JP4675006B2 - Method for forming periodic domain-inverted structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a periodic domain-inverted structure. Specifically, the present invention can be suitably used when manufacturing a SHG (Second Harmonic Generation) device using a ferroelectric single crystal substrate such as lithium niobate or lithium tantalate. The present invention also relates to a method for forming a periodic domain-inverted structure.
[0002]
[Prior art]
In the fields of printing, optical information processing, optical applied measurement control, and the like, realization of a small short-wavelength light source is strongly desired, and an SHG device is attracting attention as a means for realizing this short-wavelength light source. This SHG device generates the second harmonic using the nonlinear optical effect by passing the light emitted from the semiconductor laser. The second harmonic has a frequency twice that of the light emitted from the semiconductor laser, and therefore has a wavelength of ½. That is, by using the SHG device, it is possible to obtain short-wavelength light having a half wavelength with respect to light emitted from the semiconductor laser.
[0003]
The SHG device includes a ferroelectric single crystal substrate such as lithium niobate (hereinafter sometimes abbreviated as “LN”) or lithium tantalate (hereinafter sometimes abbreviated as “LT”). In FIG. 4, a polarization structure in which the polarization state is inverted in a periodic manner substantially perpendicular to the light traveling direction. Such a periodic domain-inverted structure is generally formed as follows.
[0004]
FIG. 1 is a diagram for explaining a method of forming a periodic domain-inverted structure. In order to clarify the features, the size and shape of each part shown in FIG. 1 are drawn differently from the actual ones. A comb-shaped first having a plurality of electrode pieces 2-1 to 2-5 arranged periodically on a main surface 1A of a ferroelectric single crystal substrate 1 made of, for example, an off-cut substrate, such as LN or LT. The flat electrode 2 and the flat second electrodes 3A and 3B are arranged on the main surface 1A and the back surface 1B so as to face the first electrode 2.
[0005]
When predetermined voltages V1 and V2 are applied between the first electrode 2 and the second electrodes 3A and 3B, the polarization inversion has a polarization direction A opposite to the polarization direction B of the ferroelectric single crystal substrate 1. A polarization region 4A having a polarization direction A and a polarization region having an original polarization direction B in which the region gradually extends from each electrode piece of the first electrode 2 toward the crystal orientation of the substrate and the polarization direction is reversed. A periodic domain-inverted structure 4 consisting of 4B is formed.
[0006]
[Problems to be solved by the invention]
The periodic domain-inverted structure 4 is formed to have a sufficient depth from the main surface 1A of the ferroelectric single crystal substrate 1 in order to be effective when the domain-inverted structure 4 is used in an SHG device or the like. There is a need to. For this reason, normally, the absolute values of the voltages V1 and V2 applied between the first electrode 2 and the second electrodes 3A and 3B are preferably as large as possible.
[0007]
However, when a high voltage is applied between the first electrode 2 and the second electrode 3, the ferroelectric single crystal substrate 1 may be destroyed. Japanese Patent Laid-Open No. 2001-66652 discloses that a pulse-like voltage is applied a plurality of times between the first electrode 2 and the second electrode 3 to prevent the ferroelectric single crystal substrate 1 from being broken. In addition, it is described that the periodic domain-inverted structure 4 having a sufficient depth is formed. Japanese Patent Application Laid-Open No. 8-220578 discloses that a DC voltage on which a pulse voltage is superimposed is applied.
[0008]
However, in any of the above methods, the periodic domain-inverted structure 4 having a sufficient depth cannot be obtained. Specifically, in the case of using a MgO-doped LN single crystal 5 degree offcut substrate, only a periodic domain-inverted structure having a depth of about 2.2 μm at the maximum could be obtained. Therefore, it has been difficult to obtain a practical high output SHG device.
[0009]
An object of the present invention is to provide a novel method capable of forming a periodic domain-inverted structure having a sufficient depth without destroying a ferroelectric single crystal substrate.
[0010]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a first electrode having a plurality of electrode pieces arranged in a periodic manner on one surface of a ferroelectric single crystal substrate, and is separated from the first electrode, A second electrode is disposed on an arbitrary surface of the ferroelectric single crystal substrate so as to be opposed to each other, and a pulsed voltage is applied between the first electrode and the second electrode. while repeatedly applying the bias voltage is applied in synchronization with the pulse voltage, the bias voltage in forming the periodic domain-inverted structure in a predetermined area of the ferroelectric in a single crystal, applied at the start The time from the maximum to 0.1 second to 5 seconds, and the time from the maximum to the application stop time is applied from 0.1 second to 5 seconds, The bias voltage becomes maximum when the pulse voltage is applied. Applied to, characterized in that, a method for forming a periodic domain inversion structure.
[0011]
The present inventors have intensively studied to form a periodic domain-inverted structure deep inside the ferroelectric single crystal substrate while preventing the ferroelectric single crystal substrate from being destroyed. As a result, when a pulse voltage is applied as in the prior art, only when the pulse voltage is applied, a predetermined bias voltage is applied in synchronization with the pulse voltage, whereby the ferroelectric single crystal substrate is The present inventors have found that a periodic domain-inverted structure having a sufficient depth can be formed without being destroyed, and have reached the present invention.
[0012]
Therefore, according to the present invention, the periodic domain-inverted structure can be formed at a sufficient depth in the ferroelectric single crystal substrate, and a high output and practical SHG device can be provided. become.
[0013]
In a preferred embodiment of the present invention, the bias voltage is applied so that the magnitude thereof increases or decreases with time and becomes maximum when the pulse voltage is applied. In another preferred aspect of the present invention, the bias voltage is applied so as to be maximized before the pulse voltage is applied and during a predetermined time after the pulse voltage is applied, including when the pulse voltage is applied.
[0014]
According to these preferred embodiments, since the bias voltage is applied so as to be maximized at the time of applying the pulse voltage so as to cause polarization reversal, the utilization efficiency of the bias voltage is increased, and a deeper period is obtained with a lower bias voltage. Can be formed efficiently.
[0015]
Further, since the pulse voltage is applied during a certain time interval when the bias voltage is applied, the maximum voltage, which is the sum of the pulse voltage and the maximum value of the bias voltage, is applied to the ferroelectric via the electrode. Instantaneous application to the body single crystal substrate can be prevented. For this reason, it is possible to prevent the ferroelectric single crystal substrate from being broken and to form the periodic domain-inverted structure deeper.
[0016]
In another preferred aspect of the present invention, a reverse bias voltage having a polarity different from the polarity of the pulse voltage is applied continuously with the bias voltage at least before and after application of the bias voltage. In this case, the effective value of the bias voltage increases, which is equivalent to a case where a voltage substantially larger than the bias voltage value actually applied in synchronization with the pulse voltage is applied. Therefore, the periodic domain-inverted structure can be formed deeper.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments of the invention with specific examples.
[0018]
In the method for forming a periodic domain-inverted structure of the present invention, for example, as shown in FIG. 1, an electrode piece 2-is formed on a main surface 1 A of a ferroelectric single crystal substrate 1 made of an LN or LT off-cut substrate. A comb-shaped first electrode 2 having 1 to 2-5 is formed, and a flat plate-like second electrode 3A is formed so as to face the first electrode 2. Thereafter, a flat plate-like second electrode 3B is formed on the back surface 1B so as to face the first electrode 2. Next, a pulse voltage and a bias voltage for polarization inversion are applied between the first electrode 2 and the second electrodes 3A and 3B according to the following applied voltage profile.
[0019]
A voltage is not applied between the first electrode 2 and the second electrode 3A formed on the main surface 1A, and the second electrode 3B formed on the first electrode 2 and the back surface 1B. Since the periodic domain-inverted structure 4 can be obtained even when a voltage is applied only between the electrodes 2 and 3, the voltage profile between the electrode 2 and the electrode 3B will be described in the following description. In this case, since it is only necessary to apply a voltage between a pair of electrodes, the system configuration can be simplified, and a domain-inverted structure can be obtained with inexpensive equipment.
[0020]
FIG. 2 is a graph showing a time profile of applied voltage in a preferred embodiment of the method for forming a periodic domain-inverted structure of the present invention. 2, the bias voltage V _B, the pulse voltage V _P is applied to a maximum value V _BMAX at the time it is applied. Thus, in order to give rise to polarization reversal, in the pulse voltage V _P applied at tp, it can be utilized bias voltage V _B to the maximum. Therefore, it is possible to increase utilization efficiency of the bias voltage V _B is efficiently formed deeper periodic domain inversion structure with a lower voltage value.
[0021]
Further, before and after the pulse voltage _{V P} applied at tp, the bias voltage _{V B} of a predetermined time interval t1 (bias voltage VB is applied at the start ts for increasing and decreasing toward the maximum value _{V BMAX} until the pulse voltage application time tp Time) and t2 (time from pulse voltage application time tp to bias voltage VB application end time te).
[0022]
That is, when the polarization inversion occurs, V _MAX that is the total maximum value of the pulse voltage V _P and the bias voltage V _B is not instantaneously applied to the ferroelectric single crystal substrate 1. Therefore, it is possible to effectively prevent the ferroelectric single crystal substrate from being broken by applying a high voltage instantaneously. In this case, the domain-inverted structure is formed according to the same mechanism as described in FIG.
[0023]
That is, by adopting a voltage application profile as shown in FIG. 2, a high voltage can be applied more efficiently without destroying the ferroelectric single crystal substrate 1, and the periodic domain-inverted structure 4 can be further improved. It can be formed deeply.
[0024]
In order to make the applied voltage profile shown in FIG. 2 more effective, the time interval t1 is preferably 0.1 seconds to 5 seconds, and more preferably 0.5 seconds to 2 seconds. The time interval t2 is preferably 0.1 second to 5 seconds, and more preferably 0.5 seconds to 2 seconds.
[0025]
The total maximum value _{V MAX} of the pulse voltage _{V P} and the bias voltage _{V B} is ferroelectric single crystal unit thickness of the substrate 1 (mm) per be a 0.2kV~20kV preferred, and 4kV It is preferable that it is -10kV. Thereby, the periodic domain-inverted structure 4 can be formed deeper. In addition, when V _MAX exceeding the above range is applied, the ferroelectric single crystal substrate 1 may be destroyed.
[0026]
The maximum value V _BMAX of the bias voltage is preferably applied at a ratio of 0.4 to 0.6 of the V _MAX .
[0027]
FIG. 3 is a graph showing a time profile of applied voltage in another preferred embodiment of the method for forming a periodic domain-inverted structure of the present invention. In the profile shown in FIG. 3, the bias voltage reaches the _{V B} applied at the start up value _{V BMAX} during time t3 from ts, the pulse voltage _{V P} applied at tp before and after a predetermined time interval t4 (bias voltage _{V B} is the maximum value time) and t5 from time tm1 reaching the V _BMAX until the pulse voltage _{V P} applied at tp in (time from the pulse voltage VP is applied at the time tp until time tm2 bias voltage _{V B} starts to decrease from the maximum value _{V BMAX)} The maximum value V _BMAX is indicated. Then, the bias voltage V _B becomes 0 between the time tm2 and the time t6. That is, in this case, the pulse voltage V _P, the maximum value V _BMAX bias voltage V _B is applied in an applied predetermined time interval.
[0028]
Therefore, when applying the pulse voltage V _P to cause polarization reversal, the maximum value V _BMAX of the bias voltage V _B is always applied, so that the bias voltage V _B is maximized at the time tp when the pulse voltage V _{P is} applied. It can be used as much as possible. Therefore, it is possible to increase utilization efficiency of the bias voltage V _B is efficiently formed deeper periodic domain inversion structure with a lower voltage value.
[0029]
Further, in the pulse voltage _{V P} applied at tp, the maximum value _{V BMAX} bias voltage _{V B} is applied instantaneously, so that the ferroelectric single crystalline substrate 1, the maximum value _{V MAX} instantaneous total voltage It is not applied. Therefore, it is possible to effectively prevent the ferroelectric single crystal substrate 1 from being broken by suppressing the instantaneous application of a high voltage. Even in this case, the domain-inverted structure is formed according to the same mechanism as that described with reference to FIG.
[0030]
Therefore, by adopting a voltage application profile as shown in FIG. 2, a high voltage can be applied more efficiently without destroying the ferroelectric single crystal substrate 1, and the periodic domain-inverted structure 4 can be further improved. It can be formed deeply.
[0031]
In order to make the applied voltage profile shown in FIG. 3 more effective, the time interval t4 is preferably 0.1 seconds to 3 seconds, and more preferably 0.2 seconds to 0.5 seconds. Further, the time interval t5 is preferably 0.1 seconds to 5 seconds, and more preferably 0.2 seconds to 0.5 seconds.
[0032]
The total maximum value _{V MAX} of the pulse voltage _{V P} and the bias voltage _{V B} is preferably the same, a ferroelectric single crystal unit thickness of the substrate 1 (mm) per, 0.2KV～20kV, Further, it is preferably 4 kV to 10 kV. Thereby, the periodic domain-inverted structure 4 can be formed deeper. In addition, when V _MAX exceeding the above range is applied, the ferroelectric single crystal substrate 1 may be destroyed.
[0033]
Note that the maximum value V _BMAX of the bias voltage is also preferably applied at a ratio of 0.4 to 0.6 of the V _MAX .
[0034]
Further, the time t3 from the start time ts of the bias voltage V _B to the maximum value V _BMAX and the time t6 from the maximum value V _BMAX to the end te of the bias voltage application are not particularly limited, and the ferroelectric single crystal substrate It can be arbitrarily determined within a time range in which 1 is not destroyed. Generally, each time is 0.01 seconds to 5 seconds.
[0035]
FIG. 4 is a modification of the applied voltage profile shown in FIG. In the applied voltage profile shown in FIG. 4, the bias voltage V _B is applied so as to instantaneously reach the maximum value V _MAX without providing the rise time t3 and the fall time t6 as shown in FIG. As long as the ferroelectric single crystal substrate 1 is not broken, it is also possible instantaneous bias voltage V _B is applied as shown in FIG. Other conditions are the same as those shown in FIG.
[0036]
FIG. 5 is a graph showing a time profile of an applied voltage in another preferred embodiment of the method for forming a periodically poled structure according to the present invention. The application time profile shown in Figure 5, the application time profile shown in FIG. 3, by continuously bias voltage V _B, the negative pulse voltage V _P and the bias voltage V _B and the polarity is reversed the reverse bias voltage V _G Applied.
[0037]
In this case, when the bias voltage V _B is not applied to the ferroelectric single crystal substrate 1, the reverse bias voltage V _G is constantly applied. Therefore, in order to give rise to polarization reversal by applying a pulse voltage V _P, when applying a bias voltage V _B is a ferroelectric single crystal substrate 1, the maximum value V _GMAX and the bias voltage of the reverse bias voltage V _G A total bias voltage (V _GMAX + V _BMAX ) with the maximum value V _{BMAX of} V _B is felt.
[0038]
That is, this is equivalent to the case where the maximum value V _GMAX of the reverse bias voltage VG is substantially applied to the ferroelectric single crystal substrate 1 in addition to the maximum value V _BMAX of the target bias voltage V _B. As a result, since the effective value of the bias voltage V _B increases, a deeper domain inversion structure can be formed with a smaller bias voltage V _B.
[0039]
In FIG. 5, the reverse bias voltage V _G is applied before and after the application of the bias voltage V _B , but may be applied at either one. However, when the domain-inverted structure is formed, the pulse voltage _VP is applied a plurality of times as shown in FIG. Therefore, it is necessary to apply the bias voltage V _B a plurality of times in synchronism with the pulse voltage _VP, and to apply the reverse bias voltage V _G continuously and simply to each bias voltage V _B application.
[0040]
For this reason, the bias voltage V _B and the reverse bias voltage V are applied by applying a reverse bias voltage in both cases as shown in FIG. 5 instead of before or after the application of the bias voltage V _B is started. Continuity with _G can be easily maintained.
[0041]
When the periodic domain-inverted structure 4 is formed with the configuration as shown in FIG. 1 using the applied voltage profile as shown in FIGS. 2 to 5, for example, a depth of 1 μm or more can be obtained. At present, when a LN single crystal 5 degree off-Y cut substrate having a thickness of 0.5 mm is used as the ferroelectric single crystal substrate 1, it is possible to obtain a periodically poled structure up to a depth of about 2.5 μm. it can.
[0042]
After the periodic domain-inverted structure 4 is formed in the ferroelectric single crystal substrate 1 as shown in FIG. 1, the comb-shaped first electrode 2 and the plate-shaped second electrode 3 are removed.
[0043]
FIG. 6 is a diagram showing a state in which an optical waveguide is formed on a ferroelectric single crystal substrate on which a periodic domain-inverted structure is formed. For simplification, FIG. 6 shows only the portion of the ferroelectric single crystal substrate where the periodic domain-inverted structure is formed.
[0044]
After obtaining a ferroelectric single crystal substrate having a periodic domain-inverted structure formed according to the steps shown in FIGS. 1 to 5, in order to use it as an actual SHG device or the like, as shown in FIG. An optical waveguide 5 is formed in the periodic domain-inverted structure 4 by an exchange method or the like, and a predetermined optical waveguide element 10 is manufactured. Thereafter, the optical waveguide element 10 is mounted and an optical fiber or the like is connected to obtain a target SHG device or the like.
[0045]
FIG. 7 to FIG. 9 are diagrams for explaining a process for forming a ridge structure type optical waveguide device using a ferroelectric single crystal substrate on which a periodic domain-inverted structure is formed.
[0046]
First, as shown in FIG. 7, the ferroelectric single crystal substrate 1 on which the periodic domain-inverted structure 4 is formed is interposed through the support substrate 11 and the adhesive layer 12 so that the main surface 1A is on the lower side. And paste them together. Next, the ferroelectric single crystal substrate 1 is thinned until the periodic domain-inverted structure 4 is exposed by grinding and polishing from the back surface 1B as shown in FIG. Thereafter, dicing processing or laser processing is performed through a predetermined mask to remove both side portions of the ferroelectric single crystal substrate 1 leaving a predetermined thickness, and a ridge type optical waveguide as shown in FIG. A ridge structure type optical waveguide device 20 having 15 is obtained.
[0047]
Thereafter, the optical waveguide element 20 is mounted and an optical fiber or the like is connected to obtain a target SHG device or the like.
[0048]
【Example】
Hereinafter, the present invention will be specifically described based on examples.
(Example)
First, an X-cut plate of MgO-doped LN single crystal having a thickness of 0.5 mm is used as the ferroelectric single crystal substrate 1, and the width d made of Ta is 0.4 μm and the pitch P is formed on the main surface 1A of the substrate. A comb-shaped first electrode 2 having an electrode piece of 2.8 μm and a flat plate-like second electrode 3A made of Ta are formed so as to face each other. Thereafter, a flat plate-like second electrode 3B made of Ta was formed on the back surface 1B so as to face the first electrode 2. Next, a pulse voltage VP and a bias voltage VB were applied between the first electrode 21 and the second electrodes 3A and 3B using an applied voltage profile as shown in FIG. .
[0049]
At this time, t4 and t5 were each 0.2 seconds, and t3 and t6 were each 2 seconds. VBMAX was 2 kV and VMAX was 4 kV. The pulse width of the pulse voltage VP was set to 50 mm seconds.
[0050]
(Comparative example)
Similar to the embodiment, a MgO-doped LN single crystal 5 degree off-Y cut substrate having a thickness of 0.5 mm is used as the ferroelectric single crystal substrate 1, and the main surface 1 </ b> A and the back surface 1 </ b> B of the substrate 1 are formed on the embodiment. The first electrode 2 and the second electrodes 3A and 3B having the same shape and size were formed. Thereafter, a periodic 2 kV DC voltage with a pulse voltage of 2 kV and a pulse width of 50 msec is constantly applied between the first electrode 2 and the second electrode 3 to periodically invert the polarization. Structure 4 was formed.
[0051]
FIG. 10 is an optical micrograph showing a cross section of the ferroelectric single crystal substrate 1 on which the periodic domain-inverted structure 4 formed in the above example is formed, and FIG. 11 is a period formed in the above comparative example. 3 is an optical micrograph showing a cross section of a ferroelectric single crystal substrate 1 on which a domain-inverted structure 4 is formed.
[0052]
As is apparent from FIGS. 10 and 11, it can be seen that a polarization inversion structure is formed in the ferroelectric single crystal substrate 1 in a periodic manner in any case. The periodic domain-inverted structure shown in FIG. 10 formed according to the present invention is sufficiently deep inside the ferroelectric single crystal substrate 1 as compared with the periodic domain-inverted structure shown in FIG. 11 formed according to the conventional method. It was confirmed that it was formed.
[0053]
Specifically, the depth of the periodically poled structure shown in FIG. 11 is 2.2 μm, and the depth of the periodically poled structure shown in FIG. 10 is 3.9 μm. Therefore, it can be seen from the measured values that the periodic domain-inverted structure formed according to the present invention has a sufficient depth in the ferroelectric single crystal substrate.
[0054]
As described above, the present invention has been described in detail based on the embodiments of the present invention with specific examples. However, the present invention is not limited to the above-described contents, and various modifications can be made without departing from the scope of the present invention. Changes and modifications are possible. For example, in the above description, the case where the ferroelectric single crystal substrate 1 is composed of, for example, a MgO-doped LN single crystal 5-degree off-cut plate is shown. It can also be used in the case of a cut substrate, an X cut substrate, a Y cut substrate, and a Z cut substrate.
[0055]
In FIG. 1, the second electrodes 3A and 3B are formed on the main surface 1A and the back surface 1B so as to face the comb-shaped first electrode 12, but the LN single crystal X-cut substrate is used. Alternatively, when using a Y-cut substrate, by forming only the second electrode 3A on the main surface 1A without forming the second electrode 3B on the back surface 1B, the target periodic domain-inverted structure can be obtained. Can be produced.
[0056]
Furthermore, when the LN single crystal Z-cut substrate or the above-described off-cut substrate is used, only the second electrode 3B is formed on the back surface 1B without forming the second electrode 3A on the main surface 1A. Thus, the desired periodic domain-inverted structure can be produced.
[0057]
【The invention's effect】
As described above, according to the present invention, it is possible to form a periodic domain-inverted structure having a sufficient depth without destroying the ferroelectric single crystal substrate, and a practical high-output SHG. Devices etc. can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a method of forming a periodic domain-inverted structure.
FIG. 2 is a graph showing a time profile of applied voltage in a preferred embodiment of the method for forming a periodically poled structure according to the present invention.
FIG. 3 is a graph showing a time profile of an applied voltage in another preferred embodiment of the method for forming a periodically poled structure according to the present invention.
4 is a modification of the applied voltage profile shown in FIG.
FIG. 5 is a graph showing a time profile of an applied voltage in another preferred embodiment of the method for forming a periodically poled structure according to the present invention.
FIG. 6 is a view showing a state in which an optical waveguide is formed on a ferroelectric single crystal substrate on which a periodic domain-inverted structure is formed.
FIG. 7 is a process diagram for explaining a method of forming a ridge structure type optical waveguide device using a ferroelectric substrate on which a periodic domain-inverted structure is formed.
FIG. 8 is a diagram showing a step subsequent to the step shown in FIG.
9 is a diagram showing a step subsequent to the step shown in FIG. 8. FIG.
FIG. 10 is an optical micrograph of a cross section of a ferroelectric single crystal substrate having a periodically poled structure formed according to the method of the present invention.
FIG. 11 is an optical micrograph of a cross section of a ferroelectric single crystal substrate having a periodically poled structure formed according to a conventional method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ferroelectric single crystal substrate, 2 1st electrode, 2nd electrode, 4 Periodic polarization inversion structure, 5, 15 Optical waveguide, 10, 20 Optical waveguide element, 11 Support substrate, 12 Adhesive layer

Claims (10)

On the one surface of the ferroelectric single crystal substrate, the first electrode having a plurality of electrode pieces arranged in a periodic manner, and the ferroelectric so as to be separated from the first electrode and located opposite to each other. A second electrode is disposed on an arbitrary surface of the body single crystal substrate, a pulse voltage is repeatedly applied between the first electrode and the second electrode, and the pulse voltage a bias voltage is applied in synchronization, in forming the periodic domain-inverted structure in a predetermined area of the ferroelectric in a single crystal
The time from the start of application to the maximum time is 0.1 second to 5 seconds, and the time from the maximum to the stop of application is 0.1 seconds to 5 seconds. Further, the bias voltage is applied so as to be maximized when the pulse voltage is applied, and the method for forming a periodic domain-inverted structure is provided. 2. The period according to claim 1, wherein the bias voltage is repeatedly applied in synchronization with a pulse voltage that is repeatedly applied so that there is a time when the bias voltage is 0 V or less both before and after the pulse application in each repetition period. Of forming a domain-inverted structure. Said bias voltage comprises at the pulse voltage application, the pulse voltage application before, and at a predetermined time after the pulse voltage application, and applying so as to maximize, according to claim 1 or 2 A method for forming a periodic domain-inverted structure. The time when the bias voltage is maximum before applying the pulse voltage is 0.1 second to 3 seconds, and the time when the bias voltage is maximum after applying the pulse voltage is 0.1 second to 3 seconds. The method for forming a periodic domain-inverted structure according to claim 3 , wherein: The maximum sum of the pulse voltage and the bias voltage, characterized in that said ferroelectric single crystal unit thickness of the substrate (mm) per, 0.2kV / mm~20kV / mm, according to claim 1 The formation method of the periodic polarization inversion structure as described in any one of -4 . The reverse bias voltage having a polarity different from the polarity of the pulse voltage is applied continuously with the bias voltage at least before and after application of the bias voltage, according to any one of claims 1 to 5. A method for forming a periodic domain-inverted structure. The periodic domain-inverted structure according to claim 1, wherein the first electrode and the second electrode are disposed on the same surface of the ferroelectric single crystal substrate. Forming method. The said 1st electrode and the said 2nd electrode are arrange | positioned on the mutually opposing different surface of the said ferroelectric single crystal substrate, respectively, The Claim 1 characterized by the above-mentioned. A method of forming a periodic domain-inverted structure. The periodic pattern according to claim 1 , wherein the second electrode is disposed on the same plane as the first electrode and on a different surface opposite to the plane. A method for forming a domain-inverted structure. 8. The periodic polarization according to claim 7 , wherein a depth of the periodic polarization reversal structure from a surface of the ferroelectric single crystal substrate on which the first electrode is formed is 1 μm or more. 9. Inversion structure forming method.

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