JPH1184434A - Light control circuit and operation method - Google Patents

Abstract

(57) [Problem] To provide an optical control circuit for adjusting or switching a distribution ratio of a light wave transmitted through an optical waveguide with low loss and high efficiency, and an operation method thereof. SOLUTION: Two input waveguides 12 are provided on an LN substrate 11,
In an optical control circuit including two output waveguides 13 and an MMI optical multiplexing / demultiplexing waveguide section 14, the MMI
A plurality of electrodes 16 and 17 are arranged in the optical multiplexing / demultiplexing waveguide section 14, and the electrodes 16 and 17 are set so as to match the distribution of the mode field excited in the multimode interference waveguide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical control circuit for adjusting or switching a distribution ratio of a light wave transmitted through an optical waveguide with low loss and high efficiency, and a method of operating the same.

[0002]

2. Description of the Related Art A directional coupler or an X-type coupler is used for distributing / combining or switching lightwaves from an optical fiber or a semiconductor laser diode (LD) to one or more waveguides or optical fibers. An optical control circuit using a wave circuit or a strongly coupled directional coupler has been widely used. FIG. 18 shows a configuration example (perspective view) of a conventional light control circuit using a directional coupler.

As shown in FIG. 18, in the prior art, as a substrate 01, a ferroelectric material LiNbO
₃ (hereinafter referred to as “LN”), and the LN substrate 0
Reference numeral 1 denotes a cladding portion of the optical waveguide. On the LN substrate 01, core portions 02 and 03 of an input waveguide and an output waveguide formed by diffusion of impurities such as titanium (Ti) or protons are formed. Note that, in FIG.
4 is a waveguide constituting a directional coupler, 05 is an electrode 06,
Reference numeral 08 denotes a buffer layer made of SiO ₂ or the like formed to prevent light propagation loss due to 07, and reference numeral 08 denotes an external power supply for applying a voltage V to the electrodes 06 and 07.

In the case of this configuration, the waveguide length L of the directional coupler
The becomes light switch is set to complete coupling length L _0. The waveguide length L when the complete coupling length half the length of (L = L _0/2) becomes 3dB optical splitter. Depending on the magnitude of the voltage V,
The distribution ratio of the output lights P ₁ and P ₂ can be controlled.

On the other hand, a multimode interference waveguide (hereinafter, referred to as MM1 (Multi-Mode Interferometer)) having a function of multiplexing / demultiplexing light waves utilizing interference between a plurality of modes in the waveguide is used. The multiplexing / demultiplexing circuit that has been used has recently been frequently used because it has a feature such as a large dimensional variation tolerance at the time of manufacturing the device structure as compared with the directional coupler. At present, an application example as an active element has not been proposed yet.

[0006]

An optical control circuit using such a conventional directional coupler greatly varies in characteristics due to a slight deviation in the dimensions and refractive index of the waveguide at the time of device fabrication. There are problems such as large degradation of crosstalk, which is a major obstacle to practical use. In addition, a conventional light control circuit that operates using an MMI waveguide while changing its effective width or effective length is M M waveguide.
It is necessary to greatly change the refractive index of the MI waveguide, and there is a problem that the efficiency is poor such as the driving voltage or the current is extremely large.

[0007] It is an object of the present invention to solve these problems and to provide an optical control circuit and an operation method for controlling switching or distribution ratio with low loss and high efficiency.

[0008]

According to a first aspect of the present invention, there is provided an optical control circuit comprising: a multimode interference waveguide having a single or a plurality of optical input units and an optical output unit; A light control circuit comprising one or more electrodes, at least one of which is disposed on the multimode interference waveguide, and one or more of the electrodes are excited in the multimode interference waveguide. Number, shape,
The arrangement is set.

According to a second aspect of the present invention, in the light control circuit according to the first aspect, one or more of the electrodes is a mode used for circuit operation among modes excited in the multimode interference waveguide. The number, shape, and arrangement are set so as to include the peak position of the mode field distribution.

According to a third aspect of the present invention, in the light control circuit according to the first or second aspect, the light emitted from the light output section of the light control circuit is equally distributed in a state where no bias is applied to the electrode. It is characterized by having done.

According to a fourth aspect of the present invention, there is provided the light control circuit according to the first or second aspect, wherein one or a part of the plurality of light output portions of the light control circuit is provided without applying a bias to the electrode. It is characterized by emitting light.

The light control circuit according to claim 5 is characterized in that, in claims 1 to 4, the plurality of electrodes constitute a traveling waveform electrode.

The light control circuit of claim 6 is characterized in that in claim 1 to 5, one or both of the multimode interference waveguide and the electrode have a tapered planar shape.

According to a seventh aspect of the present invention, in the light control circuit according to the first to sixth aspects, the multimode interference waveguide is 1 × 2, 2 × 2,
Alternatively, it is a 1 × 3 multimode interference waveguide.

On the other hand, a method for operating the light control circuit according to claim 8 is the method for operating a light control circuit according to claims 1 to 7, wherein the polarity and magnitude of the voltage applied to each of the electrodes are set to the same value. It is characterized in that it is set to match the distribution of the mode field excited in the multi-mode interference waveguide.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention and the principles and effects will be described below in detail with reference to the drawings.

FIGS. 1 and 2 show an embodiment of a 2 × 2 light control circuit according to the present invention when LN which is a ferroelectric material is used as a substrate. FIG. 1 is a perspective view of the light control circuit. FIG.
Shows a top view thereof. As shown in FIGS. 1 and 2, the light control circuit according to the present embodiment includes two input waveguides 12 and two output waveguides formed on an LN substrate 11 by diffusing impurities such as titanium (Ti) or protons. 13 and an MMI optical multiplexing / demultiplexing waveguide section 14, the plurality of electrodes 1
6 and 17 are arranged, and the electrodes 16 and 17 are set so as to match the distribution of the mode field excited in the multimode interference waveguide. The LN substrate 11
Denotes a -z cut plate (: the + z direction corresponds to the c-axis of the LN crystal), which constitutes a clad portion of the optical waveguide. The buffer layer 1 is provided on the surface of the LN substrate 11.
5 are formed. In the figure, reference numeral 16 denotes a central conductor of the control electrode, 17 denotes a ground conductor of the control electrode, 18 denotes an external power supply, and P ₁ and P ₂ denote output light. The center conductor 16 and the ground conductor 17 of the control electrode are indicated by hatching in the figure (the same applies hereinafter).

The structure of the input / output waveguides 12 and 13 is basically the same as that of a conventional light control device. For example, an optical function processing connected to an input or output waveguide by monolithic integration or hybrid integration. A device section (for example, a refractive index modulation section in which a modulation electrode using the EO effect is arranged, or an optical wavelength control section using a non-linear effect such as second harmonic generation, etc.), and an optical fiber to be connected. It has a structure that gives a spot size about the same size as the wave light, and the widths w _i , w _o ,
The dimensions of the core thickness t _g (diffusion length of the impurities) and the diffusion concentrations of the impurities are set. Here, the input / output waveguide 1
The distance d between 2 and 13 is set in consideration of the structure of the connected optical function processing section and the like, and may be different in the input / output section as needed.

The MMI optical multiplexing / demultiplexing waveguide section 14 is described, for example, in the literature [: PABesse. M. Bachmann. H. Melchior, LBSo
ldano, and MKSmit. "Optical.bandwidth and fabrica
tion tolerances of multimode interference coupler
s. "Journal of Lightwave Technology, vol.12, no.6.
pp. 1004-1009. 1994.].
It has the same configuration as the MMI waveguide of the two-multiplexing / demultiplexing circuit.

FIGS. 3A, 3B and 3C are views for explaining the principle of the embodiment of FIGS. 1 and 2 according to the present invention. FIG. 3A shows a refractive index distribution of a cross section of the MMI waveguide before and after voltage application, and FIG. 3B shows a fundamental (0th-order) mode excited in the MMI when no voltage is applied (V = 0). Higher order (:
In this case, an electric field intensity distribution diagram of the (first-order) mode, and FIG. 3C is a cross-sectional view of the center AA ′ of the MMI in FIG. The magnitude of the refractive index of the LN crystal changes according to the magnitude of an externally applied voltage due to the Pockels effect. -Z cut L
In the embodiment of FIG. 1 using the N substrate 11, FIG.
When a voltage is applied in such an electrode arrangement as described above, the effect of an externally applied electric field in the direction perpendicular to the LN substrate surface (z direction) due to the anisotropy of the Pockels effect for light waves having a polarization plane in the z direction. Since the light is greatly received, the magnitude of the refractive index greatly changes particularly immediately below the electrode portions 16 and 17.

FIG. 3A shows a change when the polarity of the voltage V is negative. At this time, M
As can be seen from the electric field intensity distribution of each light wave mode of the MMI waveguide shown in FIG. 3B with respect to the change in the refractive index at the center of the MI, the fundamental mode is large because the optical electric field intensity at the center is strong. Under the influence, the magnitude of the equivalent refractive index (propagation constant) greatly changes. On the other hand, since the mode optical electric field intensity in the refractive index changing portion is relatively weak in the first-order mode, the effect is relatively small, and the amount of change in the equivalent refractive index is small.

In the present invention, electrodes are appropriately arranged on the MMI region so as to match the electric field intensity distribution of each mode used for the optical multiplexing / demultiplexing operation among the lightwave modes excited in the MMI waveguide. Thus, the light distribution ratio adjustment or the optical switching operation is performed with high efficiency by making use of the difference in the degree of influence on each mode with respect to the change in the refractive index caused by the applied voltage.

FIGS. 4A and 4B and FIGS.
FIG. 2B is a diagram for explaining the effect of the present invention in the embodiment of FIG. 1 and shows a result of an approximate calculation using an eigenmode expansion method for a 1.53 μm band 2 × 2 MMI optical multiplexing / demultiplexing circuit. . Here, the case where the optical waveguide is formed by diffusing Ti into an LN substrate by a normal thermal diffusion method is analyzed. In order to simplify the calculation, when no voltage is applied, the slab waveguide model analysis was performed by the equivalent refractive index method, assuming that the diffused waveguide had a uniform refractive index for the core layer and the cladding had a uniform size. ing.

The width of the input and output waveguides was fixed at w _i = w _o = 6 μm, and the distance between the input and output waveguides was fixed at d = 20 μm. The electrode gap is set to G ₁ = G ₂ , and the refractive index distribution in the MMI as shown in FIG. Regarding the refractive index change Δn of LN due to an externally applied electric field,
Assuming the Pockels effect of the LN crystal and the material and thickness of the normal buffer layer 15, here, for propagating light having a polarization in the z-direction (wavelength 1.53 μm band), Δn = 1 × 10 ^−5.
/ V.

In FIG. 4A, the voltage V = 0 in FIG.
3 dB (P₁= P_Two~ P ₀/ 2) Light distribution times
The width of the MMI waveguide w_g= 29 μm, length
L is set to 3.15 mm. Do this
The extinction ratio can be increased. At this time, the electrode width W
Output light P when changing₁, P_TwoShows the applied voltage dependence of
You. From this figure, it can be seen that as W becomes smaller, the light distribution adjustment operation becomes more efficient.
Operation becomes possible, and when switching operation is performed,
It can be seen that light ratio characteristics can be obtained. This is the MMI waveguide
For the change in the refractive index at the center,
This is because the influence is relatively small. Was
However, when W becomes less than 4 μm, the influence on the fundamental mode
Has also been reduced and operating efficiency has been reduced.
You.

FIG. 4B shows that w _g = 29 μm and W = 8 μm.
This is an operation characteristic when the MMI waveguide length L is changed when m is constant. When L is longer or shorter than 3.15 mm, the excess loss increases. However, the slopes of the curves are almost the same, and if the difference between the applied voltages is the same, the rate of loss change, or P ₁ and P _{1 It} can be seen that the ratio of ₂ does not change much. From this fact, it can be seen that, although a large variation in the characteristics is caused by a slight deviation in the structure, dimensions and the like at the time of device fabrication, which was a problem of the conventional example, this problem can be alleviated in the present invention.

FIG. 5A shows that d = 20 μm and W = 8 μm.
The waveguide length L is set to 2 × by changing the MMI waveguide width w _g to be constant.
This is the characteristic when the two-light distribution operation is set to be optimal. A longer L by setting wide w _g, the ability to operate with little change in refractive index, it becomes possible to high efficiency operation. Therefore, wg is fixed, and the MMI waveguide length L 'is changed as shown in FIG.
If L ′ = L + 2nL (n = 1, 2, 3,...) Is set for L in the embodiment shown in FIGS. 5A and 5B and FIG. Therefore, more efficient operation is possible as L ′ is increased.

4 (a), 4 (b) and 5 (a)
Then, no bias is applied to the electrodes 16 and 17 (V =
0) sometimes give approximately equal output light from each of the output waveguide 13 (P ₁ ~P ₂₎ as showed If you set the MMI waveguide structure.

FIG. 5B shows the operating characteristics when the MMI waveguide structure is set so that the output light P ₁ becomes almost 0 at zero bias (V = 0). By doing so, the extinction ratio can be increased. Also in this case, the voltage V
It can be understood that the light distribution / switching operation can be performed by appropriately applying. Further, L of the embodiment of FIG.
On the other hand, if L ′ = nL (n = 1, 2, 3,...), The longer the L ′, the more efficient the operation.

In the above description, the input / output waveguide width is w _i = w _o = 6.
[mu] m, output waveguide spacing as d = 20 [mu] m constant, but the electrode gap shows a case in which the _{G 1 = G 2, w i} ,
If the MMI waveguide / electrode structure is appropriately set in accordance with w _o , d or the size of the refractive index n of the waveguide material or the size of the spot size of the guided light, the effect of the present invention can be similarly obtained. it can. Also, by appropriately setting the dimensions of the input / output waveguides, the positions connected to the MMI waveguides, or the MMI waveguide structure, the distribution ratio of P ₁ and P ₂ when V = 0 can be set to an arbitrary size. Can be set, and in this case also, the effects of the present invention can be obtained.

FIG. 6 is a top view of another embodiment of the present invention, showing the configuration of a 2 × 2 optical demultiplexing circuit using a −z cut LN substrate 21. The structures of the input / output waveguides 22 and 23 and the MMI waveguide 24 and the waveguide spacing d are the same as those in the embodiment of FIG. In this case, the electrode center conductor 26 is arranged so that the effect of the change in the refractive index due to the voltage application is small for the fundamental mode and large for the primary mode.
It is arranged in places. Therefore, when the center conductor gap G of this embodiment is set to be approximately the same size as the electrode width W of the embodiment of FIG. 1, the same operation characteristics as those of the embodiment of FIG. 1 can be obtained. However, the operation characteristics are opposite to the polarity of the voltage.

FIG. 7 is a top view of another embodiment according to the present invention, in which an x- or y-cut LN substrate 31 is used.
The configuration of the × 2 optical demultiplexing circuit is shown. I / O waveguide 3
The structures of the 2, 33 and MMI waveguides 34 are the same as in the embodiment of FIG. In the case of the present embodiment, since an externally applied electric field in a direction parallel to the surface of the LN substrate 31 (z direction) is used, the refractive index of the MMI gap between the center conductor 36 and the ground conductor 37 greatly changes. Therefore, the electrode arrangement of this configuration (G to W, W ₁ to
G ₁ , W _{2 to} G ₂ ) can realize the same operation characteristics as in the embodiment of FIG.

In FIG. 7, the effect of the present invention can be obtained also when the same waveguide and electrode configuration is used by using a -z cut LN substrate as the substrate 31. In this case, the input / output waveguide width w _i = w _o = 6 μm and the input / output waveguide interval d = 2
2 μm when the waveguide length L was changed with the MMI waveguide width w _g = 29 μm and the electrode gap G = 10 μm constant, 0 μm.
FIG. 8 shows the two light demultiplexing characteristics. When L = 3.15 mm,
The excess loss can be made relatively small, and the light distribution ratio can be changed by the applied voltage. However, in this case, since the refractive index distribution in the MMI waveguide becomes asymmetrical due to the application of the voltage, an operation characteristic different from that of the embodiment of FIG. 1 (FIG. 4B) is exhibited. That is, in the present invention, if the characteristics and magnitude of the refractive index change in the MMI waveguide are controlled by an external power supply in accordance with the field shape in the MMI waveguide, the propagation constant and the field shape of each mode can be changed simultaneously. Therefore, the distribution ratio and output characteristics of the optical demultiplexer can be more optimally controlled.

FIG. 9 is a top view of another embodiment according to the present invention.
It is a figure and 1x2 light component using the -z cut LN board | substrate 41.
2 shows a configuration of a wave circuit. I / O waveguides 42, 43 and
The structure of the MMI waveguide 44 is the same as that of the embodiment of FIG.
You. The 1 × 2 optical demultiplexing MMI waveguide 44 is the same as the conventional one.
Configuration may be adopted. In this case, the MMI waveguide 44 is excited.
The modes to be shaken are mainly the even modes (0th order, 2nd order, 4th order,
…)
The electrode structure may be set in consideration of the above. In the embodiment of FIG.
And when the applied voltage V = 0, the output light P₁, P _TwoIs 3dB
MMI waveguide width w to be split_g= 40 μm, guided
A path length L = 1.38 mm and an output waveguide width d = 20 μm.
Fig. 10 shows the dependence of the demultiplexing characteristics on the applied voltage.
Was. FIG. 10 shows that the distribution ratio can be adjusted by applying a voltage.
I understand.

FIG. 11 is a top view of another embodiment according to the present invention, and shows the configuration of a 1 × 2 optical demultiplexing circuit using a −z cut LN substrate 51. Input / output waveguides 52, 53
The structure of the MMI waveguide 54 is the same as that of the embodiment of FIG. In this case, the electrodes 56 and 57 are arranged at the center of the MM1 waveguide. For the change in refractive index due to voltage application,
The electrode configuration is such that the influence on the secondary mode is relatively smaller than the fundamental mode in the MMI. FIG. 12 shows the operation characteristics of the embodiment of FIG. 11, and the insertion loss can be reduced by applying an appropriate voltage.

FIG. 13 is a top view of another embodiment of the present invention, showing a 1 × 3 using a −z cut LN substrate 161.
3 shows a configuration of an optical demultiplexing circuit. Input / output waveguides 62, 6
The structures of the MMI waveguide 3 and the MMI waveguide 64 are the same as those of the embodiment of FIG. In this case, the two electrode center conductors 66-1, 66
-2 are connected to different power supplies 68, respectively. In the embodiment of FIG. 13, when no voltage is applied (V ₁ = V ₂ = 0), the MMI is set so that the outputs P ₁ , P ₂ , and P ₃ are equally distributed.
FIG. 14 shows an example of operation characteristics when the waveguide 64 is formed.
(A) and (b) show. FIG. 14A shows that two center conductors 66-1 and 66-2 are set to the same voltage (V ₂ = V ₁ ).
FIG. 4B shows the characteristics when the polarity is reversed (V ₂ = −V ₁ ). That is, 1 ×
Three optical switching operations are possible.

FIG. 15 is a top view of another embodiment according to the present invention, and shows the configuration of a 1 × 2 optical demultiplexing circuit using a −z cut LN substrate 71. In this case, the width w _g and the core thickness t _g of the 1 × 2 optical demultiplexing MMI waveguide 74 are tapered, and input / output waveguides 72 and 73 are formed in this tapered waveguide. ing. The input waveguide 72
The side structure basically has the same structure as the conventional MMI, and has waveguide widths w _i and w _gi that provide the same spot size as the guided light of, for example, a semiconductor optical function device connected to the input waveguide. , The dimensions of the core thickness t _gi and their materials are set. On the output waveguide 73 side of the MMI, the output waveguide, the MMI waveguide width w _o , and the width of the MMI waveguide are adjusted to match the spot size of, for example, an optical fiber connected to the output waveguide.
w _go and core thickness t _go are set. In this case, an embodiment is shown in which the spot size of the output-side guided light is enlarged as compared with the input side. The horizontal spot size is MMI
The waveguide width wg is enlarged by gradually widening the waveguide width wg in a tapered shape in the optical axis direction. By making it tapered,
The size of the element can be reduced, and the spot size can be converted.

The taper shape may be, for example, a curve shape such as a parabolic shape or an exponential shape, a linear shape, or a combination thereof. In this case, the spot size in the vertical (: depth) direction is enlarged by gradually reducing the core thickness t _g in the z-axis direction to weaken the vertical waveguide confinement effect. Conversely, the core thickness may be gradually increased in accordance with the required spot size. The effects of the present invention can be obtained by forming the electrodes 76 and 77 in a tapered shape in accordance with the field shape of the light wave propagating in the MMI waveguide.
In addition, the input and output waveguide width to the same _{(w i = w o),} M
1 × 2 if the MI waveguide / electrode taper shape is set appropriately
Optical switch operation is also possible.

FIG. 16 is a top view of another embodiment of the present invention, in which a traveling waveform coplanar electrode (: :) in which the dimensions and shape of the electrodes 86 and 87 are formed as a part of a microwave line.
CPW) is shown. Input / output waveguides 82, 83
The structure of the MMI waveguide 84 is the same as that of the embodiment of FIG. A microwave signal from a signal source 89 is input from the light incident side of the electrode, and a terminating resistor (R) 90 is connected to the output side of the electrode. In such a traveling waveform electrode configuration,
The coplanar electrode 86 is set so that the propagation speeds of the microwave and the light wave are matched (the speed matching ratio), and the characteristic impedance of the electrode is adjusted to the impedance Zi, R (usually Zi = R = 50Ω) of the signal line and the terminating resistor. , 87, a high-speed light distribution / switch operation becomes possible.

FIG. 17 is a perspective view of another embodiment of the present invention, showing an example in which the light control circuit is made of a semiconductor material. 111 is an n-type semiconductor having a part of the cladding portion of the waveguide and part of the ground electrode 107; 112 is a single-layer or a multi-layer semiconductor core layer made of a different material such as a multilayer quantum well layer; Becomes p
Semiconductor and a cap layer. In such a configuration, the semiconductor core layer 11 immediately below the central conductor 106 is formed by utilizing an electro-optic effect such as the Pockels effect, plasma effect due to carrier injection, and quantum confined Stark effect.
If the refractive index of No. 2 is changed according to the signal from the power supply 108, the effect of the present invention can be obtained.

In the above description, 2 × 2, 1 × 2 or 1 × 3
In addition to the above, for example, an optical multiplexing circuit for obtaining a high extinction ratio characteristic, an n × m optical multiplexing / demultiplexing circuit (n, m: any integer), an optical wavelength filter, The present invention can be applied to any optical device using the characteristics of the MMI waveguide, such as an optical mode filter or an optical device that multiplexes / demultiplexes light of different wavelengths.

In the above, the case where LiNbO ₃ is used for the substrate and the Ti diffusion waveguide is used for the core layer has been mainly shown, but other ferroelectric materials such as LiTaO ₃ and PLZT or the like may be used as the waveguide material. The present invention can be applied to devices using any optical waveguide material having an electro-optical effect such as a semiconductor material, an inorganic material such as glass and quartz, and an organic material such as polyimide.

Although the case where the refractive index of the core layer in the MMI waveguide is mainly changed by an external power supply has been described above, for example, the refractive index of a part of the cladding layer arranged near the core layer of the MMI waveguide is changed. The same effect can be obtained by controlling the propagation characteristics of each mode by changing the mode. Also, the case where the input / output waveguide is arranged in the input / output section of the MMI waveguide has been described.
Even when other optical waveguide devices are directly optically coupled to the MI input / output unit at the respective waveguide end faces or connected via lenses, the MMI of the MMI is adjusted to match the spot size of the connected guided light. The effects of the present invention can be obtained by appropriately setting the structure, material, and dimensions. It is obvious that the effects of the present invention can be obtained even if other optical function devices are monolithically or hybrid-integrated in the optical control device input / output waveguide section of the present invention.

[0044]

As described above, the optical control circuit according to the present invention, as an optical multiplexing / demultiplexing circuit, has a function of multiplexing / demultiplexing light waves by utilizing interference between a plurality of modes in a waveguide. Using a mode interference waveguide, a control electrode is arranged in at least a part of the area so as to match the excitation mode field shape, and light is multiplexed / demultiplexed by applying a voltage or current from an external power supply to the control electrode. Since the control or switching operation is performed, the allowable deviation of the material, dimensions, and the like at the time of device fabrication is reduced, and furthermore, a highly efficient operation from low loss is enabled.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a light control circuit according to the present invention.

FIG. 2 is a top view showing one embodiment of the light control circuit according to the present invention.

FIGS. 3A, 3B and 3C are diagrams for explaining the principle of the present invention.

FIGS. 4A and 4B are diagrams for explaining the effect of the present invention.

FIGS. 5A and 5B are diagrams for explaining the effect of the present invention.

FIG. 6 is a top view showing another embodiment of the present invention.

FIG. 7 is a top view showing another embodiment of the present invention.

FIG. 8 is a diagram for explaining the effect of the present invention.

FIG. 9 is a top view showing another embodiment of the present invention.

FIG. 10 is a diagram for explaining an effect of the present invention.

FIG. 11 is a top view showing another embodiment of the present invention.

FIG. 12 is a diagram for explaining an effect of the present invention.

FIG. 13 is a top view showing another embodiment of the present invention.

FIG. 14 is a diagram for explaining an effect of the present invention.

FIG. 15 is a top view showing another embodiment of the present invention.

FIG. 16 is a top view showing another embodiment of the present invention.

FIG. 17 is a perspective view showing one embodiment of the present invention.

FIG. 18 is a perspective view of a conventional light control circuit.

[Explanation of symbols]

11, 21, 41, 51, 61, 71, 81 substrates 12, 22, 42, 52, 62, 72, 82 input waveguides 13, 23, 43, 53, 63, 73, 83 output waveguides 14, 24, 44, 54, 64, 74, 83 MMI waveguide 15, 25, 45, 55, 65, 75, 85 Buffer layer 16, 26, 46, 56, 66, 76 Electrode center conductor 17, 27, 47, 57, 67 , 77 Electrode ground conductor 18, 28, 48, 58, 68, 78, 88 External power supply 86, 87 Coplanar electrode 90 Termination resistor 106 Center conductor 107 Ground electrode 108 Power supply 111 N-type semiconductor 112 Semiconductor core layer 113 P-type semiconductor and cap layer

Claims (8)

[Claims] 1. An optical control circuit comprising a multi-mode interference waveguide having one or more optical input units and one or more optical output units, comprising: one or more electrodes;
One is arranged on the multimode interference waveguide, and one or more of the electrodes is adapted to the distribution of the mode field excited in the multimode interference waveguide,
A light control circuit, wherein the number, shape and arrangement are set. 2. The method according to claim 1, wherein one or more of the electrodes determine a peak position of a mode field distribution of a mode used for circuit operation among modes excited in the multi-mode interference waveguide. A light control circuit characterized in that the number, shape, and arrangement are set so as to include the light control circuit. 3. The light control circuit according to claim 1, wherein each output light from the light output section of the light control circuit is equally distributed in a state where no bias is applied to the electrode. . 4. The light control circuit according to claim 1, wherein one or a plurality of light output units of the light control circuit output the light without applying a bias to the electrode. A light control circuit characterized by the above. 5. The light control circuit according to claim 1, wherein the plurality of electrodes constitute a traveling waveform electrode. 6. The light control circuit according to claim 1, wherein a plane shape of one or both of the multimode interference waveguide and the electrode is tapered. 7. The multimode interference waveguide according to claim 1, wherein the multimode interference waveguide is 1 × 2, 2 × 2, or 1 × 3.
An optical control circuit, which is a multimode interference waveguide. 8. The operation method of the light control circuit according to claim 1, wherein a polarity and a magnitude of a voltage applied to each of the electrodes are:
An operation method of the light control circuit, wherein the operation is set so as to match a distribution of a mode field excited in the multimode interference waveguide.