be smaller than the vacancy period a in the structural region of the photonic crystal structure 4. A two-dimensional photonic crystal structure is formed at that position. This region is not scattered or reflected so as not to include the void 3 which is the same as in the sixth embodiment.

In this embodiment, the photonics are selected by appropriately selecting the second electrodes arranged in a matrix and applying a voltage between the first electrodes 1 and the selected second electrodes 5. It is characterized in that an optical circuit of any shape can be formed in the crystal structure 4. FIG. 26 is a perspective view of the optical waveguide formed in the photonic crystal structure region 4 as viewed from the top side using the tenth embodiment. Among the second electrodes 5 arranged in a matrix, the electrode 5 ′ with diagonally lower right and the electrode 5 ′ with diagonally higher right are selected, and the first electrode 1 and the right electrode 5 ′ are selected. When a voltage is applied between the lower shaded second electrode 5 ′ and between the first electrode 1 and the shaded upper electrode 5 ″, the two-dimensional photonic crystal structure region 4), the area covered by the electrode 5 ′ and the electrode 5 ′ ″ becomes a modified two-dimensional photonic crystal structure region, and the L-shaped waveguide and the T-shaped waveguide It is formed inside the nickel crystal structure 4. Thereby, Y 3 and X 3 ′, X 5 and X 5 ′, and Y 5 ′ are optically connected. By changing the voltage applied between the first electrode and the selected second electrode 5, the optical device of FIG. 26 functions as an electro-optic switch or a wavelength selection circuit in the fourth to seventh aspects. This is the same as the embodiment. It is obvious that by changing the selected second electrode 5, optical circuits of other shapes can be formed similarly.

FIGS. 27 and 28 are perspective views of the case where the cross-type optical switch is formed in the photonic crystal structure region using the tenth embodiment, as viewed from above. Figure

As shown in FIG. 27, among the second electrodes 5 arranged in a matrix, electrodes 5 ′ with diagonally lower slashes and electrodes 5 ′ with diagonally right slashes are selected. Electrodes ;! When a voltage V is applied between the first electrode 1 and the selected second electrode 5 ′, an optical waveguide is formed, X 4 and Y 5 ′ are optically connected, and the first electrode 1 and the selected second electrode 5 ′ are connected. When a voltage V is applied between 5 ′ ′, an optical waveguide is formed, and X 4 and Y 5 are optically connected. On the other hand, as shown in FIG. 28, among the second electrodes 5, the electrode 5 'with a diagonally downward slanted line and the electrode 5 "with a diagonally rightward slant were selected, and were selected as the first electrodes. When a voltage V is applied simultaneously between the second electrode 5 ′ and the first electrode and the selected second electrode 5 ′, the cross-shaped optical waveguide is formed inside the electro-optic substrate 2 and the photonic crystal structure 4. Formed Y 5 and Y 5 ′, and X 4 and X 4 ′ Connected. Here, the voltage applied between the second electrode 5 _x at the intersection of the first electrode and the selected second electrode is slightly smaller than the voltage applied to the electrode 5 ′ and the electrode 5 ″. When it is made larger, this optical waveguide becomes a high refractive index crossed optical waveguide, and no crosstalk occurs between the optical waveguides Y 5 and Y 5 ′ and the optical waveguides X 4 and X 4 ′. The embodiment of FIG. 27 operates as a cross-shaped optical switch in a buried state, and the embodiment of FIG. 28 operates as a cross-shaped cross-switch in a cross state. As described above, the present embodiment functions as a crossed optical switch by appropriately selecting the second electrode 5. The fact that an optical switch can be configured by connecting a plurality of crossed optical switches according to the present embodiment is the same as that described in the eighth and ninth embodiments.

As described above, in the present embodiment, the optical circuit structure can be arbitrarily changed by appropriately selecting the second electrode 5, and the optical circuit, the electro-optical switch, and the wavelength can be arbitrarily changed. It can be used as a selection circuit, a cross-type optical switch, an optical switch, or an optical device composed of an optical waveguide and an electro-optical switch.

(Other examples)

In the first to ninth embodiments, 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 structure region In order to form 6, it is only necessary that the electrode 1 is provided only in the portion corresponding to the pattern electrode 5, so for example, the pattern electrode corresponding to the pattern electrode 5 is lithographically formed on an appropriate semiconductor substrate surface. The electro-optical substrate 2 may be formed thereon by forming by a luffy technique.

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 structure as long as vacancies are formed periodically. The same applies to the second to ninth embodiments. A hole 3 is formed through the electro-optic substrate 2 This need not be as described in the second embodiment. Industrial applicability

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

Claims

The scope of the claims

1. a first electrode; an electro-optic substrate made of a solid material formed on one surface of the first electrode; a photonic crystal structure region made of a solid material formed in the electro-optic substrate; A second electrode patterned on the surface of the photonic crystal structure region facing the first electrode so as to have a width of 1 or more of a wavelength of light guided in the electro-optical substrate. An optical device characterized by the above.

2. An illuminator for irradiating light to the photonic crystal structure region below the second electrode and a light receiving device for receiving light guided by the photonic crystal structure region below the second electrode The optical device according to claim 1, wherein:

3. 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 the photonic crystal structure region below the second electrode. 3. The optical device according to claim 2, wherein the optical device is arranged and a voltage applied to each electrode is independently controlled.

4. The device according to claim 3, wherein the two or more separated second electrodes are arranged in a matrix.

5. A third independent electrode is placed between the two separated second electrodes about 1/2 of the wavelength of light incident on the photonic crystal structure region below the second electrode. 4. The optical device according to claim 3, wherein the voltage is applied to the second electrode, and the voltage applied to the second electrode and the voltage applied to the third independent electrode are independently controlled.

6. A layer of insulating material is formed on the upper surface of the electro-optic grave plate, and the second or third electrode uses a conductor led out through a through hole formed in the layer of insulating material. 6. The optical device according to claim 1, wherein a voltage is applied to the optical device.

7. An electro-optic substrate made of a solid material, a photonic crystal structure region made of a solid material formed in the electro-optic substrate, and the photonic A first electrode and a second electrode formed in the same pattern on both surfaces of the crystal structure region; a means for applying a voltage between the first electrode and the second electrode; A light comprising: an illuminator for entering light into a photonic crystal structure region below an electrode; and a light receiving device for receiving light guided by the photonic crystal structure region below the second electrode. device.

8. The photonic crystal structure regions corresponding to the electrode patterns are linear, L-shaped, S-shaped, acute-angled, obtuse-angled, arc-shaped and T-shaped optical waveguides, electro-optic switches, and wavelength selection. 8. The optical device according to claim 1, which functions as an optical integrated circuit including a circuit, a crossed optical switch, an optical exchanger, or an optical waveguide and an electro-optical switch.

9. The photonic crystal structure region corresponding to the electrode pattern is variable, and the optical circuit structure is arbitrarily variable, such as an optical waveguide, an electro-optic switch, a wavelength selection circuit, a cross-type optical switch, an optical switch, 8. The optical device according to claim 1, which functions as an optical circuit including an optical waveguide and an electro-optic switch.

10. a first electrode; an electro-optic substrate made of a solid material formed on one surface of the first electrode; a photonic crystal structure region made of the solid material formed in the electro-optic substrate; A second electrode patterned on a surface of the photonic crystal structure region facing the first electrode so as to have a width of 1 or more of a wavelength of light guided in the electro-optical substrate; An optical device substrate, comprising: means for applying a voltage between the first electrode and the second electrode.

1 1. The second electrode is separated into two or more, and the separated electrodes are close to about 2 of the wavelength of light incident on the photonic crystal structure region below the second electrode. 10. The optical device substrate according to claim 10, wherein the voltage is applied to each of the electrodes and is independently controlled.

12. The optical device substrate according to claim 11, wherein the two or more separated electrodes are arranged in a matrix.

13. A third independent electrode is placed between the two separated second electrodes in close proximity to about 12 wavelengths of light incident on the photonic crystal structure region below the second electrode. 21. The optical device substrate according to claim 11, wherein the arrangement is such that a voltage applied to the second electrode and a voltage applied to the third independent electrode are independently controlled.

14. An insulating material layer is formed on the upper surface of the electro-optic substrate, and the second or third electrode uses a conductor led out through a through hole formed in the insulating material layer. The optical device substrate according to any one of claims 10 to 13, wherein a voltage is applied as a voltage.

15. An electro-optic substrate made of a solid material, a photonic crystal structure region made of the solid material formed in the electro-optic substrate, and a photonic crystal structure region formed in the same pattern on both surfaces of the photonic crystal structure 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.

16. The photonic crystal structure region is formed by periodically penetrating or non-penetrating holes in the electro-optical substrate. 16. The optical device substrate according to claim 15, wherein the wavelength of the light incident on the nickel crystal structure region is 2 or less.