JP3479112B2 - Method for treating lithium niobate single crystal substrate and method for producing electro-optical article - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating an electro-optical single crystal substrate and a method for manufacturing an electro-optical article.

[0002]

2. Description of the Related Art Lithium niobate (LiNbO ₃ ) single crystal and lithium tantalate (LiTaO ₃ ) single crystal are expected as materials for optoelectronics. It is known to obtain a lithium niobate thin film by a liquid phase epitaxial method on a substrate made of a lithium niobate single crystal or the like. For example, "Appl. Phys. Letters" Vo
According to the description on pages 8 to 10 of l.26 No. 1 (1975), a lithium niobate single crystal thin film is formed on a lithium tantalate single crystal substrate by a liquid phase epitaxial method.
"Mat. Res. Bull" Vol.10 (1975) No. 1373-1
According to the description on page 377, a lithium niobate single crystal thin film is formed on a lithium niobate single crystal substrate by a liquid phase epitaxial method. "J. Appl. Phys." Vo
According to pp. 2536 to 2541 of L.70, No.5, (1991), a lithium niobate single crystal thin film is formed by a liquid phase epitaxial method on a lithium niobate single crystal substrate doped with magnesium oxide. There is.

A film forming method in the liquid phase epitaxial method will be described. FIG. 5 is a graph schematically showing a temperature schedule of a melt in the liquid phase epitaxial method, and FIG. 6 is a graph showing a solubility curve of, for example, LiNbO ₃ —LiVO ₃ pseudo binary system. First, for example, lithium niobate (solute) and LiVO ₃ (melting medium) are charged and mixed. The saturation temperature corresponding to the composition of the melt charged is T ₀ . The temperature of the melt is held at a high temperature T ₁ than the saturation temperature T _0, uniformly melt lithium niobate and LiVO _3. In FIG. 5, “A” corresponds to this molten state. Then, the temperature of the melt is set to the saturation temperature T
_{It is} cooled to a temperature T ₄ lower than ₀ to bring the melt into a supercooled state. In FIG. 5, “C” corresponds to this supercooled state. The substrate is brought into contact with the melt in the supercooled state.

The crystallinity of such a single crystal can be evaluated by the half width of the X-ray rocking curve. For example, according to the description of “J. Cryst. Growth.” 132 (1993), pages 48 to 60, a lithium oxide niobate single crystal substrate doped with magnesium oxide is used, and the half width is as small as this substrate. A lithium niobate single crystal thin film having

[0005]

Currently, LiNbO _{3 is used.}
A substrate such as a single crystal is formed by a pulling method. However, conventionally, a single crystal film having better crystallinity than this single crystal substrate could not be formed on such a single crystal substrate. As a result, when an optical waveguide substrate, an SHG device, or the like is formed on this single crystal film, the optical waveguide is inferior in optical damage resistance, and the threshold of light energy that can be guided in the optical waveguide is low. It was Therefore, conventionally, the substrate prepared by the pulling method is machined and used as the optical waveguide substrate, and the single crystal film by the liquid phase epitaxial method is not effectively used as a material for such products. , There was a long-awaited solution.

An object of the present invention is to provide a method for improving the crystallinity of an electro-optical single crystal substrate manufactured by a pulling method or the like. A further object of the present invention is to improve the crystallinity of such an electro-optical single crystal substrate,
A single crystal film having good crystallinity can be formed on this substrate.

[0007]

According to the method of processing an electro-optic single crystal substrate of the present invention, at least the processed surface of the electro-optic single crystal substrate is brought into contact with a melt in an equilibrium state containing a solute and a melting medium. It is characterized in that the crystallinity of the machined surface is modified by doing so.

Further, the present invention is a method for manufacturing an electro-optical product having an electro-optical single crystal substrate and an electro-optical single crystal film, wherein at least the processed surface of the electro-optical single crystal substrate is provided with a solute and a molten medium. The electro-optic single crystal film on the processed surface side is modified by bringing the melted material into equilibrium containing The present invention relates to a method of forming

[0009]

The present inventor has examined the reason why it is difficult to form a single crystal film having better crystallinity than the single crystal substrate on an optical grade electro-optical single crystal substrate.
As a result, the following causes were discovered.

That is, in order to manufacture an electro-optic single crystal substrate generally used for an optical waveguide or the like, first, a boule having a substantially cylindrical shape is prepared by a pulling method. In this case, the electro-optical single crystal has a so-called harmonic melting composition. Next, this boule is ground into a cylindrical shape, and this cylindrical boule is cut perpendicularly to its axial direction to form a disk-shaped wafer. After precisely polishing the surface of this wafer, an electro-optic single crystal film is formed on this processed surface by a liquid phase epitaxial method.

However, as schematically shown in FIG. 2 (a), during the above-mentioned cutting and polishing, stress-induced strain and disorder of the crystal lattice are introduced into the surface 2a of the electro-optical single crystal substrate 2. Often. In such a state, when a device such as an optical waveguide is manufactured next time, the characteristics of the device vary, causing defective products and lowering the yield.

Further, the present inventors have been conducting research to modify the electro-optical single crystal substrate having the surface thus damaged, but in the process, the following method was developed. did.

That is, as schematically shown in FIG. 1, a melt 4 usually used in a liquid phase epitaxial method is first kept in a crucible 3 in a state of being cooled to a saturation temperature or lower for a long time, and a solid phase is obtained. 5 was deposited. In this state, the melt 4 is completely in equilibrium with the solid phase 5 and the liquid phase 1. Therefore, even if the electro-optic single crystal substrate 2 is brought into contact with the melt 4,
Of course the film does not grow, and apparently nothing happens.

However, as schematically shown in FIG. 2B, when this electro-optic single crystal substrate 7 is taken out of the melt 4 and the processed surface 7a side is analyzed, the processed surface is compared with that before processing. It was found that the damage of 7a was improved and its crystallinity was improved.

The reason for this is not clear. However, since the melt is in a solid-liquid equilibrium state, microscopic molecule replacement and rearrangement probably occur near the substrate surface 2a. In this process, the crystallinity near the substrate surface 2a is improved. It is presumed that it might have happened.

The present inventor further brings the processed surface 2a of the electro-optical single crystal substrate 2 into contact with the melt 6 in an unsaturated state, and then melts the substrate, as schematically shown in FIG. It was taken out from the body 6 and the processed surface was analyzed. As a result,
As shown in FIG. 4 (a), the substrate 8 is also compared with that before processing.
It was found that the damage of the processed surface 8a was improved and the crystallinity thereof was improved.

Therefore, it is considered that the crystallinity of the processed surface 2a can be modified by bringing at least the processed surface 2a of the electro-optic single crystal substrate 2 into contact with the melt in the equilibrium state.

Further, the present inventor has found that the electro-optic single crystal substrate 2
By contacting at least the processed surface 2a with the melt 4 in a solid-liquid equilibrium state containing a solute and a melting medium,
By modifying the crystallinity of the processed surface 2a and then bringing the liquid phase 1 of the melt 4 into a supercooled state, an electro-optic single crystal film is formed on the processed surface 7a whose crystallinity is modified. saw.
As a result, we succeeded in forming a single crystal film having a half-width of the X-ray rocking curve smaller than that of the electro-optic single crystal substrate, which could not be prepared conventionally.

The present inventor has also found that the electro-optic single crystal substrate 2
By contacting at least the processed surface 2a of the liquid phase with the liquid phase of the melt 6 in an unsaturated state schematically shown in FIG.
After modifying the crystallinity of the machined surface 2a, the liquid phase 6 is placed in a supercooled state, so that the modified machined surface 8a is
As shown in FIG. 4B, the electro-optic single crystal film 10 was formed and viewed. As a result, it has succeeded in forming the single crystal film 10 having a half width of the X-ray rocking curve smaller than that of the electro-optic single crystal substrate, which could not be prepared conventionally. These results are probably because the crystallinity of the single crystal film is largely influenced by the crystallinity of the substrate surface.

The present inventor formed a single crystal film having a half width of the X-ray rocking curve smaller than that of the single crystal substrate by the above method, formed an optical waveguide on the single crystal film, and measured its optical characteristics. As a result, it was confirmed that the optical damage resistance of the optical waveguide was significantly improved. As a result, the electro-optical product 9 of the present invention can be used as various optical components.

The full width at half maximum of the X-ray rocking curve will be described below. The crystallinity of the single crystal substrate and the single crystal film is
It can be evaluated by the full width at half maximum of the X-ray rocking curve. In general, it can be judged that the smaller the half width is, the better the crystallinity of the single crystal is. This value itself is X
The absolute value cannot be specified because it varies depending on the reference crystal used in the line measuring device.

However, the crystallinity of the single crystal thin film produced by the liquid phase epitaxial method is strongly influenced by the crystallinity of the single crystal substrate. Therefore, in order to judge the crystallinity of the produced single crystal film, the half width of the X-ray rocking curve of the substrate used must be used as a reference. In particular, since an optical grade single crystal substrate is currently produced by the pulling method, it is preferable that the full width at half maximum of the X-ray rocking curve of the single crystal film is smaller than that of the optical grade single crystal substrate.

At least the processed surface of the electro-optical single crystal substrate is brought into contact with the liquid phase of the unsaturated melt to modify the crystallinity of the processed surface, and then the liquid phase is supercooled. When the electro-optic single crystal film is formed on the processed surface by doing so, the following effect is further obtained.

According to the research conducted by the present inventor, in the liquid phase epitaxial method, there is a problem that the composition of the melt changes due to the decrease of the precipitation component during the repeated film formation, and the film growth rate or the film characteristic changes. is there. However,
When brought into contact with the liquid phase of the unsaturated melt, the solute is eluted from the electro-optic single crystal substrate into the melt. If the saturation temperature of this melt is T ₀ and the temperature of the melt is T _{1 which} is higher than T ₀ by ΔT, this melt is in an unsaturated state corresponding to ΔT, and when the substrate is dipped. ,
The solute is eluted by a predetermined amount corresponding to ΔT.

However, after the substrate is melted by a predetermined amount, if the temperature of the melt is lowered to the saturation temperature T ₀ or lower and the melt is supercooled, the same amount as the amount melted back into the melt is obtained. A single crystal film grows. That is, in the unsaturated state, the concentration of the melt increases due to the melt back of the solute from the substrate, but in the next film growth stage, the same amount of solute as the melted back amount adheres to the substrate. , A single crystal film grows homoepitaxially. Therefore, the composition of the melt does not change before and after film formation.

As a result, even if the film formation by the liquid phase epitaxial method is repeated many times using the same melt, the growth rate or film characteristics of the single crystal film is not deteriorated or changed.

[0027]

EXAMPLES In the present invention, since there is a process of elution from the electro-optical single crystal substrate toward the melt, the electro-optical single crystal substrate and the solute of the melt may be the same. Therefore, it is preferable that the electro-optic single crystal substrate and the electro-optic single crystal film are formed of the same material.

As the electro-optic single crystal, lithium niobate (LiNbO ₃ ) single crystal, lithium tantalate (Li
TaO ₃ ) single crystal, LiNb _x Ta _1-x O ₃ single crystal (0
<X <1) is preferable.

At present, the electro-optical single crystal substrate is manufactured by the pulling method, and as the lithium niobate single crystal substrate, an optical grade single crystal substrate having good crystallinity has been obtained. However, at the present stage, the crystallinity of the lithium tantalate single crystal substrate manufactured by the pulling method is worse than that of the lithium niobate single crystal substrate. Even if a single crystal film is formed on a lithium tantalate single crystal substrate that is originally poor in crystallinity, a single crystal film having better crystallinity than a film formed on an optical grade lithium niobate single crystal substrate is obtained. Hard to get.

For this reason, at this stage, it is preferable to use an optical grade lithium niobate single crystal as the substrate. However, this problem is a problem with the manufacturing technology by the pulling method, so if an optical grade lithium tantalate single crystal substrate with crystallinity equivalent to that of the lithium niobate single crystal substrate is developed in the future, this will be the substrate. Can be preferably used as.

The solute is lithium niobate or lithium tantalate.
Um and LiNb_xTa _1-xO₃Selected from the group consisting of
In the case of one or more solutes, the melting medium is LiVO
₃And LiBO₂One or more melts selected from the group consisting of
It is preferable to use a melting medium. Between this solute and the melting medium
When a combination is used, the composition of the melt
Is solute 10 mol% -solvent 90 mol% to solute 60 m
ol% -solvent 40 mol% is preferable.

When the ratio of solute is less than 10 mol%, as shown in FIG. 6, for example, in the pseudo-binary phase diagram of solute-melt medium, the slope of the liquidus line becomes too steep,
The change in the concentration of the melt due to film growth becomes large, and it becomes difficult to maintain stable film forming conditions. Solute ratio is 60mo
If it is larger than 1%, the saturation temperature becomes high,
The film forming temperature becomes too high, which makes it difficult to form a single crystal film having good crystallinity.

In one embodiment of the present invention, at least the processed surface 2a of the electro-optic single crystal substrate 2 is brought into contact with a melt 4 in a solid-liquid equilibrium state containing a solute and a melting medium, so that the processed surface 2a is processed. The crystallinity of 2a is modified, and then the liquid phase 1 of the melt 4 is supercooled to form an electro-optic single crystal film on the processed surface 7a side of which the crystallinity is modified.

In this embodiment, preferably, first,
The solute and the melting medium are charged into the crucible 3 and mixed.
The saturation temperature of this melt is the concentration of solute in the melt,
That is, it is set to a constant value according to the composition of the charge. This saturation temperature can be calculated, for example, from the liquidus line as shown in FIG.

First, the temperature of the melt is maintained at a temperature higher than the saturation temperature to uniformly melt the solute and the melting medium. The temperature of the melt is then cooled to a solid phase precipitation temperature below the saturation temperature. In this state, the melt is initially in a supercooled state, but if kept at this temperature for a sufficiently long time, as shown schematically in FIG.
Are precipitated and the melt is separated into a liquid phase 1 and a solid phase 5. The solid phase 5 is mainly deposited along the wall surface of the crucible 3.

At this point, as described above, according to the present invention, the processed surface of the electro-optical single crystal substrate is brought into contact with the liquid phase 1 to be modified. Next, the temperature of the melt 4 is further lowered to bring the liquid phase 1 into a supercooled state. The substrate 2 is brought into contact with the supercooled liquid phase 1 to epitaxially grow a single crystal film.

In this embodiment, the state where the solid phase and the liquid phase coexist stably (state of FIG. 1) is used as the starting point, and the temperature is lowered from this state to bring the liquid phase into the supercooled state. . As described above, in the state where the solid phase 5 and the liquid phase 1 coexist, the liquid phase 1 does not exceed the saturation temperature of the entire system.
The concentration of solute in is maintained at a saturated concentration at the solid phase deposition temperature.

For example, when the concentration of the solute in the melt 4 is reduced, the amount of the solid phase 5 is reduced by that amount at the solid phase deposition temperature, and when the concentration of the solute is increased, the solid phase 5 is increased.
The amount of increases. Therefore, the temperature and concentration of the liquid phase 1 are always kept constant. Since the film forming temperature is also set to a constant value, the difference (supercooling degree) between the solid phase deposition temperature and the film forming temperature is also kept constant, and the supercooled state is accurately controlled.

According to this aspect, as described above, not only can a single crystal film of constant quality be produced with good reproducibility, but the crystallinity of the single crystal film itself is significantly improved. The reason for this is not clear, but is probably due to the following reasons.

In the conventional liquid phase epitaxial method, when the substrate is brought into contact with the melt, the entire melt is in a uniform liquid phase. Therefore, at the moment when the substrate comes into contact with the melt, the solid phase is first deposited in the entire liquid phase on the surface of the substrate. Therefore, in order to start the growth of the single crystal film,
It can be estimated that a relatively large nucleation energy is required. Therefore, when the growth of the film starts at the interface between the substrate and the film, the nucleation energy is large, so that the crystallinity of the film is disturbed at this interface, and the crystallinity of the film deposited on the interface is It seems to reflect the disorder.

On the other hand, in this embodiment, as shown in FIG. 1, before the electro-optical single crystal substrate 2 comes into contact with the melt 4,
The solid phase 5 coexists in the melt 4 in advance. In this state, at the interface between the solid phase 5 and the liquid phase 4, melting and precipitation have occurred microscopically. Therefore, even if the substrate 2 is newly brought into contact with the melt 4, it is considered that the film growth is started smoothly and a single crystal film having excellent crystallinity can be produced.

Further, concrete experimental results will be described. (Experiment 1) The method described with reference to FIGS. 1 and 2 was performed. 20 mol% LiNbO ₃ (solute) -80 mol
A melt consisting of% LiVO ₃ (melting medium) was used.
The saturation temperature of this melt was approximately 955 ° C.
Hold this melt at 1000 ° C-1300 ° C,
It was completely and uniformly dissolved, then cooled to 900 ° C and kept for 24 hours or more. During this period, supersaturated Li
NbO ₃ was precipitated as the solid phase 5, and the liquid phase portion 1 was completely saturated.

The temperature of this melt was set to 900 ° C., and a Z-cut optical grade lithium niobate single crystal substrate 2 having a thickness of 1 mm was immersed in a liquid phase 1. Then, the lithium niobate single crystal substrate 7 was pulled up, and the full width at half maximum of the X-ray rocking curve of the processed surface 7a was measured.

The full width at half maximum of the X-ray rocking curve is measured by
The double crystal method was used with reflection of the (001 2) plane.
CuKα1 was used as the incident X-ray, and the (422) plane of GaAs single crystal was used as the monochromator. The half widths of the X-ray rocking curves of the optical grade lithium niobate single crystal substrates used by the present inventors were all 6.8 to 6.9 [arc sec].

Table 1 shows the relationship between the immersion time and the full width at half maximum of the X-ray rocking curve near the processed surface of the substrate.

[0046]

[Table 1]

As can be seen from Table 1, when the lithium niobate single crystal substrate 2 was not immersed in the liquid phase 1, the half width was 6.9 arc sec. It can be seen that the half width is remarkably reduced and the crystallinity is improved by immersing in the liquid phase 1 in the state.

In particular, the contact time between the processed surface 2a of the substrate 2 and the liquid phase is preferably 1 minute or longer, more preferably 5 minutes or longer. Further, even if the immersion time is increased within the range of more than 5 minutes, the full width at half maximum is not decreased. Therefore, practically, it is preferable to set the time within 20 minutes.

(Experiment 2) The substrate was modified by the method described with reference to FIGS. 20 mol% LiN
A melt consisting of bO ₃ -80 mol% LiVO ₃ was used. The saturation temperature of this melt was approximately 955 ° C. This melt was kept at 1000 ° C to 1300 ° C to completely and uniformly dissolve it, then cooled to 960 ° C and kept for 24 hours or more to be sufficiently stabilized.

The Z-cut optical grade lithium niobate single crystal substrate 2 having a thickness of 1 mm was immersed in the liquid phase 6. Then, the lithium niobate single crystal substrate 7 was pulled up, and the half width of the X-ray rocking curve in the vicinity of the processed surface 7a was measured. Table 2 shows the relationship between the immersion time and the full width at half maximum of the X-ray rocking curve near the processed surface of the substrate.

[0051]

[Table 2]

As can be seen from Table 2, unsaturated melt 6
In the case where the lithium niobate single crystal substrate 2 was not dipped in, the half width was 6.9 arc sec, but when this was dipped into the unsaturated melt 6 and treated, It can be seen that the full width at half maximum is significantly reduced and the crystallinity is improved.

In particular, the contact time between the processed surface 2a of the substrate 2 and the liquid phase is preferably 1 minute or longer, more preferably 5 minutes or longer. Further, even if the immersion time is increased within the range of more than 5 minutes, the full width at half maximum is not decreased. Therefore, practically, it is preferable to set the time within 20 minutes.

(Experiment 3) Using the method described with reference to FIGS. 3 and 4, a single crystal film was formed on an electro-optic single crystal substrate and its crystallinity was compared.

20 mol% LiNbO ₃ -80 mol%
A melt consisting of LiVO ₃ was used. 1 of this melt
It was kept at 000 ° C to 1300 ° C to completely and uniformly dissolve it, then cooled to 960 ° C and kept for 24 hours or more to be sufficiently stabilized.

A Z-cut optical grade lithium niobate single crystal substrate 2 having a thickness of 1 mm is horizontally held with a platinum holder so that the −Z surface faces downward, and 20 r
While rotating at pm, the single crystal substrate 2 and the melt 6 were lowered at a descent rate of 1 mm / min to about 5 mm above the liquid surface of the melt.
The single crystal substrate 2 was sufficiently preheated so that it would be in equilibrium with the temperature of.

Then, the single crystal substrate 2 was lowered at a descent rate of 5 mm / min, and the processed surface 2a of the substrate 2 was brought into contact with the liquid surface of the melt 6 and held for 10 minutes. Next, the temperature of the melt 6 is lowered to 950 ° C., the melt is supercooled, and the modified processed surface 7a of the lithium niobate single crystal substrate 7 is processed.
Then, a single crystal film of lithium niobate was homoepitaxially grown.

After the film formation, the single crystal substrate is set to 100 mm /
The melt was pulled away from the melt at a rise rate of 1 minute and then the single crystal substrate was spun at 800 rpm for 30 seconds to shake off the melt remaining on the substrate. After that, the substrate was slowly cooled to room temperature, and the melt remaining on the substrate surface was washed with water and removed.

This film forming process was repeated for the number of times shown in Table 3. The half width of the X-ray rocking curve of the lithium niobate single crystal film, the film growth rate, and the saturation temperature of the melt were measured for each number of times of film formation.

[0060]

[Table 3]

As can be seen from Table 3, at each film forming step, the solute was once eluted from the substrate 2 into the unsaturated melt 6 at 960 ° C, and the supercooled melt was melted at 950 ° C from the melt. The film is formed on the modified substrate 7. Moreover, 96
The substrate 2 is reformed by bringing the substrate 2 into contact with the unsaturated melt 6 once at 0 ° C. Therefore, a lithium niobate single crystal film having a half width smaller than that of the lithium niobate single crystal substrate can be formed, and the half width of the lithium niobate single crystal film does not deteriorate even if the number of times of film formation increases.

(Experiment 4) 20 mol% LiNbO ₃ -8
A melt consisting of 0 mol% LiVO ₃ was used. The melt was held at 1000 ° C-1300 ° C to completely and uniformly dissolve it, then cooled to 960 ° C and
It was kept for 4 hours or more and sufficiently stabilized.

The Z-cut optical grade lithium niobate single crystal substrate 2 having a thickness of 1 mm was held horizontally by a holder made of platinum so that the −Z plane faced down, and 20 r
While rotating at pm, the single crystal substrate 2 and the melt 6 were lowered at a descent rate of 1 mm / min to about 5 mm above the liquid surface of the melt.
The single crystal substrate 2 was sufficiently preheated so that it would be in equilibrium with the temperature of.

Next, the temperature of the melt 6 was lowered to 950 ° C. and the melt was supercooled. Then, the single crystal substrate 2 is lowered at a descent rate of 5 mm / min, and the processed surface 2a of the substrate 2 is lowered.
Was brought into contact with the liquid surface of the melt 6 to epitaxially grow a lithium niobate single crystal film.

After the film formation, the single crystal substrate is set to 100 mm /
The melt was pulled away from the melt at a rise rate of 1 minute and then the single crystal substrate was spun at 800 rpm for 30 seconds to shake off the melt remaining on the substrate. After that, the substrate was slowly cooled to room temperature, and the melt remaining on the substrate surface was washed with water and removed.

This film forming process was repeated for the number of times shown in Table 4. The half width of the X-ray rocking curve of the lithium niobate single crystal film, the film growth rate, and the saturation temperature of the melt were measured for each number of times of film formation.

[0067]

[Table 4]

As can be seen from Table 4, even when the number of times of film formation is the first, since there is no modification action on the processed surface, the half width of the lithium niobate single crystal film is smaller than that in Table 3. Relatively large. Moreover, as the number of times of film formation increases, the film growth rate significantly decreases, and along with this, the full width at half maximum of the X-ray rocking curve of the single crystal film deteriorates more significantly. However, since the weight of solute required for film formation is small,
It is considered that such deterioration in characteristics is due to instability of the supercooled state.

[0069]

As described above, according to the present invention, the electro-optical single crystal substrate manufactured by the pulling method or the like can be modified to improve its crystallinity. Further, according to the present invention, by improving the crystallinity of such an electro-optical single crystal substrate, a single crystal film having good crystallinity can be formed on this substrate.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a state where a processed surface of an electro-optic single crystal substrate 2 is in contact with a liquid phase 1 of a melt 4 in a solid-liquid equilibrium state.

FIG. 2A is a processed surface 2a of an electro-optic single crystal substrate 2.
3B is a schematic cross-sectional view for explaining a state in which strain or the like is introduced, and FIG. 6B is a schematic cross-sectional view for explaining a state in which the processed surface 7a of the electro-optic single crystal substrate 7 is modified FIG.

FIG. 3 is a cross-sectional view schematically showing a state where the processed surface of the electro-optic single crystal substrate 2 is in contact with the melt 6 in an unsaturated state.

FIG. 4A is a processed surface 8a of the electro-optic single crystal substrate 8.
Is a schematic cross-sectional view for explaining a state modified by contact with the melt 6 in an unsaturated state,
(B) shows the film 10 on the processed surface 8 a of the electro-optic single crystal substrate 8.
It is sectional drawing which shows the state in which was formed typically.

FIG. 5 is a graph schematically showing a temperature schedule of a melt in the liquid phase epitaxial method.

FIG. 6 is a graph showing a solubility curve of a LiNbO ₃ —LiVO ₃ pseudo binary system.

[Explanation of symbols]

1 saturated liquid phase 2 electro-optic single crystal substrate 2
a Worked surface 3 Crucible 4 Melt in solid-liquid equilibrium 5 Solid phase 6 Unsaturated melt 7 Electro-optical single crystal substrate modified by contact with saturated liquid phase 1 8 Unsaturated melt Electro-optic single crystal substrate modified by contact with 6 9 Electro-optic product
10 Electro-optic single crystal film

Continuation of front page (56) Reference JP-A-55-33034 (JP, A) JP-A-3-136322 (JP, A) JP-A-5-47684 (JP, A) JP-A-49-64576 (JP , A) JP-A-3-69586 (JP, A) JP-A-5-319992 (JP, A) JP-A-6-64996 (JP, A) JP-A-6-345594 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C30B 1/00-35/00 G02B 1/02 CA (STN)

Claims (4)

(57) [Claims] 1. The crystallinity of this processed surface is modified by bringing at least the processed surface of a lithium niobate single crystal substrate into contact with a melt in an equilibrium state containing a solute and a melting medium. A method for treating a lithium niobate single crystal substrate. 2. The method for treating an electro-optical single crystal substrate according to claim 1, wherein the melt is in a solid-liquid equilibrium state. 3. The method for treating an electro-optical single crystal substrate according to claim 1, wherein the melt is in a liquid phase in an unsaturated state. 4. A method of manufacturing an electro-optical article having an electro-optical single crystal substrate and an electro-optical single crystal film, wherein at least a processed surface of the electro-optical single crystal substrate is in an equilibrium state containing a solute and a melting medium. By contacting the melt of
Modify the crystallinity of the processed surface, then the melt in the liquid phase to form said electro-optical single crystal film on the processed surface side by the supercooled state, X-rays rocking mosquito single crystal film
Full width at half maximum of that of an optical grade single crystal substrate
A method for manufacturing an electro-optical product, characterized in that it is also small .