JPS60195528A - Waveguide type optical switch - Google Patents

Abstract

PURPOSE:To execute easily switching operation of light by providing a TE polarization control waveguide and a TM polarization control waveguide between an input branch path and an output branch path, and executing said operation through the TE polarization controlling electrode and the TM polarization controlling electrode. CONSTITUTION:The light which is made incident on an input waveguide 1 is divided into a ''0''-order mode light 15 and a primary mode light 18 by an input branch part 3. This phase difference is varied together with a propagation of light, and in case a phase difference of the ''0''-order mode light 15 and the primary mode light 18 is the same in phase or different in phase by pi in an output branch part 6, the light is emitted selectively to output waveguides 4, 5, respectively. In this case, a phase constant difference of the ''0''-order mode light 15 and the primary mode light 18 can be controlled by applying a voltage to TE polarization controlling electrodes 9, 10 and TM polarization controlling electrodes 11, 12 and 13, and varying a refractive index of a TE polarization control waveguide 7 and a TM polarization control waveguide 8 by an electro-optical effect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a waveguide optical switch that electrically deflects the direction of light traveling through a waveguide.

[Prior art]

Conventionally, this type of optical switch has had the drawback that the switching characteristics vary depending on the direction of polarization of the guided light. In order to solve this drawback, optical switches using asymmetric branching and Δβ coupler switches with modified electrode shapes were devised.

However, Kotobuki has learned that such optical switches have the drawbacks of high operating voltage and low extinction ratio in the former case, and poor manufacturability as the latter requires high dimensional accuracy for each part of the switch. There are many drawbacks.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned drawbacks, and its purpose is to provide a waveguide type optical switch that has no polarization dependence and is easy to manufacture and can be operated at a relatively low voltage. It is in.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention provides a bipolar optical switch that can be manufactured with moderate dimensional accuracy and has the advantage of having a high extinction ratio. It is characterized by eliminating the polarization dependence, which is a drawback, while taking advantage of the advantages of an optical switch.

〔Example〕

An embodiment of the present invention is shown in FIGS. 1 and 2 (A) below.

This will be explained based on (B) and FIG.

In FIG. 1, 1 and 2 are optical input waveguides, 3 is an input branch of the input waveguides 1 and 2, and 4 and 5 are the input waveguides 1.
, 2 are optical output waveguides arranged symmetrically with the output waveguides 4 and 5, 6 is the output branch of the output waveguides 4 and 5, and 7.8 is the input branch 3.
A TE polarization control waveguide and a TM polarization control waveguide are respectively arranged adjacently between the TE and the output branching section 6;
TE polarization control electrodes 11, 12, and 13 are attached to the polarization control waveguide 7 to control the TE light, and TM polarization control electrodes 11, 12, and 13 are attached to the TM polarization control waveguide 8 to control the 7M light.

This type of optical switch usually has a structure in which a waveguide is formed by diffusing Ti into a Z-cut substrate of LiNbO3, which has a large electro-optic effect, and the waveguide-type optical switch according to the present invention also has a structure in which a waveguide is formed by diffusing Ti into a Z-cut substrate of LiNbO3, which has a large electro-optic effect. The branches are attached back to back to form a 0-gear directional combiner, and a TE polarization control waveguide and a TM polarization control waveguide are arranged adjacently between the two input waveguides and the output waveguide. be. Furthermore, the light is assumed to be X-propagated.

2(A) and 2(B), the same figure shows the operating principle of a waveguide type switch, 14 is input light, and its electric field intensity distribution is shown. 15, 16, and 17 are zero-order mode lights, and their electric field intensity distributions are shown. 18, 19, and 20 are first-order mode lights, and their electric field intensity distributions are shown. Reference numerals 21 and 22 indicate output light and its electric field intensity distribution.

Next, to explain the operation of the above configuration, first, the input waveguide 1
The incident light is split into the 0th-order mode light 15 and - at the input branching section 3.
The light is separated into first-order mode light 18. The phase difference between the two zero-order mode lights 15 and the first-order mode light 18 changes with the propagation of the light, and at the output branching section 6, the zero-order mode light 15 and the first-order mode light 18 change.
When the phase difference with the next mode light 18 is the same phase or there is a phase difference of π, the light is selectively emitted to the output waveguides 4 and 5, respectively.

Here, the phase constant difference between the 0th-order mode light 15 and the 1st-order mode light 18 is determined by applying a voltage to the TE polarization control electrodes 9 and 10 and the TM polarization control electrodes 11 and 12° 13 shown in FIG. By this, the TE polarization control waveguide 7 is
and can be controlled by changing the refractive index of the TM polarization control waveguide 8. By the way, since the magnitude of the electro-optic effect differs depending on the polarization and also depends on the direction of the applied electric field, in order to obtain the same switching characteristics for arbitrary polarization, it is necessary to use the waveguide type optical switch according to the present invention. Like (T
A configuration is required to control E and TM separately.

Therefore, how to control the polarization of TE and TM will be explained using the following formula. In FIG. 1, when no electric field is applied to the TE polarization control waveguide 7 and the TM polarization control waveguide 8, Output branch section 6 for the light incident on the input waveguide 1
TE is the phase difference between the 0th mode light and the 1st mode light at ψ
If 0 and TM are ψe, the conditions for selectively emitting light to the output waveguides 4 and 5 can be expressed by the following equation.

Conditions for light to be emitted to the output waveguide 4 Conditions for light to be emitted to the output waveguide 5 δK. , δKIll+δKo′ and δ′, are
TE polarization control electrodes 9 and 10 and TM polarization control electrode 1
T changed by applying voltage to 1°12.13
E and TMqxiang are the differences and are given by the following equation.

Note that the above-mentioned δKoG and δKo6' are the electric field E6°E generated by applying a voltage to the TE polarization control electrodes 9 and 10.
6' shows the change in the phase constant difference between the 0-order mode light and the 1st-order mode light of TE, and also the above-mentioned δKo7 and δK. 7
' is an electric field ET + E? generated by applying a voltage to the TM polarization control electrodes 11 and 12.13. TF200 by '
Indicates the change in the phase constant difference between the next mode light and the first mode light,
Furthermore, δ above and δK e3 L are the phase constants of the 0th-order mode light and the 1st-order mode light of the TM due to the electric fields E7 and E7' generated by applying a voltage to the TM polarization control electrodes 11, 12, and 13. Indicates a change in difference. Also, L2 and L5
indicate the lengths of the TE polarization control waveguide 7 and the 7M polarization control waveguide 8, respectively.

Therefore, the voltage required for the switching operation can be calculated from the above-mentioned equations (a) to (h).

For example, if we consider the case of creating a LiNbO3 -Z root plate waveguide type optical switch, in this case, the TE
The polarization control electrodes 9 and 1o provide opposite polarities to Y.
The 7M polarization control electrodes 11, 12.13 generate an electric field EG t E6' in the direction of the TM polarization control electrodes 12 and 7.
Provide opposite polarity between the M polarization control electrodes 11 and 13 to generate an electric field E7+E7' in the Z direction. 06' to δ + 07 to δ. δKo7'+δKa7
and δKe 7'' are expressed as follows using the electro-optic coefficient riT of the crystal.

δKo62 δKoor22E6 --(t, 1) 0 for δ
7: δKoorF5E6 --(t-2) 8.2 δ in δ
Keor9. E7...(6,3)δKo&'=
δKoOr22E6' ・=-...(to4) δKo?
"""δKoOr115E6'Moe" (t, 5) δK
ey""δKaor>>E7' (t, 6) Here, FIG. 3 shows δKo6. 07+δK for δ. 6. 0 for δ
Ct 07' and δKe□/ to 6'1δ, l) 2~(
This is an explanatory diagram of an example in which equations (a) to (h) are graphed when expressed by equations (t, 6), and the electric field E6+E7 ``*or electric field'''6 when TE and TM switch simultaneously. '
The conditions for +E7' are (-) and (b) or (c
) and (d) hold true at the same time, and this is represented by the intersection of these two straight lines, either (a) and (b) or (c) and (d). The coordinate value EY of this intersection
*EZ is E61, E7 and J”l: E6
' , becomes the value of E7'.

On the other hand, in FIG. 1, the TE polarization control waveguides 7 and 7M
When no electric field is applied to the polarization control waveguide 8, the phase difference between the 0th mode light and the 1st mode light at the output branch path 6 of the light incident through the input waveguide 2 is The conditions for light to be emitted to the output waveguide 4 and the conditions for light to be emitted to the output waveguide 4 are as follows.

Therefore, based on formulas (a)2 to (d) and formulas (,) to (r), the TE polarization control electrode 9 is connected to the TE polarization control waveguide 7.
When an electric field E6 is applied at 10 °C and an electric field E7 is applied to the 7M polarization control waveguide 8 at the 7M polarization control electrodes 11, 12, and 13, the light flows from input waveguide 1 to output waveguide 4 to input waveguide 2. → Proceeds like the output waveguide 5.

Furthermore, the TE polarization control waveguide 7 is provided with a TE polarization control electrode 9,
10, an electric field E 6/ is applied, and a 7M polarization control waveguide 8 is applied.
%' at 7M polarization control electrodes 11, 12, and 13, field E7
', the light travels from the input waveguide 1 to the output waveguide 5 and from the input waveguide 2 to the output waveguide 4, and in this way the waveguide type optical switch can be operated.

Note that the width of the TE polarization control electrodes 9 and 10 described above is TE
The size must be smaller than 1/4 of the width of the polarization control waveguide 7. That is, this is done in order to prevent the propagation constant of the guided light from changing due to a change in the refractive index of the side surface of the TE polarization waveguide T.

〔Effect of the invention〕

As described above, according to the waveguide type optical switch according to the present invention, Y branches are attached back to back to form an O-gap directional coupler, and a T is formed between the input branch and the output branch.
An E polarization control waveguide and a TM polarization control waveguide are provided, a TE polarization control electrode for controlling TE light is attached to the TE polarization control waveguide, and a TM polarization control waveguide is provided to the TM polarization control waveguide.
By attaching the TM polarization control electrode that controls light, the light switching operation can be easily performed via the TE polarization control electrode and the TM polarization control electrode, which produces the significant effects shown below. Shine.

That is, since the polarization dependence can be eliminated, the extinction ratio can theoretically be improved by about 8 dB during the switching operation of guided light having the same intensity of TE and TM acid components, which can improve functionality. Furthermore, by simply adjusting the lengths of the TE polarization control waveguide and the TM polarization control waveguide, it is possible to easily reduce the operating voltage, which was difficult with conventional optical switches using asymmetric X-branches. .

In addition, the extinction ratio is the lowest compared to interference-type optical switches that use asymmetric branching, which can easily lower the operating voltage, and it can be experimentally improved by 4 dB and has a simple configuration. Compared to a switch, it has a simpler configuration and does not require high dimensional accuracy.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG.
B) is an explanatory diagram of the operating principle, and FIG. 3 is an explanatory diagram of the electric field during switching operation in the embodiment. 3...Input branch path 6...Output branch path 7...T
E polarization control waveguide 8...TM polarization control waveguide 9,
10...'l Polarization control electrode 11, 12.13...
・TM polarization control electrode patent applicant: Oki Electric Industry Co., Ltd. Representative Patent Attorney Kanakura n Bigonal IC 1ll Capacity 20 (A) (B) @3- Procedural amendment (voluntary) September 12, 1980 Patent Office Director Manabu Shiga1, Indication of the case 1982 Patent Application No. 0511192, Title of the invention Waveguide type optical switch 3, Relationship to the amended person case Patent applicant address 1-chome Toranomon, Minato-ku, Tokyo No. 7 No. 12 Name (
029) Oki Electric Industry Co., Ltd. Representative Nankai Hashimoto 4, Agent 5, Date of amendment order Contents of voluntary amendment 1 From page 6, line 9 of the specification to page 9, line 20, 1 are as follows: to correct. Note that δKo7 and δKo7' described above are caused by the electric field E7. which is generated by applying a voltage to the TEE light control electrode 9.10. E7
' shows the change in the phase constant difference between the 0-order mode light and the 1st-order mode light of TE, and also the above-mentioned δKo3 and δKo8'
shows the change in the phase constant difference between the 0th-order mode light and the 1st-order mode light of TE due to the electric field E8 + E8' generated by applying a voltage to the TM polarization control electrode 11°12.13, and also the above-mentioned δKeB and δKeB' is the electric field E8. which is generated by applying a voltage to the 1M polarization control electrodes 11, 12.13.
It shows the change in the phase constant difference between the 0th-order mode light and the 1st-order mode light of TM due to E〆. Also, L2 and RI are each TE
Polarization control waveguide color TM The length of the polarization control waveguide 8 is shown. Therefore, the voltage required for the switching operation can be calculated from the above-mentioned equations (,) to (h). For example, if we consider the case where a waveguide type optical switch is fabricated on one or two LiNbO3 plates, in this case, the TE
The E light control electrodes 9 and 10 are given opposite polarities to Y.
Electric field in direction E7. E7', and the 1M polarization control electrode 11.12.13 provides opposite polarity between the 1M polarization control electrode 12 and the 1M polarization control electrode 11.13.
This produces an electric field in the direction E8+chest'. Here, δKo7. δ
Ko7'. δKog, δKoB', δKe8, and δKaB' are expressed as follows using the electro-optic coefficient J7 of the crystal. 07 to δ = δKoor22E7 ・・・・・・(Mu1)
δKo8°δ00r13E5 ・== (t, 2) δ
KeB°δKeor55E8 “”” (Mu3)δKo7
'=δKoor22E7' -==・(z+4) 0 for δ
8′. δKoor15Eg' ・,, (t, 5) δK
eB'=δKeOr55E8' (t, 6) Here, FIG. 3 shows that δ is 07. δKo8. δKeg. δKo7', 08' and δKe B' to δ(2,1
)2~(Z,6) When expressed by the formula (,)2~(h)
This is an explanatory diagram of an example in which the formula is graphed, and the electric field "7 + E8 or electric field E when TE and TM switch simultaneously.
The conditions for 7' and E8' are formulas (a) and (b) or (c
) and (d) are simultaneously established, and this is expressed by the intersection of these two straight lines, (,) and (b), or (c) and (d). The coordinate value of this intersection EYJ
Z has a value of E7°E8 or E7'14', respectively. On the other hand, in FIG. 1, the TEE optical control waveguide 7 and the TM
When no electric field is applied to the polarization control waveguide 8, the light entering the input waveguide 2 is at the same level as the 0th mode light and the 1st mode light at the output branch path 6, The conditions for the light to be emitted are as follows.The conditions for the light to be emitted to the output waveguide 4 are as follows. Therefore, based on formulas (a)2 to (d) and formulas (0)2 to (r), the TE polarization control waveguide 7KTE polarization control electrode 9
．． When an electric field E7 is applied to the TM polarization control waveguide 8 and an electric field E8 is applied to the TM polarization control waveguide 8 at the TM polarization control electrodes 11, 12. → Proceed like the output waveguide 5. It's a moat, TE polarization control waveguide 7KTE polarization control electrode 9,
When an electric field E7' is applied to the TM polarization control waveguide 8 at 10, and an electric field E8' is applied to the TM polarization control waveguide 8 at the TM polarization control electrodes 11, 12 and 13, the light flows from the input waveguide 1 to the output waveguide 5 to the input waveguide. 2→output waveguide 4, and in this way the waveguide type optical switch can be operated. 2. On page 11 of the specification, lines 9 and 10, the phrase "becomes the lowest," is amended to "becomes higher." 3. Figure 3 is amended as shown in the attached drawing.

Claims (1)

[Claims] The I and Y branches are attached back to back to form a 0 gear directional combiner, and a T is connected between the input branch and the output branch.
An E polarization control waveguide and a 7M polarization control waveguide are provided, a TE polarization control electrode for controlling TE light is attached to the TE polarization control waveguide, and a TM polarization control waveguide is provided to the 7M polarization control waveguide.
A waveguide optical switch characterized by having a polarization control electrode attached.