Optical waveguide and optical density measuring instrument

Abstract

To provide an optical waveguide with which it is possible to gain an optical path length per unit area, and in which optical transmission losses are suppressed.SOLUTION: Provided is an optical waveguide comprising: a light introduction unit; a light derivation unit; an elliptical light circulation unit; a first waveguide connected to the light introduction unit at a beginning end in a light propagation direction and connected to the light circulation unit at a terminating end; a second waveguide connected to the light circulation unit at the beginning end in the light propagation direction at a position different from the position at which the light circulation unit and the first waveguide connect to each other, and connected to the light derivation unit at the terminating end; a clad layer for supporting the light circulation unit; and a substrate for supporting the clad layer. The center of gravity of the light circulation unit located at a position shifted from the extending direction of the first and second waveguides, and the light introduced from the light introduction unit propagates through the first waveguide, the light circulation unit, and the second waveguide in the order stated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical waveguide and an optical concentration measuring instrument. [Background technology]

[0002] Patent Document 1 discloses a "solid state microcavity optical device including a solid state microcavity light emitter." [Prior art document] [Patent documents] [Patent Document 1] U.S. Patent Application Publication No. 2008 / 0089367 Summary of the Invention

[0003] In a first aspect of the present invention, there is provided an optical waveguide comprising: an elliptical optical circulation unit; a first waveguide connected to the optical circulation unit at an end of the light propagation direction; a second waveguide connected to the optical circulation unit at a start of the light propagation direction at a position different from a position where the optical circulation unit and the first waveguide are connected; a clad layer supporting the optical circulation unit; and a substrate supporting the clad layer, wherein, in a top view, the center of gravity of the optical circulation unit is positioned at a position shifted from the extension direction of the first waveguide and the second waveguide, and light introduced from a light introducing unit propagates through the first waveguide, the optical circulation unit, and the second waveguide in that order.

[0004] The first waveguide and the second waveguide may be out of contact with the cladding layer and the substrate.

[0005] The optical circulation unit may have a peripheral floating unit that is not in contact with the cladding layer and the substrate.

[0006] The first waveguide and the second waveguide may be connected to the outer circulating portion of the optical circulation portion.

[0007] The radius of the optical circulation section may be at least twice the radial length of the outer circumferential floating section.

[0008] The width of the first waveguide and the second waveguide may be equal to or less than the radial length of the outer circumferential floating portion.

[0009] The radial length of the outer circumferential floating portion may be equal to or less than twice the width of the first waveguide and the second waveguide.

[0010] The first waveguide or the second waveguide may be connected to the optical circulation unit at an angle along a tangent to the ellipse of the optical circulation unit.

[0011] The first waveguide or the second waveguide may be connected to the optical circulation unit at an angle that is not along a tangent to the ellipse of the optical circulation unit.

[0012] The first waveguide or the second waveguide may be connected to the optical circulation unit in a direction opposite to the direction of light circulation in the optical circulation unit.

[0013] The refractive index of the material forming the first waveguide, the second waveguide, and the optical circulation section may be higher than the refractive index of the material forming the cladding layer.

[0014] The refractive index of the material forming the optical circulation section may be equal to or greater than the refractive index of the material forming the first waveguide and the second waveguide.

[0015] The first waveguide and the second waveguide may have a length of 200 μm or less.

[0016] The optical fiber may further include an elliptical second optical circulation section that connects to the second waveguide at the end of the light propagation direction, and a third waveguide that connects to the second optical circulation section at the start of the light propagation direction at a position different from the position where the second optical circulation section and the second waveguide are connected.

[0017] In a second aspect of the present invention, there is provided an optical concentration measuring instrument having the above optical waveguide.

[0018] The above summary of the invention does not list all of the features of the present invention, and subcombinations of these features may also be inventions. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a top view showing a schematic configuration of an optical waveguide 100 according to a first embodiment. [Figure 2] 1 is a side view showing a schematic configuration of an optical waveguide 100 according to a first embodiment. [Figure 3] 1 is a side view showing a schematic configuration of an optical waveguide 100 according to a first embodiment. [Figure 4] FIG. 10 is a top view showing a schematic configuration of an optical waveguide 110 according to a second embodiment. [Figure 5] FIG. 10 is a top view showing a schematic configuration of an optical waveguide 120 according to a third embodiment. [Figure 6] FIG. 10 is a top view showing a schematic configuration of an optical waveguide 130 according to a fourth embodiment. [Figure 7] FIG. 10 is a top view showing a schematic configuration of an optical waveguide 140 according to a fifth embodiment. [Figure 8] FIG. 10 is a top view showing a schematic configuration of an optical waveguide 150 according to a sixth embodiment. [Figure 9] 2A to 2C are side views illustrating a method for manufacturing the optical waveguide 100 according to the first embodiment. [Figure 10] FIG. 13 is a side view showing a schematic configuration of an optical waveguide 160 according to a seventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] 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.

[0021] Fig. 1 is a top view showing a schematic configuration of an optical waveguide 100 according to the first embodiment. Fig. 2 and Fig. 3 are side views showing a schematic configuration of an optical waveguide 100 according to the first embodiment. Fig. 2 shows a view from the +x direction in Fig. 1, and Fig. 3 shows a view from the +y direction in Fig. 1.

[0022] The optical waveguide 100 in the first embodiment has an elliptical light circulation section 10, a first waveguide 20, a second waveguide 30, an LED (Light Emitting Diode) 40 as a light introduction section, and a PD (photodiode) 50 as a light extraction section. The dashed-dotted arrow in FIG. 1 indicates the propagation direction of light L. Light L emitted from the LED 40 propagates through the first waveguide 20, the light circulation section 10, the second waveguide 30, and the PD 50 in this order. An xyz coordinate system is shown in the figure. The optical waveguide 100 is used in optical concentration measuring devices such as gas sensors that detect the concentration of a target gas based on the transmittance of light, etc.

[0023] The optical circulation unit 10 has an elliptical shape. The optical circulation unit 10 has an outer circumferential floating portion 11 outside the dotted line 13 and a central portion 12 inside the dotted line 13. When light is introduced into an elliptical optical waveguide member from its periphery, a phenomenon occurs in which the light is localized in the circumferential portion. In other words, the outer circumferential floating portion 11 is the outer circumferential portion of the optical circulation unit 10, and is the portion where most of the light L incident from the first waveguide 20 propagates in a circular motion. The outer circumferential floating portion 11 and the central portion 12 are made of the same material. The radial length of the outer circumferential floating portion 11 is W1. It is desirable that the minor axis of the optical circulation unit 10 be at least twice the radial length W1 of the outer circumferential floating portion 11. It is desirable that the ratio of the major axis to the minor axis, i.e., the major axis:minor axis, is 1:1 to 4:1. As shown in FIG. 1, the center of gravity P of the optical circulation unit 10 is disposed at a position shifted from the direction in which the first waveguide 20 and the second waveguide 30 extend in a top view.

[0024] The first waveguide 20 is a linear optical waveguide. The first waveguide 20 has a starting point 21 and a terminal end 22 in the propagation direction of light L. Light L propagates from the starting point 21 to the terminal end 22. The first waveguide 20 connects to the LED 40, which is the light introduction section, at the starting point 21 and to the outer circulating section 11 of the optical circulation section 10 at the terminal end 22. The first waveguide 20 is preferably connected to the optical circulation section 10 at an angle along the elliptical tangent of the optical circulation section 10. That is, the elliptical tangent of the outer edge of the optical circulation section 10 overlaps the outer edge of the waveguide 20. This allows light L to be efficiently propagated from the first waveguide 20 to the optical circulation section 10 and suppresses propagation loss of light L. In addition, the first waveguide 20 terminates at the terminal end 22 and does not penetrate to the opposite side of the optical circulation section 10.

[0025] The second waveguide 30 is a linear optical waveguide. The second waveguide 30 has a starting point 31 and a terminal end 32 in the propagation direction of the light L. The light L propagates from the starting point 31 to the terminal end 32. The second waveguide 30 connects to the outer circulating portion 11 of the optical circulation unit 10 at the starting point 31 and to a photodiode (PD) 50, which is an optical output portion, at the terminal end 32. The second waveguide 30 connects to the optical circulation unit 10 at a position different from the position where the optical circulation unit 10 and the first waveguide 20 connect. It is desirable that the second waveguide 30 connects to the optical circulation unit 10 at an angle along the tangent of the ellipse of the optical circulation unit 10. This allows the light L to propagate efficiently from the optical circulation unit 10 to the second waveguide 30, and suppresses propagation loss of the light L. In addition, the second waveguide 30 starts from the starting end 31 and does not penetrate through to the opposite side of the optical circulation unit 10 .

[0026] It is desirable that the width W2 of the first waveguide 20 and the width W3 of the second waveguide 30 are shorter than the radial length W1 of the periphery floating portion 11. This allows the cladding layer to be spaced away from the connection between the optical circulation portion 10 and the first waveguide 20, improving the optical coupling efficiency and reducing the propagation loss of the light L. It is also desirable that the radial length W1 of the periphery floating portion 11 be equal to or less than twice the width W2 of the first waveguide 20 and the width W3 of the second waveguide 30. This prevents the periphery floating portion 11 from bending.

[0027] As shown in FIG. 1, light L propagating from first waveguide 20 to optical circulation unit 10 circulates around outer circulating floating portion 11 of optical circulation unit 10. A portion of light L circulating around outer circulating floating portion 11 of optical circulation unit 10 enters second waveguide 30 from the connection portion between optical circulation unit 10 and second waveguide 30. Another portion of light L circulating around outer circulating floating portion 11 of optical circulation unit 10 circulates around optical circulation unit 10 again without entering second waveguide 30. In this way, light L enters second waveguide 30 little by little while circulating around outer circulating floating portion 11 of optical circulation unit 10 multiple times.

[0028] 1 shows the minor axis M of the elliptical optical circulation unit 10. The minor axis M of the optical circulation unit 10 is tilted from the extension direction (y direction) of the first waveguide 20 and the second waveguide 30. This makes it possible to make the connection angle between the first waveguide 20 and the optical circulation unit 10 gentle, allowing the light L to be efficiently propagated from the first waveguide 20 to the optical circulation unit 10 and suppressing the propagation loss of the light L. Similarly, the connection angle between the second waveguide 30 and the optical circulation unit 10 can be made gentle, allowing the light L to be efficiently propagated from the optical circulation unit 10 to the second waveguide 30 and suppressing the propagation loss of the light L.

[0029] The first waveguide 20, the second waveguide 30, and the optical circulation unit 10 are made of a material through which light L can propagate. Specific examples include gallium arsenide (GaAs), silicon (Si), and germanium (Ge). The first waveguide 20, the second waveguide 30, and the optical circulation unit 10 may each be made of a single material, or may be made by laminating multiple materials. The refractive index of the material making up the first waveguide 20, the second waveguide 30, and the optical circulation unit 10 is preferably higher than the refractive index of the material making up the cladding layer 60.

[0030] When the material of optical circulation unit 10 is different from the materials of first waveguide 20 and second waveguide 30, it is desirable that the refractive index of the material constituting optical circulation unit 10 is equal to or greater than the refractive index of the material constituting first waveguide 20 and second waveguide 30. By increasing the refractive index of the material constituting optical circulation unit 10, the wavelength within the substance in optical circulation unit 10 can be reduced, the propagation efficiency of light L can be improved, and the ellipse of optical circulation unit 10 can be reduced.

[0031] 2 and 3, in side view, the optical circulation unit 10 is supported by the cladding layer 60, and the cladding layer 60 is supported by the substrate 70. In Fig. 2 and 3, the cladding layer 60 and the substrate 70 are indicated by hatching. By fixing the optical circulation unit 10, which has a large area, to the substrate 70 via the cladding layer 60, peeling of the optical waveguide 100 from the substrate 70 is suppressed.

[0032] 2 and 3, the outer circulating portion 11 of the optical circulation unit 10 is not in contact with the cladding layer 60 and the substrate 70. In other words, the outer circulating portion 11 is floating above the substrate 70, acting as a flange, so to speak. Because the outer circulating portion 11 of the optical circulation unit 10 is not in contact with the cladding layer 60 and the substrate 70, light L circulating in the outer circulating portion 11 is prevented from leaking out from the cladding layer 60 or the substrate 70, thereby suppressing propagation loss of the light L. In addition, the surface of the optical circulation unit 10 that is in contact with the cladding layer 60 and the portion above it is the center portion 12, and the surface that is not in contact with the cladding layer 60 and the portion above it is the outer circulating portion 11.

[0033] 2 and 3, the first waveguide 20 and the second waveguide 30 are not in contact with the cladding layer 60 and the substrate 70. That is, the first waveguide 20 and the second waveguide 30 are floating waveguides in which the portions thereof other than the portions connected to the optical circulation unit 10, the LED 40, or the PD 50 are floating in the air. This reduces leakage of the 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, as compared to when the first waveguide 20 and the second waveguide 30 are in contact with the cladding layer 60 or the substrate 70, thereby reducing the propagation loss of the light L.

[0034] The lengths of the first waveguide 20 and the second waveguide 30, which are floating waveguides, are desirably 200 μm or less, which prevents the floating portions of the first waveguide 20 and the second waveguide 30 from bending and sticking to the substrate 70.

[0035] The cladding layer is made of a material having a lower refractive index than the materials constituting the first waveguide 20, the second waveguide 30, and the optical circulation unit 10. Examples of the material include aluminum gallium arsenide (AlGaAs), aluminum gallium oxide (AlGaO), and aluminum gallium hydroxide (Al x Ga 1-x The cladding layer 20 is made of aluminum gallium arsenide (AlGaAs), aluminum gallium oxide (AlGaO), aluminum gallium hydroxide (Al x Ga 1-x When (OH)3) is used, the ratio of the number of aluminum atoms to the total number of aluminum and gallium atoms is preferably 90% or more. That is, the ratio of the number of aluminum atoms to the number of gallium atoms is preferably 0.9:0.1 to 1.0:0. Alternatively, the cladding layer 20 may be formed of, for example, silicon dioxide (SiO2).

[0036] According to the optical waveguide 100 of the first embodiment, the light L emitted from the LED 40 travels multiple times around the outer circulating portion 11 of the optical circulation unit 10 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. This improves the sensitivity when the optical waveguide 100 is used as a sensor in an optical concentration meter or the like.

[0037] 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 that supports the optical circulation section 10. As a result, the optical circulation section 10, which has a large area, serves as an anchor for fixing, and peeling of the optical waveguide 100 from the substrate 70 can be suppressed.

[0038] According to the optical waveguide 100 of the first embodiment, the first waveguide 20 and the second waveguide 30 are not in contact with the cladding layer 60 and the substrate 70. This prevents the light L passing through the first waveguide 20 and the second waveguide 30 from leaking out from the cladding layer 60 or the substrate 70, thereby suppressing the propagation loss of the light L.

[0039] According to the optical waveguide 100 of the first embodiment, the optical circulation section 10 has an elliptical shape. This improves the tolerance of the optical circulation section 10 to dimensional deviations, and makes it possible to provide an optical waveguide 100 in which the propagation characteristics of the light L do not change regardless of slight manufacturing errors.

[0040] In the first embodiment, the minor axis M of the optical circulation unit 10 is inclined from the extension direction (y direction) of the first waveguide 20 and the second waveguide 30. However, the minor axis M of the optical circulation unit 10 does not have to be inclined from the extension direction (y direction) of the first waveguide 20 and the second waveguide 30.

[0041] 4 is a top view showing a schematic configuration of an optical waveguide 110 according to the second embodiment. Hereinafter, components that are the same as or in common with the optical waveguide 100 according to the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted. In addition to the configuration of the optical waveguide 100 according to the first embodiment, the optical waveguide 110 according to the second embodiment further includes an elliptical second optical circulation unit 10a that connects to the second waveguide 30 at an end in the propagation direction of the light L, and a third waveguide 80 that connects to the second optical circulation unit 10a at a start in the propagation direction of the light L at a position different from the position where the second optical circulation unit 10a and the second waveguide 30 are connected.

[0042] The PD 50 is connected to the end of the third waveguide 80, and light L emitted from the LED 40 propagates through the first waveguide 20, the optical circulation unit 10, the second waveguide 30, the second optical circulation unit 10a, the third waveguide 80, and the PD 50 in this order. The configuration of the second optical circulation unit 10a is the same as that of the optical circulation unit 10 in the first embodiment, and the second optical circulation unit 10a also has a peripheral floating unit 11a. In the second optical circulation unit 10a, light L also circulates through the peripheral floating unit 11a of the second optical circulation unit 10a multiple times and gradually enters the third waveguide 80.

[0043] According to the optical waveguide 110 of the second embodiment, the light L emitted from the LED 40 travels multiple times through the outer circulating portion 11 of the optical circulation unit 10 and the outer circulating portion 11a of the second optical circulation unit 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. This improves the sensitivity when the optical waveguide 100 is used as a sensor in an optical concentration meter or the like.

[0044] 5 is a top view showing a schematic configuration of an optical waveguide 120 according to the third embodiment. Hereinafter, components that are the same as or in common with the optical waveguide 100 according to the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted. In addition to the configuration of the optical waveguide 110 according to the second embodiment, the optical waveguide 120 according to the third embodiment further includes an elliptical third optical circulation unit 10b that connects to the third waveguide 80 at an end in the propagation direction of the light L, and a fourth waveguide 90 that connects to the third optical circulation unit 10b at a start in the propagation direction of the light L at a position different from the position where the third optical circulation unit 10b and the third waveguide 80 are connected.

[0045] A PD 50 is connected to the end of the fourth waveguide 90, and light L emitted from the LED 40 propagates through the first waveguide 20, the optical circulation unit 10, the second waveguide 30, the second optical circulation unit 10a, the third waveguide 80, the third optical circulation unit 10b, the fourth waveguide 90, and the PD 50 in this order. The configuration of the third optical circulation unit 10b is similar to that of the optical circulation unit 10 in the first embodiment, and the third optical circulation unit 10b also has a peripheral floating unit 11b. In the third optical circulation unit 10b, light L also circulates through the peripheral floating unit 11b of the third optical circulation unit 10b multiple times and gradually enters the fourth waveguide 90.

[0046] According to the optical waveguide 120 of the third embodiment, light L emitted from the LED 40 travels multiple times through the outer circulating portion 11 of the optical circulation unit 10, the outer circulating portion 11a of the second optical circulation unit 10a, and the outer circulating portion 11b of the third optical circulation unit 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. This improves the sensitivity when the optical waveguide 100 is used as a sensor in an optical concentration meter or the like.

[0047] 6 is a top view showing a schematic configuration of an optical waveguide 130 in the fourth embodiment. Hereinafter, components that are the same as or in common with the optical waveguide 100 in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. The optical waveguide 130 in the fourth embodiment differs from the optical waveguide 100 in the first embodiment in that the second waveguide 30 extends in the opposite direction (+y direction) from the optical circulation unit 10. Therefore, the second waveguide 30 is connected to the optical circulation unit 10 in the direction opposite to the optical circulation direction in the optical circulation unit 10.

[0048] As with the optical waveguide 100 in the first embodiment, light L emitted from the LED 40 propagates through the first waveguide 20, the optical circulation unit 10, the second waveguide 30, and the PD 50 in this order. At the starting point 31, which is the connection between the optical circulation unit 10 and the second waveguide 30, the light L circulating through the optical circulation unit 10 propagates in the lower left direction in the drawing. However, the starting point 31 of the second waveguide 30 is connected in the upward direction (+y direction).

[0049] In this way, by connecting the second waveguide 30 to the optical circulation unit 10 in the direction opposite to the light circulation direction in the optical circulation unit 10, it becomes difficult for the light L to enter the second waveguide 30 from the optical circulation unit 10, and the average number of times the light L circulates in the optical circulation unit 10 increases. This makes it possible to further increase the optical path length per unit area of ​​the light L propagating from the LED 40 to the PD 50. Therefore, it is possible to improve the sensitivity when the optical waveguide 100 is used as a sensor in an optical concentration measuring instrument or the like.

[0050] 7 is a top view showing a schematic configuration of an optical waveguide 140 according to the fifth embodiment. Hereinafter, components that are the same as or in common with the optical waveguide 100 according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. The optical waveguide 140 according to the fifth embodiment differs from the optical waveguide 100 according to the first embodiment in that the second waveguide 30 is connected to the optical circulation unit 10 at an angle that is not along the elliptical tangent D of the optical circulation unit 10.

[0051] In this way, by connecting the second waveguide 30 to the optical circulation unit 10 at an angle that is not along the tangent D of the ellipse of the optical circulation unit 10, it becomes difficult for the light L to enter the second waveguide 30 from the optical circulation unit 10, and the average number of times the light L circulates through the optical circulation unit 10 increases. This makes it possible to further increase the optical path length per unit area of ​​the light L propagating from the LED 40 to the PD 50. Therefore, it is possible to improve the sensitivity when the optical waveguide 100 is used as a sensor in an optical concentration measuring instrument or the like.

[0052] FIG. 8 is a top view showing a schematic configuration of an optical waveguide 150 according to the sixth embodiment. Hereinafter, components that are the same as or common to those of the optical waveguide 100 according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. The optical waveguide 150 according to the sixth embodiment differs from the optical waveguide 100 according to the first embodiment in that the optical circulation section 10 has a perfect circular shape. In addition, a perfect circular shape can be considered an example of an ellipse in which the lengths of the minor axis and the major axis are equal. By making the shape perfect circular, symmetry can be improved, allowing light to circulate efficiently. Note that the perfect circle may be a perfect circle in terms of design, and may also include shapes that deviate slightly from a perfect circle due to variations in manufacturing.

[0053] FIG. 9 is a side view illustrating a manufacturing method of the optical waveguide 100 according to the first embodiment. First, a laminate 102 is prepared, in which layers for forming the first waveguide 20, the second waveguide 30, and the optical circulation unit 10, layers for forming the cladding layer 60, and a substrate 70 are stacked. The layers for forming the first waveguide 20, the second waveguide 30, and the optical circulation unit 10 are etched from the laminate 102. This forms an intermediate 104 having the first waveguide 20, the second waveguide 30, and the optical circulation unit 10. The layers for forming the cladding layer 60 are etched from the intermediate 104 to form the cladding layer 60. At this stage, the portions other than the cladding layer 60 below the optical circulation unit 10 are removed by etching, and the first waveguide 20 and the second waveguide 30 become floating waveguides floating above the cladding layer 60.

[0054] 10 is a side view showing a schematic configuration of an optical waveguide 160 according to the seventh embodiment. Hereinafter, components that are the same as or in common with the optical waveguide 100 according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. The optical waveguide 160 according to the seventh embodiment differs from the optical waveguide 100 according to the first embodiment in that the optical circulation section 10c of the optical waveguide 160 does not have an outer circumferential floating section that is floating above the cladding layer 60. Light L circulates in the outer circumferential portion 11c of the optical circulation section 10c that is not floating above the cladding layer 60.

[0055] Although 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 will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0056] It should be noted that the execution order of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and that the processes can be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, this does not mean that the processes must be performed in this order. [Explanation of symbols]

[0057] 10 optical circulation section, 10a second optical circulation section, 10b third optical circulation section, 10c optical circulation section, 11 peripheral floating section, 11a peripheral floating section, 11b peripheral floating section, 11c peripheral section, 12 center section, 13 dotted line, 20 first waveguide, 21 starting end, 22 ending end, 30 second waveguide, 31 starting end, 32 ending end, 40 LED, 60 cladding layer, 70 substrate, 80 third waveguide, 90 fourth waveguide, 100 optical waveguide, 102 laminate, 104 intermediate body, 110 optical waveguide, 120 optical waveguide, 130 optical waveguide, 140 optical waveguide, 150 optical waveguide, D ellipse tangent, L light, M minor axis, P center of gravity

Claims

1. a light introducing section; a light guide portion; An elliptical optical circumferential part, a first waveguide connected to the light introducing section at a start point in the propagation direction of light and connected to the light circulating section at a terminal point; a second waveguide that is connected to the optical circulation unit at a start point in the light propagation direction and to the optical output unit at a terminal point, the second waveguide being located at a position different from a position where the optical circulation unit and the first waveguide are connected; a clad layer supporting the optical circulation unit; a substrate supporting the cladding layer; a center of gravity of the optical circulation unit is disposed at a position shifted from an extension direction of the first waveguide and the second waveguide in a top view; An optical waveguide in which light introduced from a light introducing section propagates through the first waveguide, the optical circulation section, and the second waveguide in this order.

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

3. The optical waveguide according to claim 2 , wherein the optical circulation section has a peripheral floating section that is not in contact with the cladding layer and the substrate.

4. The optical waveguide according to claim 3 , wherein the first waveguide and the second waveguide are connected to the outer circulating portion of the optical circulation portion.

5. the first waveguide and the second waveguide are not in contact with the cladding layer and the substrate; 4. The optical waveguide according to claim 3.

6. 4. The optical waveguide according to claim 3, wherein the minor radius of the optical circulation portion is at least twice the radial length of the outer circumferential floating portion.

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

8. 4. The optical waveguide according to claim 3, wherein the radial length of the outer peripheral floating portion is equal to or less than 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 optical circulation section at an angle along an elliptical tangent of the optical circulation section.

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

11. The optical waveguide according to claim 1 , wherein the first waveguide or the second waveguide is connected to the optical circulation section in a direction opposite to the direction of light circulation in the optical circulation section.

12. 3. The optical waveguide according to claim 2, wherein the refractive index of the material constituting the first waveguide, the second waveguide, and the optical circulation section is higher than the refractive index of the material constituting the cladding layer.

13. 2. The optical waveguide according to claim 1, wherein the refractive index of the material forming said optical circulation section is equal to or greater than the refractive index of the material forming said first waveguide and said second waveguide.

14. 2. The optical waveguide according to claim 1, wherein the first waveguide and the second waveguide have a length of 200 [mu]m or less.

15. an elliptical second optical circulation section that connects to the second waveguide at an end in the light propagation direction; 2. The optical waveguide according to claim 1, further comprising a third waveguide connected to the second optical circulation section at a starting end in the propagation direction of light at a position different from a position where the second optical circulation section and the second waveguide are connected.

16. The optical waveguide according to claim 4 , wherein the first waveguide or the second waveguide is connected to the optical circulation section at an angle along an elliptical tangent of the optical circulation section.

17. 5. The optical waveguide according to claim 4, wherein the first waveguide or the second waveguide is connected to the optical circulation section at an angle that is not along a tangent to an ellipse of the optical circulation section.

18. The optical waveguide according to claim 4 , wherein the first waveguide or the second waveguide is connected to the optical circulation section in a direction opposite to the direction of light circulation in the optical circulation section.

19. 5. The optical waveguide according to claim 4, wherein the refractive index of the material constituting the first waveguide, the second waveguide, and the optical circulation section is higher than the refractive index of the material constituting the cladding layer.

20. 5. The optical waveguide according to claim 4, wherein the refractive index of the material forming said optical circulation section is equal to or greater than the refractive index of the material forming said first waveguide and said second waveguide.

21. 5. The optical waveguide according to claim 4, wherein the first waveguide and the second waveguide have a length of 200 [mu]m or less.

22. an elliptical second optical circulation section that connects to the second waveguide at an end in the light propagation direction; 5. The optical waveguide according to claim 4, further comprising a third waveguide connected to the second optical circulation section at a starting end in the propagation direction of light at a position different from a position where the second optical circulation section and the second waveguide are connected.

23. An optical concentration measuring instrument comprising the optical waveguide according to any one of claims 1 to 22.

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