JP4369802B2 - Optical devices using photonic crystals - Google Patents

Description

  The present invention relates to various optical devices used for optical communication and the like, and more specifically, the wavelength or polarization dispersion compensator of an optical fiber, an optical isolator, an optical modulator, a voltage such as a power transmission line and a distribution line, or the like. The present invention relates to an optical device such as an optical sensor used to detect an electric current.

  First, various conventional optical devices will be described below. FIG. 31 is a schematic view showing the structure of an optical isolator which is a conventional optical device. This optical isolator includes first and second lenses 1003 and 1004 for coupling an optical system between a first optical fiber 1001 and a second optical fiber 1002, and a polarizer 1005 and a Faraday element are interposed between them. 1006 and an analyzer 1007. In FIG. 31, the extension of the light beam 1009 in the optical system is shown by a straight line. Further, the present optical isolator has a magnetic field 1008 sufficient to saturate the Faraday element 1006. In addition, the polarizer 1005 and the analyzer 1007 are at an angle of 45 °. As the Faraday crystal 1006, a garnet crystal or the like is used.

  Next, the principle of the optical isolator will be described. In the optical isolator of FIG. 31, the non-polarized light emitted from the first optical fiber 1001 is first converted into linearly polarized light by the polarizer 1005 coupled by the first lens 1003. Next, the plane of polarization of the linearly polarized light is rotated by 45 ° by the Faraday element 1006. The linearly polarized light whose polarization plane is rotated by 45 ° is all coupled to the second optical fiber 1002 via the second lens 1004 by the analyzer 1007 having the above-described angle.

  On the other hand, the return light from the second optical fiber 1002 is coupled to the analyzer 1007 through the second lens 1004 and converted into linearly polarized light. Next, the plane of polarization of the linearly polarized light is rotated by 45 ° by the Faraday element 1006. However, in the polarizer 1005, the polarization plane of linearly polarized light is orthogonal to the polarization direction of the polarizer 1005. Accordingly, there is no return light coupled to the first optical fiber 1001 via the first lens 1003. Thus, in the conventional optical isolator, two lenses are required for coupling of the optical system between the optical fibers.

  Next, a conventional dispersion compensator will be described. A conventional dispersion compensator is provided between optical fibers. Therefore, at least two lenses are required for coupling the optical system between the optical fibers.

  Next, a conventional optical modulator will be described. For example, the optical modulator is functionally composed of a polarizer, a λ / 4 plate, a Pockels element, and an analyzer. The linearly polarized light obtained by the polarizer becomes circularly polarized light by the λ / 4 plate, and the circularly polarized light becomes elliptical according to the electric field applied in the Pockels element. Next, in the analyzer, the amount of light changes according to the ellipticalization of the circularly polarized light, so that the light modulation according to the applied electric field can be performed. As described above, the conventional optical modulator also requires at least two lenses for coupling the optical system between the optical fibers.

Further, the configuration of the conventional optical modulator will be described in detail. For example, as shown in FIG. 32, a Mach-Zehnder type modulator 2012 used as an optical modulator is formed on a substrate 2001 made of, for example, a LiNbO ₃ crystal. In the Mach-Zehnder type modulator 2012, the waveguide section 2002 is polarized on two light beams (TM light and TE light) on the incident side where a non-polarized light (TM light + TE light) 2005 is incident. Each waveguide which radiates | emits after isolate | separating, and the waveguide which couple | bonds and radiate | emits these polarized light are included. Among these, an electrode 2003 for applying an electric field is provided in the waveguide for polarization separation. A predetermined voltage is applied to the electrode 2003 from the signal source 2004. Then, the emitted light 2010 is coupled to the optical fiber 2006 by the lens 2009. The optical fiber 2006 includes a core 2007 and a clad 2008, and light is transmitted through the core 2007.

  As described above, conventionally, an optical device such as an optical modulator requires at least one lens to couple an expensive waveguide and an optical system from the optical modulator to the optical fiber. In addition, coupling of the optical system between the waveguide and the optical fiber requires a great deal of time and labor.

  Next, a conventional optical sensor will be described. FIG. 33 is a perspective front view showing a schematic structure of a conventional optical voltage sensor. This optical voltage sensor includes a sensor unit, a light emitting unit, a light receiving unit, and a light emitting side and light receiving side signal processing circuit (not shown). The sensor unit includes a polarizer 241, a quarter-wave plate (also referred to as “λ / 4 plate”) 242, an electro-optic crystal 243, and an analyzer 244 arranged on the same optical axis in order from the light incident side. Composed. The light emitting unit includes an E / O circuit including a light emitting diode (LED) as a light source, an optical fiber 246a, a ferrule 248a, a GRIN lens 247a, and a holder 245a arranged on the same optical axis. Each optical component in the input side optical system has an optical axis surface that is in contact with each other bonded by an adhesive. The light receiving unit converts the output side optical system including the optical fiber 246b, the ferrule 248b, the GRIN lens 247b, and the holder 245b disposed on the same optical axis, and converts the optical signal emitted from the output side optical system into an electrical signal. The optical component in the output side optical system is also bonded by an adhesive on the optical axis surfaces in contact with each other.

  The optical components arranged on the same optical axis in the sensor part of the optical voltage sensor, that is, the polarizer 241, the λ / 4 plate 242, the electro-optic crystal 243, and the analyzer 244 all have optical axis surfaces in contact with each other. It is bonded with an adhesive. Here, the optical axis surface means a surface perpendicular to the optical axis, and there are two light incident surfaces and light output surfaces for each optical component (the same applies hereinafter). A pair of electrodes 235 is deposited on the electro-optic crystal 243, and each of the pair of electrodes 235 is electrically connected to each of the pair of electrode terminals 249 by lead wires. A voltage (voltage to be measured) to be measured by the photovoltage sensor is applied between a pair of electrode terminals 249.

  The light emitting side and light receiving side signal processing circuits are connected to the sensor unit by a light emitting unit and a light receiving unit, respectively. The sensor-side polarizer 241 has an input-side optical axis surface of the light-emitting portion GRIN lens 247a, and the sensor-unit analyzer 244 has an output-side optical axis surface of the light-receiving portion GRIN lens 247b. Each is fixed with an adhesive. The sensor unit, the input side optical system in the light emitting unit, and the output side optical system in the light receiving unit are mechanically fixed to a case (not shown). In addition, as an adhesive for each optical component in the photovoltage sensor, an epoxy resin or a urethane resin is used.

In the above-described optical voltage sensor, Bi ₁₂ SiO ₂₀ (BSO), KH ₂ PO ₄ (KDP), LiNbO ₃ having natural birefringence, LiTaO ₃ or the like is used as the electro-optic crystal 243.

Next, the operation principle of the optical voltage sensor will be described with reference to FIG. For example, when an LED (Light Emitting Diode) having a center wavelength of 0.85 μm is used as a light source in the light emitting unit, unpolarized light of the LED is emitted from the light emitting unit and incident on the sensor unit as incident light 109. The incident light 109 becomes linearly polarized light after passing through the polarizer 241 of the sensor unit. When this linearly polarized light passes through the λ / 4 plate 242, it becomes circularly polarized light. This circularly polarized light passes through the electro-optic crystal (LiNbO ₃ ) 243 and then becomes elliptical according to the voltage Vm applied to the electro-optic crystal 243. To do. That is, the polarization state of the light passing through the electro-optic crystal 243 changes depending on the applied voltage Vm. Such elliptically polarized light passes through the analyzer 244 and is then received by the light receiving unit as outgoing light 110. The output intensity change that is the intensity change of the emitted light 110 corresponds to the polarization state of the light passing through the electro-optic crystal 243. Since this polarization state changes according to the applied voltage Vm, the change in the output intensity of the analyzer 244 is monitored at the light receiving unit via the optical fiber 246b on the light receiving side, and the degree of modulation of the light amount (intensity) is calculated. The voltage Vm can be measured. Here, the modulation amount of the light amount is a ratio between the AC component of the light amount and the DC component of the light amount.

By the way, the photovoltage sensor is often used in severe outdoor environments, and severe conditions are required for its temperature characteristics, and the change in modulation degree may be ± 1% or less at −20 ° C. to 80 ° C. desired. Factors that cause temperature characteristics in the above-described conventional optical voltage sensor include a change in refractive index due to stress at the bonding portion in the λ / 4 plate 242 and the electro-optic crystal 243, and temperature characteristics of birefringence in the λ / 4 plate 242. . When an electro-optic crystal having natural birefringence, such as LiNbO ₃ , is used, the output of the photovoltage sensor changes depending on the beam state of incident light on the electro-optic crystal 243.

  FIG. 35 is a graph illustrating the relationship between the axis deviation angle α and the axis deviation direction β and the output of the optical voltage sensor. In FIG. 35, β1 represented by a dotted line is the case where the axis deviation direction is 0, 90, 180, 270 (degrees), and β2 represented by an alternate long and short dash line is an axis deviation direction of 45,225 (degrees). .Beta.3 represented by a normal line represents the case where the axis deviation direction is 135, 315 (degrees), respectively. As shown in FIG. 35, depending on the beam state of the incident light on the electro-optic crystal 243 (axial deviation angle α, axial deviation direction β, etc.), the modulation degree that is the output of the optical voltage sensor changes, or the modulation degree The temperature characteristics change.

Currently, there are the following three methods for improving each of these factors.
(1) First, there is a method of improving the temperature characteristics of the electro-optic crystal by relaxing stress applied to the electro-optic crystal. In this method, the stress applied to the electro-optic crystal is relieved by fixing the electro-optic crystal without bonding. This method is disclosed in Japanese Patent Laid-Open No. 9-145745.
(2) Secondly, there is a method of improving the temperature characteristic of natural birefringence of the electro-optic crystal by reducing the axis deviation angle of incident light. In this method, by improving the mechanical surface accuracy of the optical component itself so that the incident angle of light in the electro-optic crystal is 0.2 ° or less, the temperature characteristic due to the axis deviation of incident light is improved. This method is disclosed in JP-A-3-44562.
(3) Third, there is a method of improving the temperature characteristics of the sensor output by changing the incident angle of the incident light with respect to the electro-optic element in accordance with the ambient temperature. In this method, an incident angle adjustment unit that changes the incident angle of incident light with respect to the electro-optic crystal (Pockels element) in accordance with the ambient temperature cancels the output change due to the temperature change by the output change due to the change in the incident angle. Thus, the temperature characteristic of the sensor output is improved. An optical sensor based on this method is disclosed in Japanese Patent Laid-Open No. 7-248339.

  As described above, in the conventional optical device, at least one or two lenses are required to couple the optical system with the optical fiber, and the number of parts increases. In addition, such optical system coupling requires a great amount of time and labor. Therefore, according to the configuration of the optical device as described above, there is a problem that the cost of the apparatus is increased.

  Furthermore, in addition to the above-described problems, the optical sensor has a specific problem related to temperature characteristics. That is, according to the method (1), fluctuations in the beam state that cause a large temperature characteristic can be prevented, but variations in the temperature characteristic cannot be avoided if the initial beam state varies. The method (2) is easy to use, but the influence of the axis deviation is related not only to the axis deviation angle but also to the axis deviation direction. For this reason, stable characteristics cannot be obtained only by reducing the axis deviation angle based on the method (2). The method (3) requires an incident angle adjusting unit that changes the incident angle of incident light with respect to the electro-optic crystal in accordance with the ambient temperature, which complicates the configuration and reduces productivity and costs. Invite. Further, as described above, the influence of the axis deviation is related not only to the axis deviation angle but also to the axis deviation direction, so that stable temperature characteristics cannot be obtained only by adjusting the incident angle of incident light, that is, the axis deviation angle.

  On the other hand, the applicant of the present application is concerned with the invention of an optical voltage sensor based on a method of controlling the temperature characteristic of the degree of modulation by utilizing the axial deviation characteristic of an electro-optic crystal having a natural birefringence, and Japanese Patent Application No. 11-215798. Has already been filed. According to the optical voltage sensor according to the invention of this application, the temperature characteristics of the optical voltage sensor are controlled by controlling the beam state (axial deviation angle and axial deviation direction, spread angle, etc.) of the incident light to the electro-optic crystal. Is improved. That is, the temperature characteristics and the like are improved by appropriately setting the axis deviation state in consideration of not only the axis deviation angle but also the axis deviation direction.

  However, the control of the beam state based on the invention of this application is disadvantageous in price because the beam state management for preventing the variation of the beam state due to the tolerance of the optical components such as the lens increases the cost. .

  Therefore, at present, in order to reduce the price of the optical voltage sensor, it is required to manage the beam state at a low cost.

  In view of the above, an object of the present invention is to provide a low-cost optical device that can be coupled to an optical fiber with an optical system in a simple and low-cost manner and has a small number of components. In the following, as a reference example, an optical sensor such as an optical voltage sensor whose temperature characteristics are stabilized by suppressing variations in beam state due to tolerances of optical components without causing an increase in cost. Also explained.

The present invention is an optical device that optically couples with an optical component and propagates light to the optical component, and includes a core that propagates light and a clad that encloses the core, and a first end face that is not perpendicular to the optical axis And an optical fiber having a functional portion made of a photonic crystal laminated directly on the first end face and in a direction perpendicular to the first end face, and a resin in contact with the photonic crystal. And a resin portion having a second end face that is perpendicular to the axis and through which the optical axis of the optical fiber passes, and is optically coupled to the optical component at the second end face so that light is transmitted to the optical component. Propagating optical device.

As described above, according to the present invention, it is possible to reduce the manufacturing cost of an optical element having a function that can be realized by a photonic crystal, and the number of parts of an optical device that uses such an optical element or an optical fiber. Can be reduced

  First, before explaining the configuration of the optical device in detail, an overview of photonic crystals used in polarizers (linear polarizers and circular polarizers), analyzers, λ / 4 plates, Pockels elements, etc., that make up each optical device In addition, the formation method will be described.

<Formation of a photonic crystal that functions as a linear polarizer>
As a literature on photonic crystals, for example, there is a literature called “Photonic crystal” written by John D. Joannopoulos, Robert D. Meade and Josua N. Winn. Published by Princeton University Press (1995). As described in this document, the photonic crystal has a 1 to 3 dimensional periodic structure composed of a relatively high refractive index material and a low refractive index material, and mainly includes a high refractive index material and a low refractive index. The periodic structure resulting from the refractive index and shape of the material, the period of spatial variation of the refractive index, the direction and wavelength of the incident light beam (hereinafter referred to as “used beam direction” and “used beam wavelength”, respectively) The light wave is controlled by utilizing the dispersion characteristic of the light wave in the inside. Therefore, if the refractive index and shape of the photonic crystal, the period of spatial change of the refractive index, and the direction of the used beam are appropriately controlled with respect to the used beam wavelength, two types of linearly polarized TM waves and TE waves are generated. A polarizer, a λ / 4 plate, or the like can be realized by utilizing the phenomenon that the dispersion characteristics are different. For example, a polarizer using such a photonic crystal is disclosed in Japanese Patent Laid-Open No. 2000-56133. Further, as described in the above-mentioned document, many types of high refractive index materials and low refractive index materials used for photonic crystals have been proposed and manufactured.

  Therefore, it is possible to form a photonic crystal layer functioning as a linear polarizer or an analyzer as used in an eighteenth reference example described later on the end face of the optical fiber. That is, when a photonic crystal layer made of a high refractive index material and a low refractive index material is formed on the end face of an optical fiber, only one of TM waves and TE waves constituting light to be transmitted through the optical fiber is changed. The refractive index and shape of the high-refractive index material and low-refractive index material, the period of spatial change of the refractive index, and the direction of the beam used can be set so as to pass through the photonic crystal layer. (For example, refer to FIG. 4 and FIG. 6 described in JP-A-2000-56133). A specific method for forming the photonic crystal on the end face of the optical fiber will be described later.

  In a thirteenth reference example to be described later, when a multilayer film is formed as a photonic crystal in which two types of layers of a high refractive index layer and a low refractive index layer are alternately stacked, the two types of layers are It is laminated in the direction of the incident light (optical axis direction) to the sensor unit, and the sum of the thickness of the high refractive index layer and the thickness of the low refractive index layer is set to be 1/4 of the wavelength of the incident light. Accordingly, it is possible to prevent both the TM wave and the TE wave from passing through the photonic layer. This means that the multilayer film formed as a one-dimensional photonic crystal functions as a reflection film for the incident light. A specific configuration of the optical device using such a function will be described later in a corresponding reference example.

<Formation of photonic crystal functioning as λ / 4 plate>
In addition, as described above, when the refractive index and shape of the photonic crystal, the period of spatial change of the refractive index, and the used beam direction are appropriately controlled with respect to the used beam wavelength, two types of linearly polarized light TM A λ / 4 plate can be realized by utilizing the phenomenon that a difference occurs between the dispersion characteristics of the wave and the TE wave. Therefore, a photonic crystal layer that functions as a λ / 4 plate can be formed on the end face of the optical fiber as in a nineteenth reference example described later. That is, when a photonic crystal layer composed of a high refractive index material and a low refractive index material is formed on the end face of the optical fiber (the specific formation method will be described later), the light to be transmitted through the optical fiber is configured. So that both the TM wave and the TE wave that pass through the photonic crystal layer and the passage causes a phase difference corresponding to 1/4 of the wavelength of the light between the TM wave and the TE wave. It is possible to set the refractive index and shape of the high refractive index material and the low refractive index material, the period of spatial change of the refractive index, and the beam direction used.

<Formation of a photonic crystal layer that functions as a circular polarizer>
Circular polarizer is a polarizer that converts the non-polarized light into circularly polarized light, implemented by photonic crystal having 1-3 dimensional periodic structure consisting of relatively high in the optical Propagation direction permeability material and low permeability material can do.

FIG. 1 is a perspective view showing an example of a photonic crystal that functions as a circular polarizer. This photonic crystal has a high permeability portion 211 and a low permeability portion 212 by periodically arranging cylindrical portions made of a material with high permeability in a low permeability medium (for example, air). Has a periodic structure in which the magnetic permeability is repeated two-dimensionally at a constant period, that is, a periodic structure in which the magnetic permeability changes two-dimensionally and periodically (hereinafter referred to as “two-dimensional periodic structure with respect to magnetic permeability”). Incidentally, high permeability portions 211 may be higher permeability for the propagation direction of the incident light to the two-dimensional photonic crystal 210 need not permeability is high in all directions. Also, low permeability portions 212 may be lower permeability with respect to propagation direction of the incident light to the two-dimensional photonic crystal 210 need not permeability is low in all directions.

Now, it is assumed that non-polarized light is incident on the photonic crystal 210 having the two-dimensional periodic structure with respect to the magnetic permeability (hereinafter, this non-polarized light is referred to as “non-polarized incident light”). as shown in FIG. 1, it is assumed that the permeability in the propagation direction and the at least one direction perpendicular to its propagation direction of the unpolarized wave incident light 215 is arranged to vary periodically . The non-polarized incident light 215 can generally be decomposed into right-handed circularly polarized light 213 whose electric field vector rotates clockwise and left-handed circularly polarized light 214 whose electric field vector rotates counterclockwise. The magnetic field of the right circularly polarized light 213 (hereinafter, this magnetic wave is referred to as “first magnetic field wave”) and the magnetic field of the left circularly polarized light 214 (hereinafter, this magnetic field wave is referred to as “second magnetic field wave”) are: It has become opposite to each other, both parallel to the propagation direction of the unpolarized wave incident light 215. With respect to the wavelength of the non-polarized incident light 215, the magnetic permeability of the high-permeability portion 211 and the low-permeability portion 212 in the two-dimensional photonic crystal 210, the period of spatial change of the magnetic permeability, the non-polarized incident light 215 Is appropriately set, when the first and second magnetic field waves are reflected at the boundary between the high permeability portion 211 and the low permeability portion 212 in the two-dimensional photonic crystal 210, before the reflection. And the phase after reflection differ between the first magnetic field wave and the second magnetic field wave. When the difference in the phase difference generated in this way satisfies a predetermined condition, for one of the first and second magnetic field waves, scattering acts in a direction that weakens the magnetic field, and for the other, scattering causes the magnetic field to strengthen. work. As a result, only one of the first and second magnetic waves passes through the two-dimensional photonic crystal 210 as in the above-described photonic crystal that functions as a linear polarizer. Therefore, in the two-dimensional photonic crystal 210, by appropriately setting the magnetic permeability of the high magnetic permeability portion 211 and the low magnetic permeability portion 212, the period of spatial change of the magnetic permeability, and the direction of the non-polarized incident light 215, The two-dimensional photonic crystal 210 can function as a circular polarizer with respect to the non-polarized incident light 215 to obtain the circularly polarized outgoing light 216. Therefore, as in a twentieth reference example described later, a photonic crystal layer functioning as a circular polarizer can be formed as a single layer on the end face of the optical fiber (a specific forming method will be described later).

<Formation of photonic crystal layer on end face of optical fiber>
Next, a method for producing a photonic crystal on the end face of the optical fiber will be described. FIG. 2 is a view for explaining a method for producing a photonic crystal having a periodic structure composed of three-dimensional high refractive index fine particles 221 and a low refractive index portion 222. In this manufacturing method, the photonic crystal 223 is formed on the end face of the optical fiber as follows. In the following, the production of a photonic crystal having a periodic structure with respect to the refractive index will be described. However, a photonic crystal having a periodic structure with respect to the magnetic permeability can be produced in the same manner.

(1) First, a plurality of optical fibers are bundled so that one end face of each optical fiber is aligned on substantially the same plane, and an optical fiber bundle 224 is created.
(2) The end face of the optical fiber bundle 224 composed of the end faces aligned on substantially the same plane as described above is used as a substrate, and the wavelength of the light beam (used beam) to be transmitted by the optical fiber on the substrate. High refractive index fine particles 221 having a particle diameter of about 20 to 80% of (wavelength) are periodically laminated.
(3) The optical fiber bundle 224 in which the high refractive index fine particles 221 are periodically laminated on the end face as described above is separated into individual optical fibers.

  Through the above steps (1) to (3), an optical fiber in which a photonic crystal is produced on the end face can be mass-produced. Of course, the number of optical fiber bundles 224 is not limited and is not suitable for mass production, but the number may be one.

  In FIG. 2, the cross section of the core 3 of the optical fiber and the high refractive index fine particles 221 are drawn with substantially the same size, but the core diameter of a normal optical fiber is 5 to 300 μm and the beam wavelength used is 0.85 μm. , The particle diameter of the high refractive index fine particles 221 is 0.17 to 0.68 μm. In the photonic crystal 223 shown in FIG. 2, the low refractive index portion 222 is air, but after the fine particles are stacked in the same manner as in the above step (2), the refractive index of the fine particles is determined in the gap between the fine particles. Alternatively, a material having a larger refractive index may be filled. In this case, a photonic crystal having a periodic structure in which the laminated fine particle portion is a low refractive index portion and the material filled between the fine particles is a high refractive portion is obtained. The photonic crystal 223 shown in FIG. 2 has a periodic structure in which a high refractive index portion and a low refractive index portion are alternately repeated, but a high permeability portion and a low permeability portion are alternately repeated. A photonic crystal having a periodic structure can be formed on the end face of the optical fiber in the same manner as described above.

  According to the method of periodically laminating the high refractive index fine particles 221 by the steps (1) to (3) as described above, the high refractive index fine particles 221 have a regular pattern, typically at regular intervals. Will be arranged. However, when the high refractive index fine particles 221 are arranged in a predetermined pattern on the end face of the optical fiber, a further process is required.

  For example, in the step (2), a step of creating a desired groove pattern on the end face of the optical fiber is added before the high refractive index fine particles 221 are laminated. If the high refractive index fine particles 221 are laminated after creating the predetermined groove pattern in this way, the high refractive index fine particles 221 can be arranged in accordance with the pattern and have a desired structure with respect to the optical fiber surface. A photonic crystal can be formed.

  Here, the groove pattern refers to a set of shallow grooves provided to fix the high refractive index fine particles 221 at predetermined positions. The width and depth of the groove are not particularly limited. In addition, the pattern is not limited to the groove pattern as long as the high refractive index fine particles 221 can be fixed at predetermined positions, respectively, and is configured by one or two or more linear or dotted protrusions. Even a pattern to be formed may be a pattern constituted by a dot-like or planar depression.

  As specific methods for creating the groove pattern as described above on the end face of the optical fiber, for example, the following three methods are conceivable. The first method is to create a groove pattern by drawing a desired groove pattern with an electron beam and developing it after forming a resin film such as PMMA (polymethyl methacrylate) on the substrate by spin coating or the like. . The second method is a method in which a mask having a desired groove pattern is arranged on a substrate, an etching process is performed, and then the mask is removed. The third method is to create a groove pattern by pressing a precision mold having a desired groove pattern against the substrate with a predetermined force.

  Incidentally, the end face of the optical fiber on which the photonic crystal 223 shown in FIG. 2 is formed is perpendicular to the central axis of the core 3 of the optical fiber, but is different from the stacking direction (growth direction) of the photonic crystal 223 described above. May correspond to optimal conditions (or suitable conditions). That is, for example, when a photonic crystal functioning as a polarizer is formed on the end face of an optical fiber, the stacking direction of the photonic crystal is the light emitting direction from the end face of the optical fiber (or the incident direction of light on the end face) ), The photonic crystal sometimes functions optimally or suitably as a polarizer. At this time, first, for example, oblique polishing is performed so that the end surface on which the photonic crystal is to be formed forms a predetermined angle with respect to the central axis of the core 3 of the optical fiber (the optical axis 225 of the core 173 in FIG. 3 described later). To process the end face of the optical fiber. That is, as shown in FIG. 3, an optical fiber 148 having an oblique end face 226 that is processed so that the angle formed between the normal direction and the optical axis 225 corresponds to the optimum condition is manufactured. Next, high refractive index fine particles 221 are periodically laminated in the normal direction 227 of the oblique end face 226 in the same manner as in the above step (2). As a result, a photonic crystal having a periodic structure in which the fine particles 221 are high refractive index portions and the air existing in the gap between the fine particles 221 is the low refractive index portion 222 is formed on the oblique end surface 226 of the optical fiber 148.

  As in the above steps (1) to (3), a plurality of optical fibers 148 formed with the oblique end surfaces 226 are bundled so that the oblique end surfaces 226 are aligned on the same plane, and an optical fiber bundle is created. After the photonic crystal is formed on the oblique end surface of the optical fiber bundle as described above, the optical fiber bundle may be separated into individual optical fibers. In this way, an optical fiber in which a photonic crystal is produced on the oblique end face 226 can be mass-produced.

  Also, as shown in FIG. 3, when a photonic crystal laminated in an oblique direction with respect to the optical axis 225 of the optical fiber 148 is optically coupled to an optical component having a plane perpendicular to the optical axis 225, Although it may be used on the end face, a resin or the like is applied onto the photonic crystal laminated obliquely so that the end face of the optical fiber 148 on which the photonic crystal is laminated is in close contact with the surface of the optical component. An end surface perpendicular to the optical axis 225 may be formed.

  Although the case where a three-dimensional photonic crystal is produced on the end face of the optical fiber has been described above, a multilayer having a periodic structure in the stacking direction instead of a three-dimensional periodic structure on an end face perpendicular to or oblique to the optical axis. A similar method can also be used when producing a one-dimensional photonic crystal having a film structure.

<Formation of photonic crystal layer in optical fiber>
Next, a method for producing a photonic crystal in an optical fiber will be described. So as to penetrate an optical fiber having a core and a cladding, to form a plurality of parallel cylindrical holes each other, the cylindrical hole is assumed to be distributed at regular intervals. Such cylindrical holes are formed by, for example, mechanical processing using a drill or the like perpendicular to the optical axis of the optical fiber, optical processing using a laser or the like, or chemical processing such as heat treatment or etching. Thus, a plurality of minute holes penetrating the core are created. Etching is performed, for example, by dry etching using anodized alumina as a mask. The cylindrical hole thus formed may be filled with air or a gas having various refractive indexes, or may be filled with a material having an arbitrary refractive index, for example, by a sol-gel method. Here, if the material to be filled is a functional material such as a Faraday crystal or a liquid crystal, the corresponding portion in the optical fiber has a function of a polarizer, a Faraday element, a λ / 4 plate, etc. according to the properties of the functional material. It will be. Specific manufacturing methods of optical devices using them will be described later in each reference example.

  The plurality of cylindrical holes as described above form a photonic crystal is related to the distribution state of the holes. FIG. 4 shows a photonic band obtained as a result of the simulation when cylindrical holes are distributed squarely in the core of the optical fiber. In FIG. 4, the horizontal axis corresponds to the propagation direction of light, and all directions in the Brillouin zone are developed. The vertical axis corresponds to the normalized frequency. A solid line indicates TM mode light, and a dotted line indicates TE mode light. The wave vector in the Brillouin zone on the horizontal axis corresponds to the propagation direction of light in the optical fiber, and the standard frequency on the vertical axis corresponds to the light source wavelength.

In the example of FIG. 4, there is no TM mode light at the light source wavelength in the TM mode forbidden band, and only TE mode light can propagate. Moreover propagation direction allowed the light of the TE mode, it can be seen that is limited to a certain propagation direction. Therefore, it is preferable to distribute the cylindrical holes so that the direction in which the TE mode can propagate matches the optical axis of the optical fiber. This optical device can function as a polarizer that propagates only the TE mode in a certain propagation direction at the light source wavelength in this frequency band. Therefore, if the cylindrical holes are distributed so that the propagation direction of the polarizer coincides with the optical axis of the optical fiber, the optical fiber acts as a polarizer for a mode propagating in the vicinity of the optical axis.

  In addition, although the photonic band shown in FIG. 4 was illustrated as a case where a cylindrical hole is distributed, it is not restricted to this. For example, when a cylindrical hole is filled with various substances to form a cylindrical body, the refractive index of the substance constituting the cylindrical body can be changed. Accordingly, not only the TE mode but also the TM mode can function as a polarizer in all propagation directions depending on conditions such as the refractive index, the outer diameter, and the distribution mode of the cylindrical hole portion.

  In this way, when a plurality of parallel cylindrical holes having a refractive index different from the refractive index of the core in the direction perpendicular to the optical axis of the optical fiber are formed at regular intervals, in addition to the optical waveguide function of the optical fiber By controlling the refractive index and outer diameter of the cylindrical hole and the distribution of the cylindrical hole, a difference occurs in the dispersion characteristics of the two types of linearly polarized light (TM, TE) with respect to the light source wavelength. Functions such as a polarizer and a λ / 4 plate can be provided. The shape of the hole is not limited to a cylindrical shape, and may be another shape. Hereinafter, embodiments in which the above method is applied to various optical devices will be described as reference examples.

Optical device according to each of the following Reference Examples, a core through which light propagation, in a certain section along the optical axis of the optical fiber comprising a cladding enclosing the core, the first functional unit and the second functional unit Or two functional parts including a third functional part. These functional units are provided at regular intervals along the optical axis of the optical fiber. The first functional unit is configured such that a plurality of parallel columnar bodies made of a material having a refractive index different from the refractive index of the material forming the core penetrate the optical fiber or its core. Specifically, this columnar body is filled with, for example, a substance having an electro-optic effect or a substance having a Faraday effect. The second and third functional parts are configured such that a plurality of parallel columnar bodies having cavities (holes) pass through the core. Since these functional units are included, the present optical device makes a difference in the dispersion characteristics of two types of linearly polarized light (TM, TE), and each functional unit as a polarizer, a λ / 4 plate, a Faraday element, etc. Can function.

(First reference example)
Hereinafter, a first reference example of the present invention will be described with reference to the drawings. FIG. 5A is a schematic side view showing the configuration of the optical device according to the first reference example of the present invention. FIG. 5B is a schematic cross-sectional view of the optical device of FIG. 5A cut perpendicularly to the optical axis 2 at the position of line BB ′ in the drawing. FIG. 5C is a schematic cross-sectional view of the optical device of FIG. 5A cut perpendicularly to the optical axis 2 at the position of line CC ′ in the drawing. In FIG. 5A, the optical fiber 1 is shown by taking out only a predetermined section corresponding to the optical device.

  As shown in FIG. 5A, the present optical device is formed in an optical fiber 1, and the optical fiber 1 includes a core 3 that transmits light and a clad 4 that surrounds the core 3. In addition, the optical fiber 1 is formed with two functional parts including a first functional part 7 and a second functional part 8 and functions as an optical device. The first functional unit 7 and the second functional unit 8 are provided at a predetermined interval along the optical axis 2 of the optical fiber 1. In the optical fiber 1, the portions other than the functional unit only realize an optical transmission function that is a normal function of the optical fiber.

  First, the first functional unit 7 is formed so as to penetrate the core 3 and the clad 4 of the optical fiber 1 in a direction perpendicular to the optical axis 2 in a certain section along the optical axis 2 of the optical fiber 1. The plurality of Faraday crystal replacement cylinders 5 are parallel to each other. The plurality of Faraday crystal-substituted cylinders 5 are formed on the cylindrical holes penetrating the core 3 and the clad 4 of the optical fiber 1 in a direction perpendicular to the optical axis 2 by, for example, a sol-gel method. Faraday crystal having a different refractive index is filled. The Faraday crystal is, for example, a garnet crystal. Further, the Faraday crystal-substituted cylinders 5 are distributed so as to form a lattice in a plane perpendicular to the longitudinal direction. Here, it is assumed that a magnetic field 20 having a sufficient strength to saturate the Faraday rotation of the plane of polarization of light exists parallel to the optical axis 2 of the optical fiber 1.

  Next, the second functional unit 8 is formed so as to penetrate the core 3 and the clad 4 of the optical fiber 1 in a direction perpendicular to the optical axis 2 in a certain section along the optical axis 2 of the optical fiber 1. The plurality of holes 6 that are hollow inside and parallel to each other are formed. The plurality of holes 6 are also distributed so as to form a lattice in a plane perpendicular to the longitudinal direction, similarly to the Faraday crystal replacement cylinder 5. However, the longitudinal direction of the plurality of holes 6 is set to have an angle of 45 ° with respect to the longitudinal direction of the Faraday crystal replacement column 5 of the first functional unit 7 along a plane perpendicular to the optical axis 2. The This cylindrical hole 6 also has a refractive index different from the refractive index of the core 3 of the optical fiber 1 by, for example, being naturally filled with air.

  Note that the Faraday crystal replacement column 5 of the first functional unit 7 and the columnar hole 6 of the second functional unit 8 form an angle of 45 ° with each other, as shown in FIGS. It is clear if (c) is compared and referenced.

  Further, the first and second functional units 7 and 8 will be described in detail. As described above, a cylinder having a refractive index different from the refractive index of the core 3 of the optical fiber 1 can be formed by a method such as drilling, laser, or etching in a direction perpendicular to the optical axis 2 of the optical fiber 1. The first functional unit 7 is composed of a plurality of Faraday crystal replacement columns 5 prepared by filling the columnar holes formed in this manner with a Faraday crystal by a sol-gel method, and functions as a polarizer and a Faraday element. Have at the same time. Further, the second functional unit 8 is composed of only a plurality of holes 6 and calculates in advance the outer diameter of the holes 6 and the distribution state of the holes 6 so as to have a function of a polarizer (analyzer). It has a hole 6 formed with the direction that forms an angle of 45 ° with the longitudinal direction of the Faraday crystal replacement column 5 of the first functional unit 7 as the longitudinal direction.

  As described above, a plurality of parallel cylindrical holes having a refractive index different from the refractive index of the core 3 in a direction perpendicular to the optical axis 2 of the optical fiber or cylinders filled with a functional material in the holes are arranged at regular intervals. If the refractive index and the outer diameter of the hole or cylinder and the distribution of the hole or cylinder are controlled with respect to the light source wavelength, the dispersion characteristics of the two types of linearly polarized light (TM, TE) are different. As a result, the first functional unit 7 in the optical fiber 1 forms a polarizer and a Faraday element, and the second functional unit 8 forms an analyzer. Acts as an isolator. Accordingly, the work of coupling the optical isolator to the waveguide by the lens is eliminated, and at the same time, the number of parts can be reduced, and the cost can be greatly reduced.

  Next, FIG. 6 is a partial schematic configuration diagram according to another example of the optical device according to the first reference example of the present invention. The hole 6 shown in FIG. 6 may be the hole 6 included in the second functional unit 8 in FIG. 5A or the hole before the Faraday crystal replacement column 5 is formed.

  In the above description, the cylindrical hole 6 or the hole for forming the Faraday crystal substituted column 5 is formed so as to penetrate through the cladding 4, but only the core 3 portion is formed as shown in FIG. 6. You may form a hole in. This is because light actually passes through only the core 3 inside the optical fiber 1, and the optical fiber 1, regardless of whether the cylindrical hole penetrates including the cladding 4 or only the core 3. This is because the effect of the light passing through the inside is hardly changed.

  In the first reference example, the shape of the hole has been described as a cylinder. However, the shape of the hole is not limited to a cylinder, and may be other shapes such as a quadrangular column, a polygonal column, and an elliptical column. The above function has been described as being realized by a two-dimensional photonic crystal composed of a plurality of holes or cylinders parallel to each other. It may be realized with a two-dimensional photonic crystal.

(Second reference example)
Hereinafter, a second reference example of the present invention will be described with reference to the drawings. FIG. 7A is a schematic side view showing the configuration of the optical device according to the second reference example of the present invention. FIG. 7B is a schematic cross-sectional view of the optical device of FIG. 7A cut out perpendicular to the optical axis 2 at the position of line BB ′ in the drawing. FIG. 7C is a schematic cross-sectional view of the optical device of FIG. 7A cut out perpendicular to the optical axis 2 at the position of line CC ′ in the drawing. In FIG. 7A, the optical fiber 1 is shown by extracting only a predetermined section corresponding to the optical device.

  As shown in FIG. 7, this device includes an incident-side optical fiber 41 that has a core 45 and a clad 46 and receives light, and an output-side optical fiber that has a core 45 and a clad 46 and emits light. 42, a Faraday element 47 provided between the incident side optical fiber 41 and the output side optical fiber 42 and rotating the polarization plane of the light, and the optical axis of the incident side optical fiber 41 and the optical axis of the Faraday element 47 It comprises a guide 48 that mechanically adjusts the optical axis of the emission side optical fiber 42. The Faraday element 47 is, for example, a garnet crystal.

  The incident-side optical fiber 41 is formed in a certain section along the optical axis 49 so as to pass through the core 45 and the clad 46 in a direction perpendicular to the optical axis 49, and is formed of a plurality of columnar first parallel to each other. 1 hole 43 is provided. The first holes 43 are distributed at regular intervals and have a refractive index different from the refractive index of the core 45 in the optical fiber 41.

  Similarly, the exit-side optical fiber 42 is formed of a plurality of circles parallel to each other and formed so as to penetrate the core 45 and the clad 46 in a direction perpendicular to the optical axis 49 for a certain section along the optical axis 49. A columnar second hole 44 is provided. The second holes 44 are also distributed at regular intervals, and have a refractive index different from the refractive index of the core 45 in the optical fiber 42.

  Here, for the first hole 43 and the second hole 44, as described in the first reference example, the plurality of first holes 43 and the plurality of second holes 44 are respectively polarizers. Is distributed to act as. The first and second holes 43 and 44 need only be periodically distributed as described above with reference to FIG. Further, the direction of the first hole 43 and the direction of the second hole are different from each other by 45 ° in the longitudinal direction, as is apparent from comparison between FIG. 7B and FIG. 7C. Is set to Here, in connection with the Faraday element 47, it is assumed that a magnetic field 40 having a strength sufficient to saturate the Faraday rotation of the plane of polarization of light exists parallel to the optical axis 49.

  The method of forming the first and second holes 43 and 44 is the same as that of the first reference example, and the holes are drilled, lasered, and etched in a direction perpendicular to the optical axis 49 of the optical fiber. Form.

  By the way, in this reference example, the incident side optical fiber 41 and the output side optical fiber 42 are mechanically related by the guide 48, and each can be freely rotated around the optical axis 49. Therefore, the angle adjustment is performed when adjusting the optical axis in the guide 48 so that the first hole 43 in the incident side optical fiber 41 and the second hole 44 in the output side optical fiber 42 form an angle of 45 ° relatively. May be. According to the configuration of such an optical device, the first hole 43 in the incident side optical fiber 41 and the second hole 44 in the output side optical fiber 42 can be manufactured in the same manner, and the relative angle of each other is later. Therefore, it can be manufactured at low cost.

  In the above description, the cylindrical hole is formed so as to penetrate through including the clad 46, but the hole may be formed only in the core 45 as in the case of FIG. Further, the first hole 43 or the second hole 44 may be filled with a substance such as a Faraday crystal having a refractive index different from the refractive index of the core 45 of each optical fiber. Here, when the Faraday crystal is filled in the first hole 43 or the second hole 44, the Faraday element 47 may be omitted.

  Furthermore, although the shape of the hole has been described as a cylinder in the second reference example, the shape is not limited to a cylinder, and may be other shapes such as a quadrangular column, a polygonal column, and an elliptical column. The above function has been described as being realized by a two-dimensional photonic crystal composed of a plurality of parallel cylinders. However, the present invention is not limited to such a case. It may be realized with a nick crystal. Further, instead of the first hole 43 in the incident side optical fiber 41 and the second hole 44 in the output side optical fiber 42, a photonic crystal layer is formed on the end faces of the incident side optical fiber 41 and the output side optical fiber 42. May be used. With respect to a method for producing a photonic crystal on an end face of an optical fiber, for example, a photonic crystal having a periodic structure composed of three-dimensional high refractive index fine particles 221 and a low refractive index portion 222 is produced using FIG. The method is described above.

  In this way, a polarizer and an analyzer can be formed simply by performing the same processing for forming a hole in an optical fiber, and a Faraday element is combined with the optical fiber acting as the polarizer and the analyzer. Thus, an optical isolator can be configured. Accordingly, the work of coupling the optical isolator to the waveguide by the lens is eliminated, and at the same time, the number of parts can be reduced, and the cost can be greatly reduced.

(Third reference example)
Below, the 3rd reference example of this invention is demonstrated with reference to drawings. FIG. 8 is a schematic side view showing the configuration of the optical device according to the third reference example of the present invention. In FIG. 8, the optical fiber 51 is shown by extracting only a predetermined section corresponding to the optical device.

  As shown in FIG. 8, the optical device includes an optical fiber 51, a pair of electrodes 59 that generate an electric field in a direction perpendicular to the optical axis 52 of the optical fiber, and a signal source that applies a predetermined voltage to the electrode 59. 50. The optical fiber 51 includes a core 53 that transmits light and a clad 54 that encloses the core 53. In addition, the optical fiber 51 is formed with two functional parts including a first functional part 57 and a second functional part 58, and functions as an optical device. The first functional unit 57 and the second functional unit 58 are provided at a predetermined interval along the optical axis 52 of the optical fiber 51.

First, the first functional unit 57 is formed so as to penetrate the core 53 and the clad 54 of the optical fiber 51 in a direction perpendicular to the optical axis 52 in a certain section along the optical axis 52 of the optical fiber 51. The plurality of Pockels crystal replacement cylinders 55 are parallel to each other. The Pockels crystal substitution cylinders 55 are distributed so as to form a lattice in a plane perpendicular to the longitudinal direction. By the way, the plurality of Pockels crystal replacement cylinders 55 are produced by filling Pockels crystals into the cylindrical holes by, for example, a sol-gel method. This Pockels crystal is known as a substance exhibiting a primary electro-optic effect. For example, a LiNbO ₃ crystal, a LiTaO ₃ crystal, a NH ₄ H ₂ PO ₄ crystal, a KH ₂ PO ₄ crystal, or the like can be used.

  Next, the second functional unit 58 is formed so as to penetrate the core 53 and the clad 54 of the optical fiber 51 in a direction perpendicular to the optical axis 52 in a certain section along the optical axis 52 of the optical fiber 51. The plurality of holes 56 that are hollow inside and parallel to each other are formed. The plurality of holes 56 are also distributed in a plane perpendicular to the longitudinal direction so as to form a lattice, and have a refractive index different from the refractive index of the core 53 of the optical fiber 5.

  Further, the first and second functional units 57 and 58 will be described in detail. As described above, a cylinder having a refractive index different from the refractive index of the core 53 of the optical fiber 51 can be formed by a method such as drilling, laser, or etching in a direction perpendicular to the optical axis 52 of the optical fiber 51. The first functional unit 57 is composed of the Pockels crystal replacement cylinder formed as described above, and has the functions of a polarizer and a Pockels element at the same time. Further, the second functional unit 58 is composed of only a plurality of holes 56 and calculates in advance the outer diameter of the holes 56 and the distribution state of the holes 56 so as to have a function of a polarizer (analyzer). The first functional unit 57 has a hole 56 formed perpendicularly or parallel to a Pockels crystal replacement cylinder 55 along a plane perpendicular to the optical axis 52. The arrangement of the holes may be distributed with the periodic structure as described above in the description of FIG.

  Further, the refractive index of the Pockels crystal replacement cylinder 55 is changed by controlling the magnitude of the electric field applied to the electrode 59 by the signal source 50 so that the Pockels crystal replacement cylinder 55 also functions as a λ / 4 plate. Further, the signal source 50 can periodically change the electric field applied to the electrode 59. Then, since the refractive index of the Pockels crystal replacement cylinder 55 changes, the optical signal transmitted through the first functional unit 57 can be changed.

  As described above, the polarizer, the Pockels element, the λ / 4 plate, and the analyzer can be formed only by processing the optical fiber 51, so that the optical fiber 51 functions as an optical modulator. Accordingly, the work of coupling the lens to the waveguide of the optical modulator is eliminated, and at the same time, the number of parts can be reduced, and the cost can be greatly reduced.

  In the above description, the cylindrical hole is formed so as to penetrate through including the clad 54, but the hole may be formed only in the core 53 as in the case of FIG. The shape of the hole has been described as a cylinder, but is not limited to a cylinder, and may be other shapes such as a quadrangular prism, a polygonal column, and an elliptical column. Further, the above function has been described as being realized by a two-dimensional photonic crystal composed of a plurality of parallel cylinders. However, the present invention is not limited to such a case, and a three-dimensional photo having a structure called a jabronovite or a woodpile. It may be realized with a nick crystal.

(Fourth reference example)
Hereinafter, a fourth reference example of the present invention will be described with reference to the drawings. FIG. 9 is a schematic side view showing an optical device according to a fourth reference example of the present invention. In FIG. 9, the optical fiber 61 is shown by extracting only a predetermined section corresponding to the optical device.

  As shown in FIG. 9, this optical device includes an optical fiber 61, an electrode 63 that generates an electric field in a direction perpendicular to the optical axis 62 of the optical fiber 61, and a signal source 60 that applies an electric field to the electrode 63. Composed. The optical fiber 61 includes a core 83 that transmits light and a clad 84 that encloses the core 83. Further, the optical fiber 61 is formed with three functional parts including a first functional part 67, a second functional part 68, and a third functional part 69, and functions as an optical device. The first to third functional units 67 to 69 are provided at a predetermined interval along the optical axis 62 of the optical fiber 61.

  Here, the first functional unit 67 in the present reference example is similar to the first functional unit 57 in the third reference example with respect to the optical axis 62 for a certain section along the optical axis 62 of the optical fiber 61. It is composed of a plurality of Pockels crystal replacement cylinders 64 which are formed so as to penetrate the core 83 and the clad 84 of the optical fiber 61 in the vertical direction and are parallel to each other.

  Further, the second and third functional units 68 and 69 in the present reference example are optically transmitted in a certain section along the optical axis 62 of the optical fiber 61 in the same manner as the second functional unit 58 in the third reference example. A plurality of first and second holes 65 and 66 are formed so as to penetrate the core 83 and the clad 84 of the optical fiber 61 in a direction perpendicular to the axis 62 and are hollow inside and parallel to each other. Is done. The plurality of first and second holes 65 and 66 are distributed so as to form a lattice in a plane perpendicular to the longitudinal direction, and have a refractive index different from the refractive index of the core 83 of the optical fiber 61. Have a rate. The first and second holes 65 and 66 are provided perpendicularly or parallel to the Pockels crystal replacement cylinder 64 in the first functional unit 67 along a plane perpendicular to the optical axis 62.

  Further, the first to third functional units 67 to 69 will be described in detail. As described above, a cylinder having a refractive index different from the refractive index of the core 83 of the optical fiber 61 can be formed by a method such as drilling, laser, or etching in the direction perpendicular to the optical axis 62 of the optical fiber 61. The first functional unit 67 is composed of the Pockels crystal replacement cylinder 64 formed as described above, and has the functions of a polarizer and a Pockels element at the same time. Further, the second functional portion 68 is composed of only a plurality of first holes 65, and the outer diameter of the first holes 65 and the distribution of the first holes 65 so as to have the function of a λ / 4 plate. The first hole 65 formed in advance or parallel to the Pockels crystal replacement cylinder 64 in the first functional unit 67 is calculated. As for the arrangement of the holes, the holes may be periodically distributed as described above with reference to FIG. Similarly to the second functional unit 68, the third functional unit 69 is also perpendicular to the Pockels crystal replacement cylinder 64 in the first functional unit 67 so as to have the function of a polarizer (analyzer). Or it has the 2nd hole 66 formed in parallel.

  Further, the signal source 50 changes the optical signal transmitted through the first functional unit 67 by changing the refractive index of the Pockels crystal replacement cylinder 55 by periodically changing the electric field applied to the electrode 59. Can do.

  As described above, the polarizer, the Pockels element, the λ / 4 plate, and the analyzer can be formed only by processing the optical fiber 61, so that the optical fiber 61 functions as an optical modulator. Accordingly, the work of coupling the lens to the waveguide of the optical modulator is eliminated, and at the same time, the number of parts can be reduced, and the cost can be greatly reduced.

  In the above description, the cylindrical hole is formed so as to penetrate through the cladding 84 and the like, but the hole may be formed only in the core 83 as in the case of FIG. The shape of the hole has been described as a cylinder, but is not limited to a cylinder, and may be other shapes such as a quadrangular prism, a polygonal column, and an elliptical column. The above function has been described as being realized by a two-dimensional photonic crystal composed of a plurality of parallel cylinders. However, the present invention is not limited to such a case. It may be realized with a nick crystal.

(Fifth reference example)
Hereinafter, a fifth reference example of the present invention will be described with reference to the drawings. FIG. 10 is an overall view of an optical device according to a fifth reference example of the present invention, and FIG. 11 is a schematic view in which the functional unit 78 shown in FIG. 10 is enlarged and the optical fiber 71 is viewed from an oblique direction. FIG.

  As shown in FIG. 11, the present optical device is formed in an optical fiber 71, and the optical fiber 71 includes a core 75 that transmits light and a clad 76 that surrounds the core 75. In addition, the optical fiber 71 is formed with a functional unit 78 and functions as an optical device.

  The functional unit 78 is formed so as to penetrate the core 75 and the clad 76 of the optical fiber 71 in a direction perpendicular to the optical axis 72 in a certain section along the optical axis 72 of the optical fiber 71. In this case, the holes 77 are parallel to each other. The plurality of holes 77 are distributed in a plane perpendicular to the longitudinal direction so as to form a lattice, and have a refractive index different from the refractive index of the core 75 of the optical fiber 71. As described above, the hole 77 can be formed in a direction perpendicular to the optical axis 72 of the optical fiber 71 by a method such as drilling, laser, or etching.

  As described above, when a plurality of parallel cylindrical holes having a refractive index different from the refractive index of the core 75 in the direction perpendicular to the optical axis 72 of the optical fiber are formed at regular intervals, the cylindrical light source wavelength is By controlling the refractive index and the outer diameter and the distribution of the cylinder, a difference occurs in the dispersion characteristics of the two types of linearly polarized light (TM, TE). As a result, the function unit 78 can have a dispersion characteristic that delays the advanced wavelength and advances the delayed wavelength. As described above, if the phase speed of the light source wavelength can be increased or delayed, the signal 79a spread due to the chromatic dispersion characteristic unique to the optical fiber also has a steep shape like the incident light 73 after passing through the function unit 78. It can be formed to have a wavelength dispersion characteristic that restores the pulse signal 79b. Therefore, since the emitted light 74 becomes a signal like the incident light 73, the present optical device functions as a dispersion compensator.

  Thus, the optical fiber 71 acts as a dispersion compensator only by processing the optical fiber 71. Accordingly, the work of coupling the lens to the waveguide of the optical modulator is eliminated, and at the same time, the number of parts can be reduced, and the cost can be greatly reduced.

  In the above description, the cylindrical hole is formed so as to penetrate through the clad 76 and the like, but the hole may be formed only in the core 75 as in the case of FIG. The shape of the hole has been described as a cylinder, but is not limited to a cylinder, and may be other shapes such as a quadrangular prism, a polygonal column, and an elliptical column. Further, the above function has been described as being realized by a two-dimensional photonic crystal composed of a plurality of parallel cylinders. However, the present invention is not limited to such a case, and a three-dimensional photo having a structure called a jabronovite or a woodpile. It may be realized with a nick crystal. However, when the optical fiber 71 is a polarization-preserving optical fiber, the arrangement direction becomes a problem, which is not suitable for realization with a three-dimensional photonic crystal.

<Specific mounting on optical fiber>
Next, in the following reference example, a case where an optical device such as an optical modulator is mounted on an optical fiber will be specifically described. In the following reference examples, it is easy to form a plurality of columnar bodies parallel to each other through the core using a plane formed by partially removing the clad. Moreover, since an electrode can be provided on this clad removal surface, a uniform and stable electric field can be applied to the functional part. This will be described in detail below.

(Sixth reference example)
Hereinafter, a sixth reference example of the present invention will be described with reference to the drawings. FIG. 12 is a horizontal sectional view showing an entire optical device according to a sixth reference example of the present invention. FIG. 13A is an enlarged side sectional view of a part shown in FIG. FIG. 13B is a schematic cross-sectional view of the optical device of FIG. 13A cut out perpendicular to the optical axis 2 at the position of line BB ′ in the drawing.

  As shown in FIGS. 12 and 13, this optical device includes an optical fiber 1 and a capillary 12 that covers the periphery of the optical fiber 1. The optical fiber 1 includes a core 3 that transmits light and a clad 4 that surrounds the core 3. In addition, the optical fiber 1 has two functional units including a first functional unit 7 and a second functional unit 8. The first functional unit 7 and the second functional unit 8 are provided at a predetermined interval along the optical axis 22 of the optical fiber 1. Since these functional units are included, this optical device can be used as a polarizer or the like by making a difference in the dispersion characteristics of the two types of linearly polarized light (TM, TE) included in the incident light 16. .

  Here, the first and second functional units 7 and 8 according to this reference example are the same as the first and second functional units 57 and 58 according to the third reference example, and the cylinder according to this reference example. Since the body 19 and the hole 6 are formed and distributed in the same manner as the Pockels crystal replacement cylinder 55 and the hole 56 according to the third reference example, description thereof will be omitted. However, the cylindrical body 19 and the hole 6 are arranged to be parallel to each other.

  Here, in the optical fiber 1, in order to form the first and second functional portions 7 and 8, the clad deletion portion 18 is removed in a predetermined section, and the clad deletion portion 18 is substantially in contact with the core 3. To the position, it has been removed from both sides of the optical fiber 1. As a result, parallel boundary surface pairs 23 are formed which are parallel to each other with the core 3 interposed therebetween and have a rectangular side cross section. Therefore, as shown in FIG. 13 (b), the optical fiber 1 has a shape in which the left and right sides of the optical fiber 1 are cut in a predetermined section, leaving the left and right portions of the clad remaining in the upper and lower portions in the drawing. The parallel boundary surface pair 23 is exposed to the outside. If produced in this way, the cylindrical body 19 and the hole 6 can be easily formed.

  Further, the pair of electrodes 9 for applying an electric field to the plurality of cylindrical bodies 19 made of Pockels crystal constituting the first functional unit 7 are provided on the parallel boundary surface pair 23 as described above. The electrode 9 is provided on the side of the optical fiber 1, and the applied electric field direction is parallel to the plurality of cylindrical bodies 19. Thus, by arranging the electrode 9 on the parallel boundary surface pair 23, an electric field can be easily and accurately applied to the cylindrical body 19. A signal source 10 that applies a voltage to the electrode 9 is installed outside the capillary 12. One electrode 9 is connected to the ground 11.

  Next, the capillary 12 covering the periphery of the optical fiber 1 has an outer diameter substantially equal to the ferrule 14 of the other optical fiber 13 to be connected. As a result, when this optical device is to be connected to another optical fiber 13, the capillary 12 is pushed by the ferrule of the other optical fiber and the split sleeve 15, and the optical axis is coupled in the same manner as the optical system coupling between the optical fibers. Since they can be combined, the optical system can be easily coupled.

(Seventh reference example)
Hereinafter, a seventh reference example of the present invention will be described with reference to the drawings. FIG. 14A is a schematic side view showing an optical device according to a seventh reference example. FIG. 14B is a schematic cross-sectional view of the optical device of FIG. 14A taken perpendicularly to the optical axis 2 at the position of line BB ′ in the drawing.

  As shown in FIG. 14, this optical device has substantially the same configuration as the optical device according to the sixth reference example shown in FIG. 13, but the installation position and shape of the parallel electrodes 24 are related to the sixth reference example. Different from the electrode 9. The parallel electrode 24 according to this reference example applies an electric field perpendicular to the longitudinal direction of the plurality of cylindrical bodies 19 made of Pockels crystal constituting the first functional unit 7 and also perpendicular to the optical axis 22. As described above, the parallel electrodes 24 are provided so as to be parallel to the optical axis 22 of the optical fiber 1 and perpendicular to the longitudinal direction of the cylindrical body 19. That is, as shown in FIG. 14A, the electrode 9 has a structure in which a pair of parallel electrodes 24 are provided above and below the plurality of columnar bodies 19 on a plane perpendicular to the longitudinal direction of the columnar body 19. It is different from the case. The plane perpendicular to the longitudinal direction of the cylindrical body 19 is parallel to each other across the core 3 formed as a result of removing the clad removal portion 18 as shown in FIG. Thus, the parallel boundary surface pair 23 has a rectangular side section. However, since the pair of parallel electrodes 24 are provided on the same plane, as shown in FIG. 14 (b), the clad removal portion 18 is removed from the left and right sides of the optical fiber 1, and two surfaces (parallel boundary surfaces) are obtained. There is no need to form pair 23). Therefore, the clad removal portion 18 may be removed so that only one of the planes for arranging the parallel electrodes 24 is formed. The light modulation function of the first functional unit 7 composed of a plurality of cylindrical bodies 19 made of Pockels crystals can be adjusted by the parallel electrodes 24 arranged as described above.

  The signal source 10 for applying a voltage to the parallel electrode 24 is installed outside the capillary 12, and the other end of the parallel electrode 24 is connected to the ground 11. The light source according to the sixth reference example is Since it is the same as the device, the description of the same component is omitted.

(Eighth reference example)
The eighth reference example of the present invention will be described below with reference to the drawings. FIG. 15A is a schematic side view showing an optical device according to an eighth reference example. FIG. 15B is a schematic cross-sectional view of the optical device of FIG. 15A cut out perpendicular to the optical axis 2 at the position of line BB ′ in the drawing.

  As shown in FIG. 15, this optical device has substantially the same configuration as the optical device according to the sixth reference example shown in FIG. 13, but the installation position and shape of the column electrode 25 are related to the sixth reference example. Different from the electrode 9. The column electrode 25 according to the present reference example applies an electric field perpendicular to the longitudinal direction of the plurality of cylindrical bodies 19 made of Pockels crystals constituting the first functional unit 7 and parallel to the optical axis 22. In addition, a column electrode 25 is provided parallel to the optical axis 22 of the optical fiber 1 and perpendicular to the longitudinal direction of the cylindrical body 19. That is, as shown in FIG. 15A, the electrode 9 has a structure in which a pair of column electrodes 25 are provided on the left and right sides of the plurality of columnar bodies 19 on a plane perpendicular to the longitudinal direction of the columnar body 19. It is different from the case. The plane perpendicular to the longitudinal direction of the cylindrical body 19 is the parallel boundary surface pair 23 shown in FIG. However, since the pair of column electrodes 25 are provided on the same plane, as shown in FIG. 15 (b), the clad removal portion 18 is removed from the left and right sides of the optical fiber 1, and two surfaces (parallel boundary surfaces) are provided. There is no need to form pair 23). Therefore, the clad removal portion 18 may be removed so that only one of the planes for arranging the column electrodes 25 is formed. The light modulation function of the first functional unit 7 composed of a plurality of cylindrical bodies 19 made of Pockels crystals can be adjusted by the column electrodes 25 arranged as described above.

  The signal source 10 for applying a voltage to the column electrode 25 is installed outside the capillary 12, and the other end of the column electrode 25 is connected to the ground 11. The light source according to the sixth reference example Since it is the same as a device, the same components are denoted by the same reference numerals and description thereof is omitted.

(Ninth Reference Example)
The ninth reference example of the present invention will be described below with reference to the drawings. FIG. 16A is a schematic side view showing an optical device according to a ninth reference example. FIG. 16B is a schematic cross-sectional view of the optical device of FIG. 16A cut out perpendicularly to the optical axis 2 at the position of line BB ′ in the drawing.

  As shown in FIG. 16, this optical device has substantially the same configuration as the optical device according to the sixth reference example shown in FIG. 13, except that the clad 4 is further removed and the position of the facing electrode 26 is the sixth. This is different from the electrode 9 according to the reference example.

  First, as shown in FIG. 16 (b), the optical fiber 1 forms the first and second functional portions 7 and 8, and the clad removal portion 18 is formed in a predetermined section in order to install the facing electrode 26. The clad deleted portion 18 has been removed from the top and bottom and the left and right of the optical fiber 1 up to a position substantially in contact with the core 3. As a result, first parallel boundary surface pairs 31 are formed on the left and right sides of the core 3 so as to be parallel to each other across the core 3 and have a rectangular side cross section, and the second parallel boundary surface pair 32 is formed on the core 3. Formed above and below. Therefore, as shown in FIG. 16 (a), the optical fiber 1 is a rectangular prism whose center axis is the optical axis 22 with the remaining clad portion 21 that has not been deleted remaining in a predetermined section so as to wrap the core 3. It has a shape, and the first and second parallel boundary surface pairs 31 and 32 are exposed to the outside. If manufactured in this way, the cylindrical body 19 and the hole 6 can be easily formed, and the facing electrode 26 can be installed on a plane different from that of the sixth reference example.

  Next, the facing electrode 26 applies an electric field perpendicular to the longitudinal direction of the plurality of cylindrical bodies 19 made of Pockels crystals constituting the first functional unit 7 and also perpendicular to the optical axis 22. The facing electrode 26 is provided parallel to the optical axis 22 of the optical fiber 1 and parallel to the longitudinal direction of the cylindrical body 19. That is, as shown in FIGS. 16A and 16B, a plane parallel to the longitudinal direction of the cylindrical body 19 and parallel to the optical axis 22, that is, a second parallel boundary surface. On the pair 32, it differs from the case of the electrode 9 by the point which the pair of facing electrode 26 is provided above and below the some cylindrical body 19. FIG. The light modulation function of the first functional unit 7 composed of a plurality of cylindrical bodies 19 made of Pockels crystals can be adjusted by the facing electrode 26 arranged in this way.

  The signal source 10 for applying a voltage to the facing electrode 26 is installed outside the capillary 12, and the other end of the facing electrode 26 is connected to the ground 11. The light source according to the sixth reference example Since it is the same as a device, the same components are denoted by the same reference numerals and description thereof is omitted.

(10th reference example)
The tenth reference example of the present invention will be described below with reference to the drawings. FIG. 17A is a schematic side view showing an optical device according to a tenth reference example. FIG. 17B is a schematic cross-sectional view of the optical device of FIG. 17A cut out perpendicular to the optical axis 2 at the position of line BB ′ in the drawing.

  As shown in FIG. 17A, this optical device has substantially the same configuration as the optical device according to the ninth reference example shown in FIG. 16, but the longitudinal direction of the hole 6 is the sixth reference example. Is different. That is, the optical device according to this reference example includes the longitudinal direction of the plurality of cylindrical bodies 19 constituting the first functional unit 7 provided in the optical fiber 1 and the plurality of holes 6 constituting the second functional unit 8. The longitudinal directions are perpendicular to each other. That is, the optical device according to this reference example includes the longitudinal direction of the plurality of cylindrical bodies 19 constituting the first functional unit 7 provided in the optical fiber 1 and the plurality of holes 6 constituting the second functional unit 8. The longitudinal directions are perpendicular to each other. Specifically, as shown in FIG. 17B, the longitudinal direction of the cylindrical body 19 extends in the horizontal direction in the figure, while the longitudinal direction of the hole 6 extends in the vertical direction in the figure.

  As described above, by making the longitudinal direction of the cylindrical body 19 and the hole 6 constituting the first and second functional portions 7 and 8 perpendicular to each other, the action of the light modulation function in each functional portion can be adjusted. it can.

  Although the case where there are two functional units has been described above, the present invention can be similarly applied even when there are three functional units as in the optical device according to the fourth reference example.

(Eleventh reference example)
An optical device according to an eleventh reference example of the present invention is characterized in that an electrode to which an electric field is applied is provided on a surface in which the electric field direction forms an angle θ with the longitudinal direction of the columnar body constituting the first functional unit. . Thus, the light modulation function of the first functional unit can be adjusted by making the longitudinal direction of the columnar body and the electric field direction have a constant angle θ.

  In this optical device, in the cross section of the optical fiber 1 shown in FIG. 18 (a), the parallel electrode 87 for applying an electric field is compared with the optical device according to the ninth or tenth reference example in the direction of the electric field. It differs in that it is provided so as to form an angle θ with the longitudinal direction of the cylindrical body 19 constituting one functional unit 7. Specifically, in a predetermined section, the clad 4 is substantially removed while leaving the core 3, and a pair of parallel electrodes 87 is formed at an angle θ with the longitudinal direction of the cylindrical body 19 at a position in contact with or substantially in contact with the core 3. Is provided. Instead of the flat parallel electrode 87 as shown in FIG. 18A, this optical device uses a curved electrode 88 that is distorted substantially along the curved surface of the core 3 as shown in FIG. 18B. May be. When the curved electrode 88 is used, it is provided so that the longitudinal direction of the cylindrical body 19 and the normal direction 35 at the center of the curved surface form an angle θ.

(Twelfth reference example)
An optical device according to a twelfth reference example of the present invention is characterized in that the first functional portion of the optical fiber is composed of a plurality of cylindrical bodies made of crystals having a Faraday effect penetrating the core. To do. Thus, since the 1st functional part is comprised by the cylindrical body which consists of a crystal | crystallization which has a Faraday effect, the Faraday rotation angle of a 1st functional part can be adjusted by applying a magnetic field. Therefore, this optical device functions as an optical isolator.

  FIG. 19 is a horizontal sectional view showing an optical device according to a twelfth reference example of the present invention. As shown in FIG. 19, the present optical device has a Faraday effect that penetrates the first functional unit 7 of the optical fiber 1 through the core 3 as compared with the optical modulator according to the sixth reference example. It is different in that it is composed of a plurality of cylindrical bodies 91 made of crystals. Specifically, the cylindrical body constituting the first functional unit 7 is not a Pockels crystal but a crystal having a Faraday effect. As the crystal having the Faraday effect, for example, a garnet crystal, a rare earth iron garnet crystal (YIG, etc.) or the like can be used. Further, a magnet 95 for applying a magnetic field 94 to the crystal having the Faraday effect is provided on the outer surface of the capillary 12 (or so that the outer surface is processed and fitted). As the magnet 95, any permanent magnet such as a rare earth magnet or an electromagnet may be used as long as it generates a magnetic field with sufficient strength to saturate the Faraday rotation of the plane of polarization of light. . Further, since the Faraday rotation angle does not depend on the direction of the magnetic field, the direction in which the magnetic field 94 is applied can be selected in various ways.

<Reference examples for optical sensors>
Next, in the following reference examples, the configuration and operation of an optical sensor such as a photovoltage sensor, a photocurrent sensor, and an optical magnetic field sensor according to the present invention will be specifically described.

(13th reference example)
First, an optical voltage sensor according to a thirteenth reference example of the present invention will be described.
As shown in FIG. 20, the optical voltage sensor of this reference example includes a sensor unit, a light emitting unit 118, and a light receiving unit 119. The sensor units are arranged on the same optical axis 108 in order from the light incident side. The polarizer 101, the λ / 4 plate 102, the first conductive reflection film 106, the electro-optic crystal 103, the second conductive reflection film 107, and the analyzer 104 are arranged.

  The light emitting unit 118 includes an E / O circuit including a light emitting element such as an LED as a light source, and an input side optical system including an optical fiber or the like. The light beam emitted from the light source enters the sensor unit through the input side optical system.

In the sensor unit, the polarizer 101, the λ / 4 plate 102, the first conductive reflection film 106, the electro-optic crystal 103, the second conductive reflection film 107, and the analyzer 104 are sequentially arranged in the optical path of the light beam. The optical beam is emitted after being modulated by the measured voltage Vm by these optical elements. In the present embodiment, an electro-optical crystal 103, Z Jikuden transportable LiNbO3 crystal is used, the electro-optic crystal 103 is arranged to align its Z axis (C-axis) to the optical axis 108. In addition, the first conductive reflective film 106 and the second conductive reflective film 107 are arranged such that their reflective surfaces are perpendicular to the optical axis 108 and the first conductive reflective film 106 and the second conductive reflective film. The distance dr to 107 is arranged to be an integral multiple of half the wavelength of the incident light 109 to the sensor unit. As shown in FIG. 20, the coordinate system is set so that the Z-axis is along the optical axis 108 and the X-axis and the Y-axis are along two directions perpendicular to each other in a plane perpendicular to the optical axis 108. And In this case, electro-optical constant related to the modulation of the case, namely the vertical modulation to Z Jikuden transportable LiNbO3 crystal is applied an electric field in the Z-axis direction is γ33 and Ganma31, the Z Jikuden transportable LiNbO3 crystal 103 When the setting direction is the X-axis direction, the setting direction of the polarizer 101 and the analyzer 104 is ± 45 ° with respect to the X-axis, and the setting direction of the λ / 4 plate 102 is the X-axis direction or the Y-axis direction. Here, the setting direction refers to the principal axis direction of an ellipse indicating a refractive index with respect to a light beam incident on an electro-optic crystal, a λ / 4 plate, or the like.

The light receiving unit 119 includes an output side optical system including an optical fiber and the like, and an O / E circuit including a photoelectric conversion element that converts an optical signal into an electric signal. The light beam emitted from the sensor unit is received by the photoelectric conversion element in the O / E circuit through the output side optical system and converted into an electric signal. This electric signal corresponds to the polarization state of the light beam after passing through the LiNbO ₃ crystal 103, and the polarization state changes according to the voltage to be measured Vm. In a light receiving side signal processing circuit (not shown) connected to the light receiving unit 119, the value of the voltage to be measured is obtained by calculating the modulation degree based on this electric signal.

  A specific structure of the optical voltage sensor configured as described above is, for example, a structure as shown in FIG. Details of these structures will be described later as other reference examples, and detailed description thereof will be omitted here.

In the optical voltage sensor of this reference example, as described above, the interval dr between the first conductive reflective film 106 and the second conductive reflective film 107 in the sensor unit is an integer that is half the wavelength of the incident light 109 entering the sensor unit. It is set to be doubled. With this setting, an etalon resonator (also referred to as a “Fabry-Perot resonator”) is formed between the first conductive reflective film 106 and the second conductive reflective film 107. Thus, light propagation is dominant in the direction of the optical axis 108 is perpendicular to the first electrically conductive reflective film 106 and the second electrically conductive reflective film 107, as shown in FIG. 20, the beam angle distribution 115 Becomes steep. That is, an etalon resonator constituted by the first conductive reflective film 106 and the second conductive reflective film 107 even if the center direction and distribution of the incident light 109 vary due to tolerances of optical parts, structural variations, and the like. Thus, the light passing through the electro-optic crystal 103 has a central direction perpendicular to the reflecting surface (parallel to the optical axis 108) and a uniform distribution. Furthermore, the wavelength of light passing through the electro-optic crystal 103 is made constant by such an etalon resonator.

  As described above, according to this reference example, the center direction and distribution of the light passing through the electro-optic crystal 103 are constant by the etalon resonator constituted by the first conductive reflective film 106 and the second conductive reflective film 107. It becomes. That is, the beam state of the incident light beam on the electro-optic crystal 103 and the light beam after passing through the electro-optic crystal 103 is stabilized. As a result, even if the beam state of the incident light 109 to the sensor unit varies due to tolerances of the optical components, the modulation degree that is the output of the photovoltage sensor of this reference example is stabilized. If the center direction of the incident light 109 to the sensor unit varies, the intensity of the light beam incident on the electro-optic crystal 103 changes, but the distribution is constant, so the center direction of the incident light 109 to the sensor unit is constant. This variation does not substantially affect the variation in the modulation degree given as the ratio of the AC component to the DC component of the received light amount in the light receiving unit 119.

  The beam angle distribution 115 depends on the reflectivities of the first conductive reflective film 106 and the second conductive reflective film 107. The higher the reflectivity, the smaller the beam angle distribution 115. Therefore, the reflectivity is 0. .6 or more is preferable. Thus, when the beam angle distribution 115 becomes small, a certain characteristic can be obtained with respect to the axis deviation characteristic due to birefringence as shown in FIG.

In the present embodiment, although the vertical modulation scheme field is applied is employed to Z Jikuden transportable LiNbO3 crystal 103 in the direction of the Z-axis direction, that is the optical axis 108, instead of this, Z Jikuden transportable LiNbO3 A lateral modulation method in which an electric field is applied to the crystal 103 in the X-axis direction may be employed. As a specific configuration of the horizontal modulation type optical voltage sensor, for example, a configuration as described later can be cited (see FIG. 25).

When employing a horizontal modulation scheme, an electro-optical constant related to the modulation of the optical voltage sensor is Ganma22, setting the direction of the Z Jikuden transportable LiNbO3 crystal film 103 may in the X-axis direction, of the polarizer 101 and the analyzer 104 The setting direction is the X-axis direction or the Y-axis direction, and the setting direction of the λ / 4 plate 102 is ± 45 ° with respect to the X-axis. Since the temperature characteristic of the electro-optic constant γ22 is small, in the case of the horizontal modulation method, the contribution due to the temperature characteristic of the LiNbO3 crystal 103 in the change (hereinafter referred to as “output change due to temperature”) of the output (modulation degree) of the optical voltage sensor The minute is almost negligible as shown by the dotted line in FIG. 21 (in FIG. 21, the vertical axis represents the relative output change based on the output (modulation degree) of the photovoltage sensor at 25 ° C. Represent). However, due to the birefringence temperature characteristic of the λ / 4 plate 102, the modulation degree, which is the output of the lateral modulation type optical voltage sensor, has temperature characteristics. However, since the etalon resonator is formed in the region surrounding the LiNbO3 crystal film 103 as described above and the light beam state is stabilized, the beam state of the incident light 109 to the sensor unit varies due to tolerances of optical components. Even if there is, there is no variation in the temperature characteristic of the output of the photovoltage sensor, and it is stabilized. From this, when the horizontal modulation method is adopted, it can be used as a temperature sensor.

In the case of employing the vertical modulation scheme as in the present embodiment, as described above, the electro-optical constant related to the degree of modulation which is the output of the optical voltage sensor is γ33 and γ31, Z Jikuden transportable LiNbO3 crystal When the setting direction 103 is the X-axis direction, the setting direction of the polarizer 101 and the analyzer 104 is ± 45 ° with respect to the X-axis, and the setting direction of the λ / 4 plate 102 is the X-axis direction or the Y-axis direction. It is. In the case of the vertical modulation method, due to the temperature characteristics of the electro-optic constants γ33 and γ31, the contribution due to the temperature characteristics of the LiNbO3 crystal 103 in the output change due to the temperature in the optical voltage sensor is shown by the dotted line in FIG. Become. That is, when the temperature rises, the output of the photovoltage sensor decreases due to the temperature characteristics of the LiNbO3 crystal 103. In addition, the output change due to the temperature of the optical voltage sensor includes a component due to the birefringence temperature characteristic of the λ / 4 plate 102 (hereinafter referred to as “output change due to the temperature characteristic of the λ / 4 plate 102”). ). By the way, the ellipse (hereinafter referred to as “refractive index ellipse”) indicating the refractive index of the λ / 4 plate 102 with respect to the incident light approaches a perfect circle as the temperature increases. On the other hand, the ellipse (refractive index ellipse) indicating the refractive index of the LiNbO3 crystal 103 with respect to the incident light becomes flatter as the temperature increases. Therefore, if the fast axis direction of the refractive index ellipse of the λ / 4 plate 102 and the fast axis direction of the refractive index ellipse of the LiNbO3 crystal 103 are matched, the temperature dependence of the sensor output due to the temperature characteristics of the two is obtained. Canceling each other (refer to the straight line of the dotted line and the solid line in FIG. 21), and as a result, the output change of the photovoltage sensor due to temperature is reduced. That is, when the setting direction of the LiNbO3 crystal 103 is the X-axis direction, the temperature characteristics of the output of the optical voltage sensor can be improved by setting the setting direction of the λ / 4 plate 102 to be the X-axis direction. .

(14th reference example)
Next, an optical voltage sensor according to a fourteenth reference example of the present invention will be described.
The photovoltage sensor of this reference example has basically the same configuration as that of the thirteenth reference example, that is, the configuration shown in FIG. Of the components in the photovoltage sensor of the present reference example, the same components as those in the thirteenth reference example are assigned the same reference numerals, and descriptions thereof are omitted. The overall operation of the photovoltage sensor of this reference example is also substantially the same as that of the thirteenth reference example, and detailed description thereof is omitted.

  In this reference example, as shown in FIG. 22, the conductive reflective film for constituting the etalon resonator in the sensor unit is realized by a multilayer film composed of a reflective film and a transparent conductive film. That is, the first conductive reflective film 106 in the thirteenth reference example is realized by a multilayer film composed of the first transparent conductive film 121 and the first reflective film 122 in this reference example (this multi-layered film). The first conductive reflective film of this reference example realized by a film is denoted by reference numeral 106b). Further, the second conductive reflective film 107 in the thirteenth reference example is realized by a multilayer film composed of the second transparent conductive film 123 and the second reflective film 124 in this reference example (this multi-layered film). The second conductive reflective film of this reference example realized by a film is indicated by reference numeral 107b). Therefore, in this reference example, the distance dr2 between the first reflective film 122 and the second reflective film 124 is arranged to be an integral multiple of half the wavelength of the incident light 109 to the sensor unit. As the first and second transparent conductive films 121 and 123, for example, an ITO (Indium-Tin-Oxide) film or the like can be used.

FIG. 22 shows that the first transparent conductive film 121 constituting the first conductive reflective film 106b and the second transparent conductive film 123 constituting the second conductive reflective film 107b are both LiNbO ₃ crystals (electrical). The optical crystal) 103 is shown as an example, but the order of the first transparent conductive film 121 and the first reflective film 122 and the second transparent conductive film 123 and the second reflective film 124 are shown. The order of is arbitrary. However, as described above, the first reflective film 122 and the second reflective film 124 are arranged so that the interval between the first reflective film 122 and the second reflective film 124 is an integral multiple of half the wavelength of the incident light 109 to the sensor unit, regardless of the order. .

  According to this reference example, the first conductive reflective film 106b and the second conductive reflective film 107b, which are realized as a multilayer film composed of a transparent conductive film and a reflective film, are used in the same manner as in the thirteenth reference example. A resonator is formed, whereby the central direction and distribution of light passing through the electro-optic crystal 103 is constant. As a result, even if the beam state of the incident light 109 to the sensor unit varies due to tolerances of the optical components, the modulation degree that is the output of the photovoltage sensor of this reference example is stabilized. Furthermore, according to this reference example, the first conductive reflection film 106b and the second conductive reflection film 107b are realized as a multilayer film composed of a transparent conductive film and a reflective film. When the reflection films 106b and 107b are manufactured, their conductivity and reflectance can be controlled separately. Therefore, compared to the case where the conductive reflective film is realized by a single layer film, a conductive reflective film having a high reflectivity can be easily created, so that the effect of stabilizing the beam state can be further enhanced.

(15th reference example)
Next, an optical voltage sensor according to a fifteenth reference example of the present invention will be described.
The photovoltage sensor of this reference example has basically the same configuration as that of the thirteenth reference example, that is, the configuration shown in FIG. Of the components in the photovoltage sensor of the present reference example, the same components as those in the thirteenth reference example are assigned the same reference numerals, and descriptions thereof are omitted. The overall operation of the photovoltage sensor of this reference example is also substantially the same as that of the thirteenth reference example, and thus detailed description thereof is omitted.

In this reference example, the two conductive reflective films arranged so as to sandwich the LiNbO ₃ crystal film that is the electro-optic crystal 103 in the sensor unit are realized as a multilayer film as shown in FIG. That is, the first conductive reflective film 106 in the thirteenth reference example is composed of the first transparent conductive film 121 and the first multilayer film 133 functioning as a reflective film in this reference example (in this way) In this reference example, the first conductive reflective film composed of the first transparent conductive film 121 and the first multilayer film 133 is denoted by reference numeral 106c). Further, the second conductive reflective film 107 in the thirteenth reference example is composed of the second transparent conductive film 123 and the second multilayer film 134 functioning as a reflective film in this reference example (in this way) In this reference example, the second conductive reflective film composed of the second transparent conductive film 123 and the second multilayer film 134 is denoted by reference numeral 107c). Each of the first multilayer film 133 and the second multilayer film 134 is a multilayer film in which two types of layers of a high refractive index layer 131 and a low refractive index layer 132 are alternately stacked in the direction of the optical axis 108. It has a periodic structure in which the rate changes periodically in the direction of the optical axis 108. That is, the first multilayer film 133 and the second multilayer film 134 are one-dimensional photonic crystals. In this reference example, the first transparent conductive film 121 is between the first multilayer film 133 and the LiNbO ₃ crystal film 103, and the second transparent conductive film 123 is the second multilayer film 134 and the LiNbO ₃ crystal film 103. Between them. Of the layers constituting the first multilayer film 133, the layer in contact with the first transparent conductive film 121, that is, the layer closest to the LiNbO ₃ crystal film 103 (hereinafter referred to as “first proximity layer”), and the second multilayer Of the layers constituting the film 134, the layer in contact with the second transparent conductive film 123, that is, the layer closest to the LiNbO ₃ crystal film 103 (hereinafter referred to as “second adjacent layer”) is the same type of layer ( That is, they have the same refractive index). In the example shown in FIG. 23, the first and second proximity layers are both high refractive index layers 131. As the first and second transparent conductive films 121 and 123, for example, an ITO (Indium-Tin-Oxide) film can be used. Further, as the material of the high refractive index layer 131, Ta ₂ O ₅ , TiO ₂ , Ge, Si, or the like (for example, a material having a refractive index of about 3.4 to 3.6) can be used. As a material of the layer 132, SiO ₂ (refractive index of about 1.46), air (refractive index 1), or the like can be used.

  In the first conductive reflective film 106c and the second conductive reflective film 107c, the sum of the thickness of one high refractive index layer 131 and the thickness of one low refractive index layer 132 is the incident light 109 incident on the sensor unit. Each layer is formed so as to be 1/4 of the wavelength. The first multilayer film 133 and the second multilayer film 134 are the distance between the first proximity layer and the second proximity layer, that is, the surface of the first multilayer film 133 in contact with the first transparent conductive film 121 and the second multilayer film. The distance dr3 between the surface of the film 134 and the surface in contact with the second transparent conductive film 123 is arranged to be an integral multiple of half the wavelength of the incident light 109 entering the sensor unit.

  The first conductive reflection film 106c and the second conductive reflection film 107c configured and arranged as described above function as a so-called PBG (Photonic Band Gap) reflection mirror with respect to the incident light 109, and these PBG reflection mirrors. Strong resonance occurs in the space surrounded by. That is, a stronger effect of the same quality as the etalon resonator in the thirteenth reference example can be obtained. As a result, the center direction and distribution of the light passing through the electro-optic crystal 103 is constant, and as a result, even if the beam state of the incident light 109 to the sensor unit varies due to the tolerance of the optical parts, etc. The degree of modulation that is the output of the photovoltage sensor is stabilized.

  By the way, in the above configuration, the first conductive reflective film 106c and the first conductive film 106c and the first conductive reflective film 106c are arranged so that the sum of the thickness of the high refractive index layer 131 and the thickness of the low refractive index layer 132 becomes 1/4 of the wavelength of the incident light 109 to the sensor unit. In order to enhance the above effect, the thickness of the high refractive index layer 131 and the thickness of the low refractive index layer 132 are both set to 1 / wavelength of the incident light 109 entering the sensor unit. 8 is preferable.

  The application of the PBG reflector has already been introduced in a plurality of documents, and is disclosed in, for example, US Pat. No. 5,365,541.

(16th reference example)
Next, an optical voltage sensor according to a sixteenth reference example of the present invention will be described.
The photovoltage sensor of this reference example has the same configuration as that of the thirteenth reference example, that is, the configuration shown in FIG. Of the components in the photovoltage sensor of the present reference example, the same components as those in the thirteenth reference example are assigned the same reference numerals, and descriptions thereof are omitted. The overall operation of the photovoltage sensor of this reference example is also substantially the same as that of the thirteenth reference example, and detailed description thereof is omitted.

FIG. 24 is a perspective front view showing a specific structure of a main part of the optical voltage sensor according to this reference example. This optical voltage sensor includes a substrate 144. A polarizer 101, a λ / 4 plate 102, a first conductive reflection film 106, and a LiNbO ₃ crystal film as an electro-optic crystal, which constitute a sensor unit of the optical voltage sensor. 103, a component guide 143 that positions the second conductive reflective film 107 and the analyzer 104 in close contact with each other and sequentially arranges them on a predetermined optical axis 108 is provided at the center of the substrate 144. The component guide 143 is composed of four edges, and optical fiber guides 142a and 142b that are vertically connected to two opposite edges of the four edges are further provided on the substrate 144. Among these, the optical fiber guide 142 a guides the optical fiber 246 a so as to optically couple the optical fiber 246 a constituting the input side optical system of the light emitting unit 118 to the polarizer 101 positioned by the component guide 143. The optical fiber guide 142b guides the optical fiber 246b so as to optically couple the optical fiber 246b constituting the output side optical system of the light receiving unit 119 to the analyzer 104 positioned by the component guide 143. In addition, a pair of electrodes 141 is attached to the substrate 144, and one of the pair of electrodes 141 is positioned on the first conductive reflective film 106 positioned by the component guide 143, and the other is positioned by the component guide 143. The second conductive reflective film 107 is electrically connected to each other by a lead wire 145. Therefore, when the voltage to be measured Vm is applied between the pair of electrodes 141, the voltage Vm is applied to the LiNbO ₃ film 103, which is an electro-optic crystal, in the Z-axis direction (the direction of the optical axis 108).

In this reference example, as in the thirteenth reference example, the distance dr between the first conductive reflective film 106 and the second conductive reflective film 107 in the sensor unit is half the wavelength of the incident light 109 entering the sensor unit. It is set to be an integer multiple of. As a result, an etalon resonator is formed between the first conductive reflective film 106 and the second conductive reflective film 107, so that the direction is perpendicular to the first conductive reflective film 106 and the second conductive reflective film 107. light propagation is dominant in the direction of the optical axis 108, the beam angle distribution 115 becomes steeper. As a result, even if there is a variation in the beam state of the incident light 109 to the sensor unit due to tolerances of optical parts, the effect of stabilizing the modulation degree that is the output of the photovoltage sensor of this reference example is obtained. The effect of improving the directivity of light passing through the sensor unit can be obtained.

As described above, according to the present reference example, since the etalon resonator is configured in the region surrounding the LiNbO ₃ crystal film 103 in the sensor unit, the directivity of light passing through the sensor unit is improved and the LiNbO ₃ crystal film is formed. The axial deviation of the incident light beam to 103 is suppressed. In addition, each optical component constituting the sensor unit is plate-like or film-like, and each optical component is positioned by the component guide 143 so that the optical path length in the sensor unit is conventional. (See FIG. 33) (this optical path length can be set to, for example, about 2 to 3 mm). In this reference example, the directivity of light passing through the sensor unit is increased and the optical path length in the sensor unit is shortened as described above, and the optical fiber 246a of the input side optical system is directly polarized by the optical fiber guide 142a. The optical fiber 246b of the output side optical system is directly optically coupled to the analyzer 104 by the optical fiber guide 142b. That is, in this reference example, the optical fiber 246a coupling loss on the polarizer 101 side and the analyzer 104 side can be reduced without using a lens by improving the light directivity and shortening the optical path length in the sensor unit. The coupling loss of the optical fiber 246b can be kept within a range where there is no practical problem. As described above, according to this reference example, it is possible to reduce the cost by reducing the number of parts by eliminating the need for a lens while suppressing a decrease in performance as an optical sensor.

(17th reference example)
Next, an optical voltage sensor according to a seventeenth reference example of the present invention will be described.
Optical voltage sensor of the present embodiment is a sensor of a lateral modulation scheme, with respect to Z Jikuden transportable LiNbO3 crystal film 103 which is an electro-optical crystal electric field is applied to the X-axis direction (see FIG. 20 for the coordinate system) This is different from the thirteenth reference example and the sixteenth reference example, which are vertical modulation type photovoltage sensors. In the present reference example, the direction of application of the electric field to the LiNbO3 crystal film 103 is not the Z-axis direction (the direction of the optical axis 108) but the X-axis direction. 106, the first reflective film 122 is used, and the second reflective film 124 is used instead of the second conductive reflective film 107 (the first and second reflective films 122 and 124 are not required to have conductivity). A pair of application electrodes 151 for applying the voltage Vm to be measured to the LiNbO3 crystal film 103 are arranged so as to face the X-axis direction and sandwich the LiNbO3 crystal film 103 in the X-axis direction. Further, the electro-optic constant related to the degree of modulation when an electric field is applied to the X-axis direction with respect to Z Jikuden transportable LiNbO3 crystal film 103 as in this reference example is Ganma22, setting of the polarizer 101 and the analyzer 104 The direction is the X-axis direction or the Y-axis direction, and the setting direction of the λ / 4 plate 102 is ± 45 ° with respect to the X-axis.

  Since the basic configuration of the reference example other than the above is the same as the configuration of the thirteenth reference example shown in FIG. 20, the constituent elements of the photovoltage sensor of the reference example are the same as those of the thirteenth reference example. Components that are the same as those in FIG. Further, the overall operation of the photovoltage sensor of this reference example is substantially the same as that of the thirteenth reference example, and thus detailed description thereof is omitted.

FIG. 25 is a transparent front view showing a specific structure of a main part of the optical voltage sensor according to this reference example. This optical voltage sensor includes a substrate 144 as in the sixteenth reference example. The polarizer 101, the λ / 4 plate 102, the first reflective film 122, and the electro-optic crystal that constitute the sensor unit of the optical voltage sensor. A component guide 143 that positions the LiNbO ₃ crystal film 103, the second reflective film 124, and the analyzer 104 as a close contact with each other and sequentially arranges them on the predetermined optical axis 108 is provided at the center of the substrate 144. Yes. In addition, optical fiber guides 142a and 142b having the same configuration as in the sixteenth reference example are provided on the substrate 144, and the optical fiber guide 142a includes an optical fiber 246a that constitutes the input-side optical system of the light emitting unit 118. The optical fiber 246a is guided so as to be optically coupled to the polarizer 101 positioned by the component guide 143. The optical fiber guide 142b guides the optical fiber 246b so as to optically couple the optical fiber 246b constituting the output side optical system of the light receiving unit 119 to the analyzer 104 positioned by the component guide 143. A pair of electrodes 152 are attached to the substrate 144, and one and the other of the pair of electrodes 152 are connected to one and the other of the pair of application electrodes 151 by lead wires, respectively. Therefore, when the voltage Vm to be measured is applied between the pair of application electrodes 151, the voltage Vm is applied to the LiNbO ₃ film 103, which is an electro-optic crystal, in the X-axis direction.

In this reference example, the distance between the first reflective film 122 and the second reflective film 124 in the sensor unit is set to be an integral multiple of half the wavelength of the incident light 109 entering the sensor unit. As a result, as in the thirteenth and sixteenth reference examples, an etalon resonator is configured between the first reflective film 122 and the second reflective film 124, and thus is perpendicular to the first reflective film 122 and the second reflective film 124. light propagation is dominant in the direction of the optical axis 108 is the direction, the beam angle distribution 115 becomes steeper. As a result, in addition to the effect that the modulation degree that is the output of the photovoltage sensor of the present reference example is stabilized even if the beam state of the incident light 109 to the sensor unit varies due to tolerances of optical components, etc., the sensor The effect that the directivity of the light which passes a part improves is acquired.

As described above, according to this reference example, as in the sixteenth reference example, the etalon resonator is configured in the region surrounding the LiNbO ₃ crystal film 103 in the sensor unit, so that the directivity of light passing through the sensor unit is set. As a result, the axial shift of the incident light beam on the LiNbO ₃ crystal film 103 is suppressed. In addition, each optical component constituting the sensor unit is in a plate shape or a film shape, and each optical component is positioned in close contact with the component guide 143, so that the optical path length in the sensor unit is shortened. (This optical path length can be set to about 2 to 3 mm, for example). That is, also in this reference example, the optical fiber 246a coupling loss on the polarizer 101 side and the analyzer 104 side can be reduced without using a lens by improving the directivity of light in the sensor unit and shortening the optical path length. The coupling loss of the optical fiber 246b can be kept within a range where there is no practical problem. Therefore, as in the sixteenth reference example, the cost can be reduced by reducing the number of parts by eliminating the need for a lens while suppressing a decrease in performance as an optical sensor.

(18th reference example)
Next, an optical voltage sensor according to an eighteenth reference example of the present invention will be described.
The photovoltage sensor of this reference example has basically the same configuration as that of the thirteenth reference example, that is, the configuration shown in FIG. Among the components in the photovoltage sensor of the present reference example, the same components as those in the thirteenth reference example are denoted by the same reference numerals. Note that the overall operation of the optical voltage sensor of this reference example is substantially the same as that of the thirteenth reference example, and thus detailed description thereof is omitted.

  FIG. 26 is a transparent front view showing a specific structure of the main part of the optical voltage sensor of this reference example. Similar to the sixteenth reference example, this optical voltage sensor includes a substrate 144, and a component guide 143 for positioning optical components constituting the sensor unit of the optical voltage sensor so as to be disposed on a predetermined optical axis 108. And an input side optical fiber for optically coupling an optical fiber (hereinafter referred to as “input side optical fiber”) 148a constituting the input side optical system of the light emitting unit 118 to a predetermined optical component positioned by the component guide 143. An output side for optically coupling the guide 142a and an optical fiber (hereinafter referred to as “output side optical fiber”) 148b constituting the output side optical system of the light receiving unit 119 to a predetermined optical component positioned by the component guide 143 An optical fiber guide 142b is provided on the substrate 144.

In this reference example, a photonic crystal layer (hereinafter referred to as “photonic crystal polarizer”) 171 that functions as a polarizer is formed on one end face of the input-side optical fiber 148a. A photonic crystal layer (hereinafter referred to as “photonic crystal analyzer”) 172 that functions as an analyzer is formed on one end face. Further, unlike the sixteenth reference example, the component guide 143 in the present reference example is a λ / 4 plate 102, a first conductive reflective film 106, and a LiNbO as an electro-optic crystal among optical components constituting the sensor unit. _{The three} crystal film 103 and the second conductive reflective film 107 are configured to be in close contact with each other. Then, the input side optical fiber guide 142a inputs the photonic crystal polarizer 171 formed on the end surface of the input side optical fiber 148a so as to optically couple to the λ / 4 plate 102 positioned by the component guide 143. The side optical fiber 148a is guided. The output side optical fiber guide 142b outputs an optically coupled optical photonic crystal analyzer 172 formed on the end face of the output side optical fiber 148b to the second conductive reflective film 107 positioned by the component guide 143. The side optical fiber 148b is guided. Since the points other than the above in the specific structure of the photovoltage sensor of this reference example are the same as those of the sixteenth reference example, the same components are denoted by the same reference numerals and the description thereof is omitted. . The formation of the photonic crystal polarizer 171 and the photonic crystal analyzer 172 will be described later.

As in the sixteenth reference example, the present reference example as described above has a configuration that eliminates the need for a lens by improving the light directivity and shortening the optical path length in the sensor unit. Photons are formed on the end face of the optical fiber as a photonic crystal layer. For this reason, the number of parts of the optical voltage sensor is further reduced, and the cost can be further reduced. Forming the polarizer and analyzer as a photonic crystal layer on the end face of the optical fiber also contributes to shortening the optical path length. In the present reference example, as in the sixteenth reference example, the etalon resonator is formed in the region surrounding the LiNbO ₃ crystal film 103 in the sensor unit to improve the directivity of the light beam. If the optical path length is shortened enough to eliminate the need for a lens without increasing the performance, it is not necessary to form an etalon resonator or the like, and therefore the first and second conductive reflective films 106 are not required. Alternatively, a transparent conductive film may be used instead of.

(19th reference example)
Next, an optical voltage sensor according to a nineteenth reference example of the present invention will be described.
The photovoltage sensor of this reference example has basically the same configuration as that of the thirteenth reference example, that is, the configuration shown in FIG. Of the components in the photovoltage sensor of this reference example, the same components as those in the thirteenth reference example are assigned the same reference numerals. Note that the overall operation of the optical voltage sensor of this reference example is substantially the same as that of the thirteenth reference example, and thus detailed description thereof is omitted.

  FIG. 27 is a transparent front view showing a specific structure of the main part of the optical voltage sensor of this reference example. Similar to the eighteenth reference example, this optical voltage sensor includes a substrate 144, and a component guide 143 for positioning optical components constituting the sensor unit of the optical voltage sensor so as to be disposed on a predetermined optical axis 108. An input-side optical fiber guide 142a for optically coupling the input-side optical fiber 148a constituting the input-side optical system of the light-emitting unit 118 to a predetermined optical component positioned by the component guide 143, and the light-receiving unit 119 An output-side optical fiber guide 142b for optically coupling the output-side optical fiber 148b constituting the output-side optical system to a predetermined optical component positioned by the component guide 143 is provided on the substrate 144.

  In this reference example, a photonic crystal polarizer 171 that is a photonic crystal layer that functions as a linear polarizer is formed on one end face of the input side optical fiber 148a, and further functions as a λ / 4 plate. A photonic crystal λ / 4 plate 181 which is a photonic crystal layer to be formed is formed. That is, a multilayer film of photonic crystals functioning as a circular polarizer is formed on one end face of the input side optical fiber 148a by laminating the photonic crystal polarizer 171 and the photonic crystal λ / 4 plate 181. ing. Further, a photonic crystal analyzer 172 that is a photonic crystal layer functioning as an analyzer is formed on one end face of the output side optical fiber 148b.

Unlike the eighteenth reference example, the component guide 143 in the present reference example is the first conductive reflective film 106, the LiNbO ₃ crystal film 103 as the electro-optic crystal, and the second conductive among the optical components constituting the sensor unit. The reflective reflective film 107 is configured to be in close contact with each other for positioning. The input side optical fiber guide 142 a optically couples the photonic crystal λ / 4 plate 181 formed on the end face of the input side optical fiber 148 a to the first conductive reflective film 106 positioned by the component guide 143. Thus, the input side optical fiber 148a is guided. The output side optical fiber guide 142b outputs an optically coupled optical photonic crystal analyzer 172 formed on the end face of the output side optical fiber 148b to the second conductive reflective film 107 positioned by the component guide 143. The side optical fiber 148b is guided.

  Since the points other than the above in the specific structure of the photovoltage sensor of this reference example are the same as those of the sixteenth reference example, the same components are denoted by the same reference numerals and the description thereof is omitted. . The formation of the photonic crystal polarizer 171, the photonic crystal λ / 4 plate 181 and the photonic crystal analyzer 172 will be described later.

  As described above, in this reference example, as in the sixteenth reference example, the lens is not required by improving the directivity of light in the sensor unit and shortening the optical path length. A linear polarizer and a λ / 4 plate are formed as a photonic crystal layer on the end face of 148a, and an analyzer is formed as a photonic crystal layer on the end face of the output side optical fiber 148b. For this reason, the number of parts of the optical voltage sensor is further reduced, and the cost can be further reduced. Note that forming the polarizer, λ / 4 plate, and analyzer as a photonic crystal layer on the end face of the optical fiber also contributes to shortening the optical path length.

(20th reference example)
Next, an optical voltage sensor according to a twentieth reference example of the present invention will be described.
The photovoltage sensor of this reference example has basically the same configuration as that of the thirteenth reference example, that is, the configuration shown in FIG. However, the polarizer 101 and the λ / 4 plate 102 in the thirteenth reference example are realized as one circular polarizer in this reference example. Of the components in the photovoltage sensor of this reference example, the same components as those in the thirteenth reference example are assigned the same reference numerals. Note that the overall operation of the optical voltage sensor of this reference example is substantially the same as that of the thirteenth reference example, and thus detailed description thereof is omitted.

  FIG. 28 is a transparent front view showing a specific structure of a main part of the optical voltage sensor of this reference example. The main part of this optical voltage sensor has a structure substantially similar to the structure of the main part in the nineteenth reference example shown in FIG. However, in this reference example, a photonic crystal layer (hereinafter referred to as “photonic crystal circular polarizer”) 191 that functions as a circular polarizer is formed as a single layer on one end face of the input-side optical fiber 148a. This is different from the nineteenth reference example in which a circular polarizer is realized by laminating a photonic crystal polarizer 171 and a photonic crystal λ / 4 plate 181. In this reference example, the input-side optical fiber guide 142a includes the first conductive reflective film 106 in which the above-described photonic crystal circular polarizer 191 formed on the end surface of the input-side optical fiber 148a is positioned by the component guide 143. The input side optical fiber 148a is guided so as to be optically coupled to the optical fiber. Since the structure of the present reference example other than the above points is the same as the structure of the nineteenth reference example, the structure of the main part of the photovoltage sensor of the present reference example is the same as that of the nineteenth reference example. About the same part, the same referential mark is attached | subjected and detailed description is abbreviate | omitted. The formation of the photonic crystal circular polarizer 191 and the photonic crystal analyzer 172 is as described above (see FIG. 1).

  As described above, in the present reference example, as in the nineteenth reference example, the lens is not required by improving the directivity of light in the sensor unit and shortening the optical path length. A circular polarizer is formed as a photonic crystal layer on the end face of 148a, and an analyzer is formed as a photonic crystal layer on the end face of the output-side optical fiber 148b. For this reason, this reference example has the advantage that the number of parts of the optical voltage sensor is reduced and the cost is reduced, as in the nineteenth reference example. Further, in this reference example, the photonic crystal polarizer 171 and the photonic crystal λ / 4 plate 181 in the nineteenth reference example are a single photonic crystal layer that functions as a circular polarizer. Since this embodiment is realized as a polarizer 191, this reference example is more advantageous in cost than the nineteenth reference example.

(21st reference example)
Next, an optical magnetic field sensor according to the twenty-first reference example of the present invention will be described.
The optical magnetic field sensor of this reference example is the λ / 4 plate 102, the first conductive reflective film 106, and the LiNbO ₃ positioned by the component guide 143 in the optical voltage sensor according to the eighteenth reference example shown in FIG. Instead of the crystal film 103 and the second conductive reflective film 107, a magneto-optical crystal film 201 is provided. This optical magnetic field sensor is used to apply a magnetic field induced by a current flowing through a power transmission line, a distribution line, etc. to the magneto-optical crystal film 201 in the X-axis direction (optical axis direction) and measure the magnetic field strength. The Therefore, an electrode or a lead wire for applying an electric field (voltage) to the LiNbO ₃ crystal film 103 which is an electro-optic crystal is unnecessary. Since the configuration of the optical magnetic field sensor of the present reference example other than the above is substantially the same as that of the eighteenth reference example, the same components are denoted by the same reference numerals and detailed description thereof is omitted. In addition, according to such an optical magnetic field sensor, the magnitude | size of the electric current can be detected by measuring the intensity | strength of the magnetic field induced by the electric current which flows through a power transmission line, a distribution line, etc.

  FIG. 29 is a transparent front view showing a specific structure of a main part of the optical magnetic field sensor of this reference example. This optical magnetic field sensor includes a substrate 144, a component guide 143 for positioning the magneto-optical crystal film 201 so as to be disposed on a predetermined optical axis 108, and an input side constituting an input-side optical system of the light emitting unit. An input-side optical fiber guide 142a for optically coupling the optical fiber 148a to the magneto-optic crystal film 201 positioned by the component guide 143, and an output-side optical fiber 148b constituting the output-side optical system of the light receiving unit 119 are parts. An output-side optical fiber guide 142 b for optically coupling to the magneto-optical crystal film 201 positioned by the guide 143 is provided on the substrate 144.

  In this reference example, similarly to the eighteenth reference example, a photonic crystal polarizer 171 that functions as a linear polarizer is formed on one end face of the input side optical fiber 148a, and one of the output side optical fibers 148b is formed. A photonic crystal analyzer 172 is formed on the end face. The input-side optical fiber guide 142a optically couples the photonic crystal polarizer 171 formed on the end surface of the input-side optical fiber 148a to one surface of the magneto-optic crystal film 201 positioned by the component guide 143. Thus, the input side optical fiber 148a is guided. The output-side optical fiber guide 142b optically couples the photonic crystal analyzer 172 formed on the end face of the output-side optical fiber 148b to the other surface of the magneto-optic crystal film 201 positioned by the component guide 143. The output side optical fiber 148b is guided. The photonic crystal polarizer 171 and the photonic crystal analyzer 172 that are optically coupled to the two surfaces of the magneto-optical crystal film 201 as described above are set so that their setting directions are 45 degrees. . Therefore, the polarization direction of the linearly polarized light after passing through the photonic crystal polarizer 171 and the polarization direction of the linearly polarized light after passing through the photonic crystal analyzer 172 are shifted from each other by 45 degrees.

  In the optical magnetic field sensor configured as described above, the non-polarized light emitted from the light source of the light emitting unit passes through the input side optical fiber 148a and travels toward the magneto-optic crystal film 201. It passes through a photonic crystal polarizer 171 formed on the end face. The light that has passed through the photonic crystal polarizer 171 becomes linearly polarized light and enters the magneto-optical crystal film 201. When this linearly polarized light passes through the magneto-optical crystal film 201, the polarization direction of the magnetic field Hm applied to the magneto-optical crystal film 201 is an angle corresponding to the intensity of the component in the direction perpendicular to the magneto-optical crystal film 201. Only rotate. The linearly polarized light that has passed through the magneto-optic crystal film 201 passes through the photonic crystal analyzer 172 formed on the end face of the output side optical fiber 148b, and is transmitted to the photoelectric conversion element in the light receiving unit by the output side optical fiber 148b. And converted into an electrical signal. Since the amount of linearly polarized light after passing through the photonic crystal analyzer 172 changes according to the rotation angle of the polarization direction in the magneto-optic crystal film 201, based on the electrical signal output from the photoelectric conversion element in the light receiving unit, The intensity of the magnetic field Hm applied to the magneto-optical crystal film 201 can be obtained.

  According to the above reference example, the polarizer and the analyzer are formed on the end face of the optical fiber as a photonic crystal layer, so that the number of parts is reduced and light from the light source in the light emitting unit is input. The optical path length from the exit from the side optical fiber 148a to the end face of the output side optical fiber 148b through the polarizer 171, the magneto-optic crystal film 201 and the analyzer 172 is shortened. This reference example has a configuration in which no lens is used due to the shortening of the optical path length, which also reduces the number of parts. According to this reference example, the cost can be reduced by reducing the number of parts.

(22nd reference example)
Next, an optical voltage sensor according to a twenty-second reference example of the present invention will be described.
The photovoltage sensor of this reference example is a vertical modulation type photovoltage sensor and has basically the same configuration as the thirteenth reference example (see FIG. 20). On the other hand, in terms of a specific structure, this optical voltage sensor is similar to the conventional structure shown in FIG. 33, and a right-angle PBS (Polarization Beam Splitter) is used as a polarizer and an analyzer.

  FIG. 30 is a perspective front view showing a specific structure of the optical voltage sensor according to this reference example. This optical voltage sensor includes a sensor unit, a light emitting unit, a light receiving unit, and a light emitting side and light receiving side signal processing circuit (not shown). The sensor unit is arranged on the same optical axis in order from the light incident side, and is a right angle PBS 241 as a polarizer, a λ / 4 plate 242, a first conductive reflection film 106, an electro-optic crystal 243, and a second conductive reflection. It is composed of a film 107 and a right angle PBS 244 as an analyzer. The light emitting unit is an input side including an E / O circuit including a light emitting element as a light source, an optical fiber 246a, a ferrule 248a, a 0.25 pitch GRIN lens 247a, and a holder 245a arranged on the same optical axis. Each optical component in the input side optical system has an optical axis surface that is in contact with each other bonded by an adhesive. The light-receiving unit outputs an optical signal radiated from the output-side optical system including an optical fiber 246b, a ferrule 248b, a 0.25 pitch GRIN lens 247b, and a holder 245b arranged on the same optical axis. It is composed of an O / E circuit including a conversion element that converts it into an electric signal, and each optical component in the output-side optical system is also bonded by an adhesive on the optical axis surfaces that are in contact with each other.

  The optical components arranged on the same optical axis in the sensor portion of the optical voltage sensor, that is, the polarizer 241, the λ / 4 plate 242, the first conductive reflection film 106, the electro-optic crystal 243, and the second conductive reflection. The film 107 and the analyzer 244 are all bonded with an adhesive on the optical axis surfaces in contact with each other. The first conductive reflective film 106 is connected to one of the pair of electrode terminals 249, and the second conductive reflective film 107 is connected to the other of the pair of electrode terminals 249. The measured voltage Vm of the optical voltage sensor is applied between the pair of electrode terminals 249.

The light emitting side and light receiving side signal processing circuits are connected to the sensor unit by a light emitting unit and a light receiving unit, respectively. The sensor-side polarizer 241 has an input-side optical axis surface of the light-emitting portion GRIN lens 247a, and the sensor-unit analyzer 244 has an output-side optical axis surface of the light-receiving portion GRIN lens 247b. Each is fixed with an adhesive. The sensor unit, the input side optical system in the light emitting unit, and the output side optical system in the light receiving unit are mechanically fixed to a case (not shown). In addition, as an adhesive for each optical component in the photovoltage sensor, an epoxy resin or a urethane resin is used. In the above-described optical voltage sensor, Bi ₁₂ SiO ₂₀ (BSO), KH ₂ PO ₄ (KDP), LiNbO ₃ having natural birefringence, LiTaO ₃ or the like is used as the electro-optic crystal 243.

  By the way, in the said structure, each optical component in a light emission part and a light-receiving part and each optical component which comprises a sensor part are joined by the adhesive agent in the optical-axis surface which mutually contacts, a light-emitting part, a sensor part, and a light-receiving part And the sensor unit are also bonded by an adhesive at the optical axis surfaces in contact with each other. However, it is preferable that each optical component constituting the sensor unit is held by a frictional force acting between the respective joint surfaces without using an adhesive. That is, the exit side optical axis surface of the right angle PBS which is the polarizer 241, the incident side optical axis surface of the λ / 4 plate 242, the exit side optical axis surface of the λ / 4 plate 242, and the incident side of the first conductive reflective film 106. The optical axis surface, the outgoing optical axis surface of the first conductive reflective film 106 and the incident optical axis surface of the electro-optic crystal 243, the outgoing optical axis surface of the electro-optic crystal 243, and the incident side of the second conductive reflective film 107 The λ / 4 wavelength plate is connected to the optical axis surface and five non-adhesive bonding surfaces of the exit-side optical axis surface of the second conductive reflecting film 107 and the incident-side optical axis surface of the right angle PBS as the analyzer 244. 242, the first conductive reflective film 106, the electro-optic crystal 243, and the second conductive reflective film 107 are sandwiched with appropriate force. The λ / 4 wavelength plate 242, the first conductive reflective film 106, the electro-optic crystal 243, and the second conductive reflective film 107 are formed in the input-side optical system by the frictional force generated at these five non-adhesive joint surfaces. It is fixed and held between the bonded polarizer 241 and the analyzer 244 bonded to the output side optical system. According to such a configuration, the temperature characteristic of the electro-optic crystal is improved by relaxing the stress applied to the electro-optic crystal 243 (see Japanese Patent Application Laid-Open No. 9-145745).

  In the sensor unit of this reference example, as in the thirteenth reference example, the interval between the first conductive reflective film 106 and the second conductive reflective film 107 is an integral multiple of half the wavelength of the incident light on the sensor unit. Thus, the thickness of each optical component constituting the sensor unit is set. Thereby, an etalon resonator is formed in a region surrounding the electro-optic crystal 243 by the first conductive reflective film 106 and the second conductive reflective film 107.

  According to the reference example as described above, the etalon resonator is configured in the region surrounding the electro-optic crystal 243 by the first conductive reflective film 106 and the second conductive reflective film 107, and the light beam state is stabilized. Therefore, even if the beam state of the incident light to the sensor unit varies due to tolerances of the optical components, the temperature characteristics of the output of the photovoltage sensor are stabilized without variation.

  Since the optical device of the present invention is low in manufacturing cost and can contribute to the reduction in the number of parts of optical equipment, it can be used for various optical equipment.

It is a perspective view which shows the structure of a photonic crystal circular polarizer. It is a figure which shows the preparation methods of the photonic crystal which functions as a polarizer, an analyzer, a circular polarizer, etc. It is a figure which shows the other preparation methods of the photonic crystal which functions as a polarizer, an analyzer, a circular polarizer, etc. It is a figure which shows the photonic band at the time of carrying out square distribution of the cylindrical hole in the core of an optical fiber. It is the schematic which showed the structure of the optical device which concerns on the 1st reference example of this invention. It is a partial structure outline figure concerning another example of the optical device concerning the 1st reference example of the present invention. It is the schematic which showed the structure of the optical device which concerns on the 2nd reference example of this invention. It is the side schematic diagram which showed the structure of the optical device which concerns on the 3rd reference example of this invention. It is the side schematic diagram which showed the structure of the optical device which concerns on the 4th reference example of this invention. It is a general view of the optical device which concerns on the 5th reference example of this invention. FIG. 11 is a schematic perspective view in which a functional unit 78 shown in FIG. 10 is enlarged and an optical fiber 71 is viewed from an oblique direction. It is the horizontal sectional view which showed the whole optical device which concerns on the 6th reference example of this invention. It is the schematic which showed the structure of the optical device which concerns on the 6th reference example of this invention. It is the schematic which showed the structure of the optical device which concerns on the 7th reference example of this invention. It is the schematic which showed the structure of the optical device which concerns on the 8th reference example of this invention. It is the schematic which showed the structure of the optical device which concerns on the 9th reference example of this invention. It is the schematic which showed the structure of the optical device which concerns on the 10th reference example of this invention. In the optical device which concerns on the 11th reference example of this invention, it is the cross-sectional schematic which showed the example of arrangement | positioning of an electrode. It is the horizontal sectional view which showed the optical device which concerns on the 12th reference example of this invention. It is a schematic diagram which shows the structure of the optical voltage sensor which concerns on the 13th reference example of this invention. Change in the output of the optical voltage sensor due to the temperature characteristics of the quartz lambda / 4 plate, the vertical modulation scheme according to the temperature characteristics of the LiNbO ₃ which is an electro-optical crystal change in the output of the optical voltage sensors, and, of LiNbO ₃ which is an electro-optical crystal It is a temperature characteristic figure which shows the output change of the optical voltage sensor of a horizontal modulation system by a temperature characteristic. It is a figure which shows the electroconductive reflection film in the optical voltage sensor which concerns on the 14th reference example of this invention. It is a figure which shows the electroconductive reflection film comprised with the multilayer film by which the low-refractive-index layer and the high refractive index layer are laminated | stacked alternately in the optical voltage sensor which concerns on the 15th reference example of this invention. It is a see-through | perspective front view which shows the principal part structure of the optical voltage sensor which concerns on the 16th reference example of this invention. It is a see-through | perspective front view which shows the principal part structure of the optical voltage sensor which concerns on the 17th reference example of this invention. It is a see-through | perspective front view which shows the principal part structure of the optical voltage sensor which concerns on the 18th reference example of this invention. It is a see-through | perspective front view which shows the principal part structure of the optical voltage sensor which concerns on the 19th reference example of this invention. It is a see-through | perspective front view which shows the principal part structure of the optical voltage sensor which concerns on the 20th reference example of this invention. It is a see-through | perspective front view which shows the principal part structure of the optical magnetic field sensor which concerns on the 21st reference example of this invention. It is a see-through | perspective front view which shows the structure of the optical voltage sensor which concerns on the 22nd reference example of this invention. It is the schematic which shows the structure of the optical isolator which is the conventional optical device. It is the schematic which shows the structure of the conventional Mach-Zehnder type | mold modulator. It is a see-through | perspective front view which shows the structure of the conventional optical voltage sensor. It is a figure for demonstrating the principle of operation of a photovoltage sensor. It is a characteristic view which shows the relationship between the output in the conventional optical voltage sensor, and the axial deviation angle of the incident light to an electro-optic crystal.

Explanation of symbols

θ Angle formed by cylindrical body and electrode surface normal line k beam direction dr Distance between first conductive reflective film and second conductive reflective film Vm Applied voltage (measured voltage)
Hm Applied magnetic field (measured magnetic field)
DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Optical axis 3 Core 4 Clad 5 Faraday crystal substitution cylinder 6 Hole 7 1st function part 8 2nd function part 9 Electrode 10 Signal source 11 Ground 12 Capillary 13 Optical fiber 14 Ferrule 15 Split sleeve 16 Incident light 17 Outgoing light 18 Clad deleted portion 19 Cylinder body 20 Magnetic field 21 Clad residual portion 22 Optical axis 23 Parallel boundary surface pair 24 Parallel electrode 25 Column electrode 26 Facing electrode 31 First parallel boundary surface pair 32 Second parallel boundary surface pair 35 Method Linear direction 40 Magnetic field 41 Incident side optical fiber 42 Outgoing side optical fiber 43 First hole 44 Second hole 45 Core 46 Cladding 47 Faraday element 48 Guide 49 Optical axis 50 Signal source 51 Optical fiber 52 Optical axis 55 Pockels crystal substitution cylinder 56 holes 57 first functional part 58 second functional part 59 Electrode 60 Signal source 61 Optical fiber 62 Optical axis 63 Electrode 64 Pockels crystal filled cylinder 65 First hole 66 Second hole 67 First functional part 68 Second functional part 69 Third functional part 71 Optical fiber 72 Optical axis 73 Incident light 74 Emission light 75 Core 76 Clad 77 Hole 78 Functional part 83 Core 84 Clad 87 Parallel electrode 88 Curved electrode 91 Cylinder 94 Magnetic field 95 Magnet 101 Polarizer 102 λ / 4 plate 103 LiNbO3 Crystal film (electro-optic crystal) )
104 analyzer 106 first conductive reflective film 107 second conductive reflective film 108 optical axis 109 incident light 110 outgoing light 115 beam angle distribution 118 light emitting part 119 light receiving part 121 first transparent conductive film 122 first reflective film 123 first reflective film 123 2 transparent conductive film 124 second reflective film 131 high refractive index layer 132 low refractive index layer 133 first multilayer film 134 second multilayer film 141 electrode (electrode in the case of vertical modulation)
142a Input-side optical fiber guide 142b Output-side optical fiber guide 143 Parts guide 148a Input-side optical fiber 148b Output-side optical fiber 148 Optical fiber 151 Applied electrode 152 Electrode (electrode in the case of horizontal modulation)
171 photonic crystal polarizer 172 photonic crystal analyzer 181 photonic crystal lambda / 4 plate 191 photonic crystal circular polarizers 201 magneto-optical crystal film 210 two-dimensional photonic crystal 211 light Propagation direction high permeability portion 212 optical transmission transportable direction low permeability portions 213 right times circularly polarized light 214 left times circularly polarized light 215 unpolarized wave incident light 216 circular polarization light emitted 221 high refractive index particles 222 low refractive index portion 223 three-dimensional photonic crystal 224 optical fiber bundle 225 light Optical axis 226 Oblique end face 227 Stacking direction 241 PBS polarizer 242 λ / 4 plate 243 LiNbO3 crystal 244 PBS analyzer 246a Input side optical fiber 246b Output side optical fiber 249 Electrode terminal 1010 First optical fiber 1020 Second light Fiber 1030 First lens 104 0 Second lens 1050 Polarizer 1060 Faraday element 1070 Analyzer 1080 Magnetic field 2001 Substrate 2002 Waveguide 2003 Electrode 2004 Signal source 2005 Incident light 2006 Optical fiber 2007 Core 2008 Cladding 2009 Lens 2010 Emission light 2011 Earth zander 2012 Mach Zehnder) type modulator

Claims (1)

An optical device that optically couples with an optical component and propagates light to the optical component,
An optical fiber comprising a core for propagating light and a clad surrounding the core, and having a first end face that is not perpendicular to the optical axis;
A functional unit made of a photonic crystal laminated directly on the first end face and in a direction perpendicular to the first end face;
A resin portion made of a resin in contact with the photonic crystal, and having a second end face perpendicular to the optical axis of the optical fiber and through which the optical axis of the optical fiber passes,
An optical device that propagates light to the optical component by optically coupling with the optical component at the second end face.

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