Optical waveguide and optical concentration meter

Abstract

The invention provides an optical waveguide and an optical concentration meter. The optical waveguide has a light introduction part. A light guide-out part; an elliptical light surrounding portion; a first waveguide, a starting end of which is connected to the light introduction part in a light propagation direction, and a terminal end of which is connected to the light encircling part; a second waveguide having a starting end connected to the light encircling part in a light propagation direction and a terminal end connected to the light guide-out part at a position different from a position at which the light encircling part and the first waveguide are connected, the starting end of the second waveguide being connected to the light encircling part, and the terminal end of the second waveguide being connected to the light guide-out part at a position different from a position at which the light encircling part and the first waveguide are connected; a support layer supporting the light surrounding portion; and a substrate supporting the support layer, in which, in a plan view, the center of gravity of the light encircling part is disposed at a position offset from the direction in which the first waveguide and the second waveguide extend, and light introduced from the light introduction part propagates in the order of the first waveguide, the light encircling part, and the second waveguide.

Description

[0001] The contents of the following Japanese patent application are incorporated herein by reference: Application No. 2024-048807, filed on Mar. 25, 2024. Technical Field

[0002] The present invention relates to an optical waveguide and an optical concentration measuring device. Background Art

[0003] Patent Document 1 discloses a “solid microcavity optical device including a solid microcavity light-emitting body”.

[0004] [Prior art literature]

[0005] [Patent Document]

[0006] [Patent Document 1] U.S. Patent Application Publication No. 2008 / 0089367 Summary of the Invention

[0007] In a first aspect of the present invention, there is provided an optical waveguide comprising: an elliptical light surrounding portion; a first waveguide, wherein the terminal end of the first waveguide in the light propagation direction is connected to the light surrounding portion; a second waveguide, wherein the starting end of the second waveguide in the light propagation direction is connected to the light surrounding portion at a position different from the position where the light surrounding portion and the first waveguide are connected; a supporting layer for supporting the light surrounding portion; and a substrate for supporting the supporting layer, wherein, in a top view, the center of gravity of the light surrounding portion is arranged at a position deviated from the extension direction of the first waveguide and the second waveguide, and the light introduced from the light introduction portion propagates in the order of the first waveguide, the light surrounding portion, and the second waveguide.

[0008] The above summary of the invention does not list all the features of the present invention, and subcombinations of these feature groups may also constitute inventions. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a plan view showing a schematic structure of the optical waveguide 100 in the first embodiment.

[0010] Figure 2 This is a side view showing a schematic structure of the optical waveguide 100 in the first embodiment.

[0011] Figure 3 This is a side view showing a schematic structure of the optical waveguide 100 in the first embodiment.

[0012] Figure 4 It is a plan view showing a schematic structure of an optical waveguide 110 in the second embodiment.

[0013] Figure 5It is a plan view showing a schematic structure of an optical waveguide 120 in the third embodiment.

[0014] Figure 6 It is a plan view showing a schematic structure of an optical waveguide 130 in the fourth embodiment.

[0015] Figure 7 It is a plan view showing a schematic structure of an optical waveguide 140 in the fifth embodiment.

[0016] Figure 8 It is a plan view showing a schematic structure of an optical waveguide 150 in the sixth embodiment.

[0017] Figure 9 This is a side view for explaining the method of manufacturing the optical waveguide 100 in the first embodiment.

[0018] Figure 10 It is a side view showing a schematic structure of an optical waveguide 160 in the seventh embodiment.

[0019] Figure 11 It is a plan view showing a schematic structure of an optical waveguide 170 in the eighth embodiment.

[0020] [Explanation of Reference Numerals]

[0021] 10 Light surround portion, 10a Second light surround portion, 10b Third light surround portion, 10c Light surround portion, 11 Peripheral suspended portion, 11a Peripheral suspended portion, 11b Peripheral suspended portion, 11c Peripheral portion, 12 Center portion, 13 Dashed line, 20 First waveguide, 21 Starting end, 22 End, 30 Second waveguide, 31 Starting end, 32 End, 40 LED, 50 PD, 60 Cladding layer, 70 Substrate, 80 Third waveguide, 90 Fourth waveguide, 100 Optical waveguide, 102 Laminated body, 104 Intermediate body, 110 Optical waveguide, 120 Optical waveguide, 130 Optical waveguide, 140 Optical waveguide, 150 Optical waveguide, 160 Optical waveguide, 170 Optical waveguide, D Ellipse tangent, L Light, M Minor axis, P Center of gravity DETAILED DESCRIPTION

[0022] The present invention will be described below by way of embodiments of the invention, but the following embodiments do not limit the invention as defined in the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution provided by the invention.

[0023] Figure 1 It is a plan view showing a schematic structure of the optical waveguide 100 in the first embodiment. Figure 2 and Figure 3 1 is a side view showing a schematic structure of the optical waveguide 100 according to the first embodiment. Figure 2 Indicates from Figure 1The figure viewed from the +x direction, Figure 3 Indicates from Figure 1 The figure is viewed from the +y direction side.

[0024] The optical waveguide 100 in the first embodiment includes an elliptical light surrounding portion 10 , a first waveguide 20 , a second waveguide 30 , an LED (Light Emitting Diode) 40 as a light introducing portion, and a PD (Photodiode) 50 as a light output portion.

[0025] In the side view, the light surrounding portion 10 is supported by the cladding layer 60, and the cladding layer 60 is supported by the substrate 70. In addition, the cladding layer 60 is an example of a supporting layer that supports the light surrounding portion 10.

[0026] Figure 1 The dashed arrow in FIG. 1 indicates the propagation direction of light L. Light L emitted from LED 40 propagates sequentially through first waveguide 20, light surround 10, second waveguide 30, and PD 50. The figure shows an xyz coordinate system. Optical waveguide 100 is used in optical concentration measuring devices such as gas sensors that detect the concentration of a target gas based on light transmittance or other factors.

[0027] The light surrounding portion 10 has an elliptical shape. The light surrounding portion 10 has a peripheral suspended portion 11 located outside the dotted line 13 and a central portion 12 located inside the dotted line 13. When light is introduced from the periphery of the elliptical optical waveguide component to the elliptical optical waveguide component, a phenomenon occurs in which the light is locally present in the circumferential portion. That is, the peripheral suspended portion 11 is the peripheral portion of the light surrounding portion 10, and is the portion where most of the light L incident from the first waveguide 20 propagates around. In addition, the peripheral suspended portion 11 and the central portion 12 are made of the same material. The radial length of the peripheral suspended portion 11 is W1. The short radius of the light surrounding portion 10 is preferably more than twice the radial length W1 of the peripheral suspended portion 11. The ratio of the long radius to the short radius, that is, the long radius:short radius is preferably 1:1 to 4:1. As Figure 1 As shown, in a plan view, the center of gravity P of the light surrounding portion 10 is arranged at a position offset from the extending direction of the first waveguide 20 and the second waveguide 30 .

[0028] The first waveguide 20 is a straight-line optical waveguide. The first waveguide 20 has a starting end 21 and a terminal end 22 in the propagation direction of the light L. The light L propagates from the starting end 21 toward the terminal end 22. The first waveguide 20 is connected to the LED 40 serving as a light introduction portion at the starting end 21, and is connected to the peripheral suspended portion 11 of the light surround portion 10 at the terminal end 22. Preferably, the first waveguide 20 is connected to the light surround portion 10 at an angle along the elliptical tangent of the light surround portion 10. That is, the elliptical tangent of the outer edge of the light surround portion 10 overlaps with the outer edge of the waveguide 20. As a result, the light L can be efficiently propagated from the first waveguide 20 to the light surround portion 10, and the propagation loss of the light L can be suppressed. In addition, the first waveguide 20 terminates at the terminal end 22 and does not pass to the opposite side of the light surround portion 10.

[0029] The second waveguide 30 is a straight-line optical waveguide. The second waveguide 30 has a starting end 31 and an ending end 32 in the propagation direction of the light L. The light L propagates from the starting end 31 toward the ending end 32. The second waveguide 30 is connected to the peripheral suspended portion 11 of the light surround portion 10 at the starting end 31, and is connected to the photodiode (PD) 50, which serves as a light guide outlet, at the ending end 32. The second waveguide 30 is connected to the light surround portion 10 at a position different from the position where the light surround portion 10 and the first waveguide 20 are connected. Preferably, the second waveguide 30 is connected to the light surround portion 10 at an angle along the tangent of the ellipse of the light surround portion 10. Thus, the light L can efficiently propagate from the light surround portion 10 to the second waveguide 30, and the propagation loss of the light L can be suppressed. In addition, the second waveguide 30 starts from the starting end 31 and does not pass through the opposite side of the light surround portion 10.

[0030] The width W2 of the first waveguide 20 and the width W3 of the second waveguide 30 are preferably shorter than the radial length W1 of the peripheral floating portion 11. This allows the cladding layer 60 to be positioned away from the connection between the light surrounding portion 10 and the first waveguide 20, thereby improving optical coupling efficiency and reducing propagation loss of light L. Furthermore, the radial length W1 of the peripheral floating portion 11 is preferably no greater than twice the width W2 of the first waveguide 20 and the width W3 of the second waveguide 30. This prevents deflection of the peripheral floating portion 11.

[0031] like Figure 1 As shown, light L propagating from the first waveguide 20 to the light surrounding portion 10 is surrounded by the peripheral suspended portion 11 of the light surrounding portion 10. A portion of the light L surrounded by the peripheral suspended portion 11 of the light surrounding portion 10 enters the second waveguide 30 from the connection portion between the light surrounding portion 10 and the second waveguide 30. Another portion of the light L surrounded by the peripheral suspended portion 11 of the light surrounding portion 10 does not enter the second waveguide 30 but is surrounded by the light surrounding portion 10 again. In this way, the light L is surrounded by the peripheral suspended portion 11 of the light surrounding portion 10 multiple times while gradually entering the second waveguide 30.

[0032] Figure 1 The minor axis M of the elliptical light surround portion 10 is shown. The minor axis M of the light surround portion 10 is tilted relative to the extension direction (y-direction) of the first waveguide 20 and the second waveguide 30. This reduces the connection angle between the first waveguide 20 and the light surround portion 10, enabling efficient propagation of light L from the first waveguide 20 to the light surround portion 10 and suppressing propagation loss of light L. Similarly, the connection angle between the second waveguide 30 and the light surround portion 10 can be reduced, enabling efficient propagation of light L from the light surround portion 10 to the second waveguide 30 and suppressing propagation loss of light L.

[0033] The first waveguide 20, the second waveguide 30, and the light surround 10 are made of a material capable of propagating light L of the wavelength used. Specifically, gallium arsenide (GaAs), silicon (Si), germanium (Ge), and the like can be mentioned. Each of the first waveguide 20, the second waveguide 30, and the light surround 10 can be formed from a single material, or by stacking multiple materials. The refractive index of the materials comprising the first waveguide 20, the second waveguide 30, and the light surround 10 at the wavelength is preferably higher than the refractive index of the material comprising the cladding layer 60 at the wavelength.

[0034] When the material of the light surrounding portion 10 is different from the material of the first waveguide 20 and the second waveguide 30, the refractive index of the material constituting the light surrounding portion 10 is preferably equal to or greater than the refractive index of the material constituting the first waveguide 20 and the second waveguide 30. By increasing the refractive index of the material constituting the light surrounding portion 10, the wavelength within the material of the light surrounding portion 10 can be reduced, thereby improving the propagation efficiency of the light L and reducing the ellipse of the light surrounding portion 10.

[0035] exist Figure 2 and Figure 3 , the cladding layer 60 and the substrate 70 are indicated by hatching. By fixing the light surrounding portion 10 having a large area to the substrate 70 via the cladding layer 60, the optical waveguide 100 is prevented from peeling off from the substrate 70.

[0036] like Figure 2 and Figure 3 As shown, the peripheral floating portion 11 of the light surrounding portion 10 does not contact the cladding layer 60 or the substrate 70. In other words, the peripheral floating portion 11 is suspended from the substrate 70, forming a so-called flange. Since the peripheral floating portion 11 of the light surrounding portion 10 does not contact the cladding layer 60 or the substrate 70, it is possible to prevent the light L surrounded by the peripheral floating portion 11 from leaking out of the cladding layer 60 or the substrate 70, thereby reducing the propagation loss of the light L. Specifically, the surface of the light surrounding portion 10 that contacts the cladding layer 60 and the portion thereof constitutes the core portion 12, while the surface that does not contact the cladding layer 60 and the portion thereof constitutes the peripheral floating portion 11.

[0037] like Figure 2 and Figure 3 As shown, the first waveguide 20 and the second waveguide 30 are not in contact with the cladding layer 60 and the substrate 70. In other words, the first waveguide 20 and the second waveguide 30 are suspended waveguides, with portions thereof suspended in the air, except for portions connected to the light surround 10, the LED 40, or the PD 50. Consequently, compared to a case where the first waveguide 20 and the second waveguide 30 are in contact with the cladding layer 60 or the substrate 70, it is possible to suppress leakage of light L passing through the first waveguide 20 and the second waveguide 30 from the cladding layer 60 or the substrate 70 to the outside, thereby suppressing propagation loss of the light L.

[0038] The lengths of the first waveguide 20 and the second waveguide 30 as floating waveguides are preferably 200 μm or less. This prevents the floating portions of the first waveguide 20 and the second waveguide 30 from being bent and attached to the substrate 70 .

[0039] The cladding layer 60 is made of a material with a refractive index lower than that of the material constituting the first waveguide 20, the second waveguide 30 and the light surrounding portion 10. The cladding layer 60 is made of aluminum gallium arsenide (AlGaAs), aluminum gallium oxide (AlGaO), aluminum gallium hydroxide (AlGaO), and aluminum gallium arsenide (AlGaO). x Ga 1-x (OH)3) etc. x Ga 1-x When (OH)₃ is used as the material for the coating layer 60, the ratio of aluminum atoms to the total number of aluminum and gallium atoms is preferably 90% or greater. Specifically, the ratio of aluminum atoms to gallium atoms is preferably 0.9:0.1 to 1.0:0. Alternatively, the coating layer 60 may be formed of silicon dioxide (SiO₂), for example.

[0040] According to the optical waveguide 100 of the first embodiment, light L emitted from the LED 40 surrounds the outer peripheral floating portion 11 of the light surrounding portion 10 multiple times before reaching the PD 50. This increases the optical path length per unit area of ​​the light L propagating from the LED 40 to the PD 50. Consequently, the sensitivity of the optical waveguide 100 when used as a sensor such as an optical density meter can be improved.

[0041] According to the optical waveguide 100 of the first embodiment, the optical waveguide 100 is fixed to the substrate 70 by the cladding layer 60 supporting the light surrounding portion 10. Thus, the light surrounding portion 10 having a large area functions as an anchor for fixing, and the optical waveguide 100 can be prevented from peeling off from the substrate 70.

[0042] According to the optical waveguide 100 of the first embodiment, the light surrounding portion 10 has an elliptical shape. This improves the tolerance of the light surrounding portion 10 to dimensional variations, and enables the provision of an optical waveguide 100 in which the propagation characteristics of the light L remain constant regardless of manufacturing errors.

[0043] In the first embodiment, the minor axis M of the light surrounding portion 10 is inclined from the extending direction (y direction) of the first waveguide 20 and the second waveguide 30. However, the minor axis M of the light surrounding portion 10 may not be inclined from the extending direction (y direction) of the first waveguide 20 and the second waveguide 30.

[0044] Furthermore, since the light L hardly propagates to the center portion 12 of the light surround portion 10, a hole may be formed near the center portion 12. By changing the shape of the cladding layer through the hole, the contact area between the cladding layer and the light surround portion 10 can be adjusted. This makes it possible to adjust the holding force of the light surround portion 10 and / or the stress applied to the interface due to the internal stress difference between the cladding layer and the light surround portion. In addition, the support layer supporting the light surround portion 10 does not have to be an optical cladding layer 60. For example, the support layer may be made of a material that is opaque to the light L used. These modifications can also be applied to other embodiments.

[0045] Figure 4 This is a top view schematically illustrating the structure of an optical waveguide 110 in the second embodiment. Components identical or common to those in the optical waveguide 100 in the first embodiment are denoted by the same reference numerals, and their descriptions are omitted. In addition to the components of the optical waveguide 100 in the first embodiment, the optical waveguide 110 in the second embodiment further comprises: an elliptical second light-encircling portion 10a, which is connected to the second waveguide 30 at its terminal end in the propagation direction of light L; and a third waveguide 80, which is connected to the second light-encircling portion 10a at its starting end in the propagation direction of light L, at a position different from the position where the second light-encircling portion 10a and the second waveguide 30 are connected.

[0046] The PD 50 is connected to the terminal end of the third waveguide 80. Light L emitted from the LED 40 propagates sequentially through the first waveguide 20, the light surround 10, the second waveguide 30, the second light surround 10a, the third waveguide 80, and the PD 50. The structure of the second light surround 10a is the same as that of the light surround 10 in the first embodiment, and the second light surround 10a also includes a peripheral suspended portion 11a. Within the second light surround 10a, the light L also repeatedly circulates around the peripheral suspended portion 11a of the second light surround 10a while gradually entering the third waveguide 80.

[0047] According to the optical waveguide 110 of the second embodiment, light L emitted from the LED 40 circulates multiple times around the peripheral floating portion 11 of the light surround portion 10 and the peripheral floating portion 11a of the second light surround portion 10a before reaching the PD 50. This further increases the optical path length per unit area of ​​the light L propagating from the LED 40 to the PD 50. Consequently, the sensitivity of the optical waveguide 100 when used as a sensor such as an optical density meter can be improved.

[0048] Figure 5 This is a top view schematically illustrating the structure of an optical waveguide 120 in the third embodiment. Components identical or common to the optical waveguide 100 in the first embodiment are denoted by the same reference numerals, and their descriptions are omitted. In addition to the components of the optical waveguide 110 in the second embodiment, the optical waveguide 120 in the third embodiment further includes: an elliptical third light surrounding portion 10b connected to the third waveguide 80 at its terminal end in the propagation direction of light L; and a fourth waveguide 90 connected to the third light surrounding portion 10b at its starting end in the propagation direction of light L, at a position different from the position where the third light surrounding portion 10b is connected to the third waveguide 80.

[0049] A PD 50 is connected to the terminal end of the fourth waveguide 90. Light L emitted from the LED 40 propagates sequentially through the first waveguide 20, the light surround portion 10, the second waveguide 30, the second light surround portion 10a, the third waveguide 80, the third light surround portion 10b, the fourth waveguide 90, and the PD 50. The structure of the third light surround portion 10b is identical to that of the light surround portion 10 in the first embodiment, and the third light surround portion 10b also includes a peripheral suspended portion 11b. Within the third light surround portion 10b, the light L also repeatedly circulates around the peripheral suspended portion 11b of the third light surround portion 10b while gradually entering the fourth waveguide 90.

[0050] According to the optical waveguide 120 of the third embodiment, light L emitted from the LED 40 circulates multiple times around the peripheral floating portion 11 of the light surround portion 10, the peripheral floating portion 11a of the second light surround portion 10a, and the peripheral floating portion 11b of the third light surround portion 10b before reaching the PD 50. This further increases the optical path length per unit area of ​​the light L propagating from the LED 40 to the PD 50. Consequently, the sensitivity of the optical waveguide 100 when used as a sensor such as an optical density meter can be improved.

[0051] Figure 6 This is a plan view schematically illustrating the structure of an optical waveguide 130 according to the fourth embodiment. Components identical or common to those in the optical waveguide 100 according to the first embodiment are denoted by the same reference numerals, and their descriptions are omitted. Unlike the optical waveguide 100 according to the first embodiment, the optical waveguide 130 according to the fourth embodiment has a second waveguide 30 extending in the opposite direction (+y direction) from the light surrounding portion 10. Therefore, the second waveguide 30 is connected to the light surrounding portion 10 in a direction opposite to the light surrounding portion 10.

[0052] As with the optical waveguide 100 in the first embodiment, light L emitted from the LED 40 propagates in the order of the first waveguide 20, the light surround section 10, the second waveguide 30, and the PD 50. At the starting end 31, which is the connection between the light surround section 10 and the second waveguide 30, the light L surrounded by the light surround section 10 propagates toward the lower left in the drawing. However, the starting end 31 of the second waveguide 30 is connected toward the upper direction (+y direction).

[0053] In this manner, the second waveguide 30 is connected to the light surrounding portion 10 in a direction opposite to the direction in which light is circling within the light surrounding portion 10. This makes it difficult for light L to enter the second waveguide 30 from the light surrounding portion 10, thereby increasing the average number of times light L circles the light surrounding portion 10. This further increases the optical path length per unit area of ​​the light L propagating from the LED 40 to the PD 50. Consequently, the sensitivity of the optical waveguide 100 when used as a sensor such as an optical density meter can be improved.

[0054] Figure 7 This is a plan view schematically illustrating the structure of an optical waveguide 140 according to the fifth embodiment. Hereinafter, components identical or common to those of the optical waveguide 100 according to the first embodiment are denoted by the same reference numerals, and their descriptions are omitted. Unlike the optical waveguide 100 according to the first embodiment, in the optical waveguide 140 according to the fifth embodiment, the second waveguide 30 is connected to the light surrounding portion 10 at an angle that does not coincide with the tangent line D of the ellipse of the light surrounding portion 10.

[0055] In this manner, the second waveguide 30 is connected to the light surround portion 10 at an angle that is not aligned with the tangent line D of the ellipse of the light surround portion 10. This makes it difficult for light L to enter the second waveguide 30 from the light surround portion 10, thereby increasing the average number of times light L circles the light surround portion 10. This further increases the optical path length per unit area of ​​the light L propagating from the LED 40 to the PD 50. Consequently, the sensitivity of the light waveguide 100 when used as a sensor such as an optical density meter can be improved.

[0056] Figure 8 1 is a top view showing the schematic structure of the optical waveguide 150 in the sixth embodiment. Hereinafter, the same reference numerals are given to structures that are identical or common to the optical waveguide 100 in the first embodiment, and descriptions thereof are omitted. The optical waveguide 150 in the sixth embodiment differs from the optical waveguide 100 in the first embodiment in that the light encircling portion 10 has a circular shape. In addition, a perfect circular shape can also be said to be an example of an elliptical shape in which the lengths of the minor axis and the major axis are equal. By setting it to a perfect circle, symmetry can be achieved, allowing light to be efficiently encircled. Furthermore, a perfect circle is sufficient as long as it is a perfect circle in design, and also includes shapes that deviate slightly from a perfect circle due to manufacturing deviations.

[0057] Figure 9This is a side view illustrating a method for manufacturing the optical waveguide 100 according to the first embodiment. First, a stacked body 102 is prepared, comprising layers forming the first waveguide 20, the second waveguide 30, and the light surround portion 10, layers forming the cladding layer 60, and a substrate 70. The stacked body 102 is etched for the layers forming the first waveguide 20, the second waveguide 30, and the light surround portion 10. This results in an intermediate body 104 having the first waveguide 20, the second waveguide 30, and the light surround portion 10. The layers forming the cladding layer 60 are etched for the intermediate body 104, forming the cladding layer 60. At this stage, the cladding layer 60 is removed except for the portion located below the light surround portion 10 by etching, resulting in the first waveguide 20 and the second waveguide 30 becoming suspended waveguides suspended from the cladding layer 60.

[0058] Figure 10 This is a side view schematically illustrating the structure of an optical waveguide 160 according to the seventh embodiment. Components identical or common to those in the optical waveguide 100 according to the first embodiment are denoted by the same reference numerals, and their descriptions are omitted. The optical waveguide 160 according to the seventh embodiment differs from the optical waveguide 100 according to the first embodiment in that the light surrounding portion 10c of the optical waveguide 160 does not include an outer peripheral suspended portion suspended from the cladding layer 60. Light L is surrounded by an outer peripheral portion 11c of the light surrounding portion 10c that is not suspended from the cladding layer 60.

[0059] Figure 11 This is a plan view schematically illustrating the structure of an optical waveguide 170 according to the eighth embodiment. Hereinafter, components identical or common to those of the optical waveguide 100 according to the first embodiment are denoted by the same reference numerals, and their descriptions are omitted. The optical waveguide 170 according to the eighth embodiment differs from the optical waveguide 100 according to the first embodiment in that the first waveguide 20 is connected to the light surrounding portion 10 at an angle that is not aligned with the ellipse tangent line D of the light surrounding portion 10.

[0060] In this manner, the first waveguide 20 is connected to the light surround section 10 at an angle that is not aligned with the tangent line D of the ellipse of the light surround section 10. This allows the angle formed by the ellipse normal and the angle of incidence to be reduced when light L enters the outer periphery of the ellipse of the light surround section 10. This increases the distance between the reflection points where the outer periphery of the light surround section 10 contacts the trajectory of light L within the light surround section 10, causing light L to reflect into the interior of the light surround section 10. This allows the design to keep the reflection points away from specific locations on the outer periphery of the ellipse. By setting the positional relationship between the first waveguide 20 and the second waveguide 30 in this manner, light L is less likely to enter the second waveguide 30 from the light surround section 10, increasing the average number of times light L circles the light surround section 10. This further increases the optical path length per unit area of ​​light L propagating from the LED 40 to the PD 50. Consequently, the sensitivity of the optical waveguide 170 when used as a sensor, such as an optical density meter, can be improved.

[0061] While the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. As can be seen from the claims, embodiments incorporating such modifications or improvements are also within the technical scope of the present invention.

[0062] It should be noted that the order of execution of actions, steps, stages, and other processes in the apparatus, system, program, and method described in the claims, specifications, and drawings may be implemented in any order unless otherwise expressly stated as "before," "before," or the like, and unless the output of a previous process is used in a subsequent process. Even if the action flow in the claims, specifications, and drawings is described using the phrases "first," "next," or the like for convenience, it does not necessarily mean that the actions must be implemented in that order.

Claims

1. An optical waveguide having: Light introduction part; Light guide outward; Oval light surround; a first waveguide, wherein a starting end of the first waveguide in the light propagation direction is connected to the light introducing portion, and a terminal end of the first waveguide in the light propagation direction is connected to the light surrounding portion; a second waveguide, wherein a starting end of the second waveguide in the light propagation direction is connected to the light surrounding portion at a position different from a position where the light surrounding portion is connected to the first waveguide, and a terminal end of the second waveguide in the light propagation direction is connected to the light guide portion; A supporting layer, supporting the light surrounding portion; and a substrate supporting the support layer, In a plan view, the center of gravity of the light surrounding portion is arranged at a position deviated from the extending direction of the first waveguide and the second waveguide. The light introduced from the light introducing portion propagates through the first waveguide, the light surrounding portion, and the second waveguide in this order.

2. The optical waveguide according to claim 1, wherein The first waveguide and the second waveguide are not in contact with the support layer and the substrate.

3. The optical waveguide according to claim 2, wherein The light surrounding portion has an outer peripheral floating portion that is not in contact with the support layer and the substrate.

4. The optical waveguide according to claim 3, wherein The first waveguide and the second waveguide are connected to the peripheral floating portion of the light surrounding portion.

5. The optical waveguide according to claim 3, wherein The first waveguide and the second waveguide are not in contact with the support layer and the substrate.

6. The optical waveguide according to claim 3, wherein The short radius of the light surrounding portion is at least twice the radial length of the outer peripheral floating portion.

7. The optical waveguide according to claim 3, wherein The width of the first waveguide and the second waveguide is less than or equal to the radial length of the outer peripheral floating portion.

8. The optical waveguide according to claim 3, wherein The radial length of the outer peripheral floating portion is less than or equal to twice the width of the first waveguide and the second waveguide.

9. The optical waveguide according to claim 1, wherein The first waveguide or the second waveguide is connected to the light surrounding portion at an angle along a tangent line of an ellipse of the light surrounding portion.

10. The optical waveguide according to claim 1, wherein The first waveguide or the second waveguide is connected to the light surrounding portion at an angle that is not along a tangent line of an ellipse of the light surrounding portion.

11. The optical waveguide according to claim 1, wherein The first waveguide or the second waveguide is connected to the light surrounding portion from a direction opposite to a light surrounding direction in the light surrounding portion.

12. The optical waveguide according to claim 2, wherein The refractive index of the material constituting the first waveguide, the second waveguide, and the light surrounding portion is higher than the refractive index of the material constituting the support layer.

13. The optical waveguide according to claim 1, wherein The refractive index of the material constituting the light surrounding portion is equal to or greater than the refractive index of the material constituting the first waveguide and the second waveguide.

14. The optical waveguide according to claim 1, wherein The lengths of the first waveguide and the second waveguide are 200 μm or less.

15. The optical waveguide according to claim 1, wherein The optical waveguide further comprises: an elliptical second light surrounding portion, a terminal of the second waveguide in the light propagation direction being connected to the second waveguide; and The third waveguide is connected to the second light surrounding portion at a position different from the position where the second light surrounding portion and the second waveguide are connected, at a starting end of the third waveguide in the light propagation direction.

16. The optical waveguide according to claim 4, wherein The first waveguide or the second waveguide is connected to the light surrounding portion at an angle along a tangent line of an ellipse of the light surrounding portion.

17. The optical waveguide according to claim 4, wherein The first waveguide or the second waveguide is connected to the light surrounding portion at an angle that is not along a tangent line of an ellipse of the light surrounding portion.

18. The optical waveguide according to claim 4, wherein The first waveguide or the second waveguide is connected to the light surrounding portion from a direction opposite to a light surrounding direction in the light surrounding portion.

19. The optical waveguide according to claim 4, wherein The refractive index of the material constituting the first waveguide, the second waveguide, and the light surrounding portion is higher than the refractive index of the material constituting the support layer.

20. The optical waveguide according to claim 4, wherein The refractive index of the material constituting the light surrounding portion is equal to or greater than the refractive index of the material constituting the first waveguide and the second waveguide.

21. The optical waveguide according to claim 4, wherein The lengths of the first waveguide and the second waveguide are 200 μm or less.

22. The optical waveguide according to claim 4, wherein The optical waveguide further comprises: an elliptical second light surrounding portion, a terminal of the second waveguide in the light propagation direction being connected to the second waveguide; and The third waveguide is connected to the second light surrounding portion at a position different from the position where the second light surrounding portion and the second waveguide are connected, at a starting end of the third waveguide in the light propagation direction.

23. An optical concentration measuring device comprising the optical waveguide according to claim 1.

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