JP2003107545A - Manufacturing method for ridge type optical waveguide element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new manufacturing method which can stably supply a stuck type ridge type optical waveguide element. SOLUTION: An optical waveguide assembly 5 is manufactured by sticking a base substrate 3 on the reverse surface 1B of a ferroelectric single-crystal substrate 1 where a cyclic polarization inversion structure 2 is formed, across an adhesive layer 4. Then the optical waveguide element assembly 5 is fixed to a reference board 6 across an adhesive layer 6. Then the ferroelectric single- crystal substrate 1 is ground from the side of the reverse surface 1B and then polished to form the ferroelectric single-crystal substrate 1 into a thin plate. The cyclic polarization inversion structure 2 is processed into a ridge type to obtain the target ridge type optical waveguide element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ridge type optical waveguide device, and more particularly to an SHG (Second Harmonic Generation) device using a ferroelectric single crystal substrate such as lithium niobate or lithium tantalate. The present invention relates to a method of manufacturing a ridge-type optical waveguide device that can be preferably used.

[0002]

2. Description of the Related Art In the fields of printing, optical information processing, optical applied measurement control, and the like, there is a strong demand for the realization of a compact short-wavelength light source. Taking a bath. This SHG device generates the second harmonic by utilizing the nonlinear optical effect by passing the light emitted from the semiconductor laser. This second harmonic has a frequency twice that of the light emitted from the semiconductor laser, and thus has a wavelength of 1/2. That is, by using the SHG device, it is possible to obtain light of a short wavelength having a half wavelength with respect to the light emitted from the semiconductor laser.

The SHG device comprises a ferroelectric single crystal substrate such as lithium niobate (hereinafter sometimes abbreviated as "LN") or lithium tantalate (hereinafter sometimes abbreviated as "LT"), This substrate is composed of an optical waveguide element having a polarization structure in which the polarization state is periodically inverted in a direction substantially perpendicular to the light traveling direction. This optical waveguide element has an optical waveguide formed by using a proton exchange method or the like in the periodic domain-inverted structure or by processing the periodic domain-inverted structure into a ridge type. Then, a mounting process such as forming a protective film is performed on the optical waveguide element to obtain the desired SHG device.

Then, the SHG device is configured,
When a predetermined fundamental wave is made incident into the proton exchange optical waveguide or the ridge-type optical waveguide, wavelength conversion is performed by the nonlinear optical effect while traveling in the periodic domain-inverted structure. Second harmonics can be generated, and target short-wavelength light can be obtained.

In recent years, as an optical waveguide element used for a practical device such as the above-mentioned SHG device, it has a stepwise refractive index change at the boundary of the optical waveguide and can more firmly confine the introduced optical wave. Therefore, a so-called ridge-type optical waveguide device having a ridge-type optical waveguide is receiving attention.

There are two types of ridge type optical waveguide devices, so-called epitaxial growth type and laminating type.

The epitaxial growth type is characterized in that it comprises a ferroelectric single crystal thin film processed into a ridge type in which a periodic domain-inverted structure is formed on a predetermined ferroelectric single crystal substrate. . On the other hand, in the bonded type, a periodic polarization inversion structure is formed on the ferroelectric single crystal substrate itself and processed into a ridge type, and this ridge type ferroelectric single crystal substrate is bonded onto a predetermined base substrate. It is characterized by being fixed through layers.

[0008]

A micron-order processing technique is required for any type of ridge-type optical waveguide device, and particularly for the attachment-type ridge-type optical waveguide device, a high-precision bonding technique is required. In addition, high-precision processing technology associated therewith is required. For this reason, a technology capable of stably supplying the bonded ridge type optical waveguide device has not yet been established.

It is an object of the present invention to provide a novel manufacturing method capable of stably supplying a bonded ridge type optical waveguide device.

[0010]

[Means for Solving the Problems] In order to achieve the above object,
The present invention relates to a step of adhering a ferroelectric single crystal substrate having a periodic domain-inverted structure and a base substrate and adhering them together to produce an optical waveguide device assembly, and adhering the base substrate to a reference plate. A step of fixing the optical waveguide device assembly to the reference plate; and a step of grinding the ferroelectric single crystal substrate and subsequently performing a polishing process on the basis of the reference plate to obtain the ferroelectric substance. A step of thinning the single crystal substrate, and processing the periodic domain-inverted structure portion of the thinned ferroelectric single crystal substrate into a ridge shape,
And a step of forming a ridge-type optical waveguide, the present invention relates to a method for manufacturing a ridge-type optical waveguide element.

According to the above-described manufacturing method of the present invention, it is possible to stably supply the bonded ridge type optical waveguide device.

Detailed requirements for the method of manufacturing the ridge type optical waveguide device of the present invention will be described in detail in the following embodiments with specific examples.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION (Ferroelectric Single Crystal Substrate) In the manufacturing method of the present invention, a ferroelectric single crystal substrate having a periodic domain inversion structure is used. The periodic domain-inverted structure can be formed by using a known method such as a voltage application method or a corona discharge method. An SHG device was produced from the obtained ridge type optical waveguide device, and the wavelength was 820n.
When obtaining SHG light with a wavelength of 410 nm from m fundamental light, the inversion period of the periodic polarization inversion structure is about 2.8 μm.
To

Further, the ferroelectric single crystal substrate can be manufactured from any ferroelectric single crystal material and member. However, lithium niobate (LN) and lithium tantalate have a large electro-optical effect and stably exhibit relatively large nonlinear optical characteristics when the periodic domain-inverted structure is formed. It is preferable to use a single crystal material such as (LT) and a single crystal member, and it is particularly preferable to use an LN single crystal material and a single crystal member.

In order to improve the light damage resistance, Mg, Zn, and
Elements such as Sc and In can be added. When an oxide such as LN is used, the above-mentioned elements are usually added in the form of oxide.

As the single crystal member, the LN
A single crystal X-cut plate, Y-cut plate, Z-cut plate, off-cut plate, or the like can be used.

FIG. 1 is a view showing a state in which a periodic domain-inverted structure is formed in a ferroelectric single crystal substrate made of an X cut plate of LN single crystal, and FIG. 2 is a Z cut of LN single crystal. It is a figure which shows the state in which the periodic domain inversion structure was formed in the ferroelectric single crystal substrate which consists of plates. In general, as shown in FIG. 1, when the ferroelectric single crystal substrate 1 is composed of an LN single crystal X-cut plate, a periodic domain-inverted structure 2 is formed in the surface layer portion thereof, as shown in FIG. In addition, when the ferroelectric single crystal substrate 1 is composed of an LN single crystal Z-cut plate, the periodic domain-inverted structure 2 is formed over the entire thickness direction thereof.

When the above-mentioned LN single crystal or the like is used, the ferroelectric single crystal substrate can be composed of an LN single crystal wafer, and if the wafer is circular, it may have a square shape or other shapes as necessary. It can be processed into any shape and used.

Since the LN single crystal wafer has a size on the order of cm, and the periodic domain-inverted structure has a size on the order of mm, in this case, the same wafer is shown in FIGS. 1 and 2. A plurality of such periodic polarization inversion structures are formed and cut into inversion structure units to obtain a final optical waveguide device.

The thickness of the ferroelectric single crystal substrate is preferably 0.3 mm to 1 mm. If the thickness of the ferroelectric single crystal substrate is less than 0.3 mm, it may be broken during handling. When the thickness of the ferroelectric single crystal substrate is larger than 1 mm,
In the subsequent thinning process, it takes a long time to increase the tact time.

The parallelism of the ferroelectric single crystal substrate is preferably 0.3 μm or less. by this,
In the subsequent thinning step, the fluctuation range of the thickness of the processed ferroelectric single crystal substrate can be easily reduced. The "parallelism" means a fluctuation range of the distance between the upper surface and the lower surface of the ferroelectric single crystal substrate, that is, a fluctuation range of the thickness of the ferroelectric single crystal substrate, and this value is small. In other words, it means that the upper surface and the lower surface of the ferroelectric single crystal substrate come closer to being completely parallel to each other.

(Base Substrate) The base substrate to be bonded to the ferroelectric single crystal substrate is a ferroelectric single crystal material forming the ferroelectric single crystal substrate, and further a ferroelectric substance having the same crystal orientation. It is preferably composed of a single crystal member. When the ferroelectric single crystal substrate and the base substrate are bonded together to produce an optical waveguide device assembly, and the optical waveguide device assembly is subjected to a subsequent thinning process,
May be exposed to various environmental temperatures.

In this case, even if the ferroelectric single crystal substrate and the base substrate are made of different ferroelectric single crystal materials, or even if they are made of the same material, their crystal orientations are different. If so, the optical waveguide element assembly may be warped due to the stress caused by the difference in thermal expansion. When the optical waveguide element assembly is warped as described above, sufficient parallelism cannot be obtained when the optical waveguide element assembly is fixed to the reference plate so as to be subjected to a later thinning process. Therefore, the ferroelectric single crystal substrate cannot be sufficiently thinned, and even if the ferroelectric single crystal substrate can be thinned, the thickness of the ferroelectric single crystal substrate is made uniform to a level at which it can be put to practical use. I can't.

Therefore, as described above, by forming the ferroelectric single crystal substrate and the base substrate from the same ferroelectric single crystal material, and further from the same ferroelectric single crystal member having the same crystal orientation, The inconvenience caused by the warp of the optical waveguide element assembly as described above can be avoided.

The thickness of the base substrate is 0.3 m.
It is preferably m to 2 mm, and more preferably about 1 mm. The base substrate has a thickness of 0.3.
If it is smaller than mm, it may crack during handling. On the other hand, if the thickness exceeds 2 mm, the thickness of the ridge-type optical waveguide device finally obtained becomes large as a whole, which may result in oversize when used as an SHG device.

Further, the parallelism of the base substrate is 0.5.
It is preferably μm or less. As a result, as described above, the fluctuation range of the thickness of the processed ferroelectric single crystal substrate can be easily reduced. The "parallelism" means a fluctuation range of the distance between the upper surface and the lower surface of the base substrate, that is, a fluctuation range of the thickness of the base substrate,
The smaller this value is, the closer the upper surface and the lower surface of the base substrate are to being completely parallel to each other.

The flatness of the base substrate is preferably 1 μm or less. The base substrate is fixed to the reference plate with an adhesive when it is subjected to a subsequent thinning process. However, if the flatness exceeds 1 μm, the thickness accuracy of the adhesive is lowered, and as a result, the processed substrate is In some cases, the fluctuation range of the thickness of the ferroelectric single crystal substrate cannot be sufficiently reduced. In addition,
The "flatness" means a degree of openness from a geometrically correct plane of one plane of the base substrate, for example, a plane bonded and fixed to the reference board, and the smaller this value is, the flatter the plane is. Means flat.

Further, the size of the surface of the base substrate to be bonded to the ferroelectric single crystal substrate is 1. The size of the surface of the ferroelectric single crystal substrate to be bonded to the base substrate is 1. It is preferably 1 to 2 times. As a result, the entire surface of the ferroelectric single crystal substrate can be easily adhered and fixed to the base substrate. Further, as will be described later in detail, when the base substrate is adhered and fixed to the reference board, the thickness of the adhesive layer can be easily controlled.

(Lamination of Ferroelectric Single Crystal Substrate and Base Substrate) FIG. 3 is a side view showing a state in which the ferroelectric single crystal substrate and the base substrate are attached to each other, that is, an optical waveguide device assembly. In the manufacturing method of the present invention, the ferroelectric single crystal substrate 1 and the base substrate 3 are bonded together using a predetermined adhesive to manufacture an optical waveguide device assembly 5 as shown in FIG. The adhesive is used as the adhesive layer 4
Remains as.

When the ferroelectric single crystal substrate 1 is made of, for example, an LN single crystal X-cut plate or the like, the ferroelectric single crystal substrate 1 is formed so that the periodic domain-inverted structure 2 remains after thinning. The main surface 1A of 1 is bonded and fixed to the base substrate 3. On the other hand, when the LN single crystal Z-cut plate or the like is used, the periodic domain-inverted structure 2 is formed on the substrate 1.
Is formed in the entire thickness direction. Therefore, the main surface 1
The periodic domain-inverted structure 2 will remain regardless of which side of the main surface 1 or the back surface 1B is thinned.
Either A or the back surface 1B may be bonded to the base substrate 3.

For example, in the case of forming the periodic polarization inversion structure on the Z-cut substrate by the voltage application method, the periodic electrode pattern is formed on the + Z plane side, and the polarization inversion is formed from this + Z plane side. In many cases, the closer to the + Z plane side, the higher the shape accuracy of the inverted portion. Therefore, when the periodic domain-inverted structure is formed on the Z-cut substrate in this manner, it is preferable to bond the + Z plane side thereof.

The adhesive used for bonding the ferroelectric single crystal substrate 1 and the base substrate 3 preferably has a small light absorption coefficient in the adhered / cured state, and especially in the completed ridge type optical waveguide device. It is preferable that the absorption coefficient is small for the wavelengths of these light waves for which the absorption loss of the guided light waves should be reduced. Specifically, it is preferably 1 cm ^-1 or less, and more preferably 0.1 cm ^-1 or less.

Further, in order to make the thickness distribution of the adhesive layer 4 formed by adhering and curing the adhesive uniform, it is preferable that the viscosity of the adhesive is small, specifically, a viscosity of 100 cp or less. Is preferred.

As the adhesive, a heat-curing type, U
Among known adhesives such as V-curable type and room temperature-curable type, adhesives preferably satisfying the above conditions can be arbitrarily selected. In addition, in order to prevent warpage of the ferroelectric single crystal substrate 1 and the base substrate 3 as much as possible, it is preferable to use one of the known adhesives that can be bonded near room temperature. Specifically, acrylic resin, epoxy resin,
Silicone resin and polyimide resin can be exemplified.

The thickness of the adhesive layer 4 is 0.01 μm-1.
It is preferably 0 μm. The thickness of the adhesive layer 4 is 0.0
When it is smaller than 1 μm, when a predetermined light wave is propagated in the optical waveguide of the finally obtained ridge-type optical waveguide element, the light wave easily leaks to the base substrate 3 side, and the optical propagation loss may increase. is there. On the other hand, the thickness of the adhesive layer 4 is 10 μm
If the thickness exceeds the range, the thickness accuracy of the adhesive layer 4 itself decreases, and the fluctuation range increases, so that the subsequent step of thinning the ferroelectric single crystal substrate 1 becomes difficult, and the final thinning is performed. It becomes impossible to keep the fluctuation range of the thickness of the ferroelectric single crystal substrate 1 within a predetermined range.

The fluctuation range of the thickness of the adhesive layer 4 is preferably determined by irradiating the adhesive layer 4 with predetermined light from the ferroelectric single crystal substrate 1 side or the base substrate 3 side to obtain the number of fringes of the optical interference fringes. It is preferable to reduce by controlling.

FIG. 4 is a diagram showing an example of a state of optical interference fringes obtained in the adhesive layer 4. The interference fringes obtained when a predetermined light is introduced into the adhesive layer 4 is, for example, as shown in FIG.
The state shown in (a) or FIG. 4 (b) is exhibited.
In these interference fringes, like the contour lines in the topographic map, one interference fringe is formed due to the difference in thickness of a certain size from the relationship with the wavelength of the light. That is, the larger the number of interference fringes, the larger the fluctuation range of the thickness of the adhesive layer 4, and the smaller the number of interference fringes, the smaller the fluctuation range of the thickness of the adhesive layer 4.

The thickness variation is similar to the contour lines in the topographic map. For example, in FIG. 4A, the line formed by connecting the convex portions of the interference fringes corresponding to the ridge of the topographic map is indicated by an arrow. In the direction shown, the thickness of the adhesive layer 4 increases. On the other hand, in the case shown in FIG. 4B, the thickness of the adhesive layer 4 is large in the island-shaped portion arranged on the upper side.

FIG. 5 is a diagram showing a state of interference fringes when the variation width of the thickness of the adhesive layer 4 is set to a preferable state in the present invention. In the present invention, when light of 633 nm is used, the number of interference fringes is, for example, as shown in FIG.
It is preferable that the number is two or less in the state as shown in. When the light having a wavelength of 633 nm is used and the refractive index n of the adhesive layer is about 2, as shown in FIG.
Due to the interference fringes of the book, the fluctuation range of the thickness of the adhesive layer 4 is 0.15 μm between them.

Therefore, in this case, by setting the number of the interference fringes to be two or less, the variation width of the thickness of the adhesive layer 4 is ideally 0.3 when the thinning step is performed later.
It can be set to μm or less.

(Adhesive Fixing of Optical Waveguide Element Assembly and Reference Plate) FIG. 6 shows the optical waveguide element assembly 5 shown in FIG.
It is a side view which shows the state which adhered and fixed to the reference board 6. As shown in FIG. 6, the optical waveguide element assembly 5 is adhesively fixed to the reference plate 6 with a predetermined adhesive, and the adhesive remains as an adhesive layer 7. The following advantages are obtained by fixing the optical waveguide device assembly 5 to the reference plate 6 when the ferroelectric single crystal substrate 1 is subjected to the subsequent thinning process.

Since the ferroelectric single crystal substrate 1 and the base substrate 3 are bonded to each other in the optical waveguide device assembly 5, it is presumed that the difference in the degree of thermal expansion between the two and the stress caused by the adhesive layer, etc. 0.1 μm to 1 depending on various causes
A warp of about μm may occur. Although this warpage is very small, it is 0.1 μm in the present invention.
Since processing accuracy on the order of is required, even such a slight warp may cause a decrease in processing accuracy and a yield. Therefore, as shown in FIG. 6, it is preferable to fix the optical waveguide device assembly 5 to the reference plate 6 and reduce the minute warp as much as possible, and then perform the thinning process of the ferroelectric single crystal substrate 1.

From this point of view, the flatness of the reference plate 6 is preferably 1 μm or less, more preferably 0.3 μm.
The following is preferable. The "flatness" means the degree of openness from a geometrically correct plane within one plane of the reference board 6, for example, the plane bonded and fixed to the optical waveguide device assembly 5, and this value is The smaller the size, the flatter the plane is.

The parallelism of the reference plate 6 is preferably 1 μm or less, more preferably 0.3 μm or less. If the parallelism of the reference plate becomes larger than 1 μm, the processing accuracy of the ferroelectric single crystal substrate 1 may be deteriorated in the subsequent step of thinning the ferroelectric single crystal substrate 1. The "parallelism" means a fluctuation range of the distance between the upper surface and the lower surface of the reference plate 6, that is, a fluctuation range of the thickness of the reference plate. The smaller this value is, the upper surface and the lower surface of the reference plate. It means that and are almost parallel.

A hot melt resin can be used as an adhesive used for fixing the optical waveguide device assembly 5 and the reference plate 6. In this case, in the optical waveguide device assembly 5, the area of the bonding surface 3A of the base substrate 3 with respect to the ferroelectric single crystal substrate 1 is set to the ferroelectric single crystal substrate 1
Is larger than the main surface 1A corresponding to the adhesive surface to the base substrate 3, specifically, 1.1 to 2 times. Then,
Since the end portion of the base substrate 3 is exposed from the ferroelectric single crystal substrate 1, the thickness of the adhesive layer 7 can be adjusted only by pressing the end portion of the base substrate 3 as shown by the arrow.

That is, since it is not necessary to press the ferroelectric single crystal substrate 1 when adjusting the thickness of the adhesive layer 7, it is possible to prevent the ferroelectric single crystal substrate 1 from being damaged such as cracked. You can Therefore, the accuracy of the optical waveguide device assembly 5 for use in the subsequent thinning process,
In addition, the accuracy of bonding and fixing the optical waveguide device assembly 5 and the reference plate 6 can be kept sufficiently high.

The optical waveguide element assembly 5 and the reference plate 6 can be fixed by optical contact without using such a hot melt resin. In this case, the adhesive layer 7 does not remain in a definite form.

(Thinning process of ferroelectric single crystal substrate) FIG.
FIG. 4 is a side view showing a state where the ferroelectric single crystal substrate 1 is thinned by the thinning process. In FIG. 7, a thin ferroelectric single crystal substrate 11 is formed on the base substrate 3 with an adhesive layer 4 interposed therebetween.

In the present invention, as shown in FIG. 6, after the optical waveguide device assembly 5 and the reference plate are adhered and fixed, the ferroelectric single crystal substrate 1 is thinned. The thinning process includes a grinding process and a polishing process that follows. Then, the polishing process is performed from the back surface 1B side of the ferroelectric single crystal substrate 1.

In the present invention, it is preferable that the grinding process comprises a rough grinding process and a subsequent precision lapping process. The rough grinding process is a machining process using a milling machine or the like. By performing the grinding process in such a two-step process, even when the thickness of the ferroelectric single crystal substrate 1 is relatively large, it is possible to accurately perform the grinding process to a predetermined thickness in a relatively short time so as to be used for the polishing process. It can be thinned.

A QPM-S having a fundamental wavelength of 820 nm and an SHG wavelength of 410 nm was obtained from the finally obtained ridge type optical waveguide device.
When manufacturing an HG device, the thickness of the ferroelectric single crystal substrate 1 needs to be finally thinned to 3 μm. That is, the thinned ferroelectric single crystal substrate 1 shown in FIG.
It is necessary to set the thickness h of 1 to 3 μm.

Therefore, in this case, the ferroelectric single crystal substrate 1 is made to have a thickness of 50 by the rough grinding processing.
The thickness of the ferroelectric single crystal substrate 1 is reduced to 5 μm by a precision lapping process. Then, by performing a polishing process, the ferroelectric single crystal substrate 1
Is thinned to a thickness of 3 μm to obtain a thinned ferroelectric single crystal substrate 11 having a thickness h of 3 μm.

Although the ferroelectric single crystal substrate 1 is thinned from 5 μm to 3 μm depending on the polishing process, extremely high processing accuracy is required in this polishing process. Therefore, in this polishing step, it is preferable to improve the processing accuracy by irradiating the ferroelectric single crystal substrate 1 with predetermined light as described above and controlling the number of fringes of the optical interference fringes.

The form of the obtained interference fringes is similar to that shown in FIG. 4, and in this case also, it is preferable that the number of the interference fringes is 2 or less when the light of the wavelength of 633 nm is used. . As shown in FIG. 5, the distance between the two interference fringes corresponds to a thickness fluctuation range of 0.15 μm. Therefore, by setting the number of the interference fringes to 2 or less, the fluctuation range of the thickness of the finally thinned ferroelectric single crystal substrate 1 can be kept within about ± 0.2 μm.

The above-mentioned polishing treatment is preferably carried out in an Oscar type polishing apparatus, preferably using colloidal silica abrasive grains. As a result, the above-described highly accurate polishing process can be performed relatively easily. The particle size of the colloidal silica abrasive is 0.01 μm.
It is preferably 0.1 μm.

(Formation of Ridge Type Optical Waveguide) FIGS. 8 and 9
FIG. 4 is a diagram showing a state in which a ridge type optical waveguide 8 is formed by subjecting the ferroelectric single crystal substrate 11 thinned as described above to a predetermined processing treatment. Figure 8
Shows the case where the ferroelectric single crystal substrate 1 is composed of, for example, an X-cut plate of LN single crystal, and the periodic domain-inverted structure 2 as shown in FIG. 1 is formed. Figure 9
The case where the ferroelectric single crystal substrate 1 is composed of, for example, a Z-cut plate of LN single crystal or the like, and the periodic domain-inverted structure 2 as shown in FIG. 2 is formed is shown.

In order to clarify the morphological characteristics of the ridge type optical waveguide 8 in FIGS. 8 and 9, the size and the like are different from the actual ones.

A ridge type optical waveguide 8 shown in FIGS. 8 and 9.
Is preferably performed using at least one of mechanical cutting, laser processing, and etching processing. Mechanical cutting, for example, using a dicing device. Laser processing is performed using an excimer laser or the like. The etching process is performed using reactive ion etching (RIE) or the like.

In the dicing process, a predetermined rotating blade is brought into contact with both ends of the thinned ferroelectric single crystal substrate 11, and processing is carried out under the conditions of, for example, a rotation speed of 1000 rpm and a traveling speed of 0.1 mm / sec. As a result, the portion corresponding to the ridge-type optical waveguide 8 is removed by cutting. Similarly, in the laser processing, a laser beam having a predetermined energy density, for example, 1 J / cm ² is irradiated to both ends of the thinned ferroelectric single crystal substrate 11, and a portion corresponding to the ridge type optical waveguide 8 is irradiated. Evaporate to leave and remove.

On the other hand, in the case of RIE or the like, the thinned ferroelectric single crystal substrate 11 is placed in a predetermined atmosphere of fluorine gas or the like, the fluorine gas or the like is turned into plasma, and the reactive ions turned into the plasma. The ferroelectric single crystal substrate 11 is irradiated with gas while masking the portion corresponding to the ridge type optical waveguide 8. Then, this reactive ion gas reacts with the exposed end portion of the ferroelectric single crystal substrate 11, and this portion is removed by etching to obtain the target ridge type optical waveguide device 8.

Basic wavelength 820 nm, SH as described above
When manufacturing a QPM-SHG device having a G wavelength of 410 nm, the width W of the ridge portion of the ridge type optical waveguide 8 is 2 μm.
10 μm is preferable, and the height d of the ridge portion is
Is preferably 0.5 μm to 2.5 μm.

The formation of the ridge type optical waveguide 8 is performed as shown in FIG.
As shown in, the optical waveguide device assembly 5 having the thinned ferroelectric single crystal substrate 11 can be fixed to the reference plate 6 or can be removed from the reference plate 6.

Further, the portions of the base substrate 3 protruding from both sides of the ferroelectric single crystal substrate 1 are removed by cutting if necessary. In general, since a wafer of LN single crystal or the like is used as the ferroelectric single crystal substrate 1, a plurality of ridge type optical waveguides 8 are formed on one wafer. Therefore, in order to use it as an actual optical waveguide device, when the base substrate 3 is cut into chips in ridge type optical waveguide units.
The excess part of is removed by cutting. When the overcoat layer as described below is formed, the base substrate 3 is removed by cutting after removing the overcoat layer after forming the overcoat layer.

(Formation of Overcoat Layer) In the present invention, after forming the ridge type optical waveguide 8 as shown in FIGS. 8 and 9, an unillustrated overcoat layer may be formed so as to cover the ridge type optical waveguide 8. preferable. As a result, damage to the ridge-type optical waveguide 8 due to an external factor can be reduced. The overcoat layer can be composed of, for example, a SiO ₂ film formed by using a sputtering method or a vapor deposition method. Alternatively, a predetermined resin material may be dissolved in a solvent or the like to obtain a solution, and the solution may be applied by spin coating or the like.

(Polishing and Cutting, etc.) After the overcoat layer is formed as described above, the end face of the ridge type optical waveguide 8 is optionally subjected to optical polishing.
When a single ridge type optical waveguide 8 is formed on the thinned ferroelectric single crystal substrate 11, this polishing process is performed to obtain a final ridge type optical waveguide device. On the other hand, the ferroelectric single crystal substrate 1 is composed of a wafer,
When a plurality of ridge type optical waveguides are formed on this wafer, each ridge type optical waveguide element is obtained by cutting each optical waveguide into chips.

When the ridge-type optical waveguide device thus obtained is used as the above-mentioned QPM-SHG device, it is preferable to form an AR coat (antireflection film) on the end face of the ridge-type optical waveguide, and to enter and emit it. The reflectance of light is reduced to improve the incidence efficiency and the emission efficiency of light. Further, in the case of a QPM-SHG device, the AR coat is to cope with light of two kinds of wavelengths, that is, basic light and SHG light,
It is preferably performed as a two-wavelength AR coat.

In the above QPM-SHG device, a semiconductor laser can be used as a light source of basic light, and specifically, a tunable DBR laser or the like is used, and tuning is performed so as to match the phase matching wavelength of SHG. Is desirable.

Although the present invention has been described in detail based on the embodiments of the invention with reference to the specific examples, the present invention is not limited to the above contents and does not depart from the scope of the present invention. In, all changes and modifications are possible.

[0069]

As described above, according to the present invention,
It is possible to provide a novel manufacturing method capable of stably supplying a bonded ridge type optical waveguide device.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which a periodic domain inversion structure is formed in a ferroelectric single crystal substrate made of an LN single crystal X-cut plate.

FIG. 2 is a diagram showing a state in which a periodic domain-inverted structure is formed in a ferroelectric single crystal substrate made of an LN single crystal Z-cut plate.

FIG. 3 is a side view showing an optical waveguide device assembly in which a ferroelectric single crystal substrate and a base substrate are bonded together.

FIG. 4 is a diagram showing an example of a state of optical interference fringes obtained on the adhesive layer 4 or the ferroelectric single crystal substrate 1.

FIG. 5 is a diagram showing a state of interference fringes when the variation width of the thickness of the adhesive layer 4 or the ferroelectric single crystal substrate 1 is set to a preferable state.

6 is a side view showing a state in which the optical waveguide device assembly 5 shown in FIG. 3 is adhesively fixed to a reference board 6. FIG.

FIG. 7 is a side view showing a state where the ferroelectric single crystal substrate 1 is thinned by the thinning process.

FIG. 8 is a view showing a state in which a ridge type optical waveguide 8 is formed on a thinned ferroelectric single crystal substrate 11.

FIG. 9 is a view showing a state in which a ridge-type optical waveguide 8 is formed on a thinned ferroelectric single crystal substrate 11.

[Explanation of symbols]

1 Ferroelectric single crystal substrate, 2 Periodic polarization inversion structure, 3
Base substrate, 4, 7 adhesive layer, 5 Optical waveguide device assembly, 8 Ridge type optical waveguide, 11 Thinned ferroelectric single crystal substrate

Continued front page    F term (reference) 2H047 KA05 NA02 PA14 QA03 RA00                 2K002 AA01 AA04 AA06 AB12 BA01                       CA03 DA06 EA07 FA19 FA27                       FA29 FA30 GA10 HA20

Claims (35)

[Claims] 1. A step of adhering a ferroelectric single crystal substrate on which a periodic domain-inverted structure is formed and a base substrate and adhering them together to produce an optical waveguide device assembly, and adhering the base substrate to a reference plate. Then, the step of fixing the optical waveguide device assembly to the reference plate, and the ferroelectric single crystal substrate is subjected to a grinding process and a subsequent polishing process on the basis of the reference plate to obtain the ferroelectric substance. A step of thinning the body single crystal substrate, and a step of processing the periodic domain-inverted structure portion of the thinned ferroelectric single crystal substrate into a ridge type to form a ridge type optical waveguide. A method for manufacturing a ridge-type optical waveguide device, comprising: 2. The ridge type optical waveguide device according to claim 1, wherein the ferroelectric single crystal substrate and the base substrate are made of the same ferroelectric single crystal material. Production method. 3. The ridge according to claim 2, wherein the ferroelectric single crystal substrate and the base substrate are composed of the same ferroelectric single crystal member having the same crystal orientation. Method of manufacturing optical waveguide device. 4. The method of manufacturing a ridge-type optical waveguide device according to claim 3, wherein the ferroelectric single crystal member is a lithium niobate single crystal member. 5. The ferroelectric single crystal substrate has a thickness of 0.3 m.
It is m-1 mm, The manufacturing method of the ridge type optical waveguide element as described in any one of Claims 1-4 characterized by the above-mentioned. 6. The parallelism of the ferroelectric single crystal substrate is 0.3.
The method for manufacturing a ridge-type optical waveguide device according to claim 1, wherein the ridge-type optical waveguide device has a thickness of μm or less. 7. The base substrate has a thickness of 0.3 mm to 2 m.
7. The method for manufacturing a ridge-type optical waveguide device according to claim 1, wherein m is m. 8. The method of manufacturing a ridge type optical waveguide device according to claim 1, wherein the parallelism of the base substrate is 0.5 μm or less. 9. The method of manufacturing a ridge-type optical waveguide device according to claim 1, wherein the flatness of the base substrate is 1 μm or less. 10. The size of the surface of the base substrate to be bonded to the ferroelectric single crystal substrate is 1. the size of the surface of the ferroelectric single crystal substrate to be bonded to the base substrate. 1
The method for manufacturing a ridge-type optical waveguide element according to claim 1, wherein the ridge-type optical waveguide element has a twelfth increase. 11. adhesion between the base substrate and the ferroelectric single crystal substrate, in bonding and curing conditions, 1 cm with respect to the optical wave guided through the ridge-type optical waveguide element ^{- 1} or less of the optical absorption coefficient The method for manufacturing a ridge-type optical waveguide element according to claim 1, wherein the method is performed using the adhesive of item 1. 12. The light absorption coefficient of the adhesive is 0.1 cm.
^{It is -1} or less, The manufacturing method of the ridge type optical waveguide device of Claim 11 characterized by the above-mentioned. 13. The method according to claim 1, wherein the ferroelectric single crystal substrate and the base substrate are bonded to each other by using an adhesive having a viscosity of 100 cp or less. Manufacturing method of ridge type optical waveguide device. 14. The thickness of the adhesive layer when the ferroelectric single crystal substrate and the base substrate are bonded together is 0.01 μm to 1 μm.
It is 0 micrometer, The manufacturing method of the ridge type optical waveguide device as described in any one of Claims 1-13 characterized by the above-mentioned. 15. A method for reducing a fluctuation range of a thickness of an adhesive layer when the ferroelectric single crystal substrate and the base substrate are adhered to each other by controlling the number of optical interference fringes of the adhesive layer. The method for manufacturing a ridge-type optical waveguide device according to any one of claims 1 to 14, which is characterized in that. 16. When the light having a wavelength of 633 nm is used, the number of fringes of the optical interference fringes is controlled to be 2 or less to reduce the fluctuation range of the thickness of the adhesive layer. A method for manufacturing a ridge-type optical waveguide device according to claim 15. 17. The ridge type optical waveguide device according to claim 15, wherein the fluctuation range of the thickness of the adhesive layer is 0.3 μm or less within the adhesive surface of the adhesive layer. Production method. 18. The method of manufacturing a ridge-type optical waveguide device according to claim 1, wherein the flatness of the reference plate is 1 μm or less. 19. The method of manufacturing a ridge-type optical waveguide device according to claim 18, wherein the flatness of the reference plate is 0.3 μm or less. 20. The ridge-type optical waveguide device according to claim 1, wherein the parallelism between the bonding surface of the base substrate and the bonding surface of the reference board is 1 μm or less. Manufacturing method. 21. The method for manufacturing a ridge-type optical waveguide device according to claim 20, wherein the parallelism between the bonding surface of the base substrate and the bonding surface of the reference board is 0.3 μm or less. 22. The method of manufacturing a ridge-type optical waveguide device according to claim 1, wherein the base substrate and the reference plate are bonded to each other by using a hot melt resin. . 23. The method for manufacturing a ridge-type optical waveguide device according to claim 1, wherein the base substrate and the reference plate are bonded to each other by using an optical contact. 24. The grinding process for the ferroelectric single crystal substrate comprises a rough grinding process and a precision lapping process continuous with the rough grinding process, according to any one of claims 1 to 23. Method for manufacturing ridge type optical waveguide device of. 25. The method of manufacturing a ridge type optical waveguide device according to claim 24, wherein the ferroelectric single crystal substrate is ground to a thickness of 50 μm by the rough grinding process. 26. The method of manufacturing a ridge type optical waveguide device according to claim 25, wherein the ferroelectric single crystal substrate is ground to a thickness of 5 μm by the precision lapping process. 27. The ferroelectric single crystal substrate is polished to a thickness of 3 μm by the polishing process.
A method for manufacturing a ridge-type optical waveguide device according to claim 26. 28. In the polishing process, controlling the variation width of the thickness of the ferroelectric single crystal substrate, and controlling the number of fringes of optical interference fringes of the optical waveguide device assembly including the ferroelectric single crystal substrate. 28. The method for manufacturing a ridge type optical waveguide device according to claim 27, wherein 29. When light having a wavelength of 633 nm is used, the number of fringes of the optical interference fringes is controlled to be 2 or less to reduce the fluctuation width of the thickness of the ferroelectric single crystal substrate. 29. The method for manufacturing a ridge-type optical waveguide device according to claim 28, wherein 30. The fluctuation range of the thickness of the ferroelectric single crystal substrate is ± 0.2 μm.
9. The method for manufacturing the ridge-type optical waveguide device according to item 9. 31. The method of manufacturing a ridge-type optical waveguide device according to claim 1, wherein the polishing treatment is performed using colloidal silica abrasive grains. 32. The particle size of the colloidal silica abrasive grains is 0.
32. The method for manufacturing a ridge-type optical waveguide device according to claim 31, wherein the ridge-type optical waveguide device has a thickness of 01 μm to 0.1 μm. 33. The method according to claim 1, wherein at least one of mechanical grinding, laser processing, and etching processing is used to process the periodic domain-inverted structure into a ridge type structure. 7. A method for manufacturing a ridge-type optical waveguide device according to item 1. 34. The width of the ridge portion of the ridge type optical waveguide is 2 μm to 10 μm, and the height of the ridge portion is 0.5.
μm to 2.5 μm.
34. A method for manufacturing a ridge-type optical waveguide device according to any one of 33. 35. The method according to claim 1, further comprising forming an overcoat layer on the thinned ferroelectric single crystal substrate so as to cover the ridge type optical waveguide.
34. A method for manufacturing a ridge-type optical waveguide device according to any one of 34.