JP2004264631A - Optical switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an optical switch capable of reducing crosstalk. <P>SOLUTION: In the optical switch switching transmission pathways of an optical signal by a change in refractive index, an optical waveguide layer in which optical waveguides wherein the optical signal is made incident from one direction and branched on its way into two signals to be emitted are formed and light absorbing bodies formed at parts other than the parts where the optical waveguides are formed are provided. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
The present invention relates to an optical switch that switches a transmission path of an optical signal by a change in refractive index, and more particularly to an optical switch that can reduce crosstalk.
[0002]
[Prior art]
Current communication networks such as a LAN (Local Area Network) and a WAN (Wide Area Network) generally use a communication method of transmitting information using electric signals.
[0003]
Communication methods for transmitting information using optical signals are only used in backbone networks for transmitting large amounts of data and some other networks. In addition, these networks are “point to point” communications, and at present the communication networks that can be called “photonic networks” have not been developed.
[0004]
In order to realize such a “photonic network”, an “optical router” or “optical switching hub” having the same function as a device such as a router or a switching hub for switching a transmission destination of an electric signal is required. .
[0005]
Further, such a device requires an optical switch for switching a transmission path at high speed, and a device using a ferroelectric material such as lithium niobate or PLZT (Lead Lanthanum Zirconate Titanate) or a semiconductor using an optical path waveguide is formed. There is a type in which a carrier is injected into a semiconductor to change a refractive index to switch a transmission path of an optical signal.
[0006]
Further, recently, there is a type in which a switching operation is performed by generating heat with a heater integrated on a flat glass optical waveguide and changing a refractive index of a portion where the heater is formed.
[0007]
There are the following prior art documents relating to an optical switch in which an optical path waveguide is formed in a conventional semiconductor and a carrier is injected into the semiconductor to change a refractive index to switch a transmission path of an optical signal.
[0008]
[Patent Document 1]
JP-A-6-059294 [Patent Document 2]
JP-A-6-130236 [Non-Patent Document 1]
"2x2 Optical Waveguide Switch with Bow-Tie Electrode Based on Carrier-Injection Total Internal Reflection in SiGe Alloy", Baojun Li and Soo-Jin Chua, p206-p208, IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 13, NO. 3, MARCH 2001
[0009]
5 and 6 are a plan view and a cross-sectional view showing an example of such a conventional optical switch. In FIG. 5, 1 is an optical waveguide layer having an "X-shaped" optical waveguide, and 2 and 3 are a pair of electrodes for injecting carriers.
[0010]
In FIG. 5, an "X-shaped" optical waveguide is formed on the optical waveguide layer 1, and a rectangular electrode 2 is formed at the intersection of the "X-shaped" optical waveguide as indicated by "CP01" in FIG. Is formed. A rectangular electrode 3 is formed near the intersection of the “X-shaped” optical waveguides and in parallel with the electrode 2.
[0011]
On the other hand, FIG. 6 is a cross-sectional view taken along the line “AA ′” in FIG. 5. In FIG. 6, 1, “WG01” and “WG02” have the same reference numerals as in FIG. Is a substrate.
[0012]
A clad layer 4 and an optical waveguide layer 1 are sequentially formed on a substrate 5, and an “X-shaped” optical waveguide such as “WG01” and “WG02” in FIG. 6 is formed on the optical waveguide layer 1. . The optical waveguide formed in the optical waveguide layer 1 is a ridge-type optical waveguide, and an optical signal is distributed and propagated, for example, as indicated by “PS01” in FIG.
[0013]
Here, the operation of the conventional example shown in FIG. 5 will be described with reference to FIG. When the optical switch is “OFF”, no current is supplied to the electrodes 2 and 3.
[0014]
For this reason, since the refractive index does not change at the intersection of the “X-shaped” optical waveguides indicated by “CP01” in FIG. 5, for example, the optical signal incident from the incident end indicated by “PI01” in FIG. The light goes straight through the intersection and is emitted from the emission end indicated by “PO01” in FIG.
[0015]
On the other hand, when the optical switch is "ON", electrons are injected from the electrode 2 and holes are injected from the electrode 3, so that carriers (electrons and holes) are injected into the intersection.
[0016]
For this reason, the refractive index at the intersection of the “X-shaped” optical waveguides indicated by “CP01” in FIG. 5 is changed by the plasma effect so as to decrease. For example, from the incident end indicated by “PI01” in FIG. The incident optical signal is totally reflected by the low refractive index portion generated at the intersection indicated by “CP01” in FIG. 5 and is emitted from the emission end indicated by “PO02” in FIG.
[0017]
As a result, a current is supplied to the electrode to inject carriers (electrons and holes) into the intersection of the "X-shaped" optical waveguides to control the refractive index of the intersection, thereby emitting an optical signal. It is possible to control the position, in other words, switch the propagation path of the optical signal.
[0018]
[Problems to be solved by the invention]
However, in the conventional example shown in FIGS. 5 and 6, when the path of the optical signal is examined by simulation or the like, the optical waveguide through which the optical signal propagates is switched by the "ON / OFF" operation of the optical switch. There is a problem that a part of the optical signal leaks out to a portion other than the optical waveguide regardless of the “ON” or “OFF”.
[0019]
It is presumed that the cause of such a problem is that, at a portion where two or more optical waveguides intersect, the shape of the optical waveguide changes significantly, so that the waveguide mode of light changes, causing reflection and scattering. Is done.
[0020]
That is, in an optical switch in which a plurality of optical waveguides intersect, light leakage due to reflection or scattering exists with a slight difference.
[0021]
Such leakage of light in the configuration of the optical switch as shown in FIG. 5 is difficult because light leaked to portions other than the optical waveguide does not reach the emission ends indicated by “PO01” and “PO02” in FIG. The effect of light leakage is small.
[0022]
However, when an optical switch as shown in FIG. 5 is integrated as shown in FIG. 7, there is a possibility that light leaked to a portion other than the optical waveguide flows into another optical waveguide again (coupling). Will be higher.
[0023]
FIG. 7 is a plan view of an optical switch in which the optical switches as shown in FIG. 5 are integrated. In FIG. 7, reference numeral 6 denotes an optical waveguide layer having "X-shaped" optical waveguides and having "y-shaped" optical waveguides branched at different angles from the middle of the optical waveguides on the emission end side.
[0024]
However, in FIG. 7, an electrode pair for injecting carriers is provided at the intersection of the optical waveguides indicated by “CP11” in FIG. 7 and the branch of the optical waveguide on the emission end side indicated by “BP11” and “BP12” in FIG. Although necessary for each part, their description is omitted in FIG.
[0025]
Here, the operation of the conventional example shown in FIG. 7 will be briefly described. For example, if the optical signal incident from the incident end indicated by “PI11” in FIG. 7 has a low refractive index (“ON” state) when carriers are injected into the intersection indicated by “CP11” in FIG. 7 is reflected toward the branch portion indicated by “BP11” in FIG. 7, and further, when the carrier is injected into the branch portion indicated by “BP11” in FIG. 7 and the refractive index decreases (“ON” state), FIG. The light is further reflected by the branch portion indicated by "BP11" in the middle and is emitted from the emission end indicated by "PO12" in FIG.
[0026]
In addition, for example, the optical signal incident from the incident end indicated by “PI11” in FIG. 7 does not have carriers injected into the intersection indicated by “CP11” in FIG. 7 (“OFF” state). Go straight to the branch shown by BP12 ", and if no carrier is injected into the branch shown by" BP12 "in FIG. 7 (" OFF "state), go further straight to" PO14 "in FIG. Are emitted from the emission end shown in FIG.
[0027]
That is, by controlling the injection of carriers into the intersection shown by “CP11” in FIG. 7 and the branch shown by “BP11” and “BP12” in FIG. 7, the light enters from the incidence end shown by “PI11” in FIG. The emitted optical signal can be emitted from any of the emission ends indicated by “PO11”, “PO12”, “PO13” or “PO14” in FIG.
[0028]
Here, as shown by "LK11" in FIG. 7, the light leaked from the portion other than the optical waveguide at the intersection shown by "CP11" in FIG. 7 is the light guide shown by "WG13" or "WG14" in FIG. The possibility of flowing into (coupling with) the wave path increases.
[0029]
For example, even when control is performed such that an optical signal is emitted from the emission end indicated by “PO14” in FIG. 7 by switching, an optical signal is also emitted from the emission end indicated by “PO12” or “PO13” in FIG. In other words, in other words, crosstalk occurs.
Therefore, an object of the present invention is to realize an optical switch capable of reducing crosstalk.
[0030]
[Means for Solving the Problems]
In order to achieve such an object, the invention according to claim 1 of the present invention is:
In an optical switch that switches a transmission path of an optical signal by a change in refractive index,
By providing an optical waveguide layer in which an optical waveguide in which the optical signal is incident from one side and branched out in the middle and emitted is formed, and a light absorber formed in a portion other than the optical waveguide, Crosstalk can be reduced.
[0031]
The invention according to claim 2 is
The optical switch according to claim 1,
A semiconductor substrate; a cladding layer formed on the semiconductor substrate; the optical waveguide layer formed on the cladding layer; and a pair of electrodes for injecting carriers into a branch portion of the optical waveguide. Thus, crosstalk can be reduced.
[0032]
The invention according to claim 3 is
The optical switch according to claim 1,
Crosstalk can be reduced by providing the optical waveguide layer formed of a ferroelectric material and a pair of electrodes for applying an electric field to the optical waveguide to shift the phase of light by half a wavelength. Become.
[0033]
The invention according to claim 4 is
The optical switch according to claim 1,
The provision of the optical waveguide layer made of glass and the heater that applies heat to the optical waveguide to shift the phase of light by a half wavelength enables crosstalk to be reduced.
[0034]
The invention according to claim 5 is
In the optical switch according to any one of claims 2 to 4,
The light absorber,
The crosstalk can be reduced by being formed in a portion other than the optical waveguide in the optical waveguide layer.
[0035]
The invention according to claim 6 is
In the optical switch according to any one of claims 2 to 4,
The light absorber,
The crosstalk can be reduced by being formed in a portion other than the optical waveguide on the optical waveguide layer.
[0036]
The invention according to claim 7 is
In the optical switch according to any one of claims 2 to 4,
The light absorber,
The crosstalk can be reduced by being formed in a portion other than the optical waveguide in the optical waveguide layer and in a portion other than the optical waveguide on the optical waveguide layer.
[0037]
The invention according to claim 8 is
The optical switch according to claim 2,
The light absorber,
The crosstalk can be reduced by using a material having a smaller energy bandwidth than the semiconductor constituting the optical waveguide.
[0038]
The invention according to claim 9 is
In the optical switch according to any one of claims 2 to 4,
The light absorber,
By depositing the optical waveguide layer after etching, crosstalk can be reduced.
[0039]
The invention according to claim 10 is
In the optical switch according to any one of claims 2 to 4,
The light absorber,
Crosstalk can be reduced by forming the optical waveguide layer by diffusion or ion implantation.
[0040]
The invention according to claim 11 is
In the optical switch according to any one of claims 2 to 4,
The optical waveguide layer,
By having an optical waveguide in which two straight optical waveguides intersect, crosstalk can be reduced.
[0041]
The invention according to claim 12 is
In the optical switch according to any one of claims 2 to 4,
The optical waveguide layer,
By having an optical waveguide that branches at a different angle from the middle of one straight optical waveguide, crosstalk can be reduced.
[0042]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. 1 and 2 are a plan view and a sectional view showing an embodiment of the optical switch according to the present invention.
[0043]
In FIG. 1, reference numeral 7 denotes an "X-shaped" optical waveguide, and optical waveguide layers respectively having "y-shaped" optical waveguides branched at different angles from the middle of the optical waveguides on the emission end side thereof. Reference numerals 9, 10, 11 and 12 are light absorbers made of a material having a smaller energy band width than the semiconductor constituting the optical waveguide.
[0044]
In FIG. 1, an "X-shaped" optical waveguide is provided on the optical waveguide layer 7, and a "y-shaped" optical waveguide is formed which branches at a different angle from the middle of the optical waveguide on the emission end side. Light absorbers 8, 9, 10, 11 and 12 are formed in portions of the optical waveguide layer 7 other than the optical waveguide and other than the portion sandwiched between the two incident ends.
[0045]
However, in FIG. 1, a pair of electrodes for injecting carriers is an intersection of the optical waveguides indicated by “CP21” in FIG. 1 and a branch of the optical waveguide on the emission end side indicated by “BP21” and “BP22” in FIG. Although necessary for each part, the description is omitted in FIG.
[0046]
On the other hand, FIG. 2 is a cross-sectional view along “BB ′” in FIG. 1. In FIG. 2, 7, “WG21” and “WG22” are denoted by the same reference numerals as in FIG. Is a substrate.
[0047]
A cladding layer 13 and an optical waveguide layer 7 are sequentially formed on a substrate 14, and an optical waveguide as shown by "WG21" and "WG22" in FIG. 2 is formed in the optical waveguide layer 7. The optical waveguide formed in the optical waveguide layer 7 is a ridge-type optical waveguide, and optical signals are distributed and propagated, for example, as indicated by “PS21” in FIG.
[0048]
Light absorbers 8, 9, and 12 are formed in portions other than the optical waveguides indicated by "WG21" and "WG22" in FIG. 2 in the optical waveguide layer 7, respectively.
[0049]
Here, the operation of the embodiment shown in FIGS. 1 and 2 will be described. For example, an optical signal incident from the incident end indicated by “PI21” in FIG. 1 has a low refractive index (“ON” state) when carriers are injected into the intersection indicated by “CP21” in FIG. 1 is reflected toward a branch portion indicated by "BP21" in FIG. 1, and further, if carriers are injected into the branch portion indicated by "BP21" in FIG. 1 to lower the refractive index ("ON" state), FIG. The light is further reflected at a branch portion indicated by "BP21" in the middle and is emitted from the emission end indicated by "PO22" in FIG.
[0050]
Also, for example, in the optical signal incident from the incident end indicated by “PI21” in FIG. 1 unless the carrier is injected into the intersection indicated by “CP21” in FIG. 1 (“OFF” state), “1” in FIG. Go straight to the branch shown by BP22 ", and if no carrier is injected into the branch shown by" BP22 "in FIG. 1 (" OFF "state), go further straight to" PO24 "in FIG. Are emitted from the emission end shown in FIG.
[0051]
That is, by controlling the injection of carriers into the intersection shown by “CP21” in FIG. 1 and the branch shown by “BP21” and “BP22” in FIG. 1, the light enters from the incidence end shown by “PI21” in FIG. The emitted optical signal can be emitted from any of the emission ends indicated by “PO21”, “PO22”, “PO23”, or “PO24” in FIG.
[0052]
In this state, even if the light leaks out of the portion other than the optical waveguide at the intersection indicated by “CP21” in FIG. 1 as indicated by “LK21” in FIG. The absorbed light is absorbed, so that it is possible to prevent the light from flowing into (coupled to) an optical waveguide such as “WG23” or “WG24” in FIG. 1, as in the conventional example shown in FIG. . In other words, crosstalk can be reduced.
[0053]
As a result, a light absorber that absorbs light leaking due to reflection or scattering at the intersection or branch portion of the optical waveguide is sandwiched between the two incident ends in a portion other than the optical waveguide in the optical waveguide layer 7. By forming the portions other than the portions, crosstalk can be reduced.
[0054]
In the embodiment shown in FIG. 1, the light absorbers 8 to 12 are formed in the optical waveguide layer 7. However, the portions other than the optical waveguide on the optical waveguide layer 7 are sandwiched between two incident ends. It may be formed in a portion other than the portion.
[0055]
FIG. 3 is a sectional view showing another embodiment of the optical switch according to the present invention. However, since the plan view is the same as the embodiment shown in FIG. 1, the description and description are omitted.
[0056]
3, 7, 13 and 14 are denoted by the same reference numerals as in FIG. 2, and 15, 16, and 17 are light absorbers.
[0057]
A cladding layer 13 and an optical waveguide layer 7 are sequentially formed on a substrate 14, and optical waveguides such as “WG31” and “WG32” in FIG. 3 are formed in the optical waveguide layer 7. The optical waveguide formed in the optical waveguide layer 7 is a ridge-type optical waveguide, and an optical signal is distributed and propagated, for example, as indicated by “PS31” in FIG.
[0058]
Light absorbers 15, 16 and 17 are formed on portions other than the optical waveguides indicated by "WG31" and "WG32" in FIG. 3 on the optical waveguide layer 7, respectively.
[0059]
In this case, even when light leaks out of the portion other than the optical waveguide at the intersection shown by “CP21” in FIG. 1 as indicated by “LK21” in FIG. Since light is absorbed, it is possible to prevent the light from flowing into (coupled to) an optical waveguide such as “WG23” or “WG24” in FIG. 1, as in the conventional example shown in FIG. In other words, crosstalk can be reduced.
[0060]
Further, the configuration shown in FIG. 3 has an effect that if the absorption coefficient of the light absorber is substantially the same, the crosstalk reduction effect is low, but the fabrication becomes easy, as compared with the configurations shown in FIGS. 1 and 2. .
[0061]
Further, the configuration shown in FIG. 2 and the configuration shown in FIG. 3 may be combined. FIG. 4 is a sectional view showing another embodiment of such an optical switch according to the present invention. However, since the plan view is the same as the embodiment shown in FIG. 1, the description and description are omitted.
[0062]
4, 7, 8, 9, 12, 13 and 14 are denoted by the same reference numerals as in FIG. 2, and 15, 16, and 17 are denoted by the same reference numerals as in FIG.
[0063]
The clad layer 13 and the optical waveguide layer 7 are sequentially formed on the substrate 14, and an optical waveguide as shown by "WG41" and "WG42" in FIG. 4 is formed in the optical waveguide layer 7. The optical waveguide formed in the optical waveguide layer 7 is a ridge-type optical waveguide, and an optical signal is distributed and propagated, for example, as indicated by “PS41” in FIG.
[0064]
Light absorbers 8, 9 and 12 are formed in the optical waveguide layer 7 at portions other than the optical waveguides indicated by "WG41" and "WG42" in FIG. 4, respectively, and the light absorbers 8, 9 and 12 are formed. Light absorbers 15, 17 and 16 are respectively formed on the substrate.
[0065]
Also in this case, as shown by "LK21" in FIG. 1, even if light leaks out of the intersection shown by "CP21" in FIG. Since the leaked light is absorbed by the light guide 16, the light flows (couples) into an optical waveguide such as "WG23" or "WG24" in FIG. 1 as in the conventional example shown in FIG. Can be prevented. In other words, crosstalk can be reduced.
[0066]
Further, in the embodiment shown in FIG. 1, a light absorber is not formed in a portion of the optical waveguide layer 7 other than the optical waveguide and sandwiched between the two incident ends. A configuration in which a light absorber is formed also in a portion to be sandwiched may be used.
[0067]
In addition, in the embodiments shown in FIGS. 1, 2, 3 and 4, a material having a smaller energy band width than the semiconductor constituting the optical waveguide is exemplified as the light absorber. In the case of “1.5 μm” light, when the optical waveguide is InP, InGaAs or the like can be used as the light absorber.
[0068]
When the optical waveguide is made of a material such as glass or lithium niobate, a metal such as chromium, or an organic film or resin containing a filler (powder) of the metal can be used as the light absorber.
[0069]
As a method for forming the light absorber, the light absorber may be deposited after etching the optical waveguide layer, or the light absorber may be formed by diffusion or ion implantation in the optical waveguide layer.
[0070]
In the embodiment shown in FIG. 1, an "X-shaped" optical waveguide is provided in the optical waveguide layer, and a "y-shaped" optical waveguide that branches at a different angle from the middle of the optical waveguide on the emission end side is used. The optical waveguide is formed, but any configuration may be used as long as an optical waveguide is formed in which an optical signal is incident from one side and is branched into two in the middle and emitted.
[0071]
Further, the configuration may be such that the optical waveguide is simply formed in an “X shape”, in other words, a shape in which two straight optical waveguides intersect.
[0072]
Of course, an optical waveguide having two optical waveguides for emission may have a "y-shape" or another shape. Here, the “y-shaped” optical waveguide has a shape that branches at a different angle from the middle of one straight optical waveguide.
[0073]
Further, as in the embodiment shown in FIG. 1, an optical waveguide having a combination of "X-shape" and "y-shape" may be used.
[0074]
Also, in the embodiment shown in FIG. 1 and the like, an optical switch that switches the transmission path of an optical signal by a change in refractive index due to carrier injection is illustrated. The switch may be an optical switch using the electro-optical effect or an optical switch using heat.
[0075]
For example, as the former, an electric field is applied to the optical waveguide using a ferroelectric material such as lithium niobate, and the refractive index of the optical waveguide to which the electric field is applied is changed (the refractive index is lowered to change the phase of light). The transmission path of the optical signal is switched by shifting the wavelength by half a wavelength).
[0076]
For example, as the latter, a glass is used to form a Mach-Zehnder structure having a 50% directional coupling portion on the input side and the output side, and one of two optical waveguides branched after the input side directional coupling portion. Alternatively, a heater is provided on both.
[0077]
Here, by supplying heat to the optical waveguide by the heater, the refractive index of the optical waveguide to which the heat is supplied is changed (the refractive index is increased and the phase of light is delayed by half a wavelength), so that the output is increased. The optical signal transmission path is switched at the directional coupling portion on the side.
[0078]
【The invention's effect】
As is apparent from the above description, the present invention has the following effects.
According to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, and twelfth aspects of the present invention, leakage due to reflection or scattering at the intersection or branch of the optical waveguide is caused. Crosstalk is reduced by forming a light absorber that absorbs emitted light in the optical waveguide layer, or on the optical waveguide layer, or in a portion other than the optical waveguide in the optical waveguide layer and on the optical waveguide layer. Becomes possible.
[Brief description of the drawings]
FIG. 1 is a plan view showing an embodiment of an optical switch according to the present invention.
FIG. 2 is a sectional view showing an embodiment of the optical switch according to the present invention.
FIG. 3 is a sectional view showing another embodiment of the optical switch according to the present invention.
FIG. 4 is a sectional view showing another embodiment of the optical switch according to the present invention.
FIG. 5 is a plan view showing an example of a conventional optical switch.
FIG. 6 is a cross-sectional view illustrating an example of a conventional optical switch.
FIG. 7 is a plan view of an optical switch in which the optical switches as shown in FIG. 5 are integrated.
[Explanation of symbols]
1,6,7 Optical waveguide layer 2,3 Electrode 4,13 Cladding layer 5,14 Substrate 8,9,10,11,12,15,16,17 Light absorber

Claims (12)

In an optical switch that switches a transmission path of an optical signal by a change in refractive index,
An optical waveguide layer in which an optical waveguide in which the optical signal is incident from one side and branched and emitted in the middle in two directions is formed;
An optical switch, comprising: a light absorber formed in a portion other than the optical waveguide. A semiconductor substrate;
A cladding layer formed on the semiconductor substrate,
The optical waveguide layer formed on the cladding layer,
2. The optical switch according to claim 1, further comprising a pair of electrodes for injecting carriers into a branch portion of the optical waveguide. Said optical waveguide layer formed of a ferroelectric,
2. The optical switch according to claim 1, further comprising a pair of electrodes for applying an electric field to the optical waveguide to shift a phase of light by a half wavelength. Said optical waveguide layer formed of glass,
2. The optical switch according to claim 1, further comprising a heater for applying heat to the optical waveguide to shift a phase of light by a half wavelength. The light absorber,
The optical switch according to claim 2, wherein the optical switch is formed in a portion other than the optical waveguide in the optical waveguide layer. The light absorber,
The optical switch according to claim 2, wherein the optical switch is formed on a portion other than the optical waveguide on the optical waveguide layer. The light absorber,
The optical switch according to any one of claims 2 to 4, wherein the optical switch is formed in a portion other than the optical waveguide in the optical waveguide layer and in a portion other than the optical waveguide on the optical waveguide layer. The light absorber,
3. The optical switch according to claim 2, wherein the optical switch is made of a material having a smaller energy bandwidth than a semiconductor constituting the optical waveguide. The light absorber,
The optical switch according to claim 2, wherein the optical switch is deposited after etching the optical waveguide layer. The light absorber,
The optical switch according to any one of claims 2 to 4, wherein the optical switch is formed by diffusion or ion implantation in the optical waveguide layer. The optical waveguide layer,
The optical switch according to any one of claims 2 to 4, wherein the optical switch has an optical waveguide in which two linear optical waveguides intersect. The optical waveguide layer,
The optical switch according to any one of claims 2 to 4, further comprising an optical waveguide that branches at a different angle from the middle of one linear optical waveguide.

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