Optical chemical analysis device

Abstract

To provide an optical chemical analyzer capable of high-efficiently coupling of incoherent light emitted from a light source and an optical waveguide.SOLUTION: An optical chemical analyzer 14 includes: an optical waveguide 15 that has a light propagating part 10 where light propagates in the extending direction and a core layer 12 including a diffraction grating part that optically connects to the light propagation part (first diffraction grating section 11); and a light source 17 that emits incoherent light capable of being incident on the diffraction grating part. The diffraction grating part further has a light capture area for introducing light from the light source. The light source has a light-emitting point at a position where the difference between the shortest optical distance Lab up to the light capture area and the longest optical distance Lac up to the light capture area is less than half the wavelength of light in a vacuum.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical chemical analysis device. [Background technology]

[0002] Light propagating through a structure, such as a thin film made of a crystal, undergoes repeated total reflection at the interface with the structure's exterior if the refractive index of the material forming the structure is greater than that of the material outside the structure. When the light propagating through the structure is totally reflected at this interface, it seeps into the exterior, which has a lower refractive index. This seepage is called an evanescent wave (see Figure 9). The evanescent wave EW can be absorbed by a substance 52 adjacent to the structure 51 as the light L propagates. This allows for the detection and identification of a substance 52 in contact with the structure 51 based on changes in the intensity of the light L propagating through the structure 51. An analytical method utilizing the principle of the evanescent wave EW is called attenuated total reflection spectroscopy (ATR) and is used to analyze the chemical composition and concentration of a substance 52. Infrared light is typically used as the propagating light. Since substances have the property of selectively absorbing infrared rays of specific wavelengths, the substance can be analyzed and sensed by transmitting infrared rays that match the absorption spectrum of the substance to be measured.

[0003] Patent Document 1 proposes an optical waveguide sensor that applies the ATR method to a sensor. This optical waveguide sensor has a core layer formed on a substrate, through which light passes, and detects substances in contact with the core layer by utilizing evanescent waves.

[0004] Incidentally, sensors using the ATR method require a point where light from the light source is introduced into the core layer of the optical waveguide and a point where it is extracted from the core layer of the optical waveguide toward the photodetector. For this reason, diffraction gratings are often installed between the light source and the optical waveguide, and between the photodetector and the optical waveguide, to bend the optical axis of the light. In general, highly directional coherent light, such as laser light, is irradiated onto the diffraction grating to introduce the light into the core layer. In this case, the less light loss there is in the diffraction grating, the stronger the signal detected by the photodetector, and the higher the sensitivity of the sensor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-300212 Summary of the Invention [Problem to be solved by the invention]

[0006] Increasingly, incoherent light sources with low directivity, such as LEDs and heaters, are being used as light sources in devices that utilize optical waveguides, and the light-emitting area of ​​the light source is often relatively large, at 100 μm x 100 μm or more. A technology is needed to efficiently introduce even this type of incoherent light with low directivity into the core layer of the optical waveguide.

[0007] An object of the present invention is to provide an optical chemical analysis device that can efficiently couple incoherent light emitted from a light source with an optical waveguide. [Means for solving the problem]

[0008] An optical chemical analysis apparatus according to one aspect of the present invention comprises: an optical waveguide having a core layer including a light propagation portion through which light can propagate in an extension direction and a diffraction grating portion optically connected to the light propagation portion; a light source that emits incoherent light that can make the light incident on the diffraction grating portion, the diffraction grating portion further includes a light intake region for introducing light from the light source; The light source has a light emitting point at a position where the difference between the shortest optical distance Lab to the light receiving area and the longest optical distance Lac to the light receiving area is smaller than half the wavelength of the light in a vacuum.

[0009] An optical chemical analysis apparatus according to one aspect of the present invention comprises: an optical waveguide having a core layer including a light propagation portion through which light can propagate in an extension direction and a diffraction grating portion optically connected to the light propagation portion; a light source that emits incoherent light that can make the light incident on the diffraction grating portion, the diffraction grating portion further includes a light intake region for introducing light from the light source; the diffraction grating portion has a plurality of connection portions optically connected to the light propagation portion, The light source has a light emitting point at a position where the difference between the optical distance Lam to a point M of the diffraction grating portion that is located at the midpoint of a line segment connecting any two of the plurality of connection portions in a planar view and the optical distance Lai to the closer of the two connection portions is smaller than half the wavelength of the light in a vacuum.

[0010] An optical chemical analysis apparatus according to one aspect of the present invention comprises: an optical waveguide having a core layer including a light propagation portion through which light can propagate in an extension direction and a diffraction grating portion optically connected to the light propagation portion; a light source that emits incoherent light that can make the light incident on the diffraction grating portion, the diffraction grating portion further includes a light intake region for introducing light from the light source; The light source has a light emitting point at a position where the area of ​​the light capture area, under the condition that |sin(ΔP)|<0.1, is equal to or greater than 50% of the total area of ​​the light capture area, where ΔP is the product of the difference ΔL between the shortest optical distance Lab to the light capture area and the optical distance Lad to a point in the light capture area and the wave number of the light in a vacuum (2π / wavelength in a vacuum). [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an optical chemical analysis device that can efficiently couple incoherent light emitted from a light source with an optical waveguide. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an optical chemical analysis device of the present invention. [Figure 2] 2(a) and 2(b) are diagrams illustrating the peripheral structure of the first diffraction grating portion. [Figure 3] FIG. 3 is a diagram showing the relationship between the light source and the diffraction grating unit of the optical chemical analysis device according to the first embodiment. [Figure 4] 4(a) and 4(b) are diagrams showing the relationship between the light source and the diffraction grating unit of the optical chemical analysis device according to the second embodiment. [Figure 5] 5(a) and 5(b) are diagrams showing the relationship between the light source and the diffraction grating unit of the optical chemical analysis device according to the third embodiment. [Figure 6] FIG. 6 is a diagram showing the relationship between the light source and the diffraction grating unit of the optical chemical analysis device according to the fourth embodiment. [Figure 7] FIG. 7 is a diagram for explaining the transmission modes. [Figure 8] FIG. 8 is a diagram for explaining the close arrangement. [Figure 9] FIG. 9 is a diagram for explaining an evanescent wave of light propagating through an optical waveguide. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0014] An optical chemical analysis device according to one embodiment of the present invention includes an optical waveguide having a core layer including a light propagation portion capable of propagating light in an extension direction and a diffraction grating portion optically connected to the light propagation portion. The optical chemical analysis device also includes a light source that emits incoherent light that can be incident on the diffraction grating portion, which is a part of the core layer. The diffraction grating portion further includes a light capture region for introducing light from the light source. The light source has a light-emitting point at a position where the difference between the shortest optical distance Lab to the light capture region and the longest optical distance La to the light capture region is smaller than half the wavelength of the light in a vacuum. In this specification, the diffraction grating portion is referred to as a first diffraction grating portion and is to be distinguished from a second diffraction grating portion (a diffraction grating portion that outputs light to a photodetector) described below.

[0015] According to the optical chemical analysis device of this embodiment, the light source has a light-emitting point at a position where the difference between the shortest optical distance Lab to the light-capturing region and the longest optical distance La to the light-capturing region is less than half the wavelength of the light in a vacuum. This allows the optical chemical analysis device of this embodiment to efficiently couple incoherent light emitted from the light source to the optical waveguide. Specifically, when light emitted from a single light-emitting point of the light source spreads concentrically and reaches each point in the light-capturing region of the first diffraction grating, if the difference in optical distance to each point is less than half the wavelength of the light, even light emitted from an incoherent light source can be considered to be in phase in the light-capturing region. The light-capturing region captures light into the core layer by interfering with the wavelength of the light and the period of the structure forming the light-capturing region. Therefore, the light that reaches the light-capturing region can be considered to be in phase in the light-capturing region. Here, by having a light source with a light-emitting point at a position where the difference between the shortest optical distance Lab to the light-capturing region and the longest optical distance Lac to the light-capturing region is smaller than half the wavelength of the light in a vacuum, the light emitted from the light-emitting point is coupled to the optical waveguide in a single mode throughout the entire light-capturing region, thereby enabling highly efficient coupling of incoherent light with the optical waveguide. Here, the optical distance Lac is the shortest optical distance from the light-emitting point to the point on the light-capturing region that is optically farthest from the light-emitting point.

[0016] The principles of the present invention will now be described in more detail. Light emitted from an incoherent light source contains many light beams with different phases, even if only a single wavelength is extracted. However, even with an incoherent light source, the phases are aligned in the optical wavefront formed by light departing from the same point at the same time. That is, even with incoherent light, the first diffraction grating section (light capture region) operates for each phase-aligned component, and the phase-aligned component can be incorporated into the core layer as a single propagation mode. Light departing from the same point at the same time spreads its phase front concentrically. Here, since the surface of the light capture region is generally not spherical but has concaves and convexes formed on a plane, the light that reaches the light capture region experiences a phase shift at the surface of the light capture region. However, a slight phase shift (the difference in optical path length is less than half the wavelength of the light) that does not result in an antiphase can be treated as being in phase. However, if the area of ​​the light capture region is large, it is not possible to consider the light to be in phase at all positions in the light capture region, and multiple in-phase groups are formed within the light capture region. Therefore, if the area of ​​the light capture region is large, multiple propagation modes are formed even for light departing from the same point at the same time. On the other hand, in the light propagation section, to propagate light of multiple propagation modes, the cross-sectional area (width and height) of the light propagation section perpendicular to the extension direction must be large enough to accommodate the number of propagation modes. However, since the cross-sectional area of ​​the light propagation section is generally very small, in the case of a first diffraction grating section with a large light capture region, the light propagation section cannot propagate all of the multiple propagation modes generated in the first diffraction grating section. Therefore, it is preferable that the number of in-phase groups formed in the light capture region of the first diffraction grating section be equal to or less than the number of propagation modes that can propagate in the light propagation section. Furthermore, from the viewpoint of efficient light propagation in the light propagation section, it is preferable that the light propagation section be a so-called single-mode optical waveguide that propagates a single mode. Considering these points, when the first diffraction grating unit guides light taken in by one light taking-in region to one light propagation section, it is preferable that the first diffraction grating unit is configured so that the number of in-phase groups formed in the light taking-in region is 1. In other words, it is preferable that the first diffraction grating unit has a light taking-in region with a small area.

[0017] In this embodiment, the light source preferably has a light-emitting point at a position where the difference between the optical distance Lab and the optical distance Lac is smaller than one-fourth of the wavelength of the light in a vacuum. When the light-emitting point and the light-collecting region satisfy this relationship, the light incident on the light-collecting region from the light source can be considered to be more in-phase, and the light can be efficiently captured by the core layer.

[0018] In this embodiment, the light source preferably has a light-emitting point at a position where the difference between the optical distance Lab and the optical distance Lac is smaller than 2.13 μm. For example, in an optical chemical analyzer for analyzing CO2, a typical gas suspended in the environment, infrared light with a central wavelength of about 4.26 μm in a vacuum is generally used as the light propagating through the core layer. In this case, half of the wavelength of the light in a vacuum is 2.13 μm.

[0019] Furthermore, in this embodiment, it is preferable that more than half of the light-emitting points of the light source are arranged at positions where the difference between the optical distance Lab and the optical distance Lac is smaller than half the wavelength of the light in a vacuum, and it is more preferable that all of the light-emitting points of the light source are arranged at positions where the difference between the optical distance Lab and the optical distance Lac is smaller than half the wavelength of the light in a vacuum. When the light-emitting points and the light-collecting region satisfy this relationship, the light emitted from more than half of the light-emitting points of the light source can be considered to be in phase at all points on the light-collecting region, and the light can be efficiently captured by the core layer.

[0020] The first diffraction grating portion may include a plurality of light collecting regions. In plan view, the outer shape of the light source may be the smallest convex polygon that covers the light emitting point. For example, the outer shape of the light source may be a square or a rectangle as the convex polygon. It is preferable that, in plan view, the area of ​​the smallest convex polygon (outer shape) that covers the light emitting point of the light source is larger than the area of ​​one light collecting region, and light emitted from the light source is collected by the plurality of light collecting regions.

[0021] When the light source has a large light-emitting area (i.e., the area of ​​the convex polygon covering the light-emitting point is large), the first diffraction grating portion includes multiple light-capturing areas, and the light emitted from the light source is captured by the multiple light-capturing areas, allowing the optical chemical analysis device to efficiently capture the light emitted from the light source into the core layer.

[0022] In addition, the first diffraction grating unit may have a configuration in which multiple light capturing areas are connected and the light capturing areas cannot be distinguished from one another. In this case, the number of connection portions with the light propagation unit represents the actual number of light capturing areas, and the connection portions approximately represent the ends of the overall light capturing areas, so the size of the first diffraction grating unit can be determined using the connection portions.

[0023] In one embodiment, the light source has a light emitting point at a position where the difference between the optical distance Lam to point M of the first diffraction grating portion, which is located at the midpoint of a line segment connecting any two of the multiple connection portions in a planar view, and the optical distance Lai to the closer of the two connection portions, is smaller than half the wavelength of the light in a vacuum.

[0024] When the first diffraction grating portion is configured in a form in which a plurality of light collection regions are connected, by satisfying this relationship, the number of in-phase groups formed on the light collection region by the light emitted from at least one light-emitting point is equal to or less than the number of connecting portions. Therefore, all of the in-phase groups formed on the light collection region can be guided to a plurality of light propagation portions via a plurality of connecting portions, and the optical chemical analysis device can efficiently take in the light emitted from the light source into the core layer.

[0025] In this embodiment, the light source preferably has a light-emitting point at a position where the difference between the optical distance Lam and the optical distance Lai is smaller than one-fourth of the wavelength of the light in a vacuum. When the light-emitting point and the light capture region satisfy this relationship, the light incident on the light capture region from the light source can be considered to be more in-phase, and the light can be efficiently captured by the core layer.

[0026] In this embodiment, the light source preferably has a light-emitting point at a position where the difference between the optical distances Lam and Lai is smaller than 2.13 μm. For example, in an optical chemical analyzer for analyzing CO2, a typical gas suspended in the environment, infrared light with a central wavelength of about 4.26 μm in a vacuum is generally used as the light propagating through the core layer. In this case, half of the wavelength of the light in a vacuum is 2.13 μm.

[0027] Furthermore, in this embodiment, it is preferable that more than half of the light-emitting points of the light source are arranged at positions where the difference between the optical distance Lam and the optical distance Lai is smaller than half the wavelength of the light in a vacuum, and it is more preferable that all of the light-emitting points of the light source are arranged at positions where the difference between the optical distance Lam and the optical distance Lai is smaller than half the wavelength of the light in a vacuum. When the light-emitting points and the light capture area satisfy this relationship, the light emitted from more than half of the light-emitting points of the light source can be considered to be in phase at all points on the light capture area, and the light can be efficiently captured into the core layer.

[0028] Furthermore, as mentioned above, the light that has reached the light receiving area of ​​the first diffraction grating section from the light source's light emission point can be treated as being in phase if there is a slight phase shift. The relationship between the light source's light emission point and the light receiving area of ​​the first diffraction grating section can be determined using the phase shift instead of the difference in optical distance.

[0029] In one embodiment, the light source has a light emitting point where the area of ​​the light capture area satisfies the condition |sin(ΔP)|<0.1, where ΔP is the product of the difference ΔL between the shortest optical distance Lab to the light capture area and the optical distance Lad to a point in the light capture area and the wave number of light in a vacuum (2π / wavelength in a vacuum).

[0030] By satisfying this relationship regarding the phase of light, at least one light-emitting point can treat most of the light incident from that point to the entire light capture area as being in phase, allowing the optical chemical analysis device to efficiently capture light emitted from the light source into the core layer. Here, if the wavelength in vacuum is λ0, the phase difference ΔP is expressed as "ΔL × 2π / λ0." The value 0.1 on the right-hand side indicates that the phase difference ΔP is in a very small range. In optical systems, when θ is small, it is often discussed as an approximation of Sinθ ≒ θ, and in the above case, it is in a range where |sin(ΔP)| ≒ ΔP can be approximated.

[0031] Below, each of the components constituting the optical chemical analysis device will be explained using a specific example.

[0032] <Optical waveguide> The optical waveguide is used in an optical chemical analysis device that analyzes the chemical composition and concentration of a substance to be measured (gas, liquid, etc.). The optical waveguide includes a core layer having a light propagation portion through which light can propagate in the extension direction, and a first diffraction grating portion that receives light from a light source and guides the light to the light propagation portion. The optical waveguide also includes a substrate.

[0033] Here, the extension direction is a direction that exists so as to extend along at least one direction. For example, in a three-dimensional structure, the path that travels from one end to another end (or from one arbitrary point to another arbitrary point) in the shortest distance while touching the three-dimensional structure is the extension direction. Alternatively, the direction that travels from one end to another end (or from one arbitrary point to another arbitrary point) so as to minimize the amount of change in cross-sectional area is also the extension direction. The extension direction includes not only linear directions but also curved directions.

[0034] The first diffraction grating section guides light to the light propagation section (in other words, the light propagation section introduces light from the first diffraction grating section), and the light propagation section guides light to the second diffraction grating section (in other words, the second diffraction grating section introduces light from the light propagation section), as described below, means that as long as light can propagate between the light intake region of the first diffraction grating section, the light extraction region of the second diffraction grating section, and the light propagation section, the connection form between them is not limited. For example, this includes cases where they are made of the same material (including the same crystalline state) and are continuously connected without interruption, as well as cases where they are optically continuous. Examples of cases where they are optically continuous include cases where they are discontinuous because they are made of different materials (including cases where the same element has different crystalline states) but are optically continuous because they are located on the same axis, and cases where they are discontinuous but not located on the same axis (disconnected), such as when they are coupled by evanescent waves like a directional coupler. Here, a directional coupler refers to an optically coupled state in which the direction of light does not change before and after the transition from one side to the other using evanescent waves. In addition, hereinafter in this specification, a state in which light can be introduced or output between the first diffraction grating unit, the second diffraction grating unit, and the light propagation unit is simply referred to as the first diffraction grating unit, the second diffraction grating unit, and the light propagation unit being connected.

[0035] The first diffraction grating unit is disposed adjacent to and facing the light emitting surface of the light source. The first diffraction grating unit has one or more light receiving areas, and the light receiving areas receive light emitted from the light source. Here, the light emitting surface of the light source is the surface that contacts the substance to be measured among the surfaces from which light from the light source is emitted. The adjacent arrangement will be described later.

[0036] Furthermore, it is preferable that the optical waveguide further includes a second diffraction grating portion that introduces light from the light propagation portion and outputs the light to the photodetector, and that the second diffraction grating portion has at least one light extraction region.

[0037] <<Core Layer>> The core layer has a light propagation portion through which light can propagate in the extension direction, and a first diffraction grating portion that receives light from a light source and outputs the light to the light propagation portion. The core layer can further have a second diffraction grating portion that introduces light from the light propagation portion and outputs the light to a photodetector.

[0038] The material of the core layer is not particularly limited. Examples include core layers containing single crystal silicon and polycrystalline silicon, amorphous silicon, silicon nitride, silicon germanium, germanium, gallium arsenide, indium phosphide, indium antimony, indium gallium arsenide, indium gallium phosphide, indium fluoride, diamond, sapphire, lithium niobate, chalcogenide glass, etc. Furthermore, the core layer may be composed of a multilayer film instead of a single layer film.

[0039] The first diffraction grating portion and the light propagation portion may be formed of different materials. In this case, it is preferable that the material forming the light propagation portion is single crystal silicon, and the material forming the first diffraction grating portion contains polycrystalline silicon or amorphous silicon. Silicon is the most common material, and such a configuration reduces propagation loss in the light propagation portion and easily improves the degree of freedom in processing the first diffraction grating portion.

[0040] Furthermore, a cross section perpendicular to the extension direction at any position along the extension direction of the core layer may have a shape in which the distance from the center of the core layer to the outer surface of the cross section varies, such as a rectangle, or may have a shape in which the distance from the center of the core layer to the outer surface of the cross section does not vary, such as a circle.

[0041] Furthermore, at least a portion of the core layer may be exposed or covered with a thin film. This allows the exposed or covered portion of the core layer to come into direct contact with the substance to be measured or to come into contact with the substance to be measured via the thin film, allowing the evanescent wave to interact with the substance to be measured, thereby enabling the chemical composition and concentration of the substance to be analyzed. The thickness of the film is preferably less than ¼ of the wavelength in vacuum of the light propagating through the core layer.

[0042] Furthermore, the light propagating through the core layer may be infrared light as an analog signal. Here, infrared light as an analog signal means that the signal does not determine the change in light energy as a binary value of 0 (low level) or 1 (high level), but rather handles the amount of change in light energy. This allows the optical waveguide to be used in sensors and analytical devices. In this case, the wavelength of the infrared light in a vacuum may be 2 μm or more and less than 12 μm. This wavelength band is absorbed by gases typically suspended in the environment (CO2, CO, NO, NO, SO, CH4, HO, CHO, etc.). This allows the optical waveguide to be used as a gas sensor.

[0043] The core layer may also include a portion that extends in a curved shape, which allows the aspect ratio of the outline of the core layer to approach 1 when the entire core layer is viewed in a plane, thereby enabling the optical waveguide and optical chemical analysis device to be miniaturized.

[0044] <<<Optical propagation section>>> The light propagation portion introduces and propagates light received by the first diffraction grating portion, and outputs the light to the second diffraction grating portion. The light propagation portion refers to a portion through which light can propagate in the extension direction, has a width in a width direction perpendicular to the extension direction, and has a constant width of the core layer along the extension direction. The light propagation portion may have a cross section perpendicular to the extension direction at any position along the extension direction, for example, a shape in which the distance from the center of the core layer to the outer surface of the cross section varies, such as a rectangle, or a shape in which the distance from the center of the core layer to the outer surface of the cross section does not vary, such as a circle.

[0045] The light propagating portion can have a uniform film thickness (that is, the height of the light propagating portion) in the extending direction, and the uniform film thickness means that the difference in film thickness is, for example, 200 nm or less.

[0046] Furthermore, from the viewpoint of efficiently propagating light, the light propagation portion is preferably a so-called single-mode optical waveguide that propagates light in a single mode. That is, in at least a part of the light propagation portion, the light propagation portion preferably has a width or height (film thickness) that allows light to propagate in a single mode, and more preferably has a width and height that allow light to propagate in a single mode. That is, the light propagation portion preferably has a cross-sectional area in a cross section perpendicular to the extension direction that allows light to propagate in a single mode.

[0047] Furthermore, it is preferable that the width or height of at least a part of the light propagation portion is smaller than 1 μm, and the cross-sectional area of ​​the plane perpendicular to the extending direction of at least a part of the light propagation portion is 1 μm 2 Preferably, the width or height is less than 1 μm, and 2 The smaller cross-sectional area is the dimension of the light propagation portion that can propagate light emitted from the light source in this embodiment (infrared light with a wavelength of 2 μm or more and less than 12 μm in vacuum) in a single mode or with a mode number close to a single mode.

[0048] <<<First diffraction grating section, second diffraction grating section>>> The first diffraction grating section receives light from the light source and outputs the light to the light propagation section. The first diffraction grating section also has one or more light capture areas, with at least one light capture area receiving light emitted from the light source. The core layer can have a second diffraction grating section. The second diffraction grating section has at least one light extraction area that introduces light from the light propagation section and outputs the light to a photodetector.

[0049] The light inlet region and the light outlet region may be portions on the surface of which irregularities are formed at a specific period (which may be multiple periods), and when the optical waveguide is viewed in cross section on a plane including the irregularities or the concave and convex portions, the grooves of the concave portions of the irregularities are deep, separating the core layer. In such a configuration, the convex portions are formed discontinuously in island shapes.

[0050] The light inlet region and the light outlet region can be provided so that the patterns of parallel concaves and convexes extend linearly or arcuately in a plan view. The extending shape of the concaves and convexes can be any shape.

[0051] The shapes of the first and second diffraction grating units in a planar view can be any, including, for example, a shape having a portion whose width increases from the connection side toward the end, with the apex located near the connection side of the first and second diffraction grating units to the light propagation unit. Specifically, the shapes can include a sector whose center is near the connection side of the first and second diffraction grating units to the light propagation unit, a triangle (e.g., an isosceles triangle) whose center is near the connection side of the first and second diffraction grating units to the light propagation unit, and a portion whose apex is near the connection side of the light propagation unit and whose width increases from the connection side toward the light inlet region and the light outlet region, and a portion of any shape, such as a rectangular shape, continuing from the portion. The shapes of the light inlet region and the light outlet region are preferably symmetrical with respect to any imaginary line extending from the connection side toward the end.

[0052] As described above, the light propagation portion refers to a portion of the core layer whose width does not change in the extending direction. The connection portion refers to a connection point between the first diffraction grating portion or the second diffraction grating portion and a portion (light propagation portion) whose width does not change. The first diffraction grating portion or the second diffraction grating portion can have multiple connection portions that optically connect to the light propagation portion.

[0053] Next, we will explain the wavelength dispersion (wavelength width of propagated light) of light propagating through an optical chemical analyzer. In an optical chemical analyzer, light matching the absorption spectrum of the substance being measured propagates through the light propagation section to analyze the substance. Therefore, it is preferable for the first diffraction grating section to capture light in a wavelength band similar to the absorption spectrum of the substance being measured into the core layer. Generally, the absorption wavelength range of a substance can have a width of about ±0.1 μm around the center wavelength and is not a strictly single wavelength. For example, the typical absorption wavelength of CO2, a gas suspended in the environment, is approximately 4.20 to 4.35 μm, with a width of 0.15 μm. In this case, overselecting light to a strictly single wavelength would result in discarding the wavelength range effective for analysis, which is undesirable for an optical chemical analyzer. In particular, in the optical chemical analysis device of this embodiment, an incoherent light source such as an LED is used as the light source, and from the viewpoint of effectively utilizing light having a certain wavelength range (wavelength band) from the incoherent light source, it is preferable that the wavelength band selected in the first diffraction grating region also has a certain width (approximately ±0.1 μm from the center wavelength).

[0054] The width of the wavelength band selected by the first diffraction grating region can be explained using the uncertainty principle. When the first diffraction grating section captures light from the light source into the core layer, it is impossible to distinguish which part of the light capture region the light hits. In other words, when the one-dimensional size of the light capture region is Δx, the light has an uncertainty in its position Δx. Therefore, the uncertainty Δp of momentum p can be expressed as equation (2) using the uncertainty principle expressed in equation (1).

number

[0055] Furthermore, since the wavelength λ of light can be expressed by equation (3), the wavelength uncertainty Δλ can be expressed by equation (4).

number

[0056] Equation (5) is derived from equations (2) and (4). In other words, to have wavelength uncertainty Δλ, the position uncertainty Δx must satisfy equation (5).

number

[0057] Here, if the wavelength dispersion suitable for an optical chemical analyzer is 0.1 μm, then the wavelength uncertainty Δλ in the light capture region should be 0.1 μm. Therefore, by substituting Δλ = 0.1 into equation (5), equation (6) is derived.

number

[0058] The one-dimensional size of the light capture area is Δx, and its area S is Δx 2 Therefore, when the area S of the light capturing region satisfies formula (7), the wavelength of the light captured by the light capturing region can be made to have a dispersion of about 0.1 μm. In other words, it is preferable that the area S of the light capturing region satisfies formula (7).

number

[0059] When CO2 is analyzed using the optical chemical analysis device of the present invention, the average wavelength of light propagating through the core layer in a vacuum is set to 4.26 μm. Using equation (3), equations (6) and (7) are calculated to obtain Δx≧14.1 μm and S≧198.9 μm. 2 must be met.

[0060] Furthermore, in this embodiment, the lower limit values ​​of the difference between the optical distance Lab and the optical distance Lac, and the difference between the optical distance Lam and the optical distance Lai are uniquely determined from the lower limit value of the size of the light capture area shown in equation (6) or equation (7), and therefore only the lower limit value of the size of the light capture area is specified.

[0061] Furthermore, the structure of the second diffraction grating section can be the same as the structure of the first diffraction grating section, or can be a structure converted from the structure of the first diffraction grating section. Converted from the structure of the first diffraction grating section means that the shape, configuration, arrangement, etc. of the second diffraction grating section are rotated, enlarged, reduced, translated, line-symmetric, or point-symmetric with respect to the shape, configuration, arrangement, etc. of the first diffraction grating section. By making the structure of the second diffraction grating section the same as the structure of the first diffraction grating section, or by converting the structure of the second diffraction grating section from the structure of the first diffraction grating section, the wavelength selectivity of the first diffraction grating section and the wavelength selectivity of the second diffraction grating section can be made substantially equal, thereby avoiding optical loss that occurs when the wavelength selectivity of the first diffraction grating section and the second diffraction grating section differ.

[0062] <<Substrate>> The substrate is not particularly limited as long as it is possible to form a core layer on the substrate, and a support layer (described later) can also be formed on the substrate. Specific examples of the substrate include a silicon substrate and a GaAs substrate.

[0063] <<Support layer>> The support layer is optionally provided. The support layer connects at least a portion of the substrate and at least a portion of the core layer. The support layer is not particularly limited as long as it can bond the substrate and the core layer, but is preferably a material with a smaller refractive index than the core layer for light of any wavelength or light propagating through the core layer. As an example, the support layer may be formed from SiO2 or the like. In the present invention, the support layer is not an essential component. The core layer may be bonded to the substrate via a support layer, or the core layer may be formed directly on the substrate. Alternatively, the support layer may be partially present, and at least a portion of the core layer may be floating without being bonded to the support layer. That is, in an optical waveguide with such a configuration, a space is formed between the substrate and the core layer except for the region where the support layer is provided. By floating a portion of the core layer, the amount of interaction between the evanescent wave and the measured substance can be increased, thereby improving sensor sensitivity.

[0064] As an example of a method for forming a support layer, a structure can be formed in which the core layer (Si layer) and the substrate (Si layer) are supported by the BOX layer by etching the buried oxide (BOX: Buried Oxide) layer (SiO2 layer) of an SOI (Silicon On Insulator) substrate.

[0065] <Light source> The light source is not particularly limited as long as it can introduce light into the core layer. When infrared light is used for gas analysis, an incandescent lamp, a ceramic heater, a MEMS (Micro Electro Mechanical Systems) heater, an infrared LED (Light Emitting Diode), etc. can be used as the light source. That is, the light source may be an incoherent light source. The light source may be arranged in any form as long as it can be optically connected to the optical waveguide. For example, the light source may be arranged adjacent to the optical waveguide in the same solid body as the optical waveguide, or may be arranged as a separate solid body at a certain distance from the optical waveguide. Furthermore, when ultraviolet light is used for gas analysis, a mercury lamp, an ultraviolet LED, etc. can be used as the light source. The light source has a light-emitting surface with an area of, for example, 100 μm × 100 μm or more.

[0066] In one embodiment, the light source may include a light-emitting layer having multiple light-emitting points and a high-refractive index material layer that refracts light from the light-emitting layer and guides it to the core layer. The high-refractive index material layer is partially in contact with the substance to be measured and is located between the light-emitting layer and the substance to be measured. Here, each of the multiple light-emitting points is a light-emitting element that emits light. In the light-emitting layer, the multiple light-emitting elements may be arranged at equal intervals in a direction perpendicular to the stacking direction, for example, but not limited to this. The high-refractive index material layer may be composed of, for example, but not limited to, silicon (Si) or gallium arsenide (GaAs). For example, the light source may be an LED formed on one major surface of a GaAs substrate. The light-emitting points may be located within the LED's light-emitting layer, and light emitted from the LED's light-emitting layer may be emitted from the other major surface opposite the one major surface of the GaAs substrate. In this case, the GaAs substrate serves as the high-refractive index material layer. The high-refractive index material may be any material that can refract light from the light-emitting layer and guide it to the core layer (light capture region), but it is preferable that the high-refractive index material has a higher refractive index than the light-emitting layer. Furthermore, it is preferable that the refractive index is higher than that of the gas to be measured. By providing a high refractive index material layer, it becomes easy to have an emission point at a position where the difference between the optical distance Lab and the optical distance Lac is smaller than half the wavelength of the light in a vacuum. Similarly, it becomes easy to have an emission point at a position where the difference between the optical distance Lam and the optical distance Lai is smaller than half the wavelength of the light in a vacuum. Similarly, it becomes possible to have an emission point at a position where the area of ​​the light capture region, under the condition that |sin(ΔP)|<0.1, is equal to or greater than 50% of the total area of ​​the light capture region, with respect to the difference ΔL between the optical distance Lab and the optical distance Lad and the phase difference ΔP.

[0067] The light propagating through the core layer of the optical waveguide provided in the optical chemical analyzer may be infrared light as an analog signal. Here, infrared light as an analog signal means that the signal does not determine the change in light energy as a binary value of 0 (low level) or 1 (high level), but rather handles the amount of change in light energy. Furthermore, the wavelength of infrared light in a vacuum may be 2 μm or more and less than 12 μm. This wavelength band is absorbed by gases typically suspended in the environment (CO2, CO, NO, NO, SO, SO, CH4, HO, CHO, etc.). This makes it possible to realize an optical chemical analyzer that can analyze these gases.

[0068] The light emitting surface of the light source can be disposed facing the first diffraction grating unit in close proximity, which increases the proportion of light output from the light source toward the first diffraction grating unit that reaches the first diffraction grating unit (the solid angle formed by the first diffraction grating unit when viewed from the light source becomes wider), allowing light to be efficiently introduced into the optical waveguide.

[0069] Here, "close" refers to a length of 1 mm or less or √Ss or less, preferably 500 μm or less or 0.5 × √Ss or less, and more preferably 200 μm or less or 0.2 × √Ss or less, where Ss is the area of ​​the light-emitting surface of the light source. Furthermore, the term "length" refers to the length measured along the thickness direction (height direction) of the optical waveguide from the bottom end of the light-emitting surface of the light source on the optical waveguide side to the first diffraction grating section located closest to the light-emitting surface of the light source. It is preferable that no other components, such as lenses or optical fibers, are present between the light-emitting surface of the light source and the first diffraction grating section, and that the light output from the light-emitting surface reaches the first diffraction grating section directly via a small space. This allows for the realization of an inexpensive optical chemical analysis device.

[0070] <Photodetector> The photodetector is not particularly limited as long as it can receive light propagated through the core layer of the optical waveguide. When infrared light is used to analyze gases, thermal infrared sensors such as pyroelectric sensors, thermopiles, or bolometers, or quantum infrared sensors such as diodes or phototransistors can be used as the photodetector. When ultraviolet light is used to analyze gases, quantum ultraviolet sensors such as diodes or phototransistors can be used as the photodetector.

[0071] The photodetector can be disposed adjacent to and facing the second diffraction grating unit. In other words, the second diffraction grating unit can be disposed adjacent to and facing the photodetector. This increases the proportion of light output from the second diffraction grating unit toward the photodetector that reaches the photodetector (the solid angle formed by the photodetector when viewed from the second diffraction grating unit becomes wider), allowing light to be efficiently introduced into the photodetector. Here, "close" may be the same as the length described for the close arrangement between the light source and the first diffraction grating unit. It is preferable that no other components, such as lenses or optical fibers, are present between the second diffraction grating unit and the photodetector, and that the light output from the second diffraction grating unit reaches the photodetector directly via a small space. This allows for an inexpensive optical chemical analysis device to be realized.

[0072] [First embodiment] FIG. 1 is a diagram showing the schematic configuration of an optical chemical analysis device 14 according to a first embodiment, and is also a conceptual diagram of the ATR method using an optical waveguide 15. As shown in FIG. 1, the optical chemical analysis device 14 is installed in an external space 16 in which a gas to be analyzed (including detection) exists. The gas to be measured is, for example, air, and the gas contained in the air is analyzed. The optical chemical analysis device 14 includes an optical waveguide 15, a light source 17 capable of irradiating light onto a core layer 12 provided in the optical waveguide 15, and a photodetector 18 capable of receiving light propagated through the core layer 12. In this embodiment, the light is infrared IR.

[0073] More specifically, the optical chemical analysis device 14 is obtained by manufacturing an optical waveguide 15, and further, as shown in FIG. 1, installing a light source 17 so that infrared rays IR can be incident on a first diffraction grating portion 11 (a grating coupler as an example) of the optical waveguide 15, and arranging a photodetector 18 so that infrared rays IR emitted from a second diffraction grating portion 13 (a grating coupler as an example) of the optical waveguide 15 can be received.

[0074] The optical waveguide 15 includes a substrate 19, a core layer 12 capable of propagating infrared radiation IR, and a support layer 20 that connects at least a portion of the substrate 19 and at least a portion of the core layer 12 and supports the core layer 12 relative to the substrate 19. The core layer 12 and the substrate 19 are formed of, for example, silicon (Si). The support layer 20 is formed of, for example, silicon dioxide (SiO2). The substrate 19 and the support layer 20 have, for example, a plate shape. The support layer 20 may support at least a portion of the core layer 12, or may support the entire core layer 12. In the example of FIG. 1, the support layer 20 discontinuously supports the entire first diffraction grating portion 11 and the second diffraction grating portion 13, and a portion of the light propagation portion 10 in the extension direction. As a result, the optical waveguide 15 has the light propagation section 10 intermittently connected to the support layer 20 in the extension direction, and has a gap 21 between the light propagation section 10 and the substrate 19 without having a specified layer such as a cladding layer, except in the area where the support layer 20 is provided.

[0075] The core layer 12 has a first diffraction grating portion 11 formed at one end in the extension direction and a second diffraction grating portion 13 formed at the other end. The core layer 12 also has a light propagation portion 10 between the first diffraction grating portion 11 and the second diffraction grating portion 13 at both ends in the extension direction. In the optical waveguide 15, the light propagation portion 10 may have a uniform film thickness. In the optical waveguide 15, the light propagation portion 10 may have a uniform width. Here, the width direction is a direction perpendicular to the extension direction and the film thickness direction. In addition, the film thickness direction is a direction parallel to the stacking direction in which the substrate 19, the support layer 20, and the core layer 12 are stacked.

[0076] The first diffraction grating unit 11 is disposed in the emission direction of the light source 17. The optical waveguide 15 is disposed so that the principal surface of the substrate 19 is perpendicular to the vertical direction (the stacking direction). The principal surface of the substrate 19 is the surface perpendicular to the thickness direction of the substrate 19, in other words, the surface with the largest area among the six surfaces forming the substrate 19. In other words, the emission direction of the light source 17 is vertically downward from the light source 17 when the optical waveguide 15 is disposed in this manner. The first diffraction grating unit 11 couples infrared light IR incident from the light source 17 to the core layer 12. Therefore, light propagating through the core layer 12 is input from the film thickness direction of the first diffraction grating unit 11. The second diffraction grating unit 13 is disposed in a direction facing the photodetector 18. Here, the direction facing the photodetector 18 is vertically downward from the photodetector 18 when the optical waveguide 15 is disposed as described above. The second diffraction grating portion 13 extracts infrared light IR propagating through the core layer 12 and emits it toward the photodetector 18. Therefore, the light propagating through the core layer 12 is output in the film thickness direction of the second diffraction grating portion 13.

[0077] As described above, the core layer 12 arranged on the light source 17 side (light incident side) has a first diffraction grating portion 11. Moreover, the core layer 12 arranged on the photodetector 18 side (light exit side) has a second diffraction grating portion 13. Moreover, the core layer 12 has, between the center and both ends in the extension direction, light propagation portions 10 through which infrared light IR incident from the first diffraction grating portion 11 and emitted from the second diffraction grating portion 13 propagates. The evanescent waves EW emanating from the core layer 12 are mainly absorbed in the light propagation portions 10 by the substance to be measured present in the external space 16.

[0078] In the optical chemical analyzer 14, the first diffraction grating unit 11 is disposed adjacent to and facing the light-emitting surface of the light source 17. Specifically, the length measured along the thickness direction of the optical waveguide 15 from the lower end of the light-emitting surface of the light source 17 on the optical waveguide 15 side to the first diffraction grating unit 11 located closest to the light-emitting surface of the light source 17 is 1 mm or less, or is √Ss or less where Ss is the area of ​​the light-emitting surface of the light source 17. Furthermore, the length is preferably 500 μm or less or 0.5×√Ss or less, and more preferably 200 μm or less or 0.2×√Ss or less. By setting the length to 1 mm or √Ss or less, the proportion of light output from the light source 17 toward the first diffraction grating unit 11 that reaches the first diffraction grating unit 11 increases (the solid angle formed by the first diffraction grating unit 11 when viewed from the light source 17 becomes wider), thereby enabling light to be efficiently introduced into the optical waveguide 15. The above lengths also apply to the second diffraction grating portion 13 and the light receiving surface of the photodetector 18, and light can be introduced into the photodetector 18 efficiently.

[0079] Furthermore, from the above viewpoint, there is no lower limit to the length, and the light-emitting surface of light source 17 and first diffraction grating unit 11 may be in contact. However, from the viewpoint of properly manufacturing optical chemical analysis device 14, the length is preferably 3 μm or more. There are no lenses, optical fibers, etc. between the light-emitting surface of light source 17 and first diffraction grating unit 11, and light output from the light-emitting surface reaches first diffraction grating unit 11 directly after passing through a short space. This makes it possible to realize optical chemical analysis device 14 at low cost.

[0080] Here, FIG. 8 shows the numerical calculation results of the light arrival ratio when the length of the close arrangement is changed by optical simulation. FIG. 8 assumes that the shape of the light emitting surface of the Lambertian light source is a square with a side length of A, and when the length is D, it shows the ratio of the light emitted from the light emitting surface of the light source reaching the first diffraction grating portion 11 as a function of D / A. Since it is a square with a side length of A, the area of the light emitting surface is A squared. Here, it is assumed that the area of the first diffraction grating portion 11 that receives the light emitted from the light source is the same as the area of the light emitting surface of the light source. As shown in FIG. 8, in the region where D / A>1 (that is, when the light source is arranged far away where D>A), the ratio of the light reaching the first diffraction grating portion 11 is approximated by the inverse square law with respect to the length D. This is because at a distance, when the light reaches the first diffraction grating portion 11, the projected area formed by the arriving light increases in proportion to the square of the length D, and accordingly, the irradiance attenuates. On the other hand, in the region where D / A<1 (that is, when the light source is arranged in the vicinity where D<A), as D / A becomes smaller, the ratio of the arriving light shows a tendency to saturate at the maximum value. That is, by setting the length D to be A (the square root of the area of the light emitting surface) or less, preferably 0.5A or less, more preferably 0.2A or less, light can be efficiently introduced into the optical waveguide 15. This principle also holds for the second diffraction grating portion 13 and the light receiving surface of the photodetector 18. At that time, the area of the second diffraction grating portion 13 corresponds to the area of the light emitting surface of the above light source, and the area of the light receiving surface of the photodetector 18 corresponds to the area of the first diffraction grating portion 11 above. Also, the area of the light emitting surface of the light source and the area of the light receiving surface of the photodetector 18 may have a size of 1 mm 2 or more.

[0081] In the optical chemical analyzer 14, the light source 17 irradiates the core layer 12 with infrared rays having a wavelength of 2 μm or more and less than 12 μm. By irradiating the core layer 12 with the above infrared rays, the evanescent wave EW leaking from the core layer 12 is absorbed by the substance to be measured existing in the external space 16, such as gases such as CO2, CO, NO, N2O, SO2, CH4, H2O, C2H6O, etc., and the substance to be measured can be analyzed.

[0082] 2(a) and 2(b) are diagrams illustrating the peripheral structure of the first diffraction grating portion 11. FIG. 2(a) is a plan view of the peripheral structure of the first diffraction grating portion 11. FIG. 2(b) is a cross-sectional view of the peripheral structure of the first diffraction grating portion 11. The core layer 12 includes a light propagation portion 10 having a propagation path through which light can propagate in the extension direction, and a first diffraction grating portion 11 that receives light from a light source 17 and outputs the light to the light propagation portion 10. As shown in FIG. 2(a), the first diffraction grating portion 11 has a light intake region 113 for introducing light from the light source 17. In this embodiment, the first diffraction grating portion 11 has a shape (a sector shape) whose width increases from the connection side toward the distal end side, with the vicinity of the connection portion 112 as its apex. As described above, the connection portion 112 is the connection point between the first diffraction grating portion 11 and the portion (light propagation portion 10) that extends without changing its width.

[0083] 3 is a cross-sectional view showing the relationship between a light source 17 and a first diffraction grating unit 11 of an optical chemical analysis device 14 according to this embodiment. The light source 17 is an LED formed on one main surface of a substrate. A light-emitting point 171 is located in a light-emitting layer 172 of the LED, and light emitted from the light-emitting layer 172 of the LED passes through a high-refractive-index material layer 173 and is emitted from the other main surface of the substrate opposite to the one main surface.

[0084] As shown in FIG. 3, point A is the position of one light-emitting point 171. Points B and C are two positions in the light collecting area 113 reached by light emitted from the one light-emitting point 171 (i.e., point A). The distance along the path of the light from point A to point B is the optical distance Lab. The distance along the path of the light from point A to point C is the optical distance Lac and the optical distance Lac'. Here, point B is located directly below point A. In other words, the optical distance Lab is the shortest optical distance from point A to the light collecting area 113. Point C is located at the end of the light collecting area 113 farther from point A. In other words, the optical distance Lac is the longest optical distance from point A to the light collecting area 113. Here, the optical distance Lac' takes a detour on the way from point A to point C, and is not the shortest optical distance connecting the two points. Therefore, in the optical chemical analysis device 14 according to this embodiment, the optical distance Lac′ is excluded from the longest optical distance from the point A to the light capturing area 113.

[0085] In this embodiment, the light source 17 has a light-emitting point 171 at a position where the difference between the shortest optical distance Lab to the light capturing region 113 and the longest optical distance Lac to the light capturing region 113 is smaller than half the wavelength of light in a vacuum. In other words, when the light-emitting point 171 is located at a position where the difference between the optical distance Lab and the optical distance Lac is smaller than half the wavelength of light in a vacuum, at least one light-emitting point 171 can regard the light incident from the light-emitting point 171 to the entire light-capturing region 113 as being in phase, and therefore the light can be efficiently captured into the core layer 12.

[0086] Furthermore, in order to more efficiently capture light from light source 17 into core layer 12, light source 17 preferably has light-emitting point 171 at a position where the difference between optical distance Lab and optical distance Lac is smaller than one-fourth of the wavelength of light in a vacuum. Also, light source 17 preferably has light-emitting point 171 at a position where the difference between optical distance Lab and optical distance Lac is smaller than 2.13 μm. Furthermore, more than half of the light-emitting points 171 of light source 17 are preferably disposed at positions where the difference between optical distance Lab and optical distance Lac is smaller than half of the wavelength of light in a vacuum.

[0087] Second Embodiment 4(a) and 4(b) are diagrams showing the relationship between the light source 17 and the first diffraction grating unit 11 of the optical chemical analysis device 14 according to the second embodiment. In this embodiment, the first diffraction grating unit 11 includes a plurality of light capture areas 113 (four in the example of FIG. 4(a)). The other configuration of the optical chemical analysis device 14 is the same as that of the first embodiment. In addition, in FIGS. 4(a) and 4(b), the same elements as those in FIGS. 1 to 3 are denoted by the same reference numerals, and their description will be omitted to avoid redundant explanation.

[0088] The outer shape of light source 17 can be the smallest convex polygon that covers light-emitting point 171 in a planar view. Examples of convex polygons include a triangle, a rectangle, and an octagon. In this embodiment, the outer shape of light source 17 is rectangular. In this embodiment, first diffraction grating unit 11 has multiple light capturing areas 113, and light source 17 has a rectangular outer shape in a planar view, the area of ​​which is larger than the area of ​​one light capturing area 113, and light emitted from light source 17 is captured by multiple light capturing areas 113 (four light capturing areas 113).

[0089] When the light emitting area of ​​the light source 17 is large (i.e., the area of ​​the convex polygon covering the light emitting point 171 is large), the first diffraction grating section 11 includes multiple light capturing areas 113, and the light emitted from the light source 17 is captured by the multiple light capturing areas 113, thereby enabling the optical chemical analysis device 14 to efficiently capture the light emitted from the light source 17 into the core layer 12.

[0090] Third Embodiment 5(a) and 5(b) are diagrams showing the relationship between the light source 17 and the first diffraction grating unit 11 of an optical chemical analysis device 14 according to a third embodiment. In this embodiment, the first diffraction grating unit 11 includes a plurality of connected light capture areas 113 (four in the example of FIG. 5(a)). The other configuration of the optical chemical analysis device 14 is the same as that of the first embodiment. In addition, in FIGS. 5(a) and 5(b), the same elements as those in FIGS. 1 to 3 are denoted by the same reference numerals, and their description will be omitted to avoid redundant explanation.

[0091] The first diffraction grating unit 11 has a configuration in which a plurality of light capturing areas 113 are connected together, and the light capturing areas 113 cannot be distinguished from one another. In this case, the number of connection portions 112 with the light propagation unit 10 represents the actual number of light capturing areas 113, and the connection portions 112 approximately indicate the ends of the overall light capturing areas 113, so the size of the first diffraction grating unit 11 can be defined using the connection portions 112.

[0092] In the example of FIG. 5( a), point M of the first diffraction grating unit 11 is shown at the midpoint of the line segment connecting the two lower connection portions 112. As shown in FIG. 5( b), point A is the position of one light-emitting point 171. The distance along the optical path from point A to point M is the optical distance Lam. In the example of FIG. 5( b), the distance along the optical path from point A to the closer connection portion 112 on the right is the optical distance Lai. In this embodiment, the light source 17 has the light-emitting point 171 at a position where the difference between the optical distance Lam to point M of the first diffraction grating unit 11, which is at the midpoint of the line segment connecting any two of the multiple connection portions 112 in a plan view, and the optical distance Lai to the closer of the two connection portions 112, is smaller than half the wavelength of the light in a vacuum. When the first diffraction grating unit 11 is configured in a form in which a plurality of light collection regions 113 are connected, by satisfying this relationship, the number of in-phase groups formed on the light collection region 113 by the light emitted from at least one light-emitting point 171 is equal to or less than the number of connecting portions 112. Therefore, all of the in-phase groups formed on the light collection region 113 can be guided to a plurality of light propagation portions via a plurality of connecting portions 112, and the optical chemical analysis device 14 can efficiently take in the light emitted from the light source 17 into the core layer 12.

[0093] Furthermore, in order to more efficiently introduce light from light source 17 into core layer 12, light source 17 preferably has light-emitting point 171 at a position where the difference between optical distance Lam and optical distance Lai is smaller than one-fourth of the wavelength of light in a vacuum. Also, light source 17 preferably has light-emitting point 171 at a position where the difference between optical distance Lam and optical distance Lai is smaller than 2.13 μm. Furthermore, more than half of the light-emitting points 171 of light source 17 are preferably disposed at positions where the difference between optical distance Lam and optical distance Lai is smaller than half of the wavelength of light in a vacuum.

[0094] [Fourth embodiment] 6 is a diagram showing the relationship between a light source 17 and a first diffraction grating unit 11 of an optical chemical analysis device 14 according to a fourth embodiment. The configuration of the optical chemical analysis device 14 is the same as that of the first embodiment. In FIG. 6, the same elements as those in FIGS. 1 to 3 are denoted by the same reference numerals, and their description will be omitted to avoid redundant explanation.

[0095] Light that has reached the light capture region 113 of the first diffraction grating unit 11 from the light emission point 171 of the light source 17 can be treated as being in phase if there is a slight phase shift. The efficiency of capturing light into the core layer 12 varies depending on whether the light emitted from the light emission point 171 can be treated as being in phase. In this embodiment, the relationship between the light emission point 171 of the light source 17 and the light capture region 113 of the first diffraction grating unit 11 is determined using a phase shift instead of a difference in optical distance.

[0096] In Figure 6, point A is the position of one light-emitting point 171. Furthermore, points B and D are two positions in the light capturing area 113 reached by light emitted from that one light-emitting point 171 (i.e., point A). The distance along the path of the light from point A to point B is the optical distance Lab. Furthermore, the distance along the path of the light from point A to point D is the optical distance Lad. As in the first embodiment, the optical distance Lab is the shortest optical distance from point A to the light capturing area 113. The optical distance Lad is an optical distance different from the optical distance Lab (i.e., not the shortest).

[0097] In this embodiment, the light source 17 has a light-emitting point 171 in which the area of ​​the light-capturing region 113 satisfies the condition that |sin(ΔP)|<0.1, where ΔL is the difference between the shortest optical distance Lab to the light-capturing region 113 and the optical distance Lad to a point on the light-capturing region 113, and |sin(ΔP)|<0.1 is satisfied, where |sin(ΔP)|<0.1 is the phase difference ΔP calculated by multiplying the wavenumber of light in a vacuum (2π / wavelength in a vacuum). Since this relationship regarding the phase of light is satisfied, most of the light incident on the entire light-capturing region 113 from the light-emitting point 171 can be considered to be in phase at at least one light-emitting point 171, and the optical chemical analyzer 14 can efficiently capture the light emitted from the light source 17 into the core layer 12. Here, when the wavelength in a vacuum is λ0, the phase difference ΔP is expressed as "ΔL×2π / λ0."

[0098] Next, a preferred propagation mode will be described with reference to FIG. 7 . In this embodiment, the light source 17 is an incoherent light source. Light emitted from an incoherent light source contains many light beams with different phases. However, even with an incoherent light source, the phases are aligned in the optical wavefront formed by light departing from the same point (e.g., one light-emitting point 171) of the light source 17 at the same time. That is, even with incoherent light, the first diffraction grating section 11 (light intake region 113) operates for each phase-aligned component, and the phase-aligned component can be treated as a single propagation mode and incorporated into the core layer 12. Light departing from the same point at the same time has a phase front that spreads concentrically. Here, the surface of the light intake region 113 is not spherical but has unevenness formed on a plane, so the light that reaches the light intake region 113 is shifted in phase at the surface of the light intake region 113.

[0099] As shown in FIG. 7, when the area of ​​the light capture region 113 of the first diffraction grating portion 11 is large, multiple in-phase groups (S1 to S6) are formed within the light capture region 113. Therefore, when the light capture region 113 is large, multiple propagation modes are formed even for light that departs from the same point at the same time. In order to propagate light of multiple propagation modes in the light propagation portion 10, the cross-sectional area (width, height) of the light propagation portion 10 perpendicular to the extension direction needs to be a size corresponding to the number of propagation modes. Therefore, a light propagation portion 10 with a very small cross-sectional area as in this embodiment cannot propagate all of the multiple propagation modes generated in the first diffraction grating portion 11. Furthermore, from the viewpoint of efficient light propagation, the light propagation portion 10 is preferably a single-mode optical waveguide that propagates a single mode. Considering these points, when the first diffraction grating unit 11 guides light taken in by one light taking-in region 113 to one light propagation unit 10, it is preferable that the first diffraction grating unit 11 is configured so that the number of in-phase groups formed in the light taking-in region 113 is one. In other words, it is preferable that the first diffraction grating unit 11 has a light taking-in region 113 of a size such that the number of propagation modes formed in the light taking-in region 113 is one. It is also preferable that the light propagation unit 10 has a cross-sectional area that allows light to propagate in a single mode.

[0100] In order to allow the light from the light source 17 to be more efficiently taken into the core layer 12 and propagated therethrough, the light propagation portion 10 has a width in a width direction perpendicular to the extension direction of the light propagation portion 10 and a height in a height direction perpendicular to the extension direction and the width direction, and it is preferable that at least a portion of the light propagation portion 10 has a width or height that allows the light from the light source 17 to propagate in a single mode in at least one of the width direction and the height direction. Here, at least a portion of the light propagation portion 10 may have a width and height that allows the light to propagate in a single mode in both the width direction and the height direction. It is also preferable that the width or height of at least a portion of the light propagation portion 10 is smaller than 1 μm. Furthermore, the cross-sectional area of ​​the plane perpendicular to the extension direction of at least a portion of the light propagation portion 10 is 1 μm. 2 The width or height may be less than 1 μm, and 2The smaller cross-sectional area is the dimension of the light propagation section 10 that allows light emitted from the light source 17 in this embodiment (infrared light with a wavelength of 2 μm or more and less than 12 μm in a vacuum) to propagate in a single mode or with a mode number close to a single mode.

[0101] In this embodiment, it has been explained that it is preferable that the light propagation portion 10 has a cross-sectional area that allows light to propagate in a single mode (or a mode number close to a single mode), and this also applies to the first to third embodiments described above.

[0102] Although the embodiments of the present invention have been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications or corrections based on the present invention. Also, not all of the combinations of features described in the embodiments are necessarily essential to the solution. [Industrial Applicability]

[0103] According to the present invention, it is possible to provide an optical chemical analysis device that can efficiently couple incoherent light emitted from a light source with an optical waveguide. [Explanation of symbols]

[0104] 10: Optical propagation section 11: First diffraction grating section 12: Core layer 13: Second diffraction grating section 14: Optical chemical analyzer 15: Optical waveguide 16:External Space 17:Light source 18: Photodetector 19: Circuit board 20:Support layer 21:Void 112: Connection part 113: Light intake area 171: Light source 172: Light-emitting layer 173: High refractive index material layer

Claims

1. an optical waveguide having a core layer including a light propagation portion through which light can propagate in an extension direction and a diffraction grating portion optically connected to the light propagation portion; a light source that emits incoherent light that can make the light incident on the diffraction grating portion, the diffraction grating portion further includes a light intake region for introducing light from the light source; the light source has a light emitting point at a position where a difference between the shortest optical distance Lab to the light capturing area and the longest optical distance Lac to the light capturing area is smaller than half the wavelength of the light in a vacuum, An optical chemical analysis device in which the evanescent wave seeping out from the core layer is absorbed by the substance to be measured.

2. 2. The optical chemical analysis device according to claim 1, wherein the light source has a light emitting point at a position where the difference between the optical distance Lab and the optical distance Lac is smaller than one-fourth of the wavelength of the light in a vacuum.

3. 3. The optical chemical analysis device according to claim 1, wherein the light source has a light emitting point at a position where the difference between the optical distance Lab and the optical distance Lac is smaller than 2.13 [mu]m.

4. 4. An optical chemical analysis device according to claim 1, wherein more than half of the light source's light emitting points are positioned such that the difference between the optical distance Lab and the optical distance Lac is less than half the wavelength of the light in a vacuum.

5. 5. An optical chemical analysis device according to claim 1, wherein the diffraction grating portion has a plurality of the light capture areas, and in a planar view, the area of ​​the smallest convex polygon that covers the light emitting point of the light source is larger than the area of ​​one of the light capture areas, and the light emitted from the light source is captured by the plurality of the light capture areas.

6. 6. The optical chemical analysis device according to claim 1, wherein an area S of the light capture region in a plan view satisfies the following formula (1): [Equation 1] Here, h is Planck's constant, and p is the momentum of light, which is calculated by p=h / λ, where λ is the average wavelength of light propagating through the core layer in a vacuum.

7. 7. An optical chemical analysis device according to claim 1, wherein the light propagation section has a width in a width direction perpendicular to the extension direction of the light propagation section, and a height in a height direction perpendicular to the extension direction and the width direction, and at least a portion of the light propagation section has a width or height in at least one of the width direction and the height direction such that the light propagates in a single mode.

8. 8. The optical chemical analysis device according to claim 7, wherein at least a part of the light propagating portion has a width or height smaller than 1 [mu]m.

9. 9. The optical chemical analysis device according to claim 7, wherein at least a portion of the light propagation portion has a width and a height that allow the light to propagate in a single mode in both the width direction and the height direction.

10. The cross-sectional area of ​​the plane perpendicular to the extending direction of at least a part of the light propagating portion is 1 μm ２ 10. The optical chemical analysis device according to claim 7, wherein the optical chemical analysis device is smaller than the optical chemical analysis device according to claim 8.

11. 11. An optical chemical analysis device according to claim 1, wherein the light source is an LED formed on one main surface of the substrate, the light emitting point is within a light emitting layer of the LED, and the light emitted from the light emitting layer of the LED is emitted from the other main surface opposite to the one main surface of the substrate.

12. The optical chemical analysis device according to claim 1 , wherein the diffraction grating unit is disposed adjacent to the light source.

13. 13. The optical chemical analysis device according to claim 1, wherein the light source comprises a light-emitting layer having a plurality of the light-emitting points, and a highly refractive material layer disposed between the light-emitting layer and the light-collecting region, the highly refractive material layer refracting light from the light-emitting layer and guiding it to the light-collecting region.

14. An optical chemical analysis device described in any one of claims 1 to 13, wherein the diffraction grating portion has a plurality of connecting portions that optically connect to the light propagation portion.

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