WO2019117031A1

WO2019117031A1 - Optical waveguide

Info

Publication number: WO2019117031A1
Application number: PCT/JP2018/045069
Authority: WO
Inventors: 直人古根川; 雄一辻田
Original assignee: 日東電工株式会社
Priority date: 2017-12-13
Filing date: 2018-12-07
Publication date: 2019-06-20
Also published as: TWI814759B; TW201928432A; JP7187148B2; JP2019105774A

Abstract

An optical waveguide includes cladding and a core embedded in the cladding. The core comprises: a first incidence surface that is arranged at the end face upstream in the light transmission direction and allows light with a first wavelength to enter the core; a second incidence surface that is arranged at the end face upstream in the transmission direction separate from the first incidence surface by a gap in a direction intersecting with the transmission direction and allows light with a second wavelength shorter than the first wavelength to enter the core; a third incidence surface that is arranged at the end face upstream in the transmission direction separate from the first incidence surface and the second incidence surface by a gap in a direction intersecting with the transmission direction and allows light with a third wavelength shorter than the second wavelength to enter the core; a joint that is arranged downstream of the first incidence surface, the second incidence surface, and the third incidence surface in the transmission direction and where the light with the first wavelength, the light with the second wavelength, and the light with the third wavelength join together; and an emission surface that is arranged downstream from the joint in the transmission direction and wherefrom the light with the first wavelength, the light with the second wavelength, and the light with the third wavelength are emitted. A first area S1 of the first incidence surface, a second area S2 of the second incidence surface, a third area S3 of the third incidence surface are substantially identical. A first attenuation ratio R1 for the light with the first wavelength which is incident on the first incidence surface and emitted from the emission surface is greater than a second attenuation ratio R2 for the light with the second wavelength which is incident on the second incidence surface and emitted from the emission surface. The second attenuation ratio R2 is greater than a third attenuation ratio R3 for the light with the third wavelength which is incident on the third incidence surface and emitted from the emission surface.

Description

Optical waveguide

The present invention relates to an optical waveguide.

Conventionally, an optical waveguide in which a plurality of optical paths are bundled into one at a junction is known. In this optical waveguide, each of a plurality of light beams having different wavelengths is incident on each of a plurality of incident surfaces, and these are merged at a merging portion, and then one exit surface disposed downstream of the merging portion Emit from.

For example, a multimode optical waveguide having branch cores different in width has been proposed (see, for example, Patent Document 1). In the multimode optical waveguide of Patent Document 1, by making the widths of the plurality of branch cores different, the propagation constants of the plurality of optical paths are made different, and more light is propagated to the branch core having the larger propagation constant. .

JP 2007-225920 A

However, when light having a relatively short wavelength and light having a relatively long wavelength among a plurality of light having different wavelengths are incident on two incident planes having the same configuration, the light having a short wavelength has a long wavelength The rate of loss in the light path is larger than that of light. Therefore, among the light emitted from the emission surface, the light having a short wavelength has a greater reduction in intensity than the light having a long wavelength. As a result, there is a problem that the intensities of the two lights after merging become uneven.

On the other hand, Patent Document 1 divides the light into selective portions by making the widths of branch cores different, but as in Patent Document 1, the width is changed for each of a plurality of branch cores to widen light having a short wavelength. When light is incident on the incident surface of the branch core and light having a long wavelength is incident on the light incident surface of the narrow branch core, the decrease in the intensity of light having a short wavelength is large compared to the decrease in the intensity of light having a long wavelength It can be suppressed and the above problems can be solved.

However, if a plurality of light beams are incident on incident surfaces with different widths, misalignment easily occurs. Specifically, each of the plurality of light emitting devices and each of the plurality of incident surfaces must be aligned in accordance with the width of the plurality of incident surfaces, and such accurate alignment can not be performed. In this case, there is a problem that the two can not be optically connected accurately.

The present invention allows each of the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength to be simply and accurately incident on each of the three incident surfaces, and further combines the three lights to make them uniform. Provided is an optical waveguide capable of emitting with intensity.

The present invention (1) includes a clad and a core embedded in the clad, wherein the core is disposed at an end face upstream of the light transmission direction, and a first incident light of a first wavelength is incident on the core The light emitting element is disposed on the surface and on the upstream end face in the transmission direction so as to be separated from the first incident surface in the direction intersecting the transmission direction, and light of a second wavelength shorter than the first wavelength is incident on the core A second incident surface and an upstream end surface in the transmission direction are disposed to be spaced apart from the first incident surface and the second incident surface in a direction intersecting the transmission direction, and a third shorter than the second wavelength The light of the first wavelength is disposed downstream of the transmission direction of the third incident surface on which the light of the wavelength enters the core, the first incident surface, the second incident surface, and the third incident surface. The light of the second wavelength and the light of the third wavelength merge A junction, and an exit surface disposed downstream of the junction in the transmission direction and emitting the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength; The first area S1 of the incident surface, the second area S2 of the second incident surface, and the third area S3 of the third incident surface are substantially the same, and are incident on the first incident surface, and the emission A first attenuation ratio R1 of the light of the first wavelength emitted from the surface is incident on the second incident surface and compared to a second attenuation ratio R2 of the light of the second wavelength emitted from the emission surface The optical waveguide includes an optical waveguide that is larger than the third attenuation ratio R3 of the light of the third wavelength that is incident on the third incident surface and that is emitted from the output surface.

In this optical waveguide, each of the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength is incident on the first incident surface, the second incident surface, and the third incident surface, and Combine the light and emit three lights from the exit surface.

In addition, since the first area S1 of the first incident surface, the second area S2 of the second incident surface, and the third area S3 of the third incident surface are substantially the same, the light emitting device and the three incident surfaces are provided. Can be easily aligned, and both can be optically connected easily and accurately.

Furthermore, a third attenuation ratio R1 of the light of the first wavelength is larger than a second attenuation ratio R2 of the light of the second wavelength shorter than the first wavelength, and a second attenuation ratio R2 is shorter than the second wavelength. As compared with the third attenuation ratio R3 of the light of the wavelength, the intensities of the three lights emitted from the emission surface can be made uniform.

As a result, in this optical waveguide, it is possible to allow three lights to enter easily and accurately, and to combine them while emitting combined light having excellent optical characteristics.

In the invention (2), the light of the first wavelength includes red light, the light of the second wavelength includes green light, and the light of the third wavelength includes blue light. And the optical waveguide described above.

In this optical waveguide, the light of the first wavelength contains red light, the light of the second wavelength contains green light, and the light of the third wavelength contains blue light. Light and red light can be emitted with uniform intensity. Therefore, combined light having a desired hue can be emitted.

In the invention (3), the merging portion is a first merging portion in which any two of the light of the first wavelength, the light of the second wavelength and the light of the third wavelength are merged, and the first merging portion The optical waveguide according to (1) or (2), further including: a second merging portion disposed downstream of the merging portion in the transmission direction and in which the remaining light and the light merged in the first merging portion merge including.

In this optical waveguide, two lights are merged at the first merging section, and the remaining light and the light merged at the first merging section are merged at the second merging section. Uniformization can be achieved.

The present invention (4) is characterized in that the merging portion includes a full merging portion where three of the light of the first wavelength, the light of the second wavelength and the light of the third wavelength merge. The optical waveguide as described in.

In this optical waveguide, three light beams are merged at all junctions, which is useful when it is desired to reduce the loss at the junctions.

The present invention (5) is characterized in that the first optical path length L1 from the first incident surface to the emission surface is longer than the second optical path length L2 from the second incident surface to the emission surface. The optical waveguide according to any one of (1) to (4) is included that the optical path length L2 is longer than the third optical path length L3 from the third incident surface to the exit surface.

In this optical waveguide, since the first optical path length L1 is longer than the second optical path length L2, the first attenuation ratio R1 of the light of the first wavelength is the second attenuation ratio of the light of the second wavelength shorter than the first wavelength. It can be set larger reliably than R2.

In addition, since the second optical path length L2 is longer than the third optical path length L3, the second attenuation ratio R2 is surely set larger than the third attenuation ratio R3 of the light of the third wavelength shorter than the second wavelength. can do.

As a result, with a simple configuration in which the first optical path length L1, the second optical path length L2, and the third optical path length L3 are shortened in that order, the intensities of the three lights emitted from the emission surface can be made uniform uniformly. Can.
In the invention (6), the first leak ratio LR1 when the light of the first wavelength is transmitted from the first incident surface to the exit surface is the light of the second wavelength which is transmitted from the second incident surface The second leak ratio LR2 is larger than the second leak ratio LR2 when the light is transmitted to the light exit surface when the light of the third wavelength is transmitted from the third light incident surface to the light exit surface The optical waveguide according to any one of (1) to (5), which is larger than the third leakage ratio LR3 of

In this optical waveguide, since the first leak ratio LR1 is larger than the second leak ratio LR2, the first attenuation ratio R1 of the light of the first wavelength is the second attenuation ratio of the light of the second wavelength shorter than the first wavelength. It can be set larger reliably than R2.

Further, since the second leak ratio LR2 is larger than the third leak ratio LR3, the second attenuation ratio R2 is surely set larger than the third attenuation ratio R3 of the light of the third wavelength shorter than the second wavelength. can do.

As a result, with the configuration in which the first leak ratio LR1, the second leak ratio LR2, and the third leak ratio LR3 are reduced in that order, the intensities of the three lights emitted from the emission surface can be made uniform uniformly.

The present invention (7) is characterized in that the core is disposed on the upstream side in the transmission direction of the merging portion, and the first core portion for transmitting the light of the first wavelength incident on the first incident surface; A second core portion for transmitting the light of the second wavelength incident on the second incident surface, and a second core portion for transmitting the light of the second wavelength; And the third core portion transmitting the light of the third wavelength incident on the first and second core portions, the opening cross-sectional area of the first core portion and the second core portion being smaller toward the downstream side in the transmission direction. The third core portion has a shape in which the cross-sectional area of the opening decreases as the downstream side in the transmission direction decreases, or the cross-sectional area of the third core portion has the same shape. First open cross-sectional area OS at the downstream end of the transmission direction facing the Is smaller than a second opening cross-sectional area OS2 at the downstream end edge of the transmission direction facing the junction in the second core portion, and the second opening cross-sectional area OS2 is merged at the third core portion The optical waveguide according to any one of (1) to (6), which is smaller than the third opening cross-sectional area OS3 at the downstream end in the transmission direction facing the part.

In this optical waveguide, since the first opening cross-sectional area OS1 is smaller than the second opening cross-sectional area OS2, the first leak ratio LR1 can be set larger than the second leak ratio LR2.

Further, since the second opening cross-sectional area OS2 is smaller than the third opening cross-sectional area OS3, the second leak ratio LR2 can be set larger than the third leak ratio LR3.

As a result, the first leakage ratio LR1, the second leakage ratio LR2, and the third leakage are obtained with a simple configuration in which the first opening sectional area OS1, the second opening sectional area OS2, and the third opening sectional area OS3 are reduced in that order. The ratio LR3 can be reduced in that order.

In the invention (8), both of the first incident surface and the second incident surface are deviated from the exit surface when light is projected in a direction in which light is incident on the first incident surface and the second incident surface. And the third incident surface is disposed at the same position or at the same position as the exit surface when light is projected in a direction in which the light is incident on the third incident surface. The first light path from the entrance surface to the exit surface has a first bend, and the second light path from the second entrance surface to the exit surface in the core has a second bend, and the core The third optical path from the third incident surface to the exit surface in the second embodiment has a straight portion or a third curved portion, and the first curved portion is greatly bent with respect to the second curved portion, The bending portion is largely bent with respect to the third bending portion, in any one of (1) to (6) Re comprises or optical waveguide according to an item.

In this optical waveguide, since the first bent portion is greatly bent with respect to the second bent portion, the first leak ratio LR1 can be set larger than the second leak ratio LR2.

In addition, since the second curved portion is greatly bent with respect to the third curved portion, the second leakage ratio LR2 can be set larger than the third leakage ratio LR3.

As a result, a simple configuration in which the first bending portion and the second bending portion are enlarged in that order, or a simple configuration in which the first bending portion, the second bending portion and the third bending portion are enlarged in that order Thus, the first leak ratio LR1, the second leak ratio LR2, and the third leak ratio LR3 can be reduced in that order.

The present invention (9) is characterized in that the core comprises: a first light absorbing agent partially absorbing the light of the first wavelength; and a second light absorbing agent partially absorbing the light of the second wavelength, The first attenuation ratio R1 is larger than the second attenuation ratio R2, and the second attenuation ratio R2 is larger than the third attenuation ratio R3. The optical waveguide according to any one of the above.

The core has a first light absorbing agent and a second light absorbing agent, and the first attenuation ratio R1 is larger than the second attenuation ratio R2, and the second attenuation ratio R2 is higher than the third attenuation ratio R3. Contain to be large. Therefore, the intensities of the three lights emitted from the emission surface can be made uniform.

The present invention (10) allows the light of the first wavelength to be incident on the first incident surface, and causes the light of the second wavelength having the same intensity as the light of the first wavelength to be incident on the second incident surface. When the light of the third wavelength having the same intensity as the light of the second wavelength is made incident on the third incident surface, the first intensity I1 of the light of the first wavelength emitted from the emission surface, A ratio (I1 / I2) of the light of the second wavelength to the second intensity I2 is 0.6 or more and 1.4 or less, and a third intensity I3 of the light of the third wavelength of the first intensity I1. The optical waveguide according to any one of (1) to (9), which has a ratio (I1 / I3) to is not less than 0.6 and not more than 1.4.

In this optical waveguide, the ratio (I1 / I2) of the first intensity I1 of the light of the first wavelength to the second intensity I2 of the light of the second wavelength is 0.6 or more and 1.4 or less. Since the ratio (I1 / I3) of the intensity I1 to the third intensity I3 of the light of the third wavelength is 0.6 or more and 1.4 or less, three lights can be emitted with uniform intensity.

According to the optical waveguide of the present invention, three lights can be incident easily and accurately, and while combining them, it is possible to emit combined light having excellent optical characteristics.

FIG. 1 shows a plan view of a first embodiment of the optical waveguide of the present invention. 2A and 2B show a front view and a rear view of the optical waveguide shown in FIG. 1, and FIG. 2A is a front view seen from the upstream side in the light transmission direction, and FIG. 2B is seen from the downstream side in the light transmission direction Shows a rear view. 3A to 3C are plan views highlighting each optical path in the optical waveguide shown in FIG. 1, where FIG. 3A is a plan view highlighting the first optical path, and FIG. 3B highlights the second optical path A plan view, FIG. 3C shows a plan view highlighting the third optical path. FIG. 4 shows a plan view of a modification of the optical waveguide shown in FIG. FIG. 5 shows a plan view of a modification of the optical waveguide shown in FIG. FIG. 6 shows a plan view of a modification of the optical waveguide shown in FIG. FIG. 7 shows a plan view of a second embodiment of the optical waveguide of the present invention. FIG. 8 shows a plan view of a third embodiment of the optical waveguide of the present invention. FIG. 9 shows a plane of a modification of the optical waveguide shown in FIG. FIG. 10 shows a perspective view of a core forming the basic configuration of the present invention.

First Embodiment
A first embodiment of the optical waveguide of the present invention will be described with reference to FIGS. 1 to 3C. In FIGS. 1 and 3A, 3B, and 3C, the over clad 4 (described later) is omitted to clearly show the arrangement of the core 2 (described later).

The optical waveguide 10 is an optical coupling device that receives three (three) types of light having different wavelengths, merges them, and then emits one merged light.

As shown in FIGS. 1 and 2A and 2B, the optical waveguide 10 has a substantially rectangular shape in a plan view, and may be referred to simply as a transmission direction (hereinafter referred to simply as the transmission direction). .
In the form of a sheet (or in the form of a substantially plate). Specifically, the optical waveguides 10 face each other in the width direction (hereinafter simply referred to as the width direction) orthogonal to the transmission direction and the thickness direction with the upstream end face 5 and the downstream end face 6 facing each other in the transmission direction. A width direction one side end surface 7 and a width direction other side end surface 8 connecting the width direction both end edges of the upstream side end surface 5 and the downstream side end surface 6 are provided.

The upstream end surface 5 is a side surface extending in the width direction.

The downstream end surface 6 is a side surface along the width direction. The downstream end surface 6 is parallel to the upstream end surface 5.

The width direction one side end surface 7 and the width direction other side end surface 8 are side surfaces opposed in the width direction. The width direction one side end surface 7 and the width direction other side end surface 8 are parallel to each other along the transmission direction.

The optical waveguide 10 further has a flat upper surface 55 and a lower surface 56.

The optical waveguide 10 is a strip type optical waveguide, and includes a clad 1 and a core 2 embedded in the clad 1.

The cladding 1 has the same shape as the optical waveguide 10 when projected in the thickness direction. The clad 1 has a substantially sheet shape having a substantially rectangular shape in a plan view. Specifically, the cladding 1 includes an undercladding 3 and an overcladding 4 disposed on the undercladding 3.

The under cladding 3 is a lower layer in the cladding 1 and forms the lower surface 56 of the optical waveguide 10.

The over clad 4 is an upper layer in the clad 1 and forms the upper surface 55 of the optical waveguide 10. The lower surface of the overcladding 4 is in contact with the upper surface and the side surface of the core 2 described below.

Examples of the material of the clad 1 include transparent resins such as epoxy resins. The thickness of the cladding 1 is the same as the thickness of the optical waveguide 10 and is the total thickness of the undercladding 3 and the overcladding 4. The thickness of the cladding 1 is, for example, 10 μm or more, preferably 50 μm or more, and for example, 1000 μm or less, preferably 200 μm or less.

The core 2 is embedded in the cladding 1. Specifically, the core 2 is disposed on the upper surface of the undercladding 3 and covered with the overcladding 4.

The core 2 has three light paths (a first light path 21 (see highlight in FIG. 3A), a second light path 22 (see highlight in FIG. 3B), and a third light path 23 (see FIG. 3C). A part), a merging part 16 where three optical paths merge, and a combined channel 25 arranged on the downstream side in the transmission direction thereof.

The thickness T (vertical length) of the core 2 is the same in any part. The thickness T of the core 2 is, for example, 5 μm or more, preferably 10 μm or more, and for example, 500 μm or less, preferably 100 μm or less.

As shown in FIGS. 3A to 3C, the three optical paths are optical paths transmitting three lights having different wavelengths, and are a first optical path 21, a second optical path 22, and a third optical path 23. The first light path 21 transmits the first light, the second light path 22 transmits the second light, and the third light path 23 transmits the third light.

The first light is light having a relatively long first wavelength, and includes, for example, light having a wavelength of 580 nm or more, preferably 600 nm or more and 700 nm or less, and specifically includes red light. The second light is light of a second wavelength shorter than the first wavelength, for example, less than 580 nm, preferably less than 550 nm, and includes, for example, light of 485 nm or more, preferably 500 nm or more, In fact, it contains green light. The third light is light of a third wavelength shorter than the second wavelength, and includes, for example, light less than 485 nm, preferably 470 nm or less, and for example, 400 nm or more, preferably 420 nm or more, In fact, it contains blue light.

The end face on the upstream side in the transmission direction of the first optical path 21 is the first incident surface 11 and is exposed from the tapered surface 9. Specifically, the first incident surface 11 is flush with the tapered surface 9. The first incident surface 11 is an incident surface on which the first light enters the first light path 21.

As shown in FIG. 2A, the first incident surface 11 has a substantially rectangular shape when viewed from the upstream side in the transmission direction (hereinafter referred to as a front view). Further, the first area S1 of the first incident surface 11 is a value obtained by multiplying the thickness T of the core 2 by the width W1 along the tapered surface 9.

As shown in FIG. 3A, the first light path 21 includes a first core portion 26 including the first incident surface 11. The first core portion 26 is located at the upstream end of the first optical path 21 in the transmission direction. The first core portion 26 is an optical path for transmitting only the first light incident on the first incident surface 11 in the first optical path 21. The first core portion 26 has a substantially linear shape extending from the first incident surface 11 toward the downstream side in the transmission direction. Note that the transmission direction is based on the transmission direction of light in the total merging channel 30 described later. Specifically, the first core portion 26 extends toward one side in the transmission direction diagonal width direction, and more specifically, in the transmission direction so as to approach the width direction one side end surface 7 as proceeding to the transmission direction downstream side It is inclined against. A merging portion 16 to be described next is disposed at the downstream end of the first core portion 26 in the transmission direction, and in the first optical path 21, a combined channel 25 described later on the downstream side in the transmission direction of the merging portion 16. (Described later) is arranged.

As shown in FIG. 3B, the transmission direction upstream end surface of the second optical path 22 is the second incident surface 12 and is exposed from the upstream end surface 5. The second incident surface 12 is flush with the upstream end surface 5. The second incident surface 12 is disposed on one side in the width direction of the first incident surface 11 at an interval. The second incident surface 12 is an incident surface on which the second light enters the second optical path 22.

As shown in FIG. 2A, the second incident surface 12 has the same shape as the first incident surface 11. Therefore, the second area S2 of the second incident surface 12 is the same as the first area S1, and specifically, it is a value obtained by multiplying the thickness T of the core 2 by the width W2 along the upstream end surface 5 . Specifically, since the thickness T of the core 2 is the same in the first optical path 21 and the second optical path 22, the width W2 of the second incident surface 12 and the width W1 of the first incident surface 11 are the same. .

Further, as shown in FIG. 3B, the second optical path 22 includes a second core portion 27 including the second incident surface 12. The second core portion 27 is located at the upstream end of the second optical path 22 in the transmission direction. The second core portion 27 is an optical path for transmitting only the second light incident on the second incident surface 12 in the second optical path 22. The second core portion 27 has a substantially linear shape extending straight from the second incident surface 12 toward the downstream side in the transmission direction. A merging portion 16 to be described next is disposed at the downstream end of the second core portion 27 in the transmission direction, and in the second optical path 22 downstream of the merging portion 16 in the transmission direction, the first optical path 21 is A common combined channel 25 (described later) is disposed.

As shown in FIG. 3C, the transmission direction upstream end surface of the third optical path 23 is the third incident surface 13 and is exposed from the upstream end surface 5. Specifically, the third incident surface 13 is flush with the upstream end surface 5. The third incident surface 13 is disposed on one side in the width direction of the second incident surface 12 at an interval. That is, the third incident surface 13 is spaced apart from the first incident surface 11 and the second incident surface 12 on one side in the width direction. The third incident surface 13 is an incident surface on which the third light enters the third optical path 23.

As shown in FIG. 2A, the third incident surface 13 has the same shape as the second incident surface 12. Therefore, the third area S3 of the third incident surface 13 is the same as the second area S2, and specifically, it is a value obtained by multiplying the thickness T of the core 2 by the width W3 along the upstream end surface 5 . Specifically, since the thickness T of the core 2 is the same in the second optical path 22 and the third optical path 23, the width W3 of the third incident surface 13 and the width W2 of the second incident surface 12 are the same. . That is, the first area S1 of the first incident surface 11, S2 of the second incident surface 12, and S3 of the third incident surface 13 are the same.

As shown in FIG. 3C, the third light path 23 includes the third core portion 28 including the third incident surface 13. The third core unit 28 is located at the upstream end of the third optical path 23 in the transmission direction. The third core portion 28 is an optical path for transmitting only the third light incident on the third incident surface 13 in the third optical path 23. The third core portion 28 has a substantially linear shape extending straight from the third incident surface 13 toward the downstream side in the transmission direction. A merging portion 16 to be described next is disposed at the downstream end of the third core portion 28 in the transmission direction, and in the third optical path 23, on the downstream side of the merging portion 16 in the transmission direction, the first optical path 21 and A combined flow passage 25 (second combined portion 18) common to the second optical path 22 is disposed.

As shown in FIG. 1 and FIGS. 3A to 3C, the merging portion 16 independently includes a first merging portion 17 and a second merging portion 18.

The first joining portion 17 is a portion where the first optical path 21 and the second optical path 22 are merged for the first time, and the downstream end of the first core portion 26 in the transmission direction and the downstream side of the second core portion 27 in the transmission direction It is a part where the ends gather. In other words, the first merging portion 17 is disposed at the downstream end of the first core portion 26 and the second core portion 27 in the transmission direction. That is, the first merging portion 17 is disposed downstream of the first incident surface 11 and the second incident surface 12 in the transmission direction. In the first merging portion 17, the first light and the second light merge.

The second merging portion 18 is disposed at an interval downstream of the first merging portion 17 in the transmission direction. Specifically, the second merging portion 18 is disposed downstream of the first merging portion 17 in the transmission direction via the intermediate combined channel 29 on the downstream side of the transmission direction where the first optical path 21 and the second optical path 22 merge. ing. The second merging portion 18 is a portion where the first optical path 21, the second optical path 22 and the third optical path 23 are merged for the first time, and the downstream end of the intermediate combined channel 29 (described later) in the transmission direction and the third core The downstream end of the transmission direction of the unit 28 is a part where it gathers. In other words, the second merging portion 18 is disposed at the downstream end of the intermediate combined flow passage 29 and the third core portion 28 in the transmission direction. That is, the second merging portion 18 is disposed on the downstream side in the transmission direction of the first incident surface 11, the second incident surface 12, and the third incident surface 13. In the second merging portion 18, the first light, the second light and the third light merge for the first time.

The combined channel 25 includes an intermediate combined channel 29 and a total combined channel 30.

The middle combined channel 29 is disposed between the first joining portion 17 and the second joining portion 18 and optically connects (connects) them. The intermediate combined channel 29 is an optical path common to the central portion in the transmission direction of the first optical path 21 and the central portion in the transmission direction of the second optical path 22. The middle combined channel 29 is disposed on the extension of the first core portion 26 and has the same shape as the first core portion 26. On the other hand, the intermediate combined flow passage 29 has an angle with respect to the second core portion 27, and the angle Y formed between the intermediate combined flow passage 29 and the second core portion 27 is, for example, 170 degrees or more, preferably 175 The degree is more than 177 degrees, more preferably, for example, less than 180 degrees.

The total merging channel 30 is disposed downstream of the second merging portion 18 in the transmission direction, and is optically connected (connected) to the second merging portion 18. The total merging channel 30 is an optical path common to the downstream end of the first optical path 21 in the transmission direction, the downstream end of the second optical path 22 in the transmission direction, and the downstream end of the third optical path 23 in the transmission direction. The entire combined flow passage 30 is disposed on an extension of the third core portion 28 and has the same shape as the third core portion 28. On the other hand, the total joint flow channel 30 has an angle with respect to the intermediate joint flow channel 29, and the angle Z formed between the total joint flow channel 30 and the intermediate joint channel 29 is, for example, 170 degrees or more, preferably 175 degrees or more More preferably, it is 177 degrees or more, for example, less than 180 degrees.

As shown to FIG. 1 and FIG. 2B, the transmission direction downstream end surface of the total joint flow path 30 is the output surface 14. The exit surface 14 is disposed on the downstream side in the transmission direction of the second merging portion 18 (the merging portion 16). In addition, the emission surface 14 is exposed from the downstream end surface 6. Specifically, the exit surface 14 is flush with the downstream end surface 6. The emitting surface 14 emits the totally merged light (described later) merged at the second merging portion 18 (the merging portion 16).

Therefore, the core 2 includes the first incident surface 11, the second incident surface 12, the third incident surface 13, and the exit surface 14, and further, the first joining portion 17 and the second joining portion 18 Prepare. Therefore, light incident on each of the first incident surface 11, the second incident surface 12, and the third incident surface 13 merges at the first merging portion 17 and the second merging portion 18 (merging portion 16), and then exits. It is emitted from 14.

The first incident surface 11, the second incident surface 12, and the third incident surface 13 of the core 2 are all disposed on the upstream end surface 5 of the optical waveguide 10, while the output surface 14 of the core 2 is an optical waveguide. 10 is disposed at the downstream end face 6. Further, when projected in the transmission direction, the third incident surface 13 overlaps (is located at the same position) as the emission surface 14, while the first incident surface 11 and the second incident surface 12 have the above-described transmission direction. (Specifically, when projected in the direction in which the third light is transmitted), the light does not overlap with the exit surface 14 and is shifted to the other side in the width direction, and the first entrance surface 11 is further against the second entrance surface 12 , Located far away.

As shown in FIGS. 3A to 3C, therefore, the length L1 of the first optical path 21, that is, the first optical path length L1 from the first incident surface 11 to the exit surface 14 is the length L2 of the second optical path 22. That is, the second optical path length L2 from the second incident surface 12 to the exit surface 14 is longer (L1> L2), and the second optical path length L2 is the length L3 of the third optical path 23, that is, The third optical path length L3 from the third incident surface 13 to the exit surface 14 is long (L2> L3). That is, L1> L2> L3 is satisfied.

The ratio (L1 / L2) of the first optical path length L1 to the second optical path length L2 is, for example, 1.001 or more, preferably 1.01 or more, more preferably 1.1 or more, and, for example, 2 or less.

Further, the ratio (L2 / L3) of the second optical path length L2 to the third optical path length L3 is, for example, 1.001 or more, preferably 1.01 or more, more preferably 1.1 or more, and For example, 2 or less.

Furthermore, the ratio (L1 / L3) of the first optical path length L1 to the third optical path length L3 is, for example, 1.002 or more, preferably 1.02 or more, more preferably 1.15 or more, , For example, 3 or less.

Examples of the material of the core 2 include a transparent resin of the same material as that of the clad 1. The refractive index of the core 2 is higher than that of the cladding 1. In addition, the refractive index and the light transmittance of the core 2 are uniformly adjusted in the transmission direction. That is, the core 2 is optically homogeneous over the transmission direction.

In order to obtain the optical waveguide 10, for example, first, the undercladding 3 is prepared, and then the core 2 is formed on the top surface of the undercladding 3 by photo processing or the like, and then the overcladding 4 is formed on the top surface of the core 2 And the upper surface of the undercladding 3 so as to cover the side surfaces.

Then, in the optical waveguide 10, for example, each of the first light, the second light and the third light is incident from the light emitting device 65 to each of the first incident surface 11, the second incident surface 12 and the third incident surface 13. Let

The light emitting device 65 includes a first light emitting unit 61 that emits a first light, a second light emitting unit 62 that emits a second light, and a third light emitting unit 63 that emits a third light.

The first light emitting unit 61 generally faces the first light incident surface 11. Specifically, the first light emitting unit 61 is disposed to face the first incident surface 11 in the direction along the first light path 26 in the first core unit 26. However, the emission side surface of the first light emitting portion 61 is not parallel to the first incident surface 11 but obliquely opposed.

The second light emitting unit 62 is disposed to face the second incident surface 12 in the transmission direction.

The third light emitting unit 63 is disposed to face the third incident surface 13 in the transmission direction.

As described above, the light emitting device 65 is positioned with respect to the upstream end surface 5.

Then, the first light, the second light, and the third light are transmitted along the first light path 21, the second light path 22, and the third light path 23, respectively, and join at the merging portion 16 along the way. , And are emitted from the emission surface 14 together.

Specifically, the first light transmitted from the first incident surface 11 in the first core portion 26 and the second light transmitted from the second incident surface 12 in the second core portion 27 are the first merging portion At 17, merge to combine the intermediate merge light.

The intermediate merging light and the third light transmitted from the third incident surface 13 in the third core unit 28 merge in the second merging portion 18 to combine all merging light.

All combined light is transmitted in all combined channels 30 and then emitted from the exit surface 14.

Then, since the optical path lengths of the first optical path 21, the second optical path 22 and the third optical path 23 satisfy L1> L2> L3, the first light incident on the first incident surface 11 and emitted from the emission surface 14 The first attenuation ratio R1 is larger than the second attenuation ratio R2 of the second light emitted to the second incident surface 12 and emitted from the emission surface 14, and the second attenuation ratio R2 described above is It is larger than the third attenuation ratio R3 of the third light which is incident on the third incident surface 13 and emitted from the emission surface 14.

That is, the following formula (1) is satisfied.

First damping ratio R1> second damping ratio R2> third damping ratio R3 (1)
On the other hand, when Formula (1) is not satisfied, the intensities of the three lights emitted from the emission surface 14 can not be made uniform.

The ratio (R1 / R2) of the first attenuation ratio R1 of the first light to the second attenuation ratio R2 of the second light is, for example, 1.001 or more, preferably 1.01 or more, more preferably 1. It is one or more and, for example, two or less.

The ratio (R2 / R3) of the second attenuation ratio R2 of the second light to the third attenuation ratio R3 of the third light is, for example, 1.001 or more, preferably 1.01 or more, more preferably 1. It is one or more and, for example, two or less.

The ratio (R1 / R3) of the first attenuation ratio R1 of the first light to the third attenuation ratio R3 of the third light is, for example, 1.002 or more, preferably 1.02 or more, more preferably 1. 15 or more and, for example, 3 or less.

If the above-described ratio is equal to or more than the above-described lower limit, the intensities of the three lights emitted from the emission surface 14 can be made uniform.

Therefore, the first light is made incident on the first incident surface 11, the second light having the same intensity as the first light is made incident on the second incident surface 12, and the third light having the same intensity as the second light is made third The ratio (I1 / I2) of the first intensity I1 of the first light emitted from the emission surface 14 to the second intensity I2 of the second light when entering the incident surface 13 is 0.6 or more, 1 The ratio (I1 / I3) of the first intensity I1 to the third intensity I3 of the third light is 0.6 or more and 1.4 or less.

The ratio (I1 / I2) of the first strength I1 to the second strength I2 and the ratio (I1 / I3) of the first strength I1 to the third strength I3 are preferably 0.8 or more, more preferably 0.9 or more, and preferably 1.2 or less, more preferably 1.1 or less.

If the above-mentioned intensity ratio is more than the above-mentioned lower limit and below the upper limit, three lights can be emitted with uniform intensity.

And in this optical waveguide 10, each of the 1st light, the 2nd light, and the 3rd light enters into the 1st entrance plane 11, the 2nd entrance plane 12, and the 3rd entrance plane 13, and the 2nd junction part 18 ( In the merging section 16), the three lights are merged, and the three lights are emitted from the emission surface.

In addition, since the first area S1 of the first incident surface 11, the second area S2 of the second incident surface 12, and the third area S3 of the third incident surface 13 are the same, the light emitting device 65 and the The first incident surface 11, the second incident surface 12, and the third incident surface 13 can be easily aligned, and both can be easily optically connected.

Furthermore, the first attenuation ratio R1 of the first light is larger than the second attenuation ratio R2 of the second light whose wavelength is shorter than that of the first light, and the second attenuation ratio R2 has a wavelength shorter than that of the second light. As compared with the third attenuation ratio R3 of light, which is larger (R1> R2> R3), the intensities of the three lights emitted from the emission surface 14 can be made uniform.

As a result, in the optical waveguide 10, the three light beams of the first light, the second light and the third light are easily and accurately incident and, while combining them, emit all the combined light with excellent optical characteristics. Can.

In the optical waveguide 10, since the first light contains red light, the second light contains green light, and the third light contains blue light, red light, green light and blue light are emitted from the emission surface 14 Can be emitted with uniform intensity. Therefore, it is possible to emit all the combined light having a desired hue.

In the optical waveguide 10, the first light and the second light are joined in the first joining portion 17, and the third light which is the remaining light in the second joining portion 18 and the intermediate which is joined in the first joining portion 17 Since the merging light and the merging light are merged, the number of merging can be increased to make the light uniform.

In the optical waveguide 10, since the first optical path length L1 is longer than the second optical path length L2, the first attenuation ratio R1 of the first light is surely larger than the second attenuation ratio R2 of the second light. It can be set.

In addition, since the second optical path length L2 is longer than the third optical path length L3, the second attenuation ratio R2 can be reliably set larger than the third attenuation ratio R3 of the third light.

As a result, with a simple configuration in which the first optical path length L1, the second optical path length L2, and the third optical path length L3 are shortened in that order, the intensities of the three lights emitted from the emission surface 14 are made uniform uniformly. be able to.

In the optical waveguide 10, the ratio (I1 / I2) of the first intensity I1 of the first light to the second intensity I2 of the second light is 0.6 or more and 1.4 or less, and the first intensity I1 and Since the ratio (I1 / I3) of the third intensity I3 of the third light is not less than 0.6 and not more than 1.4, the three lights can be emitted with uniform intensity.

<Modification>
In the following modifications, the same members as those in the first embodiment described above are denoted by the same reference numerals, and the detailed description thereof will be omitted. Further, each modification can exhibit the same function and effect as those of the first embodiment except for the special mention.

The first area S1 of the first incident surface 11, the second area S2 of the second incident surface 12, and the third area S3 of the third incident surface 13 may be substantially the same, for example, the light emitting device 65 described above There may be minute differences that do not interfere with the positioning of the first incident surface 11, the second incident surface 12, and the third incident surface 13. Specifically, the width W1 of the first incident surface 11, the width W2 of the second incident surface 12, and the width W3 of the third incident surface 13 may be substantially the same, and more specifically, W1 / W2 and W1 / W3 is, for example, 0.9 or more, preferably 0.95 or more, and for example, a range of 1.1 or less, preferably 1.01 or less is acceptable.

In the first embodiment, the first light path 21 and the second light path 22 are united in the first merging portion 17 and the first light and the second light are merged. However, the first light and the second light are combined. And any two of the third lights may be merged. Although not shown, in the first merging portion 17, for example, the first light path 21 and the third light path 23 may be united, and the first light and the third light may be merged, for example, the second light path 22 and The third light path 23 may be integrated, and the second light and the third light may be merged.

Further, the core 2 has a first light absorbing agent that partially absorbs the first light and a second light absorbing agent that partially absorbs the second light, and the first attenuation ratio R1 is a second attenuation ratio R2 And the second damping ratio R2 may be larger than the third damping ratio R3.

Examples of the first light absorber include red light absorbers. Specifically, anthraquinone compounds, phthalocyanine compounds, cyanine compounds, polymethylene compounds, aluminum compounds, diimonium compounds, and imonium compounds And azo compounds.

Examples of the second light absorber include green light absorbers, and specific examples include anthraquinone compounds, phthalocyanine compounds and the like.

Furthermore, in addition to the first light absorber and the second light absorber, the core 2 has a third light absorber that partially absorbs the third light, and the second attenuation ratio R2 is compared to the third attenuation ratio R3. It can also be contained to be large.

Examples of the third light absorber include blue light absorbers, and specific examples include benzotriazole-based compounds, benzophenone-based compounds, salicylic acid-based compounds, and coumarin-based compounds.

The content ratio of the first light absorber and the second light absorber is appropriately adjusted so as to satisfy the relationship of first attenuation ratio R1> second attenuation ratio R2> third attenuation ratio R3.

And in this modification, the core 2 satisfies the relationship of the first light absorbing agent and the second light absorbing agent such that the first attenuation ratio R1> the second attenuation ratio R2> the third attenuation ratio R3. ,contains. Therefore, the intensities of the three lights emitted from the emission surface 14 can be made uniform.

In the first embodiment, the upstream end surface 5 is configured as one plane (side surface). However, as shown in FIG. 4, the tapered surface 9 can be formed on the upstream end surface 5.

In this modification, the other end in the width direction of the upstream end surface 5 is obliquely cut, whereby the tapered surface 9 is formed. An angle X between the tapered surface 9 and the widthwise central portion and the widthwise one end portion at the upstream end surface 5 is an obtuse angle, and is set such that the tapered surface 9 is parallel to a third incident surface 13 described later. Specifically, for example, it is 170 degrees or more, preferably 175 degrees or more, more preferably 177 degrees or more, and for example, less than 180 degrees.

The first area S1 of the first incident surface 11 is the same as the second area S2 of the second incident surface 12 and the third area S3 of the third incident surface 13, and the width W1 of the first incident surface 11 is , And the length in the direction along the tapered surface 9.

The first light emitting portion 61 is disposed to face the tapered surface 9 including the first incident surface 11.

In the first embodiment, the merging portion 16 includes two of the first merging portion 17 and the second merging portion 18. However, as shown in FIG. 5, the number of merging portions 16 may be one. Specifically, the merging portion 16 has only the total merging portion 19 where three of the first light, the second light and the third light merge.

The full merging portion 19 is a portion where the downstream end of the first core portion 26 in the transmission direction, the downstream end of the second core portion 27 in the transmission direction, and the downstream end of the third core portion 28 in the transmission direction gather It is. In the total merging section 19, three of the first light, the second light, and the third light merge to combine all merged light.

Further, the combined channel 25 does not include the intermediate combined channel 29 (see FIG. 1), and includes only the entire combined channel 30. The total merging channel 30 transmits the total combined light combined in the total merging section 19 toward the exit surface 14.

The second core portion 27 has a shape that extends from the second incident surface 12 toward the overall combined flow channel 30. Further, the second core portion 27 is inclined in the same manner as the first core portion 26. However, the degree of inclination of the second core portion 27 is smaller than the degree of inclination of the first core portion 26. Specifically, the inclination degree of the second core portion 27 (specifically, the second core portion 27) The ratio (the angle α1 between the first core portion 26 and the first core portion 26) (specifically, the ratio α of the angle α2) between the portion 27 and the first core portion 26 (specifically, the angle α1 between the first core portion 26 and the first core portion 26) α 2 / α 1) is, for example, 0.9 or less, preferably 0.8 or less, more preferably 0.7 or less, and for example, 0.1 or more.

Moreover, as shown in FIG. 6, the upstream end surface 5 can also be formed in a substantially step shape in plan view. The upstream end surface 5 is independently provided with a first surface 51 including the first incident surface 11, a second surface 52 including the second incident surface 12, and a third surface 53 including the third incident surface 13.

When projected in the width direction, the first surface 51, the second surface 52, and the third surface 53 are arranged at an interval in the transmission direction, and are arranged downstream in the transmission direction in this order . Therefore, in the upstream end surface 5, the first surface 51 is disposed farthest from the downstream end surface 6, and the third surface 53 is disposed closest to the downstream end surface 6. The second surface 52 is located between the first surface 51 and the third surface 53. The first surface 51, the second surface 52, and the third surface 53 are all parallel to the downstream end surface 6 along the width direction.

The first surface 51 includes a first incident surface 11.

The second surface 52 includes a second incident surface 12.

The third surface 53 includes the third incident surface 13.

Therefore, L1> L2> L3 can be satisfied more reliably.

Specifically, (L1 / L2) is, for example, 1.01 or more, preferably 1.1 or more, more preferably 1.2 or more, and for example, 5 or less.

Further, the ratio (L2 / L3) of the second optical path length L2 to the third optical path length L3 is, for example, 1.01 or more, preferably 1.1 or more, more preferably 1.2 or more, and For example, 5 or less.

Furthermore, the ratio (L1 / L3) of the first optical path length L1 to the third optical path length L3 is, for example, 1.02 or more, preferably 1.2 or more, more preferably 1.3 or more, and For example, it is 10 or less.

Second Embodiment
In the following second embodiment, the same members as those in the first embodiment and the modification thereof are denoted by the same reference numerals, and the detailed description thereof will be omitted. In addition, the second embodiment can exhibit the same effects as those of the first embodiment and the modified example thereof, unless otherwise specified.

In the first embodiment and its modification, the first optical path length L1 of the first optical path 21, the second optical path length L2 of the second optical path 22, and the third optical path length L3 of the third optical path 23 are L1> L2>. It is set to satisfy L3. Thereby, the equation (1) [first attenuation ratio R1> second attenuation ratio R2> third attenuation ratio R3] is satisfied.

On the other hand, in the second embodiment, as shown in FIG. 7, the first leak ratio LR1 of the first light, the second leak ratio LR2 of the second light, and the third leak ratio LR3 of the third light, LR1> LR2> It is also possible to set so as to satisfy LR3 and to satisfy the above-mentioned equation (1).

Specifically, as shown in FIG. 7, the first core portion 26 and the second core portion 27 both have a shape in which the cross-sectional area of the opening decreases as going downstream in the transmission direction. More specifically, the first core portion 26 and the second core portion 27 have a substantially tapered shape in plan view, in which the respective widthwise side surfaces approach each other toward the downstream side in the transmission direction. The degree of inclination (the first angle β1 formed by the virtual surface along the side surface and the axis along the transmission direction) of the width direction both sides of the first core portion 26 with respect to the transmission direction Specifically, the ratio (β1 / β2) thereof is, for example, 1.001 or more, with respect to the inclination with respect to the direction (the angle β2 between the virtual plane along the side surface and the axis along the transmission direction). Preferably, it is 1.01 or more, more preferably 1.1 or more, and for example, 2 or less.

On the other hand, the third core portion 28 has the same shape in the opening cross-sectional area as it goes downstream in the transmission direction. Specifically, the third core portion 28 has a substantially linear shape in plan view along the transmission direction.

Therefore, in the second core portion 27, the first opening cross-sectional area OS1 at the downstream end (first downstream end 31) of the first core portion 26 in the transmission direction facing the first joining portion 17 (joining portion 16) is This is smaller than the second opening cross-sectional area OS2 at the downstream end of the transmission direction facing the first joining portion 17 (the joining portion 16). Specifically, the width W4 of the first downstream side edge 31 is narrower than the width W5 of the second downstream side edge 32.

Then, since the first core portion 26 and the second core portion 27 have a substantially tapered shape in plan view, each of the first light and the second light in each of the first core portion 26 and the second core portion 27 easily leaks Further, since the width W4 of the first downstream side edge 31 is narrower than the width W5 of the second downstream side edge 32, the leakage ratio of the first light in the first core portion 26 is equal to that in the second core portion 27. It is large with respect to the leak rate of the second light.

On the other hand, the leakage ratio of the first light and the leakage ratio of the second light in the intermediate combined flow passage 29 and the total combined flow passage 30 (the combined flow passage 25) are that the first light and the second light are transmitted along the common combined flow passage 25. From the same. Then, the first leak ratio LR1 when the first light is transmitted from the first incident surface 11 to the output surface 14 is the second leak ratio when the second light is transmitted from the second incident surface 12 to the output surface Larger than LR2.

Furthermore, the second opening cross-sectional area OS2 is smaller than the third opening cross-sectional area OS3 at the downstream end (third downstream end 33) of the third core portion 28 in the transmission direction facing the junction. Specifically, the width W5 of the second downstream side edge 32 is narrower than the width W6 of the third downstream side edge 33. Therefore, the leakage rate of the second light in the second core portion 27 is larger than the leakage rate of the third light in the third core portion 28.

On the other hand, the leakage ratio of the second light and the leakage ratio of the third light in the total combined flow channel 30 are the same because the second light and the third light are transmitted through the common combined flow channel 30 in common. Then, the second leakage ratio LR2 when the second light is transmitted from the second incident surface 12 to the outgoing surface outgoing surface 14 is the second leakage ratio LR2 when the third light is transmitted from the third incident surface 13 to the outgoing surface 14 3 Large for leak rate LR3.

That is, in the optical waveguide 10, the first leakage ratio LR1> the second leakage ratio LR2>
Satisfy the relationship of the third leak rate LR3.

Then, in the optical waveguide 10, since the first leakage ratio LR1 is larger than the second leakage ratio LR2, the first attenuation ratio R1 of the first light is set to the second attenuation of the second light having a wavelength shorter than the first light. The ratio can be set larger than the ratio R2 with certainty.

Further, since the second leak ratio LR2 is larger than the third leak ratio LR3, the second attenuation ratio R2 is surely set larger than the third attenuation ratio R3 of the third light having a wavelength shorter than that of the second light. can do.

As a result, with the configuration in which the first leak ratio LR1, the second leak ratio LR2, and the third leak ratio LR3 are reduced in that order, the intensities of the three lights emitted from the emission surface 14 can be made uniform uniformly. .

Furthermore, in the optical waveguide 10, since the first opening cross-sectional area OS1 is smaller than the second opening cross-sectional area OS2, the first leak ratio LR1 can be set larger than the second leak ratio LR2.

<Modification>
In the following modifications, the same members as those in the second embodiment described above are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. Further, each modification can exhibit the same function and effect as those of the second embodiment except for the special mention.

As shown in FIG. 7, in the second embodiment, the third core portion 28 has a substantially linear shape in plan view, but for example, although not shown, the width of the third downstream side edge 33 in the third core portion 28 If W6 is wider than the width W5 of the second downstream side edge 32 of the second core portion 27, the third core portion 28 may have a substantially tapered shape in plan view.

Third Embodiment
In the following third embodiment, the same members as those in the first embodiment, the second embodiment, and their modifications described above are given the same reference numerals, and detailed descriptions thereof will be omitted. In addition, the third embodiment can exhibit the same effects as those of the first embodiment, the second embodiment, and the modifications thereof, unless otherwise specified.

In the second embodiment and its modification, at least the first core portion 26 and the second core portion 27 are formed in a tapered shape. Thereby, the equation (1) [first attenuation ratio R1> second attenuation ratio R2> third attenuation ratio R3] is satisfied.

On the other hand, as shown in FIG. 8, in the third embodiment, each of at least the first optical path 21 and the second optical path 22 includes the first bending portion 36 and the second bending portion 37 which bends smaller than the first bending portion 36. Have. On the other hand, the third optical path 23 has only the third straight portion 50. Thereby, the above-mentioned formula (1) can also be satisfied.

Specifically, the first core portion 26 has a first straight portion 48 and a first curved portion 36.

The first linear portion 48 has a substantially linear shape in plan view extending along the direction in which the first light is incident from the first incident surface 11. At the downstream end of the first linear portion 48 in the transmission direction, a first curved portion 36 is continuous.

The first bending portion 36 curves relatively small in plan view. The first bent portion 36 has a first central portion 38 and a first downstream portion 39.

The first central portion 38 has a curvature center on one side in the width direction.

The first downstream portion 39 is disposed on the downstream side of the first central portion 38 in the transmission direction, and has a center of curvature on the other side in the width direction. The first downstream side portion 39 is disposed downstream of the first central portion 38 in the transmission direction, and is continuous with the entire combined flow passage 30.

The second core portion 27 has a second straight portion 49 and a second curved portion 37.

The second linear portion 49 has a substantially linear shape in plan view extending along the direction in which the second light is incident from the second incident surface 12. At the downstream end of the second linear portion 49 in the transmission direction, the second bending portion 37 is continuous.

The second bending portion 37 curves more than the first bending portion 36 in a plan view. The second bending portion 37 has a second central portion 40 and a second downstream portion 41.

The second central portion 40 has a curvature center on one side in the width direction, and curves more than the first central portion 38.

The second downstream side portion 41 is disposed on the downstream side of the second central portion 40 in the transmission direction, and curves more largely than the first downstream side portion 39. The second downstream side portion 41 has a curvature center on the other side in the width direction. The second downstream side portion 41 is continuous with the entire combined flow passage 30.

On the other hand, the third straight portion 50 includes the third incident surface 13 and is parallel to the one end surface 7 in the width direction.

And, in the optical waveguide 10 of the third embodiment, since the first curved portion 36 is largely bent with respect to the second curved portion 37, the first leakage ratio LR1 should be set larger than the second leakage ratio LR2. it can.

Further, since the third light path 23 includes the third straight portion 50, the second leak ratio LR2 can be set larger than the third leak ratio LR3.

<Modification>
In the third embodiment, the third core portion 28 includes the third straight portion 50. For example, although not shown, the third core portion 28 may have a third curved portion bent smaller than the second curved portion 37. In this case, the third incident surface 13 is disposed so as to be offset from the exit surface 14 when projected in the transmission direction.

Further, as shown in FIG. 9, each of the first curved portion 36 and the second curved portion 37 can be formed in a bent shape.

The first core portion 26 includes a first straight portion 48, a first curved portion 36, and a first downstream straight portion 35.

The first bent portion 36 has a substantially bent shape in plan view.

The first downstream linear portion 35 extends from the first curved portion 36 toward one side in the transmission direction diagonal width direction, and has a substantially linear shape having the same width as the first linear portion 48. The downstream end of the first downstream straight portion 35 is continuous with the entire combined flow passage 30.

The second optical path 22 includes a second straight portion 49, a second curved portion 37, and a second downstream straight portion 44.

The second bent portion 37 has a substantially bent shape bent smaller than the first bent portion 36 in a plan view.

The second downstream linear portion 44 extends from the second curved portion 37 toward one side in the transmission direction diagonal width direction, and has a substantially linear shape having the same width as the second linear portion 49. The downstream end of the second downstream straight section 44 is continuous with the entire combined channel 30.

The degree of bending in the first curved portion 36 is larger than the degree of bending in the second curved portion 37. Specifically, the angle γ1 formed between the first straight portion 48 and the first downstream side straight portion 35 Is smaller than an angle γ2 formed by the second straight portion 49 and the second downstream straight portion 44.

Further, as shown in FIG. 10, in the core 2 in which the first light path length L1 of the first light path 21, the second light path length L2 of the second light path 22, and the third light path length L3 of the third light path 23 are set the same. The first damping ratio R1, the second damping ratio R2, and the third damping ratio R3 can also be reduced in that order by the following means. In the core 2 shown in FIG. 10, the first core portion 26, the second core portion 27, and the third core portion 28 are connected to the all joining portion 19, and the lengths thereof are the same. Further, in the core 2 shown in FIG. 10, when projected in the transmission direction (specifically, the direction in which the upstream end surface 5 and the downstream end surface 6 face each other), the first incident surface 11, the second incident surface 12 and the third The incident surface 13 is disposed offset with respect to the output surface 14. For example, the first incident surface 11, the second incident surface 12, and the third incident surface 13 are disposed on an imaginary circle centered on an imaginary line along the axis of the combined channel 30.

Means (1): The length of the first core portion 26, the length of the second core portion 27, and the length of the third core portion 28 are shortened in that order.

Means (2): The first leakage ratio LR1, the second leakage ratio LR2, and the third leakage ratio by decreasing the first opening sectional area OS1, the second opening sectional area OS2, and the third opening sectional area OS3 in that order. Make LR3 smaller in that order.

Means (3): increasing the first bending portion 36 and the second bending portion 37 in that order, or enlarging the first bending portion 36, the second bending portion 37 and the third bending portion in that order Thus, the first leak ratio LR1, the second leak ratio LR2, and the third leak ratio LR3 are reduced in that order.

Means (4): The core 2 is made to contain the first light absorber, the second light absorber, and, if necessary, the third light absorber.

The above-described means can be combined as appropriate.

Each embodiment and each modification which were mentioned above can be combined suitably.
Although the above invention is provided as an exemplary embodiment of the present invention, this is merely an example and should not be interpreted in a limited manner. Variations of the invention which are apparent to those skilled in the relevant art are within the scope of the following claims.

Optical waveguides are used in optical applications.

REFERENCE SIGNS LIST 1 clad 2 core 11 first incident surface 12 second incident surface 13 third incident surface 14 exit surface 16 joining portion 17 first joining portion 18 second joining portion 19 total joining portion 26 first core portion 27 second core portion 28 Third core portion 36 first curved portion 37 second curved portion 42 straight portion I1 first intensity (first light)
I2 second intensity (second light)
I3 third intensity (third light)
L1 first optical path length L2 second optical path length L3 third optical path length LR1 first leakage ratio (first light)
LR2 Second leak rate (second light)
LR3 third leak rate (third light)
OS1 1st opening cross section (1st core part)
OS2 Second Opening Cross Section (Second Core)
OS3 Third Opening Cross Section (Third Core)
R1 1st attenuation ratio (1st light)
R2 second attenuation ratio (second light)
R3 3rd attenuation ratio (3rd light)
S1 1st area (1st entrance plane)
S2 Second area (second incident surface)
S3 third area (third incident surface)

Claims

A cladding and a core embedded in the cladding;
The core is
A first incident surface disposed on the upstream end surface in the light transmission direction, and light of the first wavelength enters the core;
A second incident light is disposed on the upstream end surface in the transmission direction so as to be spaced apart from the first incident surface in a direction intersecting the transmission direction, and light of a second wavelength shorter than the first wavelength is incident on the core The face,
At the upstream end face in the transmission direction, the core is disposed so as to be spaced apart from the first incident surface and the second incident surface in a direction intersecting the transmission direction, and the light of the third wavelength shorter than the second wavelength is the core The third incident surface to be incident on the
The first light incident surface, the second light incident surface, and the third light incident surface are disposed downstream of the transmission direction, and the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength merge At the confluence,
It is disposed on the downstream side in the transmission direction of the merging section, and has an emission surface from which the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength are emitted,
The first area S1 of the first incident surface, the second area S2 of the second incident surface, and the third area S3 of the third incident surface are approximately the same.
A first attenuation ratio R1 of the light of the first wavelength that is incident on the first incident surface and that is emitted from the output surface is incident on the second incident surface, and the second wavelength that is output from the output surface Is larger than the second attenuation ratio R2 of
An optical waveguide characterized in that the second attenuation ratio R2 is larger than a third attenuation ratio R3 of the light of the third wavelength that is incident on the third incident surface and emitted from the emission surface.
The light of the first wavelength comprises red light,
The light of the second wavelength comprises green light,
The optical waveguide according to claim 1, wherein the light of the third wavelength includes blue light.
The merging section is
A first merging portion in which any two of the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength merge;
The device according to claim 1, further comprising: a second merging portion disposed downstream of the first merging portion in the transmission direction and in which the remaining light and the light merged in the first merging portion merge. Optical waveguide as described.
The merging section is
The optical waveguide according to claim 1, further comprising: a total junction where three of the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength merge.
A first optical path length L1 from the first incident surface to the emission surface is longer than a second optical path length L2 from the second incident surface to the emission surface,
The optical waveguide according to claim 1, wherein the second optical path length L2 is longer than a third optical path length L3 from the third incident surface to the exit surface.
The first leak rate LR1 when the light of the first wavelength is transmitted from the first incident surface to the exit surface is that the light of the second wavelength is transmitted from the second incident surface to the light exit surface When compared to the second leak rate LR2,
The second leak ratio LR2 is larger than a third leak ratio LR3 when the light of the third wavelength is transmitted from the light third incident surface to the light exit surface. The optical waveguide as described in.
The core is
A first core portion disposed upstream of the merging portion in the transmission direction, and transmitting the light of the first wavelength incident on the first incident surface;
A second core portion disposed upstream of the merging portion in the transmission direction and transmitting the light of the second wavelength incident on the second incident surface;
And a third core section disposed upstream of the merging section in the transmission direction and transmitting the light of the third wavelength incident on the third incident surface.
The first core portion and the second core portion both have a shape in which the cross-sectional area of the opening decreases toward the downstream side in the transmission direction,
The third core portion has a shape in which the cross-sectional area of the opening decreases as it goes to the downstream side in the transmission direction, or the shape of the cross-sectional area of the opening is the same.
In the first core portion, a first opening cross-sectional area OS1 at the downstream end edge in the transmission direction facing the junction, a second opening cross section at the downstream end edge in the transmission direction facing the junction at the second core portion Small compared to area OS2,
The second opening cross-sectional area OS2 is smaller than the third opening cross-sectional area OS3 at the downstream end edge of the transmission direction facing the junction in the third core portion. Optical waveguide.
The first incident surface and the second incident surface are both deviated from the exit surface when light is projected in a direction in which the light is incident on the first incident surface and the second incident surface,
The third incident surface is disposed at the same position as or shifted from the exit surface when light is projected in a direction in which the light is incident on the third incident surface,
A first light path from the first incident surface to the exit surface in the core has a first bend,
A second light path from the second incident surface to the exit surface in the core has a second curved portion,
The third light path from the third incident surface to the exit surface in the core has a straight portion or a third curved portion,
The first bending portion is largely bent with respect to the second bending portion.
The optical waveguide according to claim 1, wherein the second curved portion is largely bent with respect to the third curved portion.
The core is
A first light absorbing agent partially absorbing the light of the first wavelength;
A second light absorbing agent that partially absorbs the light of the second wavelength;
The first attenuation rate R1 is larger than the second attenuation rate R2, and the second attenuation rate R2 is larger than the third attenuation rate R3.
The optical waveguide according to claim 1, characterized in that it contains.
Light of the first wavelength is incident on the first incident surface, light of the second wavelength having the same intensity as the light of the first wavelength is incident on the second incident surface, and light of the second wavelength When light of the third wavelength having the same intensity is incident on the third incident surface,
A ratio (I1 / I2) of the first intensity I1 of the light of the first wavelength emitted from the emission surface to the second intensity I2 of the light of the second wavelength is 0.6 or more and 1.4 or less Yes,
The ratio (I1 / I3) of the first intensity I1 to the third intensity I3 of the light of the third wavelength is 0.6 or more and 1.4 or less. Optical waveguide.