JPH0659223A - Waveguide type optical modulator - Google Patents

Abstract

PURPOSE:To provide the waveguide type optical modulator which exhibits a wide operation band of >=100GHz at a low loss by using an org. high-polymer material as the optical modulator which has a single mode waveguide structure effective for improvement of modulation efficiency and is optimized in electrode structure so as to attain the speed matching of microwaves and light. CONSTITUTION:The film thickness of the waveguide layer 9 is specified to 4 to 6mum, the film thickness combining the film thicknesses of the waveguide layer 9 and upper and lower clad layers 8, 10 to 10 to 25mum and the difference in the specific refractive index between the waveguide layer 9 and the clad layers 8, 10 in contact therewith to 0.4 to 1.0%. This optical modulator has boundary layers 7, 11 having the refractive index smaller than the refractive index of the lower clad layer 8 and the upper clad layer 10 and >=2% difference in the specific refractive index between the clad layers 8 and 10 in the part in contact with the lower grounding electrode 6 of the lower clad layer 8 and the microstrip electrode 12 of the upper clad layer 10. The width of the upper microstrip electrode 12 is set at about twice the film thickness combining the film thicknesses of the waveguide 9 and the upper and lower clad layers 8, 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide type optical modulator applying the electro-optic effect, and more particularly to an optical modulator having a high operating speed.

[0002]

The electro-optic effect is a phenomenon in which the refractive index of an optical medium changes when an electric field is applied to the medium.
There are a linear electro-optic effect (Pockels effect) caused by the second-order optical nonlinearity and a second-order electro-optic effect (Kerr effect) caused by the third-order optical nonlinearity. Practically, since the second-order nonlinear constant is several orders of magnitude larger than the third-order nonlinear constant, the electro-optic effect utilizing the second-order nonlinearity is often used. A waveguide type optical modulator utilizing this effect is incorporated in an optical integrated circuit and can be applied to high-speed external modulation of a semiconductor laser or the like. Therefore, an optical modulator having a high operation speed (wide modulation band) is strongly demanded. . Examples of this type of external modulator include a light intensity modulator and an optical phase modulator.

As an example of a conventional external modulator, an inorganic ferroelectric crystal LiNbO ₃ (LN) whose perspective view is shown in FIG. 11 is shown.
(Reference: Izutsu et al., Transactions of the Institute of Electronics and Communication Engineers, Volume J64-C, No. 4, 264, 1981). Here, the modulation electrode 1 is a traveling wave electrode made of a metal layer such as Au or Cu, and a symmetrical or asymmetrical flat strip line is used. The optical waveguide portion 2 is a portion in which Ti ions and the like are internally diffused in the LN crystal 3 cut out in an appropriate orientation to increase the refractive index. The incident light is branched into two ports by a Y branch near the entrance, and the light propagating through one port interacts with the microwave applied by the electrode 1 to cause a phase change. The light wave that caused this phase change propagated through another port (no phase change)
The light waves that merge with the light wave at the Y-branch near the exit and are superposed cause a change in intensity due to a phase change.

In the case of this optical modulator, since the electrode 1 is constructed as a traveling wave electrode, ideally, there is no limitation on the bandwidth of an electric circuit. Further, as long as the propagation speeds of the microwave propagating through the electrode 1 and the light wave are the same, there is no limitation on the bandwidth due to the influence of the time during which the incident light travels through the optical waveguide 2. To be done.

In reality, however, there is a speed difference between the microwave and light, which limits the bandwidth. The equivalent refractive index of the LN crystal for microwave and light is n _m ,
_Assuming that n _{o is} the length of the electrode on the waveguide and l is the bandwidth BW caused by this velocity difference,

BW = 1.4c / (πl | n _m −n _o |) (1) where c is the speed of light

[0007] Here, n _o is approximately 2.3 in the 1.3 μm band, and nm can be approximately estimated by the following equation and is approximately 4.2.

Nm = [(1 + ε _g ) / 2] ^1/2 (2) where ε _g is the dielectric constant of the crystal forming the waveguide.

As described above, in the conventional optical modulator, since the dielectric constant (about 34) of the crystal itself that constitutes the waveguide is large, the equivalent refractive index of the microwave greatly exceeds the refractive index of the crystal,
Bandwidth is limited by the phase velocity difference between microwaves and light waves. Further, in order to improve this velocity mismatch, it is necessary to shorten the interaction length (electrode length) l of the microwave and the light wave, as can be seen from the equation (1). However, when the electrode length 1 is shortened, the driving voltage increases, and the modulation efficiency decreases.

On the other hand, a nonlinear optical material made of an organic polymer material has a dielectric constant smaller than that of an inorganic material, and it is expected that the above-mentioned problem of speed mismatch can be remarkably improved. It is expected to be a high-performance optical modulator material because it is highly workable and has a large second-order nonlinear optical system χ ^{(2) in a} wide wavelength range.

[0011]

As described above, the organic polymer material has various advantages as a material for an optical modulator, but in reality, it has a single mode waveguide structure effective for improving the modulation efficiency. As for the optical modulator with the electrode structure optimized so that the velocity matching between microwave and light is achieved, a waveguide type optical modulator using an organic polymer material and exhibiting a wide operating band of 100 GHz or more is used. Not reported.

The present invention has been made under such a background, and an object thereof is to solve the above problems of the existing optical modulator and to provide a low loss and high speed optical modulator. is there.

[0013]

In order to solve the above problems, in a waveguide type optical modulator according to the present invention, a lower ground electrode made of metal is arranged on a silicon substrate on which a silicon oxide film is formed, A channel waveguide layer made of a material in which a polymer having a high second-order nonlinear susceptibility dissolved or bound thereto is polarized, and the waveguides are formed on the left, right, top, and bottom of the waveguide layer. In a light modulator having a structure in which a clad layer having a lower refractive index than the layer is arranged, and a microstrip electrode made of metal is arranged on the upper clad layer, the waveguide layer has a thickness of 4 to 6 μm. The total thickness of the waveguide and the upper and lower clad layers is 10 to 25 μm, and the relative refractive index difference between the waveguide layer and the clad layer in contact with the waveguide layer is 0.
4% to 1.0%, and the refractive index is smaller than that of the lower clad layer and the upper clad layer at the portion of the lower clad layer that contacts the lower ground electrode and the portion of the upper clad layer that contacts the microstrip electrode. Is characterized in that it has a boundary layer having a relative refractive index difference of 2% or more, and the width of the upper microstrip electrode is approximately twice as large as the total thickness of the waveguide layer and the upper and lower cladding layers. .

Further, according to the present invention, a lower ground electrode made of metal is arranged on a silicon substrate having a silicon oxide film formed thereon, and a substance having a large second-order optical non-linear susceptibility is dissolved on the lower ground electrode. A channel waveguide layer made of a material obtained by subjecting a coupled polymer to polarization treatment, and clad layers having a refractive index lower than that of the waveguide layer are arranged on the left, right, top and bottom of the waveguide layer. In a waveguide type optical modulator having a structure in which a microstrip electrode made of a metal is disposed, the film thickness of the waveguide is 2 μm or less, and the film thickness of the waveguide layer and upper and lower clad layers is 10 μm or less, The relative refractive index difference between the waveguide layer and the left and right cladding layers is 0.2% to
0.5%, the relative refractive index difference between the waveguide layer and the upper and lower clad layers is 2% or more, and the width of the upper microstrip electrode is about 2 of the film thickness of the waveguide layer and the upper and lower clad layers combined. It is characterized by doubling.

In the present invention, in an optical modulator having a structure in which a microstrip electrode made of metal is arranged on the uppermost part, an organic polymer material exhibiting a primary electro-optical effect is used as a core layer material, and a surrounding clad layer material. Is characterized by optimizing the relative refractive index difference between and to form a single-mode waveguide, and narrowing the gap between the upper and lower electrodes to drive at a low voltage. Furthermore, the width of the uppermost microstrip electrode and the configuration of the connection portion (field through portion) from the coaxial cable to the microstrip electrode are optimized to perform a wide band modulation operation.

The prior art is composed of an organic polymer material exhibiting a large first-order electro-optical effect and has a single mode waveguide structure effective for improving the modulation efficiency, and the speed of microwave and light. The difference is that the microstrip electrode structure has been optimized to achieve matching.

[0017]

In the optical modulator having the structure in which the microstrip electrodes of the present invention are arranged, the electric field of the electric signal for modulation is different from that of the conventional optical modulator having the symmetrical or asymmetrical co-branner electrode as shown in FIG. Since there is a large overlap with the guided light, it is easy to reduce the drive voltage. Further, in the optical modulator of the present invention, the organic polymer material exhibiting the primary electro-optical effect is used as the core layer material, and the relative refractive index difference with the surrounding clad layer material is optimized to form a single mode waveguide. Therefore, even if the distance between the upper and lower electrodes is narrowed, it is possible to suppress the optical loss due to the metal forming the electrodes to a range that does not pose a practical problem, so that the low voltage driving which is the object of the present invention can be performed. Become.

In one optical modulator of the present invention, the thickness of the waveguide made of the organic polymer is 4 to 6 μm, which is optimal for mode matching with a polarization maintaining fiber having a small diameter (5 μm diameter).
In order to reduce the drive voltage, the total thickness of the waveguide and the upper and lower clad layers is suppressed to 10 to 25 μm.
FIG. 1 shows the dimension d of a rectangular optical waveguide that satisfies the single mode condition.
And the relative refractive index difference Δn between the waveguide and the clad layer in contact with it.
It is the result of calculating the relationship with and by the equivalent refractive index method. Figure 1
As can be seen from the above, when the thickness of the waveguide is 4 to 6 μm, if Δn is 0.4% to 1.0%, the single mode waveguide is formed at 1.3 μm and 1.55 μm. On the other hand, in order to prevent an increase in optical loss due to the electrodes, the lower cladding layer and the upper cladding layer have a smaller refractive index in the portion of the lower cladding layer that contacts the lower ground electrode and the portion of the upper cladding layer that contacts the microstrip electrode. A boundary layer having a large relative refractive index difference from the clad layer may be provided. As a result of detailed electromagnetic field analysis, it was found that the propagation loss due to the metal electrode can be suppressed to 0.1 dB / cm or less by setting the relative refractive index difference to 2% or more.

According to another optical modulator of the present invention,
The thickness of the waveguide made of the organic polymer is 2 μm or less, and the thickness of the waveguide and the upper and lower clad layers combined is 10 μm or less. FIG. 2 shows the result of calculation by the equivalent refractive index method of the relationship between the dimensions w and d of the rectangular optical waveguide satisfying the single mode condition and the relative refractive index difference Δn ₂ between the waveguide and the upper and lower clad layers in contact with it. Here, Δn ₃ is the relative refractive index difference between the waveguide and the left and right cladding layers in contact with it. As can be seen from the figure, when the film thickness of the waveguide is 2 μm or less and the film thickness of the waveguide and the upper and lower clad layers is 10 μm or less,
The relative refractive index Δn ₃ between the waveguide and the left and right cladding layers is 0.5.
% Or less, the relative refractive index difference Δn between the waveguide and the upper and lower clad layers
_{If 2} is 2% or more, the waveguide width w is small (5 μm diameter).
Optimal mode matching with polarization maintaining fiber 4
At ~ 6 μm, it becomes a single mode waveguide.

In the optical modulator according to the present invention, since the dielectric constant (about 3.6) of the organic polymer itself which constitutes the waveguide is small, the equivalent refractive index of microwave becomes almost equal to the refractive index of the organic polymer. , The band is not limited by the phase velocity difference between the microwave and the light wave. Therefore, it is not necessary to shorten the interaction length (electrode length) l of the microwave and the light wave.

Further, in the optical modulator of the present invention, the width of the uppermost microstrip electrode and the configuration of the connection portion (field through portion) from the coaxial cable to the microstrip electrode are optimized so that impedance matching of the coaxial cable can be improved. As a result, the microwave of a wide frequency band can be used as an electric signal for modulation, and the wide band modulation operation which is the object of the present invention can be performed. FIG. 3 shows the result of calculation of the relationship between the characteristic impedance Z ₀ of the microstrip electrode and the ratio of the width of the microstrip electrode to the distance between the electrodes (film thickness of the waveguide and the clad layer). As can be seen from the figure, if the width of the microstrip electrode is about twice the film thickness of the waveguide and the clad layer, the coaxial cable (characteristic impedance 50Ω)
Impedance matching with can be obtained. FIG. 4 shows the result of calculation of the relationship between the characteristic impedance Z ₀ of the field through portion and the ratio of the gap between the lower ground electrode and the upper electrode width. As can be seen from the figure, if a gap of about 1.65 to 1.70 times the width of the upper electrode is opened in the lower ground electrode just below the upper electrode, the characteristic impedance becomes 50Ω, and the coaxial cable or the microstrip electrode. Impedance matching with can be obtained.

As a polymer material in which a substance having a large second-order optical non-linear susceptibility is dissolved or bound to the present invention, it is easy to reduce the loss and have a high degree of processing freedom. Methyl methacrylate (PMMA)
Acrylic ester resins, polystyrene resins, deuterium-substituted products of these resins, or resins containing a fluorine atom as described in Japanese Patent Application No. 3-269728, and Japanese Patent Application No. No. 184080 or Japanese Patent Application No. 4-20074, a material in which an organic dye compound composed of a stilbene compound, an azo compound or an azomethine compound is dispersed in a polymer or bonded to a side chain of the polymer. Can be used.

In the optical modulator of the present invention, the materials used for the upper and lower clad layers of the waveguide and the boundary layers near the electrodes have a refractive index higher than that of the above organic polymer material forming the core layer. The epoxy resin is not particularly limited as long as it is small, and examples thereof include epoxy-based or acrylic UV-curable resins.

When the above-mentioned organic polymer used in the optical modulator of the present invention is subjected to polarization treatment, the optical modulator is sandwiched between a pair of electrodes and the glass transition temperature of the organic polymer (about 1
(100 to 150 ° C.) or higher, and a high voltage is applied between the electrodes to perform electric field orientation of the organic polymer. After that, the orientation is frozen by gradually cooling while applying the high voltage. By doing so, the primary electro-optical effect can be imparted to the core portion of the waveguide to be exhibited.

Next, the waveguide type optical modulator of the present invention will be specifically described with reference to Examples.

[0026]

EXAMPLE 1 FIG. 5 is a sectional view of a waveguide type optical intensity modulator of the present invention. As shown in FIG. 5, a lower ground electrode 6 made of gold is formed on a silicon substrate 4 on which a silicon oxide film 5 is formed by a thermal oxidation method by a plating method, and then a low refractive index An epoxy-based UV curable resin was applied to a thickness of 2 μm to form a boundary layer 7, and an epixy-based UV curable resin was applied thereon to a thickness of 4 μm to form a lower clad layer 8. At this time, the refractive indices of the two ultraviolet curable resins were adjusted so that the relative refractive index difference between the lower cladding layer 8 and the boundary layer 7 was 2%. After the organic polymer of Chemical formula 1 was applied thereon to a thickness of 5 μm by a spin coating method, a Mach-Zehnder interferometer type waveguide pattern mask was used to perform 5 by the method described in Japanese Patent Application No. 3-254352.
A channel waveguide layer 9 having a dimension of × 5 μm was formed. Next, an epoxy-based UV-curing resin is applied on this to a thickness of 4 μm from the channel waveguide to form an upper clad layer 10, and a low-refractive-index epoxy-based UV-curing resin is further formed thereon to a thickness of 2 μm. The boundary layer 11 was formed by coating. Here, the epoxy-based ultraviolet curable resin used for the upper and lower clad layers 8 and 10 had a relative refractive index difference of 0.6% from that of the channel waveguide layer 9. Further, on the boundary layer 11, a microstrip electrode 1 made of gold and having a width of 33 μm and a thickness of 10 μm is formed so as to overlap with one arm of the Mach-Zehnder interferometer type channel waveguide 9.
2 was formed by a plating method. The length of the microstrip electrode 12 overlapping the channel waveguide was 15 mm.

FIG. 6 is a sectional view of the field through portion of the waveguide type optical modulator of the present invention. As shown in FIG. 6, in the field through portion, a lower ground electrode 6 made of gold and a low refractive index epoxy-based ultraviolet curable resin (on a silicon oxide film 5 formed on a silicon substrate 4 by a thermal oxidation method). 2 μm
Thickness), a clad layer 13 made of an epoxy UV curable resin (4 μm thick), and a boundary layer 1 made of an epoxy UV curable resin (2 μm) having a low refractive index.
1 and a microstrip electrode 1 made of gold and having a maximum width of 300 μm and a thickness of 10 μm, which is formed by plating.
The microstrip electrode 14 is composed of
A structure in which a gap having a size of about 1.68 times the width of the microstrip electrode is opened in the lower ground electrode 6 directly under the electrode is adopted. The width of the microstrip electrode 14 gradually decreases toward the center of the optical modulator, and finally becomes the same width 33 μm as the microstrip electrode 12 of FIG. 5, and the gap of the lower ground electrode 6 is discontinuous at this point. To be 0 μm.

This waveguide type optical modulator was polarized by a parallel plate electrode, and then laser light having a wavelength of 1.55 μm was made incident from the end face to measure a near-field image of the emitted light.
It was confirmed that only a single mode propagated. Furthermore, when microwave was input from the field through part via the coaxial cable, 100G was generated at a drive voltage of about 4V.
It was found that optical modulation can be performed up to Hz.

[0029]

[Chemical 1]

[0030]

[Embodiment 2] FIG. 7 is a sectional view of a waveguide type optical intensity modulator of the present invention. As shown in FIG. 7, a lower ground electrode 17 made of gold is formed on a silicon substrate 15 on which a silicon oxide film 16 is formed by a thermal oxidation method by a plating method, and then epoxy-based ultraviolet curing is performed. The resin was applied to a thickness of 4 μm to form the lower clad layer 18. After the organic polymer of Chemical formula 2 was applied thereon to a thickness of 2 μm by a spin coating method, a Mach-Zehnder interferometer type waveguide pattern mask was used to perform 2 × by the method described in Japanese Patent Application No. 3-254352. Channel waveguide layer 1 having a dimension of 5 μm
9 was formed. Next, a thick layer of epoxy-based UV curable resin was applied on this, and then etched to the same height as the waveguide layer by reactive ion etching to form the clad layers 20 on the left and right of the waveguide. Here, the epoxy-based ultraviolet curable resin used for the left and right clad layers 20 had a relative refractive index difference with the channel waveguide layer 19 of 0.3%. In addition, 4μ of epoxy UV curable resin
Then, the upper clad layer 21 was formed by applying it to a thickness of m. Here, the epoxy-based ultraviolet curable resin used for the upper and lower clad layers 18 and 21 has a relative refractive index difference of 2% from that of the channel waveguide layer 19. Further, a microstrip electrode 22 made of gold and having a width of 17 μm and a thickness of 10 μm is formed on the upper clad layer 21 so as to overlap with one arm of the Mach-Zehnder interferometer type channel waveguide 19.
Was formed by a plating method. The length of the microstrip electrode 22 overlapping the channel waveguide was 15 mm.

FIG. 8 is a sectional view of the field through portion of the waveguide type optical modulator of the present invention. As shown in FIG. 8, the field through portion is composed of a lower ground electrode 17 made of gold and an epoxy ultraviolet curable resin (4 μm thick) on a silicon oxide film 16 formed on a silicon substrate 15 by a thermal oxidation method. A lower clad layer 18, a clad layer 20 made of an epoxy UV curable resin (2 μm thick) having a refractive index close to that of the organic polymer of Chemical formula 2, and an upper clad layer 21 made of an epoxy UV curable resin (4 μm thick). And a microstrip electrode 23 made of gold and having a maximum width of 300 μm and a thickness of 10 μm, which is formed on the microstrip electrode 23 directly below the microstrip electrode 23. Width of about 1.6
We adopted a structure with a gap eight times larger. The width of the microstrip electrode 23 gradually decreases toward the center of the optical modulator, and finally becomes the same width of 17 μm as the microstrip electrode 22 of FIG. 8, and the gap of the lower ground electrode 17 is discontinuous at this point. To be 0 μm.

This waveguide type optical modulator was subjected to polarization treatment by parallel plate electrodes, and then laser light having a wavelength of 1.55 μm was made incident from the end face to measure a near-field image of the emitted light.
It was confirmed that only a single mode propagated. Furthermore, when microwave was input from the field through part via the coaxial cable, 100G was generated at a driving voltage of about 2V.
It was found that optical modulation can be performed up to Hz.

[0033]

[Chemical 2]

[0034]

[Embodiment 3] FIG. 9 is a sectional view of a waveguide type optical phase modulator of the present invention. As shown in FIG. 9, a lower ground electrode 26 made of gold is formed on a silicon substrate 24 on which a silicon oxide film 25 is formed by a thermal oxidation method by a plating method, and then epoxy-based ultraviolet curing is performed. The resin was applied to a thickness of 4 μm to form the lower clad layer 27. After the organic polymer of Chemical formula 3 is applied thereon to a thickness of 2 μm by a spin coating method, a linear waveguide pattern mask is overlaid and exposed to ultraviolet rays to expose a channel waveguide layer 28 having a size of 2 × 5 μm. The clad layers 29 on the left and right of this waveguide layer were formed. At this time, the exposure amount of ultraviolet rays was adjusted so that the relative refractive index difference between the channel waveguide layer 28 and the left and right cladding layers 29 was 0.2% to 0.5%. Next, an epoxy-based ultraviolet curable resin was applied thereon to a thickness of 4 μm to form the upper clad layer 30. Here, the epoxy-based ultraviolet curable resin used for the upper and lower clad layers 27 and 30 has a relative refractive index difference of 2% from that of the channel waveguide layer 28. Further, a width 17 made of gold is formed on the upper clad layer 30 so as to overlap the channel waveguide 28.
A microstrip electrode 31 having a thickness of 10 μm and a thickness of 10 μm was formed by a plating method. The length of the microstrip electrode 31 overlapping the channel waveguide was set to 15 mm.

FIG. 10 is a sectional view of the field through portion of the waveguide type optical modulator of the present invention. As shown in FIG.
The field through portion is composed of a lower ground electrode 26 made of gold and an epoxy-based ultraviolet curable resin (4 μm) on a silicon oxide film 25 formed on a silicon substrate 24 by a thermal oxidation method.
Thickness), a lower clad layer 27 made of an organic polymer of Chemical formula 3 (thickness: 2 μm), and an upper clad layer 30 made of an epoxy ultraviolet curing resin (thickness: 4 μm).
And, it was formed on this by the plating method. Maximum width of gold 3
00 μm, 10 μm thick microstrip electrode 32
And a structure in which a gap having a size of about 1.68 times the width of the microstrip electrode is opened in the lower ground electrode 26 immediately below the microstrip electrode 32. The width of the microstrip electrode 32 gradually decreases toward the center of the optical modulator, and finally becomes the same width of 17 μm as the microstrip electrode 31 of FIG. 10, and the gap of the lower ground electrode 26 is discontinuous at this point. 0 μm
And

This waveguide type optical modulator was subjected to polarization treatment by parallel plate electrodes, and then laser light having a wavelength of 1.55 μm was made incident from the end face to measure a near-field image of the emitted light.
It was confirmed that only a single mode propagated. Furthermore, when microwave was input from the field through part via the coaxial cable, 120G was generated at a driving voltage of about 3V.
It was found that optical modulation can be performed up to Hz.

[0037]

[Chemical 3]

[0038]

As described above, in the waveguide type optical modulator according to the present invention, the organic polymer material having a large primary electro-optical effect is used as the core layer material, and the relative refractive index difference from the surrounding cladding layer material is used. Is optimized to form a single mode waveguide, and the upper and lower electrode intervals are narrowed so that low voltage driving is possible.
Furthermore, since the width of the uppermost microstrip electrode and the configuration of the connection portion (field through portion) from the coaxial cable to the microstrip electrode are optimized, the modulation operation can be realized in an extremely wide band.

[Brief description of drawings]

FIG. 1 is a waveguide parameter characteristic diagram that gives a single mode condition of a waveguide type optical modulator according to the present invention.

FIG. 2 is a waveguide parameter characteristic diagram giving a single mode condition of the waveguide type optical modulator according to the present invention.

FIG. 3 is an impedance characteristic diagram of a microstrip electrode portion of a waveguide type optical modulator according to the present invention.

FIG. 4 is an impedance characteristic diagram of a field through portion of a waveguide type optical modulator according to the present invention.

FIG. 5 is a sectional view showing a configuration of a waveguide type optical modulator according to the present invention.

FIG. 6 is a sectional view showing the structure of a field through of a waveguide type optical modulator according to the present invention.

FIG. 7 is a sectional view showing a configuration of a waveguide type optical modulator according to the present invention.

FIG. 8 is a sectional view showing the structure of a field through of a waveguide type optical modulator according to the present invention.

FIG. 9 is a sectional view showing a configuration of a waveguide type optical phase modulator according to the present invention.

FIG. 10 is a sectional view showing the structure of a field through of a waveguide type optical modulator according to the present invention.

FIG. 11 is a perspective view of a conventional waveguide type optical intensity modulator.

[Explanation of symbols]

 1 Modulation Electrode 2 Optical Waveguide Section 3 LN Crystal 4 Silicon Substrate 5 Silicon Oxide Film 6 Lower Ground Electrode 7 Boundary Layer 8 Lower Clad Layer 9 Channel Waveguide Layer 10 Upper Clad Layer 11 Boundary Layer 12 Microstrip Electrode 13 Cladding Layer 14 Micro Strip electrode 15 Silicon substrate 16 Silicon oxide film 17 Lower ground electrode 18 Lower clad layer 19 Channel waveguide layer 20 Cladding layer 21 Upper clad layer 22 Microstrip electrode 23 Microstrip electrode 24 Silicon substrate 25 Silicon oxide film 26 Lower ground electrode 27 Lower part Clad layer 28 Channel waveguide layer 29 Clad layer 30 Upper clad layer 31 Microstrip electrode 32 Microstrip electrode

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Haruki Ozawaguchi 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (4)

[Claims] 1. A lower ground electrode made of a metal is arranged on a silicon substrate having a silicon oxide film formed on the upper surface thereof, and a substance having a large second-order optical non-linear susceptibility is dissolved or bonded on the lower ground electrode. A channel waveguide layer made of a polarized polymer material, and to the left, right, top and bottom of this waveguide layer,
In a waveguide type optical modulator having a structure in which a clad layer having a refractive index lower than that of the waveguide layer is arranged, and a microstrip electrode made of metal is arranged on the upper clad layer, the film thickness of the waveguide layer is 4 to 6 μm, the total thickness of the waveguide layer and upper and lower cladding layers is 10 to 25 μm, and the relative refractive index difference between the waveguide layer and the cladding layer in contact with the waveguide layer is 0.4% to 1.0%.
The lower clad layer has a smaller refractive index than the lower clad layer and the upper clad layer, and has a relative refractive index difference of 2 with the part of the lower clad layer that contacts the lower ground electrode and the part of the upper clad layer that contacts the microstrip electrode. % Of the boundary layer, and the width of the upper microstrip electrode is about twice as large as the total thickness of the waveguide and the upper and lower cladding layers. 2. In the field through portion, the lower ground electrode directly below the upper electrode has a width of about 1.67 to 1.
The waveguide type optical modulator according to claim 1, wherein a gap having a size of 68 times is opened. 3. A lower ground electrode made of metal is disposed on a silicon substrate having a silicon oxide film formed on the upper surface thereof, and a substance having a large second-order nonlinear susceptibility is dissolved or bonded on the lower ground electrode. A channel waveguide layer made of a polarized polymer material, and to the left, right, top and bottom of this waveguide layer,
In a waveguide type optical modulator having a structure in which a clad layer having a refractive index lower than that of the waveguide layer is arranged, and a microstrip electrode made of metal is arranged on the upper clad layer, the film thickness of the waveguide layer is 2 μm or less, the total thickness of the waveguide layer and the upper and lower clad layers is 10 μm or less, and the relative refractive index difference between the waveguide layer and the left and right clad layers is 0.2% to 0.5%. And a relative refractive index difference between the upper and lower clad layers is 2% or more, and the width of the upper microstrip electrode is about twice as large as the total thickness of the waveguide and the upper and lower clad layers. Type optical modulator. 4. In the field through portion, a lower ground electrode directly below the upper electrode has a width of about 1.67 to 1.
The waveguide type optical modulator according to claim 1, wherein a gap having a size of 68 times is opened.