JP4148451B2 - Single domain method for ferroelectric single crystals - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
LiNbO invention, a method of single-domain of aligning the orientation of the spontaneous polarization of the ferroelectric single crystal in one direction, in particular the molar ratio _{Li 2 O / (Li 2 O} + Nb 2 O 5) is from 0.495 to 0.500 _{The present} invention relates to a single domain method of _three single crystals.
[0002]
[Prior art]
LiNbO ₃ single crystals have a large electro-optic effect and nonlinear optical effect, and research and development of optical modulators and optical wavelength converters are active, and some of them have been commercialized. Conventionally, a single crystal of LiNbO ₃ (hereinafter abbreviated as LN) is grown by the Czochralski method, and the crystal composition matches the melt with a molar ratio of Li ₂ O / (Li ₂ O + Nb ₂ O ₅ ) = 0.485. LiNbO ₃ (hereinafter abbreviated as CLN) single crystals having a congruent melt composition, so-called congruent composition, have been grown. The grown asgrown CLN single crystal is in a multi-domain state. If the CLN single crystal is in a range, there will be problems such as cracking during wafer processing, and the device characteristics will be affected, for example, by changing the half-wave voltage when manufacturing devices such as optical modulators. Therefore, the grown CLN single crystal needs to be single-domained.
[0003]
In recent years, for example, as disclosed in Japanese Patent No. 3049308, LiNbO ₃ (hereinafter abbreviated as SLN) single crystal near the stoichiometric composition (stoichiometry composition) of Li ₂ O / (Li ₂ O + Nb ₂ O ₅ ) = 0.50 It is grown using the double crucible method. In Japanese Patent No. 3049308, it is said that it is single-domained with as-grown. However, as shown in FIG. 7 (a), there is actually polarization in the opposite direction in the vicinity of the single crystal surface or in a very small region inside. Further, when grown in the X-axis direction or the Y-axis direction, as shown in FIG. 7B, the polarization direction is divided into two regions. Therefore, it is necessary to make a single domain even in a SLN single crystal.
[0004]
There is an electric field cooling method as a single domain method. FIG. 8 shows a set diagram of a conventional single domain single crystal. As an example, here is shown the single domain of a CLN single crystal grown in the Z-axis direction. The CLN single crystal 31 is embedded in LN powder 32 (LiNbO ₃ powder) placed in a refractory 33. Platinum electrodes 34 and 35 are set on the top and bottom of the LN powder 32. The refractory 33 on which these single crystals and platinum electrodes are set is set in a single domain treatment furnace. The platinum electrode 34 disposed on the top side of the single crystal is connected to a DC power source so that the platinum electrode 35 disposed on the bottom side is a negative electrode and the platinum electrode 35 disposed on the bottom side is a positive electrode.
[0005]
FIG. 9 shows a temperature program 36 and an electric field application program 37 of the single domain processing furnace. The temperature program corresponds to a graph of temperature and time controlled by the single domain processing, and the electric field application program corresponds to a graph of electric field magnitude and time controlled by the single domain processing. The CLN single crystal 31 is heated to a single domain treatment temperature T1 of 1170 to 1200 ° C. at 50 to 100 ° C./hr and held for 2 to 10 hours. 30 minutes to 1 hour after the start of holding at T1, an electric field of 1 to 3 V / cm is applied, and the applied electric field is 25 to 50 ° C / hr up to 1000 ° C, and then 50 to 100 ° C / hr. Single domains are achieved by lowering the temperature to room temperature. Usually, when performing single domain formation, the electric field is applied by raising the temperature to 20 ° C. to 50 ° C. higher than the Curie point of the single crystal. The unit ° C / hr represents the temperature change per hour.
[0006]
[Problems to be solved by the invention]
FIG. 10 shows the relationship between the Curie point and the melting point for the molar ratio Li ₂ O / (Li ₂ O + Nb ₂ O ₅ ) of the LN crystal. The closer the molar ratio Li ₂ O / (Li ₂ O + Nb ₂ O ₅ ) approaches 0.50, the higher the Curie point, but the lower the melting point. When the molar ratio Li ₂ O / (Li ₂ O + Nb ₂ O ₅ ) is larger than 0.495, the temperature difference between the melting point and the Curie point is small, so when held at a temperature several tens of degrees higher as in the conventional method described above Crystals are dissolved. Furthermore, crystals obtained by doping these crystals with MgO, ZnO, or the like have a Curie point higher by several degrees C. to several tens of degrees C. than non-doped crystals.
[0007]
Further, in the conventional method to hold several hours at a single poling treatment temperature, but the molar ratio _{Li 2 O / (Li 2 O} + Nb 2 O 5) is at a temperature close to the melting point in the large LiNbO ₃ single crystal than 0.495 Must be held for a long time. As a result, cracks are likely to occur in the crystal, resulting in poor yield.
[0008]
In addition, in the single domain treatment at a temperature lower than the Curie point, since the spontaneous polarization remains, it is necessary to apply a larger electric field. However, when a large electric field is applied, a large current flows through the single crystal, so that cracks occur and the yield deteriorates.
[0009]
Considering these, it is necessary to perform a single domain treatment at a temperature slightly higher than the Curie point, for example, 2 to 10 ° C. higher than the Curie point.
[0010]
However, since there is a temperature distribution in the furnace that performs the single domain treatment, and the temperature of the crystal changes depending on the size of the crystal and how it is set, set the set temperature to about 2 ° C higher than the Curie point. However, the crystal temperature is not necessarily higher than the Curie point. In addition, the Curie point of LiNbO ₃ single crystal varies greatly depending on the slight difference in molar ratio Li ₂ O / (Li ₂ O + Nb ₂ O ₅ ), so it is set by the slight compositional difference between lots of single crystals. The Curie point may be higher than the temperature. Therefore, the single domain processing may not be completely completed.
[0011]
In the case of LiNbO ₃ single crystal, a process such as cutting and polishing the crystal and etching the polished product is necessary to determine whether or not the single domain has been completely formed. It takes time to determine the quality of the digitization process. In addition, when the single domain treatment is incomplete, the single domain treatment must be performed again, and the temperature of the single crystal is raised to near the melting point, which may cause cracks. There is sex.
[0012]
The present invention has been made in view of the above circumstances, for example, a LiNbO ₃ single crystal having a molar ratio Li ₂ O / (Li ₂ O + Nb ₂ O ₃ ) of 0.495 or more, such as a Curie point and a melting point. It is an object of the present invention to provide a method for surely performing the single domain without causing a decrease in yield such as cracks when the single crystal having a short distance is made into a single domain.
[0013]
[Means for solving problems]
Single poling method according to the invention, retains the ferroelectric single crystal at a lower temperature T2 than the Curie point of the ferroelectric single crystal an electric field is applied, applying the electric field to the ferroelectric single crystal raising the temperature at a state to the single-domain treatment temperature T1 is a temperature higher than the Curie point, after holding, then cooled to room temperature while applying an electric field to the ferroelectric single crystal, the temperature T2 is the a temperature lower 10 ~ 30 ° C. than the single poling treatment temperature T1, the holding time of the temperature T2 is 1 to 3 hours.
[0015]
Also, by monitoring the value of the current flowing in the single crystal when an electric field is applied, it is confirmed that the single domain treatment temperature T1 is higher than the Curie point of the ferroelectric single crystal. be able to. More specifically, in the single domain method according to the present invention, when an electric field is applied to the ferroelectric single crystal and the temperature is raised from the temperature T2 to the single domain processing temperature T1, the ferroelectric single unit is obtained. The temperature at which the value of the current flowing through the crystal decreases is taken as the Curie point. When the temperature is raised to the single-domain treatment temperature T1 after the holding at the temperature T2, the magnitude of the electric field does not change, so that the value of the current flowing through the single crystal increases as the temperature rises. However, when the temperature of the single crystal passes through the Curie point, the value of the current flowing through the single crystal becomes small despite the constant electric field. As the temperature rises further, the value of the current flowing through the single crystal increases again, and the current value hardly changes when held at the temperature T1.
[0016]
In the single-domaining method according to the present invention, the temperature T2 is preferably 10 ° C. to 30 ° C. lower than the single-domain processing temperature T1. The temperature T2 is set to a temperature that is 10 ° C to 30 ° C lower than the single-domain treatment temperature T1, because when the temperature is increased from T2 to T1, the electric field is not changed, even if the electric field is not changed. This is because the value of the current flowing through the film is only increased by 15% or less, and it is possible to prevent a large current from flowing through the single crystal and generating cracks in the crystal. In the claims and the detailed description of the invention, “10 to 30 ° C.” is expressed as synonymous with “within a range of 10 ° C. to 30 ° C.”. “15 minutes to 1 hour” is also synonymous with “range of 15 minutes or more and within 1 hour”.
[0017]
When the single-domain treatment temperature T1 is lower than the Curie point due to the temperature distribution in the furnace or a slight compositional deviation of the single crystal, the current value does not become small as described above. In that case, the single-domain processing temperature T1 is reset to a temperature T1 ′ that is higher by several degrees C., and the temperature is increased to T1 ′. As a result, a phenomenon that the current value becomes small is confirmed, and the single domain can be surely made.
[0018]
The single domain treatment temperature T1 at this time is desirably 2 ° C. to 10 ° C. higher than the Curie point of the ferroelectric single crystal. As a result, the temperature of the ferroelectric single crystal is unnecessarily excessively raised and becomes higher than the melting point, thereby preventing the single crystal from melting.
[0019]
Further, the retention time at the single-domain treatment temperature T1 is preferably 15 minutes to 1 hour. Even if the temperature in the furnace reaches T1, there is a time difference of 5 to 15 minutes until the temperature of the single crystal reaches T1, and if the holding time exceeds 1 hour, there is a high probability that the single crystal will crack. Become. By setting the holding time at the single-domain treatment temperature T1 to 15 minutes to 1 hour, the temperature of the single crystal itself can be held at T1, and the single-domain can be surely made into a single crystal. A decrease in yield due to the occurrence of cracks can be reduced.
[0020]
The above-mentioned single domain method is particularly effective when the ferroelectric single crystal is a LiNbO ₃ single crystal and the molar ratio Li ₂ O / (Li ₂ O + Nb ₂ O ₅ ) is 0.495 to 0.500. It is. These crystals have a difference between the Curie point and the melting point of 50 ° C. or less. In addition, a single crystal in which at least one of MgO, ZnO, In ₂ O ₃ and Sc ₂ O ₃ is doped to the above LiNbO ₃ single crystal has a higher Curie point than a non-doped one. The difference between the point and the melting point becomes even smaller. In the above-described method, since the single domain treatment can be performed at a temperature slightly higher than the Curie point of the single crystal, the single domain treatment is not failed, and the treatment can be performed at a temperature lower than the melting point. Therefore, the yield reduction due to the occurrence of cracks can be reduced.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be described below. The present invention is not limited to these examples.
(Example 1)
Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. 1 and 2 show a single domain setting method, a temperature program, and an electric field application program according to an embodiment of the present invention. In Figure 1, the ferroelectric single crystal 1 is used LiNbO ₃ single crystal grown in the Z-axis direction. As shown in FIG. 1, the LN single crystal 1 was embedded in a LiTaO ₃ powder 2 put in a refractory 3. Platinum electrodes 4 and 5 were set on the top and bottom of the LiTaO ₃ powder 2. Further, a thermocouple 7 was set immediately above the platinum electrode 4. This is to measure the temperature of the LN single crystal 1 during the single domain treatment. The refractory 3 on which these single crystals and platinum electrodes are set is set in a single domain treatment furnace. The platinum electrode 4 disposed on the top side of the single crystal is connected to a DC power source so that the platinum electrode 5 disposed on the bottom side is a negative electrode and the platinum electrode 5 disposed on the bottom side is a positive electrode. Further, the ammeter 6 monitors the value of the current flowing through the LN single crystal 1 during the single domain processing.
[0022]
The LN single crystal set in the single domain processing furnace was heated to 1182 ° C. at 50 ° C./hr, with T1 set to 1202 ° C. and T2 set to 1182 ° C. in the temperature program 8 shown in FIG. In addition, as shown in the electric field application program of FIG. 2, an electric field of 1 V / cm was applied one hour after entering 1182 ° C. After holding at 1182 ° C for 3 hours, the temperature of the applied electric field was maintained at 120 ° C at 50 ° C / hr while maintaining the magnitude of the applied electric field. After holding at 1202 ° C for 1 hour, 1000 ° C while maintaining the applied electric field The temperature was lowered at 30 ° C./hr until 50 ° C./hr.
[0023]
FIG. 3 shows the current value flowing through the LN single crystal 1 when the above single domain treatment is performed, the temperature program 8 of the single domain treatment furnace, and the temperature 10 measured by the thermocouple 7 set in the vicinity of the crystal. Show. When the holding at 1182 ° C. ends in the temperature program 8 and the temperature rise to 1202 ° C. starts, the temperature 10 of the LN single crystal 1 rises slightly later. As the temperature of the LN single crystal 1 rises, the current value 11 flowing in the LN single crystal 1 also increases, but when the temperature of the LN single crystal 1 reaches 1199 ° C, the current value 11 decreases and the current value at 1200 ° C Became larger again, and after 1202 ° C, the current value was almost constant.
[0024]
There was no crack in the LN single crystal after the single domain treatment. When this LN single crystal was cut and polished on the Z plane and etched to examine the polarization state, there was no polarization in the opposite direction and it was well divided into single domains. Further, when the Curie point and crystal composition of this LN crystal were examined, the Curie point was 1199 ° C. and the molar ratio Li ₂ O / (Li ₂ O + Nb ₂ O ₅ ) was 0.497.
[0025]
(Example 2)
Similarly, another embodiment will be described with reference to FIGS. As the ferroelectric single crystal, a LiNbO ₃ single crystal (hereinafter abbreviated as Mg-LN) doped with 2 mol% of MgO was used. The orientation of the grown crystal is the Z-axis direction. Similarly to Example 1, Mg-LN single crystal 1 was set as shown in FIG. In the temperature program 8 of FIG. 2, T1 was set to 1223 ° C., T2 was set to 1203 ° C., the temperature was raised to 1203 ° C. at 50 ° C./hr, and an electric field of 1 V / cm was applied 1 hour after the start of holding at 1203 ° C. After holding at 1203 ° C. for 3 hours, the temperature of the applied electric field was maintained at 15 ° C. at 50 ° C./hr while maintaining the magnitude of the applied electric field. After holding at 1223 ° C. for 1 hour, 1000 ° C. with the electric field applied maintained. The temperature was lowered at 30 ° C./hr until 50 ° C./hr. In the description of the embodiments, similar configurations are represented by the same reference numerals, but do not mean the same.
[0026]
Fig. 4 shows the current value that flowed into the Mg-LN single crystal 1 when the above single domain treatment was performed, the temperature program of the single domain treatment furnace, and the temperature measured by the thermocouple 7 set in the vicinity of the crystal. Show. When the holding at 1203 ° C. is finished and the temperature rise to 1223 ° C. is started, the temperature 10 of the Mg-LN single crystal 1 rises with a slight delay. As the temperature of the Mg-LN single crystal 1 rises, the current value 11 flowing through the Mg-LN single crystal 1 also increases, but the current value decreases when the temperature of the Mg-LN single crystal 1 reaches 1221 ° C. The current value increased again at 1222 ° C, and after reaching 1223 ° C, the current value was almost constant.
[0027]
The single-domain Mg-LN single crystal had a small crack in the shoulder, but no crack in the straight body. When this Mg-LN single crystal was cut and polished on the Z plane and etched to examine the polarization state, there was no polarization in the opposite direction, and it was well divided into single domains. Further, when the Curie point and melting point of the Mg-LN crystal were examined, the Curie point was 1221 ° C. and the melting point was 1230 ° C.
[0028]
(Example 3)
Another embodiment will be described with reference to FIGS. 1, 2, and 5. A non-doped LN single crystal was set as shown in FIG. 1, and T1 was set to 1202 ° C. and T2 was set to 1182 ° C. with the temperature program 8 shown in FIG. 2, and the temperature was raised to 1182 ° C. at 50 ° C./hr. An electric field of 1 V / cm was applied 1 hour after entering 1182 ° C. After maintaining at 1182 ° C. for 3 hours, the temperature was increased to 1202 ° C. at 50 ° C./hr while maintaining the magnitude of the applied electric field.
[0029]
FIG. 5 shows the current value flowing through the LN single crystal 1 when the above-mentioned single domain treatment is performed, the temperature program of the single domain treatment furnace, and the temperature measured by the thermocouple 7 set in the vicinity of the crystal. As the temperature of the non-doped LN single crystal 1 was increased, the current value 11 flowing through the non-doped LN single crystal 1 increased. However, even when the temperature of the LN single crystal reached 1202 ° C. as in Example 1, the phenomenon that the current value 11 decreased was not observed. Therefore, the temperature program 8 was reset and the temperature was raised again to 1207 ° C. at 50 ° C./hr as in the temperature program 12. When the temperature of the non-doped LN single crystal reached 1203 ° C, the current value decreased, and the current value increased again at 1204 ° C. After reaching 1207 ° C, the current value was almost constant.
[0030]
There was no crack in the LN single crystal after the single domain treatment. When this LN single crystal was cut and polished on the Z plane and etched to examine the polarization state, there was no polarization in the opposite direction and it was well divided into single domains. Further, when the Curie point and crystal composition of this LN crystal were examined, the Curie point was 1203 ° C. and the molar ratio Li ₂ O / (Li ₂ O + Nb ₂ O ₅ ) was 0.498.
[0031]
In the above-described embodiments, the holding time of the temperature T2 is 3 hours, and the electric field application start is 1 hour after the start of the holding at the temperature T2, and the magnitude of the applied electric field is 1 V / cm. It is not something that can be done. The holding time of the temperature T2 may be 1 to 5 hours. However, it takes about 1 hour to stabilize the value of the current flowing in the single crystal after the electric field is applied, and the temperature T2 is higher than the single domain treatment temperature of the conventional CLN single crystal. For this reason, if it is held at temperature T2 for a long time, cracks are likely to occur. Therefore, the holding time of the temperature T2 is suitably about 2 to 3 hours.
[0032]
If the applied voltage was 0.7V / cm or more, it was possible to make a single domain, but the cracking rate was higher when the applied voltage was higher than 2.5V / cm. Accordingly, the magnitude of the applied voltage is suitably 0.7 to 2.5 V / cm.
[0033]
In the above-described embodiment, the electric field application steeply applied a 1 V / cm electric field one hour after the start of holding the temperature T2, but the electric field application may be started simultaneously with the start of holding the temperature T2 or until a predetermined applied electric field. It may be changed gradually over an hour. In addition, an electric field of about several to 20% of the magnitude of the electric field to be finally applied from the start of the temperature increase may be applied. By these, it can further prevent that a crack generate | occur | produces by a single domain process.
[0034]
Further, in the above-described examples, the rate of temperature increase was 50 ° C./hr, the rate of temperature decrease was 30 ° C./hr up to 1000 ° C., and then 50 ° C./hr. Needless to say, it is necessary to consider an optimum value according to the length and to perform single domain.
[0035]
(Comparative example)
A non-doped LN single crystal was used as shown in FIG. 1, and T1 was set to 1202 ° C. and T2 was set to 1182 ° C. with the temperature program 8 shown in FIG. 2, and the temperature was raised to 1190 ° C. at 50 ° C./hr. An electric field of 1 V / cm was applied 1 hour after entering 1182 ° C. After maintaining at 1182 ° C. for 3 hours, the temperature was increased to 1202 ° C. at 50 ° C./hr while maintaining the magnitude of the applied electric field.
[0036]
FIG. 6 shows the current value 11 flowing through the LN single crystal 1 when the above-mentioned single domain treatment is performed, the temperature program 8 of the single domain treatment furnace, and the temperature measured by the thermocouple 7 set in the vicinity of the crystal. Show. As the temperature of the LN single crystal 1 increased, the current value 11 flowing through the LN single crystal 1 increased. Even though the temperature 10 of the LN single crystal 1 reached 1202 ° C. as in Example 1, the current value 11 did not decrease, but the state of electric field application was maintained after holding at 1210 ° C. for 1 hour. The temperature was lowered to 30 ° C / hr up to 1000 ° C, and then lowered to 50 ° C / hr.
[0037]
When this LN single crystal was cut and polished on the Z-plane and etched to investigate the polarization state, polarization was reversed in the microscopic region near the center and near the center of the LN single crystal, similar to the as-grown LN single crystal. Existed and could not be made into a single domain. When the Curie point and crystal composition of this LN crystal were examined, the Curie point was 1212 ° C. and the molar ratio Li ₂ O / (Li ₂ O + Nb ₂ O ₅ ) was 0.498.
[0038]
The LN single crystal that could not be single-domained was subjected to single-domaining again at T1 of 1207 ° C and T2 of 1187 ° C. However, since this LN single crystal had cracks generated from the edge portion when cut, and the cracks also proceeded to the straight body portion, a wafer could not be obtained from this LN crystal.
[0039]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably perform the single domain at a temperature slightly higher than the Curie point. Therefore, even a single crystal with a melting point close to the Curie point, such as a LiNbO ₃ single crystal having a molar ratio Li ₂ O / (Li ₂ O + Nb ₂ O ₅ ) of 0.495 to 0.500 or MgO, ZnO, or the like is doped. It is possible to make a single domain without causing cracks or melting.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a single domain setting method according to the present invention.
FIG. 2 is a diagram showing a single domain temperature program and electric field application program according to the present invention.
FIG. 3 is a diagram showing a temperature of a single crystal during a single domain treatment and a value of a current flowing through the single crystal in an example of single domain production according to the present invention.
FIG. 4 is a diagram showing a temperature of a single crystal during a single domain treatment and a value of a current flowing through the single crystal in an example of the single domain according to the present invention.
FIG. 5 is a diagram showing a temperature of a single crystal during a single domain treatment and a value of a current flowing through the single crystal in an example of single domain production according to the present invention.
FIG. 6 is a diagram showing the temperature of a single crystal during single domain treatment and the value of current flowing through the single crystal in a comparative example of the present invention.
FIG. 7 is a diagram showing a domain state of a LiNbO ₃ single crystal.
FIG. 8 is a diagram illustrating a conventional single domain setting method.
FIG. 9 is a diagram showing a conventional single domain temperature program and electric field application program.
10 is a diagram showing the relation between the molar ratio Li2O / (Li2O + Nb2O5) and the Curie point and the melting point of the LiNbO _3.
[Explanation of symbols]
1 LiNbO ₃ single crystal,
2 LiTaO ₃ powder,
3 refractories,
4,5 platinum electrode,
6 Ammeter,
7 thermocouple,
8 Temperature program,
9 Electric field application program,
10 LiNbO ₃ single crystal temperature,
11 Current value flowing in a LiNbO ₃ single crystal,
12 Temperature program after setting change,
31 LiNbO ₃ single crystal with congruent composition,
32 LN powder,
33 refractories,
34, 35 Platinum electrode.

Claims (8)

Holding the ferroelectric single crystal at a temperature T2 lower than the Curie point of the ferroelectric single crystal and applying an electric field;
After raising the temperature to a single domain treatment temperature T1, which is a temperature higher than the Curie point with the electric field applied to the ferroelectric single crystal, and holding,
Cool to room temperature with the electric field applied ,
The temperature T2 is a temperature lower by 10 to 30 ° C. than the single domain treatment temperature T1 , and the holding time of the temperature T2 is 1 to 3 hours. Method. The Curie point is defined as a temperature at which a current value flowing through the ferroelectric single crystal decreases when an electric field is applied to the ferroelectric single crystal and the temperature is raised from the temperature T2 to the single-domain processing temperature T1. The method of claim 1, wherein the ferroelectric single crystal is single-domained.   3. The method of claim 1, wherein the temperature T <b> 2 is lower by 10 ° C. to 30 ° C. than the single domain treatment temperature T <b> 1.   4. The ferroelectric single layer according to claim 1, wherein the single domain treatment temperature T 1 is 2 ° C. to 10 ° C. higher than the Curie point of the ferroelectric single crystal. 5. A single domain method for crystals.   5. The method of single-domaining a ferroelectric single crystal according to claim 1, wherein the holding time at the single-domain processing temperature T1 is 15 minutes to 1 hour. 6. The method of claim 1, wherein the ferroelectric single crystal is a LiNbO ₃ single crystal. The method of claim 6, wherein the molar ratio of the LiNbO ₃ single crystal Li ₂ O / (Li ₂ O + Nb ₂ O ₅ ) is 0.495 to 0.500. . The ferroelectric single crystal according to claim 6 or 7, wherein the LiNbO ₃ single crystal is doped with at least one of MgO, ZnO, In ₂ O ₃ and Sc ₂ O _3. Localization method.

Images