JP2011232674A - Optical waveguide, wavelength-multiplex light multiplexing device, and medical endoscope using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide which can be miniaturized and which multiplexes two or more lights having different wavelengths and with which a multiplexed light can be obtained with light intensity distribution of each wavelength being uniform at the core surface of a light emission part, and to provide a wavelength-multiplex light multiplexing device equipped with the optical waveguide and a medical endoscope using the wavelength-multiplex light multiplexing device.SOLUTION: There is provided an optical waveguide comprising a core which multiplexes two or more lights with different wavelengths being incident from a light incident part and propagates the multiplexed light toward a light emission part. The optical waveguide includes at least a tapered core, the breadth of which narrows from the light incident part toward the light emission part. There are also provided a wavelength-multiplex light multiplexing device equipped with the optical waveguide and a medical endoscope using the wavelength-multiplex light multiplexing device.

Description

  The present invention relates to an optical waveguide, a wavelength division multiplexing optical apparatus including the same, and a medical endoscope using the same.

Various proposals have been made as a wavelength multiplexing optical multiplexer that combines light of different wavelengths emitted from a plurality of light sources.
For example, in Patent Document 1, a first light is output from a plurality of fiber combined light source units that combine light emitted from a plurality of light sources in a first fiber combiner to form first combined light, using a multimode optical fiber. An invention relating to a combined light source that guides the combined light and further combines in a second fiber combiner to form a second combined light is disclosed. In patent document 1, it aims at providing the combined light source for combining the light radiate | emitted from a several light source, and obtaining high output and high-intensity combined light.

  Further, in Patent Document 2, after two or more different wavelengths of light incident from two or more light emitting points adjacent to the surface light emitting element are combined and propagated, the combined light is demultiplexed by a wavelength selection filter. An invention relating to a combined wavelength division multiplexing optical propagation path structure capable of wavelength division multiplexing propagation is disclosed. Patent Document 2 aims to provide an optical propagation technique that can further reduce the cost, size, and capacity of an optical propagation path that is used for short-distance light propagation by the wavelength-multiplexed light propagation structure.

JP 2007-41342 A JP 2009-199038 A

However, for example, in a small illuminating device that emits white light by combining a plurality of light beams having different wavelengths, such as that used in a medical endoscope, It is required that the intensity distribution of the light having the same wavelength is uniform, and the distribution shape is the same for the light having any wavelength. In other words, it is required that the intensity distribution of the light of each wavelength is uniform on the core surface on the side of the light emitting portion of the wavelength multi-polymerizer.
However, in the combined light source described in Patent Document 1, the uniformity of the intensity distribution of the light is not mentioned, and no means for reducing the size is proposed. In order to make the light intensity distribution uniform with the combined light source of Patent Document 1, the propagation path must be lengthened, and the entire apparatus is enlarged.
Patent Document 2 also mentions light loss, but does not disclose means for making the light intensity distribution uniform. Note that the light source described here includes not only light emitting elements such as lasers and LEDs, but also optical fibers and optical waveguides to which these light emitting elements are coupled.
The present invention has been made in view of the solution of the above-mentioned problem. At the same time, the light having two or more different wavelengths is combined, and the intensity of the light of each wavelength is obtained on the core surface on the light emitting part side. An object of the present invention is to provide an optical waveguide capable of obtaining multiplexed light having a uniform distribution, a wavelength multiplexing optical multiplexing device including the optical waveguide, and a medical endoscope using the wavelength multiplexing optical multiplexing device. To do.

  The inventors of the present invention have made extensive studies in order to solve the above problems, and have found that the above problems can be solved by the following [1] to [3].

[1] An optical waveguide comprising a core that multiplexes light having two or more different wavelengths incident from the light incident portion side and propagates the light to the light emitting portion side, and the core of the optical waveguide is light incident An optical waveguide comprising: a tapered core including at least a tapered shape having a lateral width that narrows from a portion side toward a light emitting portion side.
[2] An optical waveguide body comprising the optical waveguide according to [1], and a light incident portion that emits light of different wavelengths from two or more light emitting points configured by the light emitting element to the optical waveguide body. Wavelength multiplexing optical multiplexer.
[3] A medical endoscope using the wavelength multiplexing optical multiplexer according to [2].

  According to the optical waveguide of the present invention and the wavelength multiplexing optical multiplexing device including the optical waveguide, the device is miniaturized, and at the same time, the lights having two or more different wavelengths are multiplexed, and the core on the light emitting part side On the surface, it is possible to obtain combined light in which the intensity distribution of light of each wavelength is uniform. Further, the wavelength multiplexing optical multiplexer is particularly suitable for medical endoscope applications.

It is (A) top view and (B), (C) sectional drawing which showed typically the example of a structure of the wavelength multiplexing optical multiplexer which used the optical waveguide concerning 1st Embodiment of this invention. It is the top view which showed typically the mode of the light propagation of the light guide of this invention. It is the top view which showed typically the intensity distribution of the light of the light guide of this invention. It is the top view which showed typically the structural example of the wavelength multiplexing optical multiplexing apparatus using the optical waveguide which concerns on 2nd Embodiment of this invention. It is (A) top view and (B), (C) sectional drawing which showed typically the structural example of the wavelength multiplexing optical multiplexer which used the optical waveguide concerning 3rd Embodiment of this invention. In the optical waveguide according to the first and third embodiments of the present invention, it is a graph showing the propagation loss of light at a wavelength of 550nm when the lateral width W2 of the light emitting portion side end portion is changed. It is the top view which showed typically the structural example of the wavelength multiplexing optical multiplexing apparatus using the optical waveguide which concerns on 4th Embodiment of this invention. It is the top view which showed typically the mode of the light propagation of the conventional optical waveguide. It is the top view which showed typically the intensity distribution of the light of the conventional optical waveguide.

(Wavelength multiplexing optical multiplexer)
First, referring to FIG. 1A, the configuration of the wavelength multiplexing optical multiplexer of the present invention will be described.
The wavelength multiplexing optical multiplexer 3 according to the present invention includes an optical waveguide body 10 including the optical waveguide 1 according to the present invention, and a light incident portion 20. The light incident portion 20 includes two or more light emitting points (three in FIG. 1) 22 a, 22 b, and 22 c, and these light emitting points are constituted by the light emitting element 21. The light incident part 20 emits light of different wavelengths to the optical waveguide body 10 from these light emitting points. The emitted light enters the core 31 from the light incident portion side of the optical waveguide 1 constituting the optical waveguide body 10. The incident light is combined with light of each wavelength while repeatedly propagating total reflection at the boundary surface between the core 31 and the clad 32 (hereinafter also referred to as “boundary surface”) within the core 31. It is emitted as combined light from the core surface on the emission part side.

<Light incident part>
The light emitting element 21 included in the light incident part 20 is not particularly limited as long as each can emit light having different wavelengths. For example, a light emitting diode, a surface light emitting element typified by a surface emitting laser (VCSEL), and the like are included, and an optical fiber and an optical waveguide to which these light emitting elements are coupled are also included.
The light incident part 20 includes two or more light emitting points that emit light having different wavelengths. Here, the light emitting point is constituted by the above light emitting element. Although FIG. 1 shows a case where there are three light emitting points, the number of light emitting points can be appropriately selected according to the application.
However, when the wavelength multiplexing optical multiplexing device of the present invention is used for an illumination device that needs to obtain white light such as a medical endoscope, the light incident portion has three light emitting points, which are red and green, respectively. It is preferable to emit light having a specific wavelength that becomes blue light. By combining these lights having a uniform intensity distribution, white light can be obtained.
It is known that the wavelength range of such light is generally in the range of 600 to 760 nm for red emission wavelength, 490 to 575 nm for green emission wavelength, and 390 to 485 nm for blue emission wavelength. It has been. Among these ranges, R (red): 700 nm, G (green): 546.1 nm, and B (blue): 435.8 nm specified by the RGB color system are preferable.

<Core and clad of optical waveguide>
FIG. 1B is a cross-sectional view taken along a cross-section P1-Q1 of the optical waveguide shown in the plan view of FIG.
As shown in FIG. 1B, the optical waveguide 1 includes a core 31 serving as an optical path and a clad 32 surrounding the core 31. In order for the incident light to propagate through the core 31 while causing total reflection at the boundary surface, the refractive index of the core needs to be larger than the refractive index of the cladding.
The material of the core 31 and the clad 32 may be made of the same material as long as the refractive indexes are different. Examples of the material include inorganic materials such as quartz glass and silicon, and polymer materials such as acrylic resins and epoxy resins. Among these, a polymer material is preferable. Production of polymer optical waveguides using polymer materials is easy because it is easy to increase the core thickness compared to inorganic optical waveguides, and it is possible to mass-produce with processing and molding techniques with large workpiece sizes. Can be improved.
As the base polymer used in the polymer optical waveguide, those having a certain strength and high light transmittance are preferable. For example, phenoxy resin, epoxy resin, (meth) acrylic resin, polycarbonate resin, polyarylate resin, polyether Examples thereof include amide, polyetherimide, polyethersulfone, and derivatives thereof. Here, (meth) acrylic resin means acrylic resin and methacrylic resin. These base polymers may be used alone or in combination of two or more.
Among these exemplified base polymers, from the viewpoint of excellent heat resistance, it is preferable to have an aromatic skeleton in the main chain, and phenoxy resin is particularly preferable. From the viewpoint of three-dimensional crosslinking and improving heat resistance, an epoxy resin is preferable, and an epoxy resin that is solid at room temperature is particularly preferable. Furthermore, compatibility with light or a thermopolymerizable compound is important for ensuring the transparency of the clad-forming resin film. From this viewpoint, the phenoxy resin and (meth) acrylic resin are preferable.

  The clad 32 may be composed of a plurality of materials depending on the location surrounding the core 31, and these materials may have different refractive indexes. For example, as shown in the cross-sectional view of FIG. 1C, the clad 32a located under the core 31 is made of a polymer-based material, and the other clads 32b, 32c, 32d surrounding the core 31 are Instead of using a material such as resin, a configuration in which air serves as a cladding may be employed. In the embodiment of the present invention, any configuration shown in FIGS. 1B and 1C can be adopted.

[First Embodiment of Optical Waveguide of the Present Invention]
Next, a first embodiment of the optical waveguide of the present invention will be described.
In the present invention, the core 31 has a tapered core 33 including at least a tapered shape whose lateral width becomes narrower from the light incident part side toward the light emitting part side. As shown in the cross-sectional views of FIGS. 1B and 1C, the tapered core 33 of the present embodiment has a wide core width in the cross section P1-Q1 close to the light incident part side, but the light emitting part side. The width becomes narrower as it approaches.
The term “including a tapered shape” as used herein refers not only to the case where the lateral width gradually decreases at a constant rate toward the light emitting portion as in the tapered core 33 shown in FIG. The width is increased on the way to the side, but the case where the width is reduced again in the vicinity of the light emitting portion side end portion 33b is also included. However, from the viewpoint of making the intensity distribution of light of different wavelengths uniform, the taper-shaped core 33 has a lateral width that gradually decreases at a constant rate toward the light emitting portion as shown in FIG. Is preferred.
In the present invention, since the core 31 of the optical waveguide 1 has the tapered core 33, the intensity distribution of the incident light of different wavelengths is made uniform, and the intensity distribution of the light of each wavelength from the core surface on the light emitting part side. Combined light that is uniform is obtained. Hereinafter, the reason will be described in detail.

FIG. 8 is a diagram schematically showing the state of light propagation in a conventional optical waveguide. The incident light repeats reflection at the boundary surface, so that the light distribution becomes random. However, as shown in FIG. 8, since the horizontal width of the core of the conventional optical waveguide is uniform, the incident light is less frequently reflected at the boundary surface between the core 131 and the clad 132. In particular, the frequency of reflection of light emitted from the central light emitting point 122b is low. FIG. 9 is a diagram schematically showing the intensity distribution of light emitted from the central light emitting point, focusing only on the central light emitting point 122b. At the points (a) and (b), the light intensity is localized near the center of the core. At the points (c) and (d), the light is reflected at the boundary surface to some extent, so that it is affected by interference near the boundary surface. I do not receive it. For this reason, at any point of (a) to (d), the difference in light intensity between the vicinity of the center of the core and the vicinity of the boundary surface is large, and the light intensity distribution is uneven. This is presumably because in the conventional optical waveguide, the light reflection frequency is low, the influence of interference from the boundary surface is small, and the light distribution is not easily randomized.
On the other hand, FIG. 2 is a diagram schematically showing the state of light propagation in the optical waveguide of the present invention. Since the core of the optical waveguide of the present invention has the tapered core 33 including the tapered shape whose lateral width becomes narrower toward the light emitting part side, the light at the boundary surface is moved from the light incident part side to the light emitting part side. The reflection frequency of becomes higher. By increasing the frequency of the reflection, the light distribution becomes random, and as a result, the light intensity distribution is considered to be uniform in the vicinity of the light emitting portion side end portion 33b. In order to make the light intensity distribution uniform, the core shape is such that the component of propagating light incident at the largest angle on the boundary surface is reflected at the boundary surface at least three times before reaching the exit side. It is desirable. FIG. 3 is a diagram schematically showing an intensity distribution of light emitted from the central light emitting point, focusing on only the central light emitting point 22b. In (a) near the light incident part side, the light reflection frequency is low and the influence of interference from the boundary surface is also small. Therefore, the intensity of light is small near the boundary surface. However, as the width of the core becomes narrower, the frequency of light reflection increases, the influence of interference from the boundary surface increases, and the light intensity near the boundary surface also increases. As a result, the difference in light intensity between the vicinity of the boundary surface and the center of the core is gradually reduced toward (b), (c), (d) and the light emitting portion side, and the light emitting portion side end portion 33b vicinity is reduced. In (e), the light intensity distribution can be made substantially uniform. In FIG. 3, attention is paid only to the central light emitting point 22b. However, the light intensity distribution of the other light emitting points 22a and 22c is almost uniform in the vicinity of the light emitting portion side end portion 33b. Can be.
Therefore, the wavelength multiplexing optical multiplexing device using the optical waveguide of the present invention can obtain multiplexed light in which the intensity distribution of light of each wavelength is uniform.

Moreover, it is preferable that at least a part of the tapered core of the present invention has a thickness in which the order in the thickness direction has a plurality of natural modes with respect to the wavelength of incident light. This is because, in FIGS. 1B and 1C, Y1 indicates the thickness of the tapered core, but it is possible to allow light to enter the core even when the position of the light emitting point is shifted. In order to achieve this, it is desirable that the thickness Y1 has a certain thickness or more, and in this case, the optical waveguide has an eigenmode having a plurality of orders in the thickness direction with respect to the wavelength of incident light. It is because it will have.
The thickness Y1 is preferably 30 to 300 μm.

Here, the shape of the tapered core will be described in detail. In FIG. 1, the lateral width of the light incident portion side end 33a of the tapered core 33 of the present invention is W1 (μm), the lateral width of the light output portion side end 33b is W2 (μm), and the light incidence of the tapered core 33 is performed. L1 (μm) is the length from the part side end 33a to the light emitting part side end 33b, the thickness of the tapered core is Y1 (μm), and tan ⁻¹ [(W1-W2) / 2 / L1]. It is preferable that the following (1) to (5) are satisfied, where α (degrees) is the taper angle of the tapered core defined by:
(1) 0.1 ≦ α ≦ 2.0
(2) 300 ≦ W1 ≦ 1500
(3) 50 ≦ W2 ≦ 200
(4) 1500 ≦ L1 ≦ 40000
(5) 30 ≦ Y1 ≦ 300

Conditions (2) to (4) are ranges determined in consideration of the range of the taper angle α. That is, the range of W1, W2, and L1 considers the relationship of the taper angle α = tan ⁻¹ [(W1−W2) / 2 / L1] and the range of the taper angle α.
In the condition (3), it is preferable that W2 is 50 (μm) or more because the propagation loss of light can be suppressed. Moreover, it is preferable if W2 is 200 (μm) or less because the light intensity distribution can be sufficiently uniformed.
In the condition (4), if L1 is 1500 (μm) or more, it is preferable because the frequency at which the incident light is totally reflected at the boundary surface between the core and the clad is sufficiently secured. Moreover, if L1 is 40000 (micrometer) or less, since it can be used for the use as which size reduction is required, such as a medical endoscope, it is preferable.
In addition, by satisfying the condition (5), it is possible to sufficiently secure the allowable positional deviation in the thickness direction of the element.

[Second Embodiment of Optical Waveguide of the Present Invention]
Next, a second embodiment of the optical waveguide of the present invention will be described with reference to FIG. FIG. 4 is a plan view schematically showing an example of the structure of a wavelength division multiplexing apparatus using an optical waveguide according to the second embodiment of the present invention.
In addition, description is abbreviate | omitted about the structure same as the above-mentioned embodiment, and only a different structure is demonstrated. This matter is not limited to this embodiment, and the same applies to third and fourth embodiments described later.
It is preferable that the tapered core of the wavelength multiplexing optical multiplexer according to the present embodiment includes at least a tapered shape including a curved shape near the light incident portion side end portion and having a lateral width that is curvilinearly narrowed toward the light emitting portion. As shown in FIG. 4, the boundary line between the core 31 and the clad 32 in the vicinity of the light incident portion side end portion 34a is formed in a curved shape. By making the tapered core into such a shape, light leaking at the core / cladding interface can be reduced and propagation loss can be reduced.

[Third Embodiment of Optical Waveguide of the Present Invention]
Next, a third embodiment of the optical waveguide of the present invention will be described with reference to FIG. 5A is a plan view, and FIG. 5B is a cross-sectional view illustrating a structural example of a wavelength multiplexing optical multiplexer using an optical waveguide according to the third embodiment of the present invention. .
In the optical waveguide 1b of the third embodiment, the core 31 includes the aforementioned tapered core 33 and a plurality of incident cores 35a, 35b, and 35c. As shown in FIG. Is surrounded by a clad 32. As described above, the clad 32 may be composed of a plurality of materials depending on the location surrounding the core 31, and these materials may have different refractive indexes. As shown in C), for example, the clad 32a located under the core 31 may be made of a polymer material, and the other clad surrounding the core 31 may be made of air.
The plurality of incident cores 35a, 35b, and 35c correspond to the light emitting points 22a, 22b, and 22c of the light incident portion. The plurality of incident cores play a role of propagating light incident from the respective light emitting points to the light incident portion side end portion 33 a of the tapered core 33. The incident cores have the same number of light emitting points as corresponding to the respective light emitting points, and at least one of these incident cores has a curved shape. The shape of the curved incident core is preferably substantially S-shaped. In the optical waveguide 1b of FIG. 5, the shapes of the incident cores 35a and 35c are substantially S-shaped. With such a shape, propagation loss can be reduced.

FIG. 6 is a graph showing a light propagation loss at a wavelength of 550 nm when the lateral width W2 of the light emitting portion side end portion is changed in the optical waveguides of the first and third embodiments. As the graph of FIG. 6 shows, when the lateral width W2 of the light emitting portion side end portion is narrowed, the propagation loss tends to increase. However, in the optical waveguide according to the present embodiment, since a configuration of a plurality of incident cores, at least one of which has a curved shape (substantially S-shape), is incorporated, propagation loss can be reduced. Although FIG. 6 shows light having a wavelength of 550 nm as an example, the relationship between the width W2 and the propagation loss shows the same tendency for light of other wavelengths.
Therefore, the wavelength division multiplexing optical multiplexer of this embodiment can obtain combined light with uniform intensity distribution of incident light of different wavelengths by narrowing the lateral width W2 while reducing propagation loss.

  Also in this embodiment, it is preferable that the thickness Y1 of the tapered core is a thickness that is multimode with respect to the wavelength of incident light. Further, the thickness Y2 of the incident core may be the same as or different from the thickness Y1 of the tapered core.

Here, the shape of the core of the optical waveguide of the present embodiment will be described in detail.
In the optical waveguide 1b shown in FIG. 5, the horizontal width of the light incident portion side end portion 33a of the tapered core 33 is W1 (μm), the horizontal width of the light output portion side end portion is W2 (μm), and the light incidence of the tapered core 33 is performed. L1 (μm) is the length from the portion side end 33a to the light emitting portion side end 33b, the thickness of the tapered core 33 is Y1 (μm), the thickness of the incident core 35 is Y2 (μm), and tan ^{−. 1} The taper angle of the tapered core defined by [(W1-W2) / 2 / L1] is α (degrees), and the maximum distance between the core centers of the plurality of incident cores at the light incident part side end 36a is X1 ( μm), the maximum distance between the core centers of the plurality of incident cores at the tapered core side end 36b is X2 (μm), and the length from the light incident part side end 36a of the incident core to the tapered core side end 36b When the thickness is L2 (μm), the following (1) to (9) are satisfied. It is preferable to add.
(1) 0.1 ≦ α ≦ 2.0
(2) 130 ≦ W1 ≦ 750
(3) 50 ≦ W2 ≦ 200
(4) 1000 ≦ L1 ≦ 30000
(5) 30 ≦ Y1, Y2 ≦ 300
(6) 500 ≦ X1 ≦ 1500
(7) 100 ≦ X2 ≦ 500
(8) W1 ≧ X2
(9) 1000 ≦ L2 ≦ 5000

Among the above conditions, the conditions (1) and (5) are as described in the first embodiment.
In the condition (3), it is preferable that W2 is 50 (μm) or more because the propagation loss of light can be suppressed. Moreover, it is preferable if W2 is 200 (μm) or less because the light intensity distribution can be sufficiently uniformed.
In the condition (4), it is preferable that L1 is 1000 (μm) or more because the frequency at which the incident light is totally reflected at the boundary surface between the core and the clad is sufficiently secured. Moreover, if L1 is 30000 (micrometer) or less, since it can be used for the use as which size reduction is required, such as a medical endoscope, it is preferable.
In the condition (8), W1 = X2 may be satisfied, and there is no problem as long as light incident from the light emitting point can propagate to the tapered core without leakage.

[Fourth Embodiment of Optical Waveguide of the Present Invention]
The optical waveguide 1c shown in FIG. 7 is mentioned about 4th Embodiment of the optical waveguide of this invention. The optical waveguide 1c according to the fourth embodiment has a curved shape in the vicinity of the light incident portion side end portion of the optical waveguide 1a according to the second embodiment while having the configuration of the optical waveguide 1b according to the third embodiment as a basic configuration. And a taper-shaped core 34 including at least a taper shape in which the lateral width becomes curvilinearly narrower toward the light emitting portion direction.
By having the tapered core 34 as shown in FIG. 7, the light leaking at the core / cladding interface can be reduced, the propagation loss can be reduced, and the combined light with uniform intensity distribution of light of different wavelengths. Can be obtained.
Further, by having a plurality of incident cores as shown in FIG. 7, the propagation loss can be further reduced.

[Other Embodiments]
The optical waveguide of the present invention is not limited to the above embodiment, and is included in the technical scope of the present invention as long as the intensity distribution of incident light having different wavelengths can be made uniform. For example, an optical waveguide in which the lateral width of a part of the tapered core increases as it goes to the light emitting part side or is uniform is also included in the present invention.

  The wavelength multiplexing optical multiplexing apparatus including the optical waveguide according to the present invention can achieve miniaturization of the apparatus and obtain multiplexed light with uniform intensity distribution of light of different wavelengths. Therefore, it is useful for applications such as medical endoscopes.

DESCRIPTION OF SYMBOLS 1, 1a, 1b, 1c Optical waveguide 10 Optical waveguide main body 20 Light incident part 21 Light emitting element 22a, 22b, 22c Light emission point 3 Wavelength multiplexing optical multiplexer 31 Core 32 Cladding 33, 34 Tapered core 33a, 34a (Tapered core Light incident portion side end portions 33b, 34b (light emitting portion side end portions 35a, 35b, 35c) incident core 36a (of a plurality of incident cores) light incident side light incident portion side end portions 36b Tapered core side end (of multiple incident cores)

Claims (12)

An optical waveguide comprising a core that multiplexes light having two or more different wavelengths incident from the light incident part side and propagates to the light emitting part side,
The core of the optical waveguide has a tapered core including at least a tapered shape in which a lateral width becomes narrower from a light incident part side toward a light emitting part side.   The optical waveguide according to claim 1, wherein at least a part of the tapered core has a thickness having a plurality of eigenmodes in the thickness direction with respect to the wavelength of incident light. In the optical waveguide,
The horizontal width of the light incident part side end of the tapered core is W1 (μm), the horizontal width of the light output part side end is W2 (μm), and from the light incident part side end of the tapered core to the light output part side end The taper angle of the tapered core defined by L1 (μm), the thickness of the tapered core Y1 (μm), and tan ^-1 [(W1-W2) / 2 / L1] is α (degrees). ), The optical waveguide according to claim 2 satisfying the following (1) to (5).
(1) 0.1 ≦ α ≦ 2.0
(2) 300 ≦ W1 ≦ 1500
(3) 50 ≦ W2 ≦ 200
(4) 1500 ≦ L1 ≦ 40000
(5) 30 ≦ Y1 ≦ 300 In the optical waveguide,
The core of the optical waveguide has a tapered core and a plurality of incident cores for propagating light having two or more different wavelengths to the light incident part side end of the tapered core,
The optical waveguide according to claim 1, wherein at least one of the plurality of incident cores has a curved shape.   The optical waveguide according to claim 4, wherein at least a part of the tapered core has a thickness having a plurality of eigenmodes in the thickness direction with respect to a wavelength of incident light. In the optical waveguide,
The horizontal width of the light incident part side end of the tapered core is W1 (μm), the horizontal width of the light output part side end is W2 (μm), and from the light incident part side end of the tapered core to the light output part side end Is defined by L1 (μm), the thickness of the tapered core is Y1 (μm), the thickness of the incident core is Y2 (μm), and tan ⁻¹ [(W1-W2) / 2 / L1]. The taper angle of the taper-shaped core is α (degrees), the maximum distance between the core centers of the plurality of incident cores at the light incident part side end is X1 (μm), and the cores of the plurality of incident cores at the tapered core side end part When the maximum distance between the centers is X2 (μm) and the length from the light incident part side end of the incident core to the tapered core side end is L2 (μm), the following (1) to (9) The optical waveguide according to claim 5, wherein the optical waveguide is satisfied.
(1) 0.1 ≦ α ≦ 2.0
(2) 130 ≦ W1 ≦ 750
(3) 50 ≦ W2 ≦ 200
(4) 1000 ≦ L1 ≦ 30000
(5) 30 ≦ Y1, Y2 ≦ 300
(6) 500 ≦ X1 ≦ 1500
(7) 100 ≦ X2 ≦ 500
(8) W1 ≧ X2
(9) 1000 ≦ L2 ≦ 5000   The optical waveguide according to any one of claims 4 to 6, wherein the shape of the curved incident core is substantially S-shaped.   The taper-shaped core includes at least a tapered shape including a curved shape in the vicinity of the light incident portion side end portion, and having a lateral width that is curvilinearly narrowed toward the light emitting portion direction. Optical waveguide.   The optical waveguide according to claim 1, wherein the optical waveguide is a polymer optical waveguide. An optical waveguide body comprising the optical waveguide according to any one of claims 1 to 9,
A wavelength division multiplexing optical multiplexer comprising: a light incident portion that emits light of different wavelengths from two or more light emitting points configured by light emitting elements to the optical waveguide body.   The wavelength division multiplexing optical multiplexer according to claim 10, wherein the light incident portion has three light emitting points and emits light having specific wavelengths that are red, green, and blue light, respectively.   A medical endoscope using the wavelength multiplexing optical multiplexer according to claim 10 or 11.

Images