JP2013164615A - Optical device, optical integrated device, and manufacturing method of optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical device which achieves a small waveguide loss and low voltage driving.SOLUTION: An optical device includes a ring-shaped optical waveguide and an input/output optical waveguide, and changes a resonant wavelength of the ring-shaped optical waveguide. A refractive index controller which controls a refractive index of a guided wavelength is provided at a part of the ring-shaped optical waveguide. In the ring-shaped optical waveguide, a part other than the refractive index controller is formed of an optical material having a lower absorption coefficient than an absorption coefficient of an optical material forming the refractive index controller.

Description

  The present invention relates to an optical device used for optical communication, optical wiring, optical storage, and the like, an optical integrated device including the same, and a method for manufacturing the same.

  The electro-optic effect in which the refractive index changes due to the interaction between an electric field and a substance is applied to an optical modulator because of its high speed, low power consumption due to voltage drive, and simplicity of structure.

In an optical modulator using LiNbO ₃ , a Mach-Zehnder type waveguide is formed on a single crystal LiNbO ₃ substrate by a Ti diffusion method, and an optical modulator is formed by combining electrodes. By applying a voltage, it is possible to change the refractive index of the waveguide and turn on / off the optical signal. However, it is expensive because it is necessary to use a single crystal substrate, and the electro-optic effect of LiNbO ₃ is small, and because of the planar electrode structure, the length of the waveguide is required, and the element size is in the cm range. There is a problem that it is very big.

Pb _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O ₃ (PLZT), which is a transparent ceramic, is nearly two orders of magnitude more electro-optic than the LiNbO ₃ single crystal used in current optical modulators. Since the coefficient is large, it can be expected to reduce the cost, reduce the power consumption, and increase the speed by reducing the size of the optical element, and so far, studies on the thinning by the sol-gel method have been made (Non-Patent Document 1, Non-Patent Document 1 Reference 2).

  As an innovative technology expected in the future, silicon photonic devices that enable integration of light and electronics on one chip have been studied. By realizing this, an LSI such as a CPU and a memory and an active optical element such as an optical switch can be formed on the same substrate, and the speed of the LSI can be increased. Further, since the LSI formation technology can be applied to the manufacturing process of the optical communication device, the price of the optical device can be reduced.

  However, since silicon is an indirect transition semiconductor, it is difficult to directly form a light emitting element such as a laser on a silicon substrate. For this reason, it is important to form an optical modulator for converting an electrical signal into an optical signal on a silicon substrate. This optical modulator for LSI optical wiring is required to be small in size, with low voltage and low power consumption that can be driven under LSI operating conditions.

  As an optical modulator that satisfies this requirement, a ring resonator type made of silicon has been studied (Non-Patent Document 3). The silicon ring resonator changes the refractive index by injecting carriers into the optical waveguide layer, and performs the modulation operation by changing the resonance wavelength.

K. D. Preston and G. H. Haertling: Appl. Phys. Lett. 60 (1992) 2831. K. Nashimoto, K. Haga, M. Watanabe, S. Nakamura and E. Osakabe: Appl. Phys. Lett. 75 (1999) 1054. A. Liu, L. Liao, D. Rubin, H. Nguyen, B. Ciftcioglu, Y. Chetrit, N. Izhaky, M. Paniccia: Opt. Exp., 15 (2007) 660.

  In order to form an optical wiring system at a low cost, it is important to use a low-cost external light source. A surface-emitting laser having a wavelength of about 800 nm is less expensive than an edge-emitting laser having a wavelength of 1.5 μm that is generally used for optical communication, and can be highly integrated. Therefore, if this surface emitting laser can be applied to silicon photonics, the cost can be greatly reduced. However, since silicon is opaque at a wavelength of 800 nm, it is difficult to apply it to an optical modulator. A ring resonator type modulator using PLZT or the like having a large electro-optic coefficient as an optical modulator material is expected to be realized. However, a material such as PLZT having a large electro-optic coefficient also has a large optical absorption at a wavelength of 800 nm. However, this ring resonator type modulator has a problem that the loss of light increases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical device with low waveguide loss and low voltage drive. Moreover, it aims at providing the optical integrated device provided with this optical device.

According to the present invention, there is provided an optical device having a ring-shaped optical waveguide and an input / output optical waveguide, and changing a resonance wavelength of the ring-shaped optical waveguide,
A refractive index control unit for controlling a refractive index at a wavelength to be guided is provided in a part of the ring-shaped optical waveguide,
There is provided an optical device in which the refractive index control unit is formed of an optical material having a complex refractive index different from the complex refractive index of the optical material constituting the portion of the ring-shaped optical waveguide other than the refractive index control unit. .

  According to the invention, there is also provided an optical device manufacturing method, wherein the optical material constituting the refractive index control unit is formed by an aerosol deposition method. can do.

According to the present invention, there is also provided a method for manufacturing the above optical device,
Forming an insulating layer on the silicon substrate;
Forming a lower electrode layer in a region for forming a refractive index controller of the ring-shaped optical waveguide;
Forming a lower cladding layer;
In the region where the refractive index control unit is formed, a first core layer made of a first optical material is formed on the lower cladding layer by an aerosol deposition method, and the refractive index control unit of the ring-shaped optical waveguide is formed. In a region for forming a portion other than, a second optical material having a complex refractive index different from the complex refractive index of the first optical material is formed on the lower clad layer and connected to the first core layer. Forming a core layer of 2;
Forming an upper clad layer on the first core layer and the second core layer constituting the ring-shaped optical waveguide;
And a step of forming an upper electrode layer on the upper clad layer so as to face the lower electrode layer.

  According to the present invention, an optical device with low waveguide loss and low voltage drive can be provided, and an optical integrated device including the optical device can be provided.

The schematic diagram of the ring resonance type modulator of one Example by this invention. The schematic diagram of the ring resonance type modulator used for simulation. The figure which shows the relationship between the wavelength of the ring-shaped waveguide of PLZT with uniform optical material, and the transmittance | permeability. The figure which shows the relationship between the wavelength and transmittance | permeability of a ring-shaped waveguide of silicon | silicone with a uniform optical material. The figure which shows the relationship between the applied voltage and transmittance | permeability of a ring-shaped waveguide type | mold optical modulator of PLZT with a uniform optical material. The figure which shows the relationship between the applied voltage and the transmittance | permeability of the ring-shaped waveguide type optical modulator of the Example by this invention. The cross-sectional schematic diagram which shows the refractive index control part of the optical device of the Example by this invention. The schematic of the film-forming apparatus used in the Example by this invention. The cross-sectional schematic diagram which shows ring-shaped waveguide parts other than the refractive index control part of the optical device of the Example by this invention.

  An optical device according to an embodiment of the present invention includes a ring-shaped optical waveguide and an input / output optical waveguide, and an optical device that changes a resonance wavelength of the ring-shaped optical waveguide. A rate control unit is provided in a part of the ring-shaped optical waveguide. And in this ring-shaped optical waveguide, the complex refractive index of the optical material which comprises the refractive index control part differs from the complex refractive index of the optical material which comprises parts other than the refractive index control part. Thus, by forming the refractive index control unit and the other optical waveguide part with different materials in the ring-shaped optical waveguide, it is possible to realize an optical modulator with low waveguide loss and low voltage drive.

  Below, this embodiment which performed simulation is described.

  FIG. 1 is a schematic diagram of a ring resonance type modulator according to an embodiment of the present invention. Reference numeral 11 denotes an input / output optical waveguide. The guided light is input from a and output to b. Reference numeral 12 denotes a ring-shaped optical waveguide. Reference numeral 13 (portion surrounded by a dotted line) denotes an optical coupling portion between the input / output optical waveguide 11 and the ring-shaped optical waveguide 12. Reference numeral 14 denotes a portion (refractive index control unit) capable of controlling the refractive index of the ring-shaped optical waveguide 12. The imaginary term of the complex refractive index of the refractive index control unit 14, that is, the optical absorption is larger than the portion other than the refractive index control unit of the ring-shaped optical waveguide 12. Portions other than the refractive index control unit in the ring-shaped optical waveguide 12 are made of a material having the same complex refractive index as that of the material constituting the input / output optical waveguide 11. A dotted line portion in the ring-shaped optical waveguide 12 indicates a joint portion between the refractive index control unit 14 and another portion.

  The transfer function was used for this structure, and the transmittance b / a was simulated. In the simulation, in the ring-shaped optical waveguide 12, the reflection at the junction between the refractive index control unit 14 and another part is considered.

  FIG. 2 is a schematic diagram of the modulator used in this simulation. Reference numeral 2 denotes an electrode portion, and a change in transmittance was simulated when a voltage was applied to this portion. The ring circumference was 0.8 mm and the electrode circumference was 0.4 mm.

  Next, a simulation method for the transmittance b / a using a transfer function will be described.

  The following equation is a transfer function when the input / output optical waveguide 11 of FIG. 1 and the ring-shaped optical waveguide 12 including the refractive index control unit 14 are all made of the same material.

  Here, α is an absorption coefficient, β is a propagation constant, L is a ring circumference, K is a coupling constant, and j is an imaginary unit. The square of the absolute value of b / a is the transmittance. In the simulation of the operation of the optical modulator, the change in the propagation constant at the time of voltage application is calculated from the electro-optic coefficient, and the change in transmittance is assumed.

  In the case of the present embodiment (FIG. 1) in which the propagation constant and the absorption coefficient are different between the refractive index control unit 14 and other parts in the ring-shaped optical waveguide 12, the refractive index control unit 14 in the ring-shaped optical waveguide 12 and the like. Since the reflection occurs at the junction with this part, the transfer function becomes much more complicated, but it can be simulated by the same method.

Table 1 shows the wavelength dependence of the absorption coefficient (loss coefficient) of PLZT ((Pb _0.95 La _0.05 ) (Zr _0.3 Ti _0.7 ) O ₃ ) and silicon. The unit of this absorption coefficient is 1 / mm. The absorption coefficient of PLZT is a value of a thin film formed by an aerosol deposition method, and the absorption coefficient of silicon is a value of a bulk crystal. It can be seen that in any thin film, the absorption coefficient at a wavelength of 850 nm increases with respect to a wavelength of 1550 nm. This is due to optical absorption due to the band structure.

  FIG. 3 shows the result of simulating the relationship between the wavelength and transmittance of a PLZT ring waveguide with a uniform optical material by the above method. The vertical axis represents the transmittance, and the horizontal axis represents the change in wavelength from the resonance wavelength. The resonance wavelengths are 1550 nm and 850 nm. At the wavelength of 1550 nm, the change due to the resonance of the transmittance is large, but at the wavelength of 850 nm, the change is small, and the Q value representing the sharpness of the resonance is also small. This is because the absorption coefficient becomes 7 times at a wavelength of 850 nm.

  FIG. 4 shows the result of calculation of the relationship between the wavelength and transmittance of a silicon ring waveguide with a uniform optical material at a wavelength of 850 nm. It can be seen that the transmittance change due to resonance does not occur in the silicon ring waveguide. This is because the absorption coefficient of silicon is very large at a wavelength of 850 nm. Therefore, a ring resonator type optical modulator at a wavelength of 850 nm cannot be formed with silicon.

  FIG. 5 shows the relationship between the applied voltage and the transmittance of a PLZT ring-shaped waveguide optical modulator having a uniform optical material. Simulation was performed for wavelengths of 1550 nm and 850 nm. At a wavelength of 1550 nm, an insertion loss of 5 dB and an extinction ratio of 8 dB are obtained with a voltage as small as 3 Vpp. However, at a wavelength of 850 nm, the insertion loss of 11 dB and the extinction ratio of 3 dB significantly degrade the performance. If the length of the input / output waveguide is 1 mm and the loss is added to this, the insertion loss becomes 26 dB, and it cannot be used as a modulator unless the characteristics are improved.

FIG. 6 shows the relationship between the applied voltage and the transmittance of a ring-shaped waveguide type optical modulator according to an embodiment of the present invention with improved characteristics. The wavelength is 850 nm, and the optical constants at that time are n = 2.5 and α = 3.5 (1 / mm) in the refractive index control unit of the ring-shaped optical waveguide, In the input / output waveguide, n = 2.5 and α = 0. The refractive index control unit of the ring-shaped optical waveguide is PLZT as an optical material, and the other part of the ring-shaped optical waveguide and the input / output waveguide are assumed to be TiO ₂ by sputtering. The ratio of the optical path length between the refractive index control part of the ring-shaped optical waveguide and the other part of the ring-shaped optical waveguide is 1: 1. With an insertion loss of 7 dB, the extinction ratio at an applied voltage of 3 Vpp is 7 dB, and the performance can be greatly improved. This improvement in characteristics is due to the fact that the input / output waveguide and the part other than the refractive index control part of the ring-shaped optical waveguide are configured with a material having a small absorption coefficient.

  When the ratio of the optical path length between the refractive index control unit of the ring-shaped optical waveguide and the other part of the ring-shaped optical waveguide is 1: 3, the calculation result of the insertion loss and the extinction ratio when the ratio is 1: 7 The results are summarized in Table 2.

  As shown in Table 2, the extinction ratio is slightly reduced by reducing the ratio of the refractive index control unit, but the electrode length can be shortened, and the speed and power consumption can be reduced by reducing the electric capacity. .

  Next, Table 3 shows a simulation result when the refractive index control unit of the ring-shaped optical waveguide is different from the refractive index between the other part of the ring-shaped optical waveguide and the input / output waveguide. In the refractive index control unit of the ring-shaped optical waveguide, n = 2.5 and α = 3.5 (1 / mm). In the other part of the ring-shaped optical waveguide and the input / output waveguide, the refractive index was changed from 2.5 to 1.5, and the absorption coefficient was α = 0. The ratio of the optical path length between the refractive index control part of the ring-shaped optical waveguide and the other part of the ring-shaped optical waveguide is fixed at 1: 1. The wavelength is around 850 nm.

  As shown in Table 3, the extinction ratio decreases as the refractive index difference increases, but the amount of decrease is not so large. This is because even if the refractive index difference between the refractive index control part of the ring-shaped optical waveguide and the other part of the ring-shaped optical waveguide is 1.0, the reflectance of the junction is about 6%, which is large in the resonance state. This is thought to be because it has no effect.

  As described above, in an optical device that has a ring-shaped optical waveguide and an input / output optical waveguide and changes the resonance wavelength of the ring-shaped optical waveguide, refraction at a wavelength to be guided to a part of the ring-shaped optical waveguide. A refractive index control unit for controlling the refractive index is provided, and the complex refractive index of the optical material constituting the refractive index control unit is different from the complex refractive index of the optical material constituting the other part of the ring-shaped optical waveguide. Thus, it is clear that an optical modulator with low waveguide loss and low voltage drive can be realized. By applying this result, high performance optical devices and integrated optical devices can be formed at low cost.

  In the optical device of the present embodiment having the above-described configuration, the refractive index control unit of the ring-shaped optical waveguide is formed of an optical material different from the portion other than the refractive index control unit of the ring-shaped optical waveguide. It is desirable that the optical material used for the refractive index control unit has both high refractive index variability and transparency due to voltage or the like. When the operational characteristics such as the extinction ratio are emphasized, it is important that the refractive index variability is large. In this case, it is difficult to select a material having a large refractive index modification and sufficient transparency. Even in the case where an optical material having a large refractive index change property but not so high transparency is used for the refractive index control unit, the optical component constituting the refractive index control unit in the ring-shaped optical waveguide portion other than the refractive index control unit By using an optical material having a complex refractive index different from the complex refractive index of the material, an optical device having a small transmission loss and a large extinction ratio can be formed.

  In addition, the portion other than the refractive index control unit in the ring-shaped optical waveguide can be formed of an optical material having an absorption coefficient lower than that of the optical material constituting the refractive index control unit. This makes it possible to form an optical device with a small transmission loss and a large extinction ratio.

  In the ring-shaped waveguide, the ratio of the optical path length between the refractive index control unit and the other part (refractive index control part / other part) is 1/10 or more from the viewpoint of obtaining sufficient operating characteristics such as the extinction ratio. Is preferable, 1/8 or more is more preferable, and 1/7 or more is more preferable. On the other hand, it is preferably 1 / 0.5 or less, more preferably 1 / 0.8 or less, in terms of sufficiently suppressing transmission loss, and in the case where an electrode is provided, in terms of shortening the electrode length. More preferably, it is 1 or less.

The refractive index control unit can be formed of an electro-optic material. Thereby, an optical device such as an optical modulator with high speed and low power consumption can be formed. Examples of the electro-optic material include lead zirconate titanate or lead zirconate titanate to which lanthanum is added. As the electrochemical _{materials, Pb 1-x La x (} Zr y Ti 1-y) O 3 (0 ≦ x <1,0 <y <1) be used preferably lead zirconate titanate represented by Yes ("PZT" when x = 0, "PLZT" when 0 <x). By using such a material, it is possible to form a small active device such as a low-voltage driven optical modulator or a device.

Portions other than the refractive index control unit in the ring-shaped optical waveguide can be formed of a material selected from TiO ₂ , Ta ₂ O ₅ , SrTiO ₃ , and BaTiO ₃ . As shown in Table 3, the difference in the refractive index between the refractive index control unit of the ring-shaped optical waveguide and the other parts of the ring-shaped optical waveguide and the input / output waveguide is smaller. Desirable in characteristics. When the refractive index control unit is formed of, for example, an electro-optic material having a refractive index of 2.2 to 2.5, the refractive index of the ring waveguide portion other than the refractive index control unit may have the same refractive index. desirable. By using the above optical material, a high-performance optical device can be formed.

  In one embodiment of the present invention, as shown in FIG. 2, an electrode for forming an electric field is provided in the ring-shaped optical waveguide, and an electric signal is applied to the electrode to control an optical modulator or optical switch. It can be operated. As a result, it is possible to provide an optical modulator and an optical switch that can respond at high speed and can be reduced in size or power consumption.

  In one embodiment according to the present invention, an optical integrated device having the above-mentioned first optical device and another second optical device on the same substrate can be provided. As the second device, any of a laser, an electro-optical converter, a photoelectric converter, an optical amplifier, an optical switch, and an optical filter can be applied. A silicon substrate can be applied as this substrate.

  In an embodiment according to the present invention, an optical integrated device having the optical device and the electronic circuit on the same substrate can be provided. A silicon substrate can be applied as this substrate.

  In manufacturing an optical device according to an embodiment of the present invention, an optical material constituting the refractive index control unit can be formed by an aerosol deposition method. By using such a manufacturing method, an optical device such as an optical modulator having a small waveguide loss and a low voltage drive on an arbitrary substrate such as Si, and an optical integrated device including the optical device are realized. be able to.

  Hereinafter, the present invention will be further described by way of an example.

  FIG. 7 is a schematic cross-sectional view showing the refractive index control unit of the optical device of this example. A schematic plan view of this structure is the same as FIG. 1, and a schematic plan view of the upper electrode structure is the same as FIG.

  The optical path length ratio between the refractive index control unit and the other part of the ring-shaped optical waveguide was 1: 1.

An SiO ₂ layer 72 (film thickness 1 μm) was formed on the silicon substrate 71 by thermal oxidation. As the metal lower electrode, a Ti layer (film thickness 10 nm) 73, an Au layer (film thickness 1 μm) 74, and a Ti layer (film thickness 10 nm) 75 were formed by Ti using DC magnetron sputtering and Au using plating. An ITO layer (thickness: 0.3 μm) was formed thereon as a lower transparent electrode layer 76 by DC magnetron sputtering (sputtering gas: Ar gas).

Next, a SrTiO ₃ layer (film thickness: 0.5 μm) was formed as the cladding layer 77 by RF magnetron sputtering (substrate temperature: 300 ° C., sputtering gas: Ar + O ₂ ). Next, this SrTiO ₃ layer (cladding layer 77) was etched by an ion milling method after forming a resist having a width of 3 μm in order to form an inverted ridge structure.

Next, the SiO ₂ layer 78 was formed to a thickness of 1.5 μm by a thermal CVD method.

  Next, after forming a 3 μm wide resist strip, reactive ion etching was performed to form a concave structure having a width of 3 μm and a depth of 1 μm. Next, a core layer 79 was formed by an aerosol deposition method so as to embed this concave structure. A specific film forming method will be described later. Next, after annealing in the air at 600 ° C. for 30 minutes, surface polishing was performed to flatten the core layer.

On top of this, SrTiO ₃ was formed to a thickness of 0.5 μm as the upper cladding layer 710, and then an ITO layer (thickness 0.3 μm) was formed as the upper transparent electrode layer 711. Thereafter, a Ti layer (film thickness 10 nm) 712 and an Au layer (film thickness 1 μm) 713 were formed as metal upper electrodes. The formation method of the upper cladding layer 710, the upper transparent electrode layer 711, and the metal upper electrodes 712 and 713 is the same as the formation method of the structure on the lower side.

  Next, a method for forming the core layer by the aerosol deposition method will be described.

  FIG. 8 is a schematic view of the film forming apparatus used in this example.

  A gas cylinder 81 containing oxygen gas is connected to a glass bottle 82 via a transfer tube. After the powder raw material 83 is put in the glass bottle 82 and the inside of the glass bottle 82 is evacuated to a vacuum of about 20 Torr (2.67 kPa) via the exhaust pipe 84, oxygen is introduced as a carrier gas while controlling its flow rate. The glass bottle 82 is vibrated by the vibrator 85 to generate an aerosol in which fine particles of the raw material powder are dispersed in the gas, and the carrier is transported to the film forming chamber 87 via the transport pipe 86. The film forming chamber 87 is evacuated to a predetermined degree of vacuum by a vacuum pump 88. A thin film is formed by spraying powder onto the substrate 810 from the nozzle 89.

The film forming conditions are as follows. The carrier gas is oxygen, the incident angle of the discharge material (powder) from the nozzle to the substrate surface is 30 degrees, the gas flow rate is 12 l / min, the deposition rate is 0.5 μm / min, and the vibration frequency of the vibrator is 200 rpm. It is. A silicon substrate before core formation was used as the substrate. A lanthanum-doped lead zirconate titanate (PLZT) powder, which is an oxide having a large electro-optic effect, was used as a film forming material. The composition of PLZT is (Pb _0.95 La _0.05 ) (Zr _0.3 Ti _0.7 ) O ₃ . The average particle size of the raw material powder was 0.7 μm. The film thickness of PLZT is 3 μm. The film forming material, PLZT-based powder, is a ferroelectric composition having a perovskite crystal structure, and is suitable for an optical device having a first-order large electro-optic coefficient.

  FIG. 9 is a schematic cross-sectional view showing a ring-shaped waveguide portion other than the refractive index control unit of the optical device of this example. In this portion, the material of the core is different from that of the refractive index control unit shown in FIG. 7, and no electrode is provided.

After the SiO ₂ layer 92 (72) (film thickness 1 μm) was formed on the silicon substrate 91 (71) by thermal oxidation, the SiO ₂ layer 93 was formed to a film thickness of 1.32 μm by the thermal CVD method.

Next, an SrTiO ₃ layer (film thickness: 0.5 μm) was formed as the clad layer 94 (77) by RF magnetron sputtering (substrate temperature: 300 ° C., sputtering gas: Ar + O ₂ ).

A TiO ₂ layer (film thickness: 0.5 μm) was formed thereon as the first core layer 95 by RF magnetron sputtering (substrate temperature: room temperature, sputtering gas: Ar + O ₂ ).

Next, a SrTiO ₃ layer (cladding layer) 94 and a TiO ₂ layer (first core layer) 95 were etched by an ion milling method after forming a resist having a width of 3 μm in order to form an inverted ridge structure.

Next, the SiO ₂ layer 96 was formed to a thickness of 1.0 μm by a thermal CVD method using a lift-off method.

As the second core layer, a TiO ₂ layer 97 (film thickness: 1.0 μm) was formed by RF magnetron sputtering (substrate temperature: room temperature, sputtering gas: Ar + O ₂ ). On top of this, SrTiO ₃ was formed to a thickness of 0.5 μm as an upper cladding layer 98 (710).

In the above manufacturing process of the structure shown in FIG. 7 (refractive index control section) and the structure shown in FIG. 9 (ring optical waveguide portion other than the refractive index control section), the SiO ₂ layer 72, the SiO ₂ layer 92, and the cladding The layer 77 and the clad layer 94, the upper clad layer 710 and the upper clad layer 98 are simultaneously formed on the silicon substrate (71, 91), and the formation of the other layers such as the electrode layers masks the region of one structure. It was formed in the region of the other structure in the state.

  When a CW light having a wavelength of 1.55 μm is input to the ring-type modulator manufactured as described above and modulated at 3 Vpp with a bias voltage of 3.5 V applied, modulation up to a high frequency of 10 GHz is possible. It was. The extinction ratio at that time was 4 dB.

  As described above, in an optical device having a ring-shaped optical waveguide and an input / output optical waveguide, a high-speed, small, and low-voltage drive optical modulator can be manufactured while using an electro-optical material having a large optical absorption for the refractive index control unit. .

In this embodiment, PLZT is used as the core material of the refractive index control unit. However, the present invention is not limited to this. Electro-optical materials such as lead zirconate titanate, barium titanate, strontium-added barium titanate, and KTN are used. Is applicable. As the core material of the other part of the ring-shaped waveguide, materials for forming an optical waveguide such as Ta ₂ O ₅ , SrTiO ₃ , BaTiO ₃ , SiO ₂ , silicon nitride, etc. can be applied in addition to TiO ₂ .

  In addition, by using the aerosol deposition method for film formation of the electro-optic material of the refractive index control unit, other types of optical elements such as lasers, electro-optic converters, photoelectric converters, optical amplifiers, optical waveguides, optical filters, etc. It becomes easy to manufacture the optical element according to the present invention on a substrate formed in advance or on a substrate on which an integrated circuit composed of electronic elements such as a CPU and a memory is formed in advance. Such a manufacturing method can be applied to the production of various optical integrated devices including the optical device according to the present invention and other devices or integrated circuits.

DESCRIPTION OF SYMBOLS 11 Input / output optical waveguide 12 Ring-shaped optical waveguide 13 Optical coupling part of input / output optical waveguide and ring-shaped optical waveguide 14 Refractive index control part 2 of ring-shaped optical waveguide 2 Electrode part 71 Silicon substrate 72 SiO ₂ layer 73 Ti layer 74 Au Layer 75 Ti layer 76 Lower transparent electrode layer 77 Clad layer 78 SiO ₂ layer 79 Core layer 710 Upper clad layer 711 Upper transparent electrode layer 712 Ti layer 713 Au layer 81 Gas cylinder 82 Glass bottle 83 Powder raw material 84 Exhaust pipe 85 Exciter 86 Transport pipe 87 Deposition chamber 88 Vacuum pump 89 Nozzle 810 Substrate 91 Silicon substrate 92 SiO ₂ layer 93 SiO ₂ layer 94 Clad layer 95 Core layer 96 SiO ₂ layer 97 Second core layer 98 Upper clad layer

Claims (10)

An optical device having a ring-shaped optical waveguide and an input / output optical waveguide, and changing a resonance wavelength of the ring-shaped optical waveguide,
A refractive index control unit for controlling a refractive index at a wavelength to be guided is provided in a part of the ring-shaped optical waveguide,
A structure in which the refractive index control unit is formed of an electro-optic material, an electrode for forming an electric field in the ring-shaped optical waveguide is provided in the refractive index control unit, and an electric signal is applied to the electrode to control light. Prepared,
In the ring-shaped optical waveguide, the portion other than the refractive index control unit is formed of an optical material having an absorption coefficient lower than that of the electro-optic material constituting the refractive index control unit, so that the guide of the ring-shaped optical waveguide is formed. An optical device having a structure in which wave loss is reduced and extinction ratio is increased.   The said refractive index control part is formed with the optical material which has a complex refractive index different from the complex refractive index of the optical material which comprises the part of the said ring-shaped optical waveguide other than this refractive index control part. Optical devices.   In the ring-shaped optical waveguide, a portion other than the refractive index control unit is formed of an optical material having the same complex refractive index as that of the optical material constituting the input / output optical waveguide. 3. The optical device according to 2.   4. The optical device according to claim 1, wherein the refractive index controller is formed of a material containing lead zirconate titanate or a material containing lead zirconate titanate to which lanthanum is added. 5. The ring-shaped optical waveguide according to claim 1, wherein a portion other than the refractive index control unit is formed of a material selected from TiO ₂ , Ta ₂ O ₅ , SrTiO ₃ , and BaTiO _3. Optical devices.   An optical integrated device having the first optical device according to any one of claims 1 to 5 and another second optical device on a substrate.   The optical integrated device according to claim 6, wherein the second device is one of a laser, an electro-optical converter, a photoelectric converter, an optical amplifier, an optical switch, and an optical filter.   An optical integrated device comprising the optical device according to claim 1 and an electronic circuit on a substrate.   6. The method of manufacturing an optical device according to claim 1, wherein the optical material constituting the refractive index control unit is formed by an aerosol deposition method. . A method for manufacturing an optical device according to any one of claims 1 to 5,
Forming an insulating layer on the silicon substrate;
Forming a lower electrode layer in a region for forming a refractive index controller of the ring-shaped optical waveguide;
Forming a lower cladding layer;
In the region where the refractive index control unit is formed, a first core layer made of a first optical material is formed on the lower cladding layer by an aerosol deposition method, and the refractive index control unit of the ring-shaped optical waveguide is formed. In a region for forming a portion other than, a second optical material having a complex refractive index different from the complex refractive index of the first optical material is formed on the lower clad layer and connected to the first core layer. Forming a core layer of 2;
Forming an upper clad layer on the first core layer and the second core layer constituting the ring-shaped optical waveguide;
Forming an upper electrode layer on the upper clad layer so as to face the lower electrode layer.