CN1839336A

CN1839336A - Optical waveguide device and traveling wave type opticalmodulator

Info

Publication number: CN1839336A
Application number: CN 200480023897
Authority: CN
Inventors: 近藤顺悟; 近藤厚男; 青木谦治; 三富修
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2003-08-21
Filing date: 2004-08-19
Publication date: 2006-09-27
Anticipated expiration: 2024-08-19
Also published as: CN101221296A; CN100447615C

Abstract

A device 4 has a substrate 5 of an electro-optic crystal, an optical waveguide 2 and modulation electrodes 1A, 1B, 1C, and the substrate 5 of an electro-optic material has a thickness of 30 m or smaller at least in a region where the modulation electrode applies an electric field. The device has a ridge generated when the optical waveguide is formed, and the ridge has a height H (angstrom) and a width 'W' (mu m) whose product (HW) is 7150 angstrom m or smaller to realize single mode propagation of light in the optical waveguide. Further, the optical waveguide has branched parts in the region where the modulation electrode applied an electric field. It is possible to reduce the deviation of positions of peaks and bottoms in the extinction ratio curve, by increasing the distance of the branched parts of the optical waveguide to 46 m or larger.

Description

Fiber waveguide device and travelling-wave type optical modulator

Technical field

The travelling-wave type optical modulator that the present invention relates to fiber waveguide device and utilized it.

Background technology

Lithium niobate (LiNbO ₃), lithium tantalate (LiTaO ₃), gallium arsenide (GaAs) is applied to the optical modulator of optical waveguide, particularly the travelling-wave type optical modulator possesses excellent characteristic, has the possibility that can realize the high-band broadening with high energy efficiency.Lithium niobate, lithium tantalate are unusual excellent material as ferroelectrics, and it is big that it has electro-optic constants, and the light path that can lack is carried out the advantage of the control of light.As the main cause of the modulating speed of restriction travelling-wave type optical modulator, speed does not match such as having, dispersion and export license, dielectric loss, impedance do not match etc.

The optical modulator of this common type has substrate, optical waveguide, by modulator electrode, cushion that signal electrode and ground-electrode are made, be the form of more complicated.For the size of these each key elements, proposed various schemes and carried out various discussion.

The applicant opens flat 10-133159 communique the spy, the spy drives the substrate of having announced in the 2002-169133 communique in the travelling-wave type optical modulator thinner wall section is set under optical waveguide, and the thin thickness that makes this thin-walled portion is to for example below the 10 μ m.Like this, do not form the cushion of making by monox and can carry out the high speed optical modulation yet, owing to can reduce driving voltage V π and electrode length L long-pending (V π L), thus favourable.

In addition, be accompanied by multimedia development, the broadband demand of communicating by letter is increased, expectation surpasses the practicability and the further high speed of the light broadcasting system of 10Gb/s.As the device use that the electric signal more than the 10Gb/s (microwave signal) is modulated into light is the LN optical modulator.

In order to increase the modulation band-width of optical modulator, invented by making the optical waveguide substrate attenuation obtain the structure of the speeds match of microwave and light wave.In addition, in the structure that makes the optical waveguide attenuation, in order to satisfy the speeds match condition, the substrate thickness that need make the optical waveguide periphery is about 10 μ m, in order to prevent the flattening of optical mode filter pattern, the rough surface that inhibition brings because of the processing of substrate attenuation and groove, the influence of damage and the propagation loss of the light that produces, open the spy and to have applied for 2 sections reverse groove structures in the 2002-169133 communique, and, in the making of 2 sections reverse groove structures, can also make substrate form the groove structure behind the attenuate equably, be willing to apply in the 2001-101729 communique in order to keep the physical strength of device and the auxiliary structure of strengthening substrate to be set in this occasion the spy.

Open in the device of putting down in writing in the flat 9-211402 communique the spy, by on the substrate air layer being set, and become the structure that satisfies the speeds match condition auxiliary the reinforcement.In addition, open in the device of putting down in writing in the 2001-235714 communique the spy, optical waveguide with the bonding plane that keeps matrix on.

But, open in 2002--169133 communique, the special device of being willing to 2001-101729 number record the spy, in the rear side of modulator substrate groove is set, by bonding this modulator substrate of adhesive linkage and the auxiliary substrate of strengthening that forms with dielectric materials.When this structure applied excessive load in fail-tests such as thermal shock test or temperature cycling test, temperature drift and DC drift can become big.

Open flat 10-133159 communique, spy the spy and open in the sort of slim modulator of 2002-169133 communique record, when measuring the extinction ratio curve, by detailed discovering, with the modulator of common type extinction ratio variation relatively.For example, as shown in figure 11, the summit of extinction ratio or extinction ratio curve (output power during ON) shows different values with the voltage of exerting pressure.This makes when detecting the operating point of bias voltage (normally V (pi/2) apply voltage), detects the peak value and the valley of delustring curve, and the light quantity of each peak value produces difference because of voltage as described above, and can not detect.In addition, as shown in figure 13, wavelength variations, because level or the extinction ratio characteristic difference of ON/OFF, thereby can not be as D-WDM (for example, C band or L band) in big wavelength bandwidth regional work.Usually, this LN modulator to the EA modulator of narrow wavestrip action is favourable, but the problem that has this advantage to be cancelled.

Summary of the invention

Problem of the present invention is to possess electrooptics monocrystal substrate, optical waveguide and modulator electrode, making the thickness of substrate in zone that modulator electrode at least applies electric field in 30 μ m or the fiber waveguide device below it, power out-put characteristic when improving extinction ratio characteristic and ON.

In addition, in order to address the above problem, the applicant is willing to expect in the 2002-330325 communique that the spy rear side at thickness 30 μ m or the thin optical waveguide substrate below it is provided with the next bonding maintenance substrate of the roughly constant adhesive linkage of thickness.

But the stress that produces because of optical waveguide substrate and the thermal expansion difference that keeps substrate produces the DC drift, occurs back stagnating on the extinction ratio curve.Figure 21 represents to use the LN substrate as optical waveguide substrate, with the extinction ratio curve of the big quartz glass of thermal expansion difference when keeping substrate.Luminous power when applying the sine wave signal of 1kHz, crest voltage 10V shows shown in Figure 21 returning and stagnates.Figure 20 represents there is not back stagnant state fully.

In general occasion driving optical modulator, drives the intermediate point (V (pi/2)) that bias point moves to the maximal value and the minimum value of luminous power with self-bias controller loop.But, the sort of time stagnant phenomenon of Figure 21 arranged, just can not move to this intermediate point to bias voltage, thereby can not make the optical modulator action.

And, long-term DC drift takes place, above-mentioned bias point drift can not be caught up with the self-bias control loop sometimes.

Problem of the present invention is in fiber waveguide device, time stagnant phenomenon in the luminous power when preventing to apply signal voltage, and suppress long-term DC drift.

The fiber waveguide device of the invention of first mode, it has following feature: possess electrooptics monocrystal substrate, optical waveguide and modulator electrode, at least modulator electrode apply electric field the thickness of electrooptics crystal substrate in zone at 30 μ m or below it, amass (HW) of the height H (dust) of the protuberance that produces when forming optical waveguide and the width (μ m) of protuberance is at 7150 dust μ m or below it.

In addition; the fiber waveguide device of the invention of first mode; it has following feature: possess electrooptics monocrystal substrate, optical waveguide and modulator electrode; at least modulator electrode apply electric field the thickness of electrooptics crystal substrate in zone at 30 μ m or below it, the single modeization of horizontal direction at least of the export department of above-mentioned at least optical waveguide.

The present inventor studies in great detail the reason of the extinction ratio change that above-mentioned wavelength causes, and obtains following discovery.Promptly; for example be as thin as 30 μ m or its when following at the thickness of substrate; or further be as thin as 15 μ m or its when following; the optical waveguide multimodeization; especially the higher order mode guided wave in the horizontal direction the spot size of (direction parallel) with the LN substrate surface show the tendency that diminishes, they become the reason of the change of the change of the operating point that applies voltage or the extinction ratio that wavelength causes.

Understanding based on the present inventor; discovery at the thickness of electrooptics crystal substrate when 30 μ m or its are following; by making the single modeization of horizontal direction at least of the export department of optical waveguide at least, can suppress to apply the change of operating point of voltage and the change of the extinction ratio that wavelength causes.At this, export department is meant the optical waveguide of closing the straight line portion behind the ripple from y branch optical waveguide.

Originally, when 30 μ m or its are following, produced the change of the operating point that applies voltage and the change of the extinction ratio that wavelength causes, do not know multimodeization that its reason is an optical waveguide, especially optical waveguide spot size in the horizontal direction dwindles at the thickness of optical waveguide.

The discovery that the present invention is based on this problem points and its reason makes it become possibility at first, and the value on industry is big.

And the present inventor is in order to make optical waveguide single modeization at least in the horizontal direction, and the manufacturing conditions of research optical waveguide found that diffusion part is divided into convex when forming optical waveguide upwards to arch upward that the shape of protuberance and the mode condition of optical waveguide have correlativity.Particularly, the shape of optical waveguide and protuberance is utilized laser microscope inspection.The condition that found that the single modeization of horizontal direction at least that makes optical waveguide is as follows.

(long-pending (the HW)≤7150 dust μ m of the height H (dust) of the protuberance that when forming optical waveguide, produces and the width (μ m) of protuberance)

Like this, successfully improved the extinction ratio characteristic.

According to this viewpoint, H * W is more preferably at 6900 dust μ m or below it, preferably at 6000 dust μ m or below it.

H * W is too small, and it is big that mode diameter becomes, and becomes big with the coupling loss of the optical fiber of outside.According to the viewpoint that reduces this coupling loss, H * W is more preferably at 3000 dust μ m or more than it, preferably at 3400 dust μ m or more than it.

In preferred embodiment, satisfy the condition of H≤1100 dusts and W≤6.5 μ m.Like this, can reduce the dependence of the position of the peak value of extinction ratio curve and valley to voltage.

The present invention also further obtains following discovery.That is, make optical waveguide at least in the horizontal direction during single mode, it is big that mode sizes becomes, and interfere in the waveguide portion (with the interaction portion of electrode) at Mach-Zehnder, and the Mode Coupling between optical waveguide becomes big.As a result, branching ratio departs from when closing ripple, the extinction ratio variation.Like this, the wavelength dependency of extinction ratio becomes big.

To this, by making interval between branch waveguide, can make extinction ratio at 20dB or more than it greatly to 46 μ m or more than it, can also reduce the dependence of extinction ratio to wavelength.

The invention of second mode is to possess optical waveguide substrate, the maintenance matrix that keeps this optical waveguide substrate, and in the fiber waveguide device of the adhesive linkage of bonding optical waveguide substrate and maintenance matrix, it has following feature, optical waveguide substrate is made by electrooptic material, possess: the thickness with an opposed facing interarea and another interarea is in 30 μ m or the flat-shaped substrate main body below it, the optical waveguide that on base main body, is provided with, and the electrode that on base main body, is provided with, utilize another interarea of bonding maintenance matrix of adhesive linkage and base main body, keeping the minimum value of the thermal expansivity of matrix is more than 1/5 times of minimum value of the thermal expansivity of base main body, and the maximal value that keeps the thermal expansivity of matrix is 5 times of thermal expansivity of base main body or below it.

In the present invention, used thickness 30 μ m or its following flat base main body are utilized bonding maintenance matrix of adhesive linkage and base main body.Like this, because the place that on optical waveguide substrate, does not have stress to concentrate, so stress disperses, and can reduce to be applied to the maximum stress on the optical waveguide substrate.And, grind owing to can use, thereby can remove machining damage apace with suitable method to substrate attenuation processing, prevent the reduction of breakdown strength simultaneously.

Meanwhile, be 1/5 times of minimum value of thermal expansivity of optical waveguide substrate or more than it by the minimum value that makes the thermal expansivity that keeps matrix, and, the maximal value that keeps the thermal expansivity of matrix is 5 times of thermal expansivity of optical waveguide substrate or below it, time stagnant phenomenon in the time of can preventing to apply signal voltage in the luminous power, and suppress long-term DC drift.

The reason that obtains this action effect is also indeterminate.But, in [SA-9-3 of electronic information communication association in 1994] such as pool, NTT palace, three richnesses, pointed out the correlativity of distortion and DC drift.Therefore, for this structure, we think that the inside distortion that causes because of the thermal expansion difference between base main body and optical waveguide substrate produces the DC drift.

Description of drawings

Fig. 1 is the vertical view of the device 4 of expression an embodiment of the invention.

Fig. 2 is the cross-sectional view of signal device 4.

Fig. 3 is illustrated in the cross-sectional view that is provided with the device of groove 5c between branching portion on substrate.

Fig. 4 is the enlarged drawing of the state of expression

optical waveguide

2b, 2c.

Fig. 5 is the synoptic diagram of the relation of the expression protuberance of various forms and height H and width W.

Fig. 6 is the sectional view of the device 11 of signal an embodiment of the invention.

Fig. 7 is the sectional view of the device 11A of signal other embodiment of the present invention.

Fig. 8 is the sectional view of the device 11B of signal another embodiment of the invention.

Fig. 9 is the sectional view of the device 11C of signal another embodiment of the invention.

Figure 10 is the sectional view of the device 11D of signal another embodiment of the invention.

Figure 11 be the expression comparative example device in extinction ratio to applying the dependent curve map of voltage.

Figure 12 be the expression comparative example device in extinction ratio to applying the dependent curve map of voltage.

Figure 13 be in the device of expression comparative example extinction ratio to the dependent curve map of wavelength.

Figure 14 be in the device of expression comparative example extinction ratio to the dependent curve map of wavelength.

Figure 15 is the curve map that is used to illustrate the computing method of P value.

Figure 16 is that expression waveguide arm spacing is from (L) curve map with the relation of extinction ratio.

Figure 17 is that expression waveguide arm spacing is from (L) curve map with the relation of Δ P.

Figure 18 is that expression waveguide arm spacing is from (L) curve map with the relation of extinction ratio.

Figure 19 is that expression waveguide arm spacing is from (L) curve map with the relation of Δ P.

Figure 20 is the curve map of the relation of luminous power and voltage in the device of expression embodiments of the invention.

Figure 21 is the curve map of the relation of luminous power in the device of comparative example and voltage.

Embodiment

Below, the present invention will be described in more detail with reference to accompanying drawing.Fig. 1 and Fig. 2 are the synoptic diagram of device 4 of an embodiment of the invention of expression first mode.

Base main body 5 is a tabular.On an interarea 5a of substrate 5, be formed with ground-electrode 1A, 1C and signal electrode 1B.In this example, adopt the electrode configuration of so-called coplanar type (Coplanar waveguide:CPW electrode).Optical waveguide 2 possesses inlet portion 2a, the 2d of export department and a pair of branching portion 2b, 2c.Apply zone 10 at electric field, configuration a pair of optical

waveguide branching portion

2b, 2c apply the signal electric field to each

optical waveguide

2b, 2c in general horizontal direction between adjacent electrode.Optical waveguide 2 constitutes so-called Mach-zehnder type optical waveguide from the plane.The interval L of branching

portion

2b and 2c better is at 46 μ m or more than it.

The present inventor has further obtained following discovery.Interfere waveguide portion (with the interaction portion of electrode) at Mach-Zehnder, for and optical waveguide between Mode Coupling become big problem, by between branch waveguide, forming groove 5c as shown in Figure 3, can suppress the Mode Coupling between optical waveguide.As a result,, can make extinction ratio more than 20dB, can reduce the dependence of extinction ratio wavelength making the optical waveguide occasion of single modeization at least in the horizontal direction.

Fig. 4 is the amplification sectional view of expression optical waveguide 2b, 2c.When forming

optical waveguide

2b, 2c, on interarea 5a, place suitable diffusants such as titanium, carry out heat treated.At this moment, on interarea 5a, be formed with protuberance 6 during diffusion.The shape pattern of protuberance has shown in Figure 5 various, and the height H of protuberance is defined as the peak value of protuberance, and width W is defined as the longest distance of the point of 5% the value that connects height H.Based on this, the long-pending of the width W of protuberance 6 and height H makes it at 7150 dust μ m or below it according to the present invention.

Can between base main body and electrode, cushion be set.In addition, the present invention also can be applicable to the occasion that electrode is configured to asymmetrical planar transmission line type.

Base main body by the ferroelectricity electrooptic material, better be that monocrystalline is made.Being not particularly limited as long as this monocrystalline can carry out the modulation of light, can be example with lithium niobate, lithium tantalate, lithium niobate-lithium tantalate solid solution, lithium potassium niobate, KTP and crystal etc.

Ground-electrode, signal electrode can be made of materials such as gold, silver, copper so long as low resistance, impedance operator excellent material are not particularly limited.

Cushion can use well-known materials such as monox, magnesium fluoride, silicon nitride and aluminium oxide.

Optical waveguide is the optical waveguide of diffusion method or ion exchange process formation in utilizing on base main body, better is titanium diffused optical waveguide, proton-exchanged optical waveguide, and good especially is the titanium diffused optical waveguide.Electrode is located at an interarea side of base main body, can directly form on an interarea of base main body, also can form on cushion.

The good especially formation condition of optical waveguide is in following scope.

Ti thickness 450～1000 dusts

950～1100 ° of diffusion temperatures

4～11 hours diffusion times

Width 3～7 μ m of waveguide mask pattern

On base main body, preferably the polaxis of crystal is roughly parallel with an interarea 5a of substrate.In this occasion, better be X plate or the Y plate of making by lithium niobate monocrystal, monocrystalline lithium tantalate, lithium niobate-lithium tantalate sosoloid monocrystal.In Fig. 1～Fig. 5, provided the example that the present invention is applied to X plate or Y plate.

In addition, other preferred embodiment in, the polaxis of a crystal roughly interarea 5a with substrate is vertical.In this occasion, better be the Z plate of making by lithium niobate monocrystal, monocrystalline lithium tantalate, lithium niobate-lithium tantalate sosoloid monocrystal.In the occasion of using the Z plate, optical waveguide need be arranged on electrode under, in order to reduce the propagation loss of light, better be between the surface of substrate and electrode, cushion to be set.

In the present invention, as shown in Figure 2, the base main body 5 and the maintenance matrix 7 of complicated variant are joined together.According to the influence that makes the velocity of propagation that keeps 7 pairs of microwaves of matrix is the viewpoint of irreducible minimum, and keeping the material of matrix 7 can be the material with specific inductive capacity lower than the specific inductive capacity of electrooptics monocrystalline, as this material, glass such as quartz glass is arranged.

Optical waveguide substrate 5 and the joint method and the indefinite that keep matrix 7.In preferred embodiment, bonding both.In this occasion, the refractive index of bonding agent better is lower than the refractive index of the electrooptic material that constitutes base main body 5.

The object lesson of bonding agent is epoxide resin adhesive, thermmohardening type bonding agent, UV cured type bonding agent etc., and better being has the bonding agent that has the more approaching thermal expansivity of the material of electric optical effect with lithium niobate etc.

Below, be described in detail with reference to the preferred implementation of suitable accompanying drawing the invention of second mode.

Fig. 6 mainly is the sectional view of the photomodulator 11 of the signal first working of an invention mode.In Fig. 6, provided the xsect that is approximately perpendicular to the working direction of light in the travelling-wave type optical modulator.

Optical modulator 11 possesses optical waveguide substrate 29 and keeps matrix 12.Base main body 14 and matrix 12 all are tabular.The thickness of base main body 14 is at 30 μ m or below it.On an interarea 14a of base main body 14, form fixed

electrode

17A, 17B, 17C to some extent.In this example, adopt the configuration of so-called coplanar type (Coplanar waveguide:CPW electrode) electrode, but the configuration mode of electrode is not particularly limited.It also can be ACPS (asymmetric planar transmission line) type for example.In this example, between adjacent electrode, be formed with a pair of

optical waveguide

15b, 15c, each

optical waveguide

15b, 15c are applied the signal electric field in general horizontal direction.This optical waveguide constitutes so-called Mach-zehnder type optical waveguide from the plane.This planar graph itself is well-known (aftermentioned).The roughly constant adhesive linkage 13 of thickness is between another interarea 14d of base main body 14 and keep between the bonding plane 12a of matrix 12.Adhesive base plate main body 14 and maintenance matrix 12.

In this fiber waveguide device 11, used thickness 30 μ m or its following flat base main body are utilized bonding maintenance matrix of adhesive linkage and base main body, and make the bonding plane 12a of maintenance matrix be roughly tabular surface.Like this, because the thickness of adhesive linkage 13 is roughly certain, the place that does not have stress to concentrate on optical waveguide substrate 29 is so stress disperses, and can reduce to be applied to the maximum stress on the optical waveguide substrate 29.And, owing to can be thinned to 30 μ m or adding below it used plane lapping man-hour to substrate 4, thus can remove machining damage apace with suitable method, can prevent the reduction of breakdown strength simultaneously.

In the present invention, base main body 14 is made by thickness 30 μ m or the flat board below it.Be meant the flat board that on interarea 14d, does not form recess or groove at this so-called flat board, just another interarea 14d (bonding plane) general planar.But so-called interarea 14d general planar is meant that being accompanied by processing remains in the meaning of the rough surface on surface in the scope of allowing, perhaps is accompanied by the bending of processing and the scope that perk is also being allowed.

In the present invention, an interarea 14a side in base main body 14 is provided with optical waveguide 15b, 15c.Optical waveguide can be the ridge optical waveguide that directly forms on an interarea of base main body, or the ridge optical waveguide that on an interarea of base main body, forms by other layer, perhaps also can be to utilize interior diffusion method or ion exchange process in the inner optical waveguide that forms of base main body, for example titanium diffused optical waveguide, proton-exchanged optical waveguide.Particularly, optical guided wave is to get final product from the outstanding ridge optical waveguide of interarea 14a.Ridge optical waveguide can utilize Laser Processing, machining to form.Perhaps, on base main body 14, form high refractive index film,, can form the three-dimensional optical waveguide of ridge by this high refractive index film being carried out the processing of machining or laser evaporation.High refractive index film can be formed by for example chemical vapour deposition technique, physical vaporous deposition, Metalorganic chemical vapor deposition method, sputtering method, liquid phase epitaxial method.

The base main body that constitutes optical waveguide substrate by the ferroelectricity electrooptic material, better be that monocrystalline is made.Being not particularly limited as long as this monocrystalline can carry out the modulation of light, can be example with lithium niobate, lithium tantalate, lithium niobate-lithium tantalate solid solution, lithium potassium niobate, KTP, GaAs and crystal etc.Good especially is lithium niobate monocrystal, monocrystalline lithium tantalate, lithium niobate-lithium tantalate sosoloid monocrystal.

For base main body, good especially is that the polaxis of crystal is roughly parallel with an interarea (surface) of substrate.In this occasion, better be X plate or the Y plate of making by lithium niobate monocrystal, monocrystalline lithium tantalate, lithium niobate-lithium tantalate sosoloid monocrystal.In Fig. 6～Figure 10, provided the example that the present invention is applied to X plate or Y plate.

In addition, other preferred embodiment in, the polaxis of the crystal roughly interarea (surface) with substrate is vertical.In this occasion, better be the Z plate of making by lithium niobate monocrystal, monocrystalline lithium tantalate, lithium niobate-lithium tantalate sosoloid monocrystal.In the occasion of using the Z plate, optical waveguide need be arranged on electrode under, in order to reduce the propagation loss of light, better be between the surface of substrate and electrode, cushion to be set.

In the present invention, the minimum value that keeps the thermal expansivity of matrix is 1/5 times of minimum value of thermal expansivity of optical waveguide substrate or more than it, and the maximal value that keeps the thermal expansivity of matrix is 5 times of thermal expansivity of optical waveguide substrate or below it.

At this, when each electrooptic material that constitutes base main body and maintenance matrix does not respectively have the anisotropy of thermal expansivity, make base main body and keep the thermal expansivity of minimum in the matrix consistent with maximum thermal expansivity.When each electrooptical material of formation base main body and maintenance matrix had the anisotropy of thermal expansivity, the thermal expansivity of each changed sometimes.For example, when each electrooptic material that constitutes base main body was lithium niobate, the thermal expansivity of X-direction, Y direction was 16 * 10 ^-6/ ℃, this is a maximal value.The thermal expansivity of Z-direction is 5 * 10 ^-6/ ℃, this is a minimum value.Therefore, making the minimum value of the thermal expansivity that keeps matrix is 1 * 10 ^-6/ ℃ or more than it, making the maximal value of the thermal expansivity that keeps matrix is 80 * 10 ^-6/ ℃ or below it.Also have, for example the thermal expansivity of quartz glass is 0.5 * 10 ^-6/ ℃, for example less than 1 * 10 ^-6/ ℃.

According to the viewpoint of action effect of the present invention, be more preferably the minimum value that makes the thermal expansivity that keeps matrix and be 1/2 times of minimum value of thermal expansivity of base main body or more than it.In addition, making the maximal value of the thermal expansivity that keeps matrix is peaked 2 times or below it of thermal expansivity of the base main body of optical waveguide substrate.

As long as keep the concrete material of matrix to satisfy above-mentioned condition, be not particularly limited.In the occasion of base main body being used lithium niobate monocrystal, keeping matrix can be example with lithium niobate, lithium tantalate, lithium niobate-lithium tantalate solid solution, lithium potassium niobate etc.This occasion, according to the viewpoint of thermal expansion difference, good especially is the lithium niobate monocrystal identical with the thermal expansivity of base main body.

Electrode is located at an interarea side of base main body, can directly form on an interarea of base main body, also can form on low-dielectric constant layer or cushion.Low-dielectric constant layer can use well-known materials such as monox, magnesium fluoride, silicon nitride and aluminium oxide.At this, so-called low-dielectric constant layer is meant the layer of being made by the material with specific inductive capacity littler than the specific inductive capacity of the material that constitutes base main body, and according to the viewpoint of the speeds match condition that satisfies light and microwave, the material that specific inductive capacity is low is better.When this low-dielectric constant layer not, the thickness that is more preferably base main body is at 20 μ m or below it.

In preferred embodiment, keep the bonding plane 12a of matrix 12 to be roughly smooth.But so-called bonding plane 12a general planar is meant that being accompanied by processing remains in the meaning of the rough surface on surface in the scope of allowing, in addition, is accompanied by the bending of processing and the scope that perk is also being allowed.

According to viewpoint of the present invention, the thickness T 1 of adhesive linkage 13 better is at 1000 μ m or below it, is more preferably at 300 μ m or below it, preferably at 100 μ m or below it.In addition, the thickness T 1 of adhesive linkage 13 do not have a lower limit, but, better be at 10 μ m or more than it according to the viewpoint that reduces the microwave effective refractive index.

Have, according to the viewpoint of speeds match, adhesive linkage need liken to the specific inductive capacity of the electrooptic material of base main body is lower again, and specific inductive capacity is 5 or relatively good below it.

Fig. 7 is the sectional view of the fiber waveguide device 11A of signal other embodiment of the present invention.In Fig. 7, provided the xsect that is approximately perpendicular to the working direction of light in the travelling-wave type optical modulator.

Optical modulator 11A possesses optical waveguide substrate 29 and keeps matrix 32.Base main body 14 and matrix 12 all are tabular.The thickness of base main body 14 is at 30 μ m or below it.The structure of optical waveguide substrate 29 is identical with the structure of optical waveguide substrate shown in Figure 6 29.At least be formed with recess or groove 32b with electrode interaction portion in the bonding plane 32a of base main body 32 side.Groove 32b extends to the working direction (perpendicular to the direction of paper) of light.

In this example, adhesive linkage 33 is between another interarea 14d of base main body 14 with keep between the bonding plane 32a of matrix 32.Adhesive base plate main body 14 and maintenance matrix 32.Meanwhile, the formation zone at

optical waveguide

15b, 15c is formed with groove 32b under interarea 14d, fills the low-k part of being made by bonding agent 36 in groove 32b.

In this fiber waveguide device 11A, the flat base main body 14 that used thickness 30 μ m or its are following is utilized adhesive linkage 33 bonding maintenance matrix 32 and base main body 14, and the thickness T 1 that makes adhesive linkage 33 is at 200 μ m or below it.Like this, can promote the dispersion of stress in optical waveguide substrate 29, reduce the maximum stress that is applied on the optical waveguide substrate 29.

But, in the present embodiment, to compare with the thickness T 1 of adhesive linkage 33, the thickness T 2 of the low-k part of being made by bonding agent 36 becomes big, therefore, the thickness of bonding agent is produced the step difference of (T2-T1).Therefore, the thickness of adhesive linkage is different with whole roughly constant occasion, is easy to stress at the ambient stress of step difference to base main body 14 and concentrates.Concentrating DC drift and the temperature drift that causes in order to reduce this stress, better is to make the thickness T 1 of adhesive linkage 33 at 200 μ m or below it.According to this viewpoint, the thickness T 1 of adhesive linkage 33 need be at 200 μ m or below it, but are more preferably at 150 μ m or below it, preferably at 110 μ m or below it.In addition, the thickness T 1 of adhesive linkage 33 does not have lower limit, but according to the viewpoint that reduces to be applied to the stress on the base main body 14, at 0.1 μ m or get final product more than it.

In the present invention, adhesive linkage can be at formation bonding another interarea in zone and the maintenance matrix of optical waveguide.For example, the fiber waveguide device 11 of Fig. 6, Fig. 7,11A promptly belong to this embodiment.In this occasion, as shown in Figure 6, preferably the thickness of adhesive linkage is roughly constant.Here, the thickness of so-called adhesive linkage is roughly constant is meant that the error in the manufacturing is in the scope of allowing.

In addition, in the present invention, better be formation zone in optical waveguide, setting has the lower low-k part of specific inductive capacity that permittivity ratio is formed in the electrooptic material of base main body between another interarea and maintenance matrix.Realize above-mentioned the sort of speeds match like this, easily.

The kind of low-k part is not particularly limited.In a preferred embodiment, low-k partly is an air layer, and in addition, in other embodiments, the low-k part is made (example of Fig. 6, Fig. 7) by bonding agent.In this occasion, need to use the lower bonding agent of specific inductive capacity of the above-mentioned electrooptic material of permittivity ratio.

In addition, in other embodiments, the low-k part is made by the lower advanced low-k materials of the specific inductive capacity of the above-mentioned electrooptic material of permittivity ratio, and this advanced low-k materials does not belong to bonding agent.

Fig. 8 is the sectional view of signal fiber waveguide device 11B.Optical modulator 11B possesses optical waveguide substrate 29 and keeps matrix 32.Base main body 14 is a tabular.The thickness of base main body 14 is at 30 μ m or below it.In the bonding plane 32a of base main body 32 side, form recess or groove 32b equally with Fig. 7.Groove 32b extends to the working direction (perpendicular to the direction of paper) of light.

In this example,

adhesive linkage

43A, 43B are between another interarea 14d of base main body 14 and keep between the bonding plane 32a of matrix 32, adhesive base plate main body 14 and keep matrix 32.Meanwhile, the formation zone at

optical waveguide

15b, 15c is formed with groove 32b under interarea 14d, be provided with low-k part 30.This routine low-k part 30 is made by the advanced low-k materials different with

bonding agent

43A, 43B.

Fig. 9 is the sectional view of signal fiber waveguide device 11C.Optical modulator 11C possesses optical waveguide substrate 29 and keeps matrix 12.Base main body 14 is a tabular, and the thickness of base main body 14 is at 30 μ m or below it.The bonding plane 12a that keeps matrix 12 is a general planar.

In this example,

adhesive linkage

43A, 43B are between another interarea 14d of base main body 14 and keep between the bonding plane 12a of matrix 12, adhesive base plate main body 14 and keep matrix 12.Meanwhile, the formation zone at

optical waveguide

15b, 15c is formed with air layer 31 under interarea 14d.Air layer 31 plays the low-k part.

Figure 10 is the sectional view of signal fiber waveguide device 11D.Optical modulator 11D possesses optical waveguide substrate 29 and keeps matrix 32.Base main body 14 is a tabular, and the thickness of base main body 14 is at 30 μ m or below it.Form recess or groove 32b in the bonding plane 32a of base main body 32 side.

In this example,

adhesive linkage

43A, 43B are between another interarea 14d of base main body 14 and keep between the bonding plane 32a of matrix 32, adhesive base plate main body 14 and keep matrix 32.The thickness T 1 of

adhesive linkage

43A, 43B is at 200 μ m or below it.Meanwhile, the formation zone at

optical waveguide

15b, 15c is formed with air layer 35 under interarea 14d.Air layer 35 plays the low-k part.

According to the viewpoint of speeds match, the thickness T 2 of low-

k part

30,35,36 better is at 10 μ m or more than it, is more preferably at 30 μ m or more than it.According to the viewpoint that proof stress is concentrated to optical waveguide substrate, the thickness T 2 of low-

k part

30,35,36 better is at 0.5 μ m or below it, is more preferably at 1000 μ m or below it.

The present invention can also be applied to so-called separate modulation type travelling-wave type optical modulator.

Electrode can be made of materials such as gold, silver, copper so long as low resistance, impedance operator excellent material are not particularly limited.

The object lesson of bonding agent is epoxide resin adhesive, thermmohardening type bonding agent, UV cured type bonding agent etc., better be to have アロ Application pottery C (trade name, East Asia Synesis Company system) (thermal expansivity 13 * 10 that has the more approaching thermal expansivity of the material of electric optical effect with lithium niobate etc. ^-6/ K).

In addition, as bonding with glass better be that specific inductive capacity is little, bonding temp (processing temperature) is big about the glass below 600 ℃.In addition, better be to add the glass that can obtain enough bonding strengths man-hour.Particularly, better be several so-called glass welding agent that has made up among monox, massicot, aluminium oxide, magnesium oxide, kali, the boron oxide etc.

In addition, can make the bonding agent sheet between the back side of base main body 14 with keep coming between the substrate bonding.Be preferably, make the thin slice of making by thermosetting, photo-hardening or light tackifying resin bonding agent between the back side and maintenance substrate of base main body 4, make the thin slice sclerosis.

Embodiment

(embodiment 1)

On the lithium niobate substrate of X cutting, form Ti diffused waveguide and CPW electrode (with reference to Fig. 1, Fig. 2).The gap that makes central electrode 1B and ground-electrode 1A, 1C is 25 μ m, and the width of central electrode 1B is 30 μ m, and the thickness of each electrode is 28 μ m, and electrode length is 32 μ m.Secondly, carry out attenuate and grind, made the slim modulator of making by low-dielectric constant layer and supporting substrate (lithium niobate substrate of X cutting).The thickness that makes modulator substrate 5 is 8.5 μ m, and the specific inductive capacity of low-dielectric constant layer 6 is 3.8, and thickness is 50 μ m.Then, the connecting portion of optical fiber is carried out end surface grinding, cut into chip with mold.Said modulator chip and optical fiber carry out the optical axis adjustment, are adhesively fixed with the UV hardening resin.After making device, the height H of the protuberance 6 of the optical waveguide 2 of mensuration and wide W such change as shown in table 1 in addition, gives the value of long-pending H * W in table 1.For each device that obtains, carry out pattern and observe.Table 1 provides its result.

Table 1

The wide W μ of optical waveguide m	The height H of the protuberance of optical waveguide ()
	The height H of the protuberance of optical waveguide ()				750	850	1100	1150
	3	2.2 single mode 2250	1.8 single mode 2550	1.4 single mode 3300	750	850	1100	1150	1.4 single mode 3450
4	3	2.2 single mode 2250	1.8 single mode 2550	1.4 single mode 3300	1.85 single mode 3000	1.3 single mode 3400	1.22 single mode 4400	1.3 single mode 4600	1.4 single mode 3450
4	5	1.65 single mode 3750	1.1 single mode 4250	1.09 single mode 5500	1.85 single mode 3000	1.3 single mode 3400	1.22 single mode 4400	1.3 single mode 4600	1 single mode 5750
6	5	1.65 single mode 3750	1.1 single mode 4250	1.09 single mode 5500	1.5 single mode 4500	1.05 single mode 5100	1 single mode 6600	0.9 single mode 6900	1 single mode 5750
6	6.5	1.45 single mode 4875	1.02 single mode 5525	0.98 single mode 7150	1.5 single mode 4500	1.05 single mode 5100	1 single mode 6600	0.9 single mode 6900	0.9 multimode 7475
7	6.5	1.45 single mode 4875	1.02 single mode 5525	0.98 single mode 7150	1.35 single mode 5250	1 single mode 5950	0.95 multimode 7700	0.9 multimode 8050	0.9 multimode 7475
7	8	1.3 single mode 6000	0.95 single mode 6800	0.95 multimode 8800	1.35 single mode 5250	1 single mode 5950	0.95 multimode 7700	0.9 multimode 8050	0.85 multimode 9200
9	8	1.3 single mode 6000	0.95 single mode 6800	0.95 multimode 8800	1.2 single mode 6750	0.95 multimode 7650	0.9 multimode 9900	0.85 multimode 10350	0.85 multimode 9200

Epimere: making horizontal direction (slow direction of principal axis) mode sizes of 1.55 μ m band optical fiber is 1 o'clock mode sizes in the horizontal direction of optical waveguide

Hypomere: W * H μ m 

In addition, be the occasion of 1mm to the thickness that makes the electrooptics monocrystal substrate, with above-mentioned same, such height H and wide W that changes the optical waveguide protuberance as shown in table 2 carried out the pattern observation, and table 2 provides its result.

Table 2

Optical waveguide width W (μ m)	The height () of optical waveguide protuberance	Mode sizes ※ 1	Pattern	Optical waveguide is wide * and the height of optical waveguide protuberance (μ m * )
Optical waveguide width W (μ m)	The height () of optical waveguide protuberance	Mode sizes ※ 1	Pattern		3	1150	1.4	Single mode	3450
4	1150	1.2	Single mode	4600	3	1150	1.4	Single mode	3450
4	1150	1.2	Single mode	4600	5	1150	1	Single mode	5750
6	1150	0.9	Single mode	6900	5	1150	1	Single mode	5750
6	1150	0.9	Single mode	6900	7	1150	0.85	Single mode	8050
9	1150	0.85	Multimode	10350	7	1150	0.85	Single mode	8050

It is 1 o'clock mode sizes in the horizontal direction of optical waveguide that ※ 1 expression makes horizontal direction (slow direction of principal axis) mode sizes of 1.55 μ m band optical fiber

From comparison sheet 1, table 2 as can be known, in the big occasion (table 2) of the thickness of electrooptics crystal substrate, under the size condition of single mode, in table 1 in multimodeization on a large scale.

In addition, be the occasion of 1mm at substrate thickness, when 1000  or its were following, the optical waveguide width was at 6 μ m or below it, optical waveguide is cut off at the height of the protuberance of optical waveguide, and light can not guided wave.But, also know, be 30 μ m or below it by making substrate thickness, the optical waveguide width is at 6 μ m or below it, 3 μ m for example, light is also with single entry (single-mode) guided wave.And,, can suppress to apply the change of operating point of voltage and the change of the extinction ratio that causes because of wavelength by satisfying the condition of light like this with single mode propagation.

And, at 30 μ m or the slim modulator below it, make H * W at 7150 dust μ m or be necessary for obtaining monotype below it for the thickness of electrooptics crystal substrate.

(embodiment 2)

In embodiment 1, making the distance L between the arm of optical waveguide is 55 μ m, and the height H of the protuberance 6 of optical waveguide 2 is 860 dusts, and width W is 6 μ m, both long-pending be 5160 dust μ m.

For device, when measuring S21, the wavelength coverage below 50GHz is fluctuation not, shows as level and smooth curve, is reduced to-6dB above behind the 30GHz.In addition, S11 until survey frequency 50GHz all be-10dB or below it.Having, as optical characteristics, carry out the result that pattern is observed, is single mode, and extinction ratio is 20dB or more than it, the voltage-dependent of extinction ratio curve is little to ± 5% or below it from 1530nm to 1610nm.

Figure 12 provides the extinction ratio and the relation that applies voltage in this example.The height of each peak value is almost constant, in addition the invariant position of the peak value of extinction ratio curve and valley.

In addition, Figure 14 represents the wavelength dependency that extinction ratio is concavo-convex.At this, said [ON light intensity] (Δ P) measures as described below.That is, in Figure 15, measure 3 adjacent peak value P1, P2, the height of P3, applying voltage near 0V, adjacent P1 and the ratio of P3 for P2 for example calculate as (P1-P2) * 100/P2 (%).As a result, as shown in figure 14, the wavelength dependency of ON light intensity is little to ± 5% or below it.

(embodiment 3)

In embodiment 1, the gap that makes central electrode 1B and ground-electrode 1A, 1C is 40 μ m, and the width of central electrode 1B is 30 μ m, and the thickness of each electrode is 28 μ m, and electrode length is 40mm.Making the distance L between the arm of optical waveguide is 70 μ m, and the height H of the protuberance 6 of optical waveguide 2 is 860 dusts, and width W is 6 μ m, both long-pending be 5160 dust μ m.

(embodiment 4)

Made slim modulator similarly to Example 2.But making the distance between the arm between optical waveguide is 55 μ m.The width W that makes the protuberance 6 of optical waveguide 2 is 6 μ m, and height H is 1150 dusts, and both amassing are 6900 dust μ m.

For device, when measuring S21, the wavelength coverage below 50GHz is fluctuation not, shows as level and smooth curve, is reduced to-6dB above behind the 30GHz.In addition, S11 until survey frequency 50GHz all be-10dB or below it.Having, as optical characteristics, carry out the result that pattern is observed, is single mode, and extinction ratio is 20dB or more than it from 1530nm to 1610nm.But the voltage-dependent of extinction ratio curve is big, ± 5% or more than it.

(embodiment 5)

Made slim modulator similarly to Example 2.But making central electrode is 20 μ m, and the distance between the arm between optical waveguide is little of 45 μ m.The height H that makes the protuberance 6 of optical waveguide 2 is 860 dusts, and width W is 6 μ m, and both amassing are 6900 dust μ m.For device, when measuring S21, the wavelength coverage below 50GHz is fluctuation not, shows as level and smooth curve, is reduced to-6dB above behind the 30GHz.In addition, S11 until survey frequency 50GHz all be-10dB or below it.Having, as optical characteristics, carry out the result that pattern is observed, is single mode, and extinction ratio is reduced to from 1530nm to 1610nm less than 20dB, and the voltage-dependent of extinction ratio curve is ± 5% or more than it.

(embodiment 6)

Made slim modulator similarly to Example 2.Similarly to Example 5, making central electrode is 20 μ m, and the distance between the arm between optical waveguide is little of 45 μ m.The height H that makes the protuberance 6 of optical waveguide 2 is 860 dusts, and width W is 6 μ m, and both amassing are 6900 dust μ m.Secondly, as shown in Figure 3, form the groove 5c of wide 20 μ m, dark 3 μ m from the back side 5b of modulator substrate 5 across total length under the central electrode 1B.Excimer laser is used in processing to groove.For device, when measuring S21, the wavelength coverage below 50GHz is fluctuation not, shows as level and smooth curve, is reduced to-6dB above behind the 30GHz.In addition, S11 until survey frequency 50GHz all be-10dB or below it.Having, as optical characteristics, carry out the result that pattern is observed, is single mode, extinction ratio from 1530nm to 1610nm between at 20dB or more than it, the voltage-dependent of extinction ratio curve is also ± 5% or below it.

(comparative example 1)

Made slim modulator similarly to Example 2.But making the distance between the arm between optical waveguide is 55 μ m.The width W that makes the protuberance 6 of optical waveguide 2 is 6.5 μ m, and height H is 1150 dusts, and both amassing are 7475 dust μ m.For device, when measuring S21, the wavelength coverage below 50GHz is fluctuation not, shows as level and smooth curve, is reduced to-6dB above behind the 30GHz.In addition, S11 until survey frequency 50GHz all be-10dB or below it.

Having, as optical characteristics, carry out the result that pattern is observed, is multimode, extinction ratio from 1530nm to 1610nm between less than 20dB, the voltage-dependent of extinction ratio curve is big, more than ± 5%.

Figure 11 represents the extinction ratio and the relation that applies voltage in this example.The height of each peak value does not wait, and the position of the peak value of extinction ratio curve and valley not necessarily in addition.

In addition, Figure 13 represents the wavelength dependency that extinction ratio is concavo-convex.As a result, the wavelength dependency of ON light intensity is big, rise to ± 15%.

(embodiment 7)

Made slim modulator similarly to Example 2.But the height that makes protuberance 6 is 860 dusts, and width is 5 μ m, and both amassing are 4300 dust μ m.As Figure 16, change distance (distance L between branching portion 2b and the 2c) between the waveguide arm as shown in Figure 17.Figure 16 provides the dependence of extinction ratio to L, and Figure 17 provides the dependence of Δ P to L.From this result as can be known, by making between the arm distance L, at 20dB or more than it, can be controlled at Δ P in addition ± 5% or below it in very wide wavelength coverage extinction ratio at 46 μ m or more than it.According to this viewpoint, L is at 50 μ m or better more than it.

(embodiment 8)

Made slim modulator similarly to Example 2.But the height that makes protuberance is 1150 dusts, and width is 5 μ m, and both amassing are 5750 dust μ m.And, as Figure 18, change distance (distance L between branching portion 2b and the 2c) between the waveguide arm as shown in Figure 19.Figure 18 provides the dependence of extinction ratio to L, and Figure 19 provides the dependence of Δ P to L.From this result as can be known, by making between the arm distance L at 46 μ m or more than it, in very wide wavelength coverage extinction ratio at 20dB or more than it.But can not be controlled at Δ P in this example, ± 5% or below it.

(embodiment 9: the device 11 of Fig. 6)

The optical modulator of shop drawings 6.Specifically, use 3 inches wafer (LiNbO of X cutting ₃Monocrystalline) substrate of making utilizes titanium diffusion technique and photoetch method, forms Mach-zehnder type optical waveguide 15b, 15c on the surface of wafer.The size of optical waveguide is for example at 1/e ²Can be 10 μ m.Secondly, utilize electroplating technology to form the CPW electrode.The gap that makes central electrode 17B and ground-electrode 17A, 17C is 40 μ m, and thickness of electrode is 28 μ m, and electrode length is 40 μ m.Secondly, grind, on abrasive disk, paste and grind virtual substrate, electrode surface is pasted modulator substrate thereon with thermoplastic resin down in order to carry out attenuate.Have, it is thick with transverse grinding and polishing (CMP) base main body 14 attenuates to be worked into 10 μ m again.Then, keep tabular substrate 12 to be adhesively fixed on the base main body 14, the connecting portion of optical fiber is carried out end surface grinding, cut into chip with mold.What the resin of the usefulness that is adhesively fixed used is the epoxy resin film of the thick 50 μ m of resin.The width of chip and comprise that the gross thickness of strengthening substrate is respectively 4.4mm and 1mm.At input side, make the single-core fiber array and 11 couplings of travelling-wave type optical modulator that have kept 1.55 μ m bandwidth optical fiber; At outgoing side, make the single-core fiber array and 11 couplings of travelling-wave type optical modulator that have kept single-mode fiber, light and optical waveguide are transferred core, utilize UV-cured type resin bonding.

In this example, 3 inches wafer (LiNbO of X cutting have been used ₃Monocrystalline) substrate of making.The thermal expansivity of its X-direction, Y direction is 16 * 10 ^-6/ ℃, the thermal expansivity of Z-direction is 5 * 10 ^-6/ ℃.The material that keeps matrix 2 is the lithium niobate monocrystal of X cutting.

Figure 20 provides the extinction ratio curve to the signal of 1kHz.From this result as can be known, stagnating does not appear back in luminous power.In addition, 100 ℃ of results that investigate the DC drift characteristic, the drift value of DC bias voltage has 50% with interior change to initially applying voltage.

(embodiment 10: the device 11C of Fig. 9)

The device 11C of shop drawings 9.Specifically, make optical waveguide substrate 29 similarly to Example 9.The thickness that makes base main body 14 is 12 μ m.But, air layer 31 is set as shown in Figure 9.In this example, use the LiNbO of X cutting ₃The base main body that monocrystalline is made, the material that keeps matrix 12 are the lithium niobate monocrystal of X cutting.

Stagnating does not appear back in the signal extinction ratio curve to 1kHz.In addition, 100 ℃ of results that investigate the DC drift characteristic, the drift value of DC bias voltage relatively initially applies voltage has 50% with interior change.

(embodiment 11: the device 11A of Fig. 7)

The device 11A of shop drawings 7.Specifically, make optical waveguide substrate 29 similarly to Example 9.Then, optical waveguide substrate 29 is adhesively fixed on the maintenance matrix 32 of the groove 32b that is formed with wide 0.3mm and dark 0.2mm, the connecting portion of optical fiber is carried out end surface grinding, with the square chip that cuts into.At this moment, in the groove 32b that keeps matrix 32, fill adhering resin 36.Therefore, T1 is 50 μ m, and T2 is 250 μ m.In this example, use the LiNbO of X cutting ₃The base main body that monocrystalline is made.The material that keeps matrix 12 is the lithium niobate monocrystal of X cutting.

(embodiment 12: the device 11D of Figure 10)

Make the device 11D of Figure 10.Specifically, make optical waveguide substrate 29 similarly to Example 1.The thickness of base main body 14 is 12 μ m.Then, optical waveguide substrate 29 is adhesively fixed on the maintenance matrix 32 of the groove 32b that is formed with wide 0.3mm and dark 0.2mm, the connecting portion of optical fiber is carried out end surface grinding, with the square chip that cuts into.At this moment, be air layer 35 in the groove 32b of maintenance matrix 32.T1 is 50 μ m, and T2 is 250 μ m.In this example, use the LiNbO of X cutting ₃The base main body that monocrystalline is made.The material that keeps matrix 12 is the lithium niobate monocrystal of X cutting.

(embodiment 13: the device 11 of Fig. 6)

With the same structure of Fig. 6 in, make that to keep the material of substrate 12 be monocrystalline lithium tantalate.In this example, 3 inches wafer (LiNbO of X cutting have been used ₃Monocrystalline) substrate of making.The thermal expansivity of its X-direction, Y direction is 16 * 10 ^-6/ ℃, the thermal expansivity of Z-direction is 5 * 10 ^-6/ ℃.The monocrystalline lithium tantalate that constitutes maintenance matrix 2 is 15 * 10 at the thermal expansivity of X-direction, Y direction ^-6/ ℃, the thermal expansivity of Z-direction is 1.2 * 10 ^-6/ ℃.

(device 11 of comparative example 2: Fig. 6)

In this example, 3 inches wafer (LiNbO of X cutting have been used ₃Monocrystalline) substrate of making.The thermal expansivity of its X-direction, Y direction is 16 * 10 ^-6/ ℃, the thermal expansivity of Z-direction is 5 * 10 ^-6/ ℃.Keeping the material of matrix 2 is quartz glass.The thermal expansivity of quartz glass is 50 * 10 ^-6/ ℃.

As a result, time stagnant (with reference to Figure 21) appearred in the signal extinction ratio curve to 1kHz.In addition, 100 ℃ of results that investigate the DC drift characteristics, the drift value of DC bias voltage relatively initially applies voltage change more than 50%.

According to the invention of second mode, in fiber waveguide device, returning in the luminous power in the time of can preventing to apply signal voltage stagnates, and suppresses long-term DC drift.

Claims

1. fiber waveguide device, it is characterized in that: possess, electrooptics crystal substrate, optical waveguide and modulator electrode, at least the thickness of above-mentioned optical crystal substrate in zone that applies electric field by above-mentioned modulator electrode is at 30 μ m or below it, and the height H (dust) of the protuberance that produces when forming above-mentioned optical waveguide and the width W (μ m) of protuberance long-pending (HW) are at 7150 dust μ m or below it.

2. fiber waveguide device according to claim 1 is characterized in that: the height H of raised part is at 1100 dusts or below it, and the width W of raised part is at 6.5 μ m or below it.

3. fiber waveguide device; it is characterized in that: possess; electrooptics crystal substrate, optical waveguide and modulator electrode; at least the thickness of above-mentioned optical crystal substrate in zone that applies electric field by above-mentioned modulator electrode is at 30 μ m or below it, the single modeization of horizontal direction at least of above-mentioned at least optical waveguide export department.

4. according to any described fiber waveguide device of claim 1～3, it is characterized in that: apply the zone at above-mentioned electric field, above-mentioned optical waveguide has branching portion, at the interval of the above-mentioned optical waveguide of above-mentioned branching portion at 46 μ m or more than it.

5. according to any described fiber waveguide device of claim 1～4, it is characterized in that: apply the zone at above-mentioned electric field, above-mentioned optical waveguide has branching portion, between above-mentioned branching portion, is formed with groove on above-mentioned electrooptics crystal substrate.

6. a fiber waveguide device is characterized in that: possess electrooptics crystal substrate, optical waveguide and modulator electrode, apply the zone of electric field at above-mentioned modulator electrode, above-mentioned optical waveguide has branching portion, between above-mentioned branching portion, is formed with groove on above-mentioned electrooptics crystal substrate.

7. according to any described fiber waveguide device of claim 1～6, it is characterized in that: possess the maintenance matrix of the above-mentioned electrooptics monocrystal substrate of maintenance and the adhesive linkage of bonding above-mentioned electrooptics crystal substrate and above-mentioned maintenance matrix, the minimum value of the thermal expansivity in the above-mentioned maintenance matrix is 1/5 times of minimum value of the thermal expansivity in the above-mentioned electrooptics crystal substrate or more than it, and the maximal value of the thermal expansivity in the above-mentioned maintenance matrix is peaked 5 times or below it of thermal expansivity in the above-mentioned electrooptics crystal substrate.

8. fiber waveguide device according to claim 7 is characterized in that: above-mentioned maintenance matrix is that one or more the material of choosing from the group of being made up of lithium niobate, lithium tantalate, lithium niobate-lithium tantalate solid solution and lithium potassium niobate is made.

9. fiber waveguide device according to claim 8 is characterized in that: above-mentioned maintenance matrix is made by lithium niobate monocrystal.

10. a fiber waveguide device possesses optical waveguide substrate, keeps the maintenance matrix of this optical waveguide substrate and the adhesive linkage of bonding above-mentioned optical waveguide substrate and above-mentioned maintenance matrix, it is characterized in that:

Above-mentioned optical waveguide substrate is made by electrooptic material, possess: the thickness with an opposed facing interarea and another interarea is in 30 μ m or the flat-shaped substrate main body below it, at optical waveguide that is provided with on this base main body and the electrode that on the aforesaid substrate main body, is provided with, utilize above-mentioned another interarea of bonding above-mentioned maintenance matrix of above-mentioned adhesive linkage and aforesaid substrate main body, the minimum value of the thermal expansivity in the above-mentioned maintenance matrix is 1/5 times of minimum value of the thermal expansivity in the aforesaid substrate main body or more than it, and the maximal value of the thermal expansivity in the above-mentioned maintenance matrix is in the aforesaid substrate main body 5 times of thermal expansivity or below it.

11. fiber waveguide device according to claim 10 is characterized in that: the bonding plane of above-mentioned maintenance matrix is the face of general planar, and above-mentioned adhesive linkage has the specific inductive capacity lower than the specific inductive capacity of above-mentioned electrooptic material.

12. according to claim 10 or 11 described fiber waveguide devices, it is characterized in that: the thickness of above-mentioned adhesive linkage is at 200 μ m or below it.

13. according to any described fiber waveguide device of claim 10～12, it is characterized in that: above-mentioned adhesive linkage is at formation bonding above-mentioned another interarea in zone and the above-mentioned maintenance matrix of above-mentioned optical waveguide.

14. according to any described fiber waveguide device of claim 10～13, it is characterized in that: the thickness of above-mentioned adhesive linkage is roughly constant.

15. according to any described fiber waveguide device of claim 10～14, it is characterized in that: in the formation zone of above-mentioned optical waveguide, be provided with the low-k part between above-mentioned another interarea and above-mentioned maintenance matrix, this low-k partly has the specific inductive capacity lower than the specific inductive capacity of above-mentioned electrooptic material.

16. according to any described fiber waveguide device of claim 10～15, it is characterized in that: above-mentioned maintenance matrix is made by electrooptic material.

17. fiber waveguide device according to claim 16 is characterized in that: above-mentioned maintenance matrix is that one or more the material of choosing from the group of being made up of lithium niobate, lithium tantalate, lithium niobate-lithium tantalate solid solution and lithium potassium niobate is made.

18. a travelling-wave type optical modulator is characterized in that: possess any described fiber waveguide device of claim 10～17, utilize above-mentioned electrode to apply to be used for the voltage that is modulated at the light that above-mentioned optical waveguide propagates.