CN104793287A - Production method of ferroelectric superlattice - Google Patents

Abstract

The invention discloses a method for preparing a ferroelectric superlattice. Using a ferroelectric material as a substrate, patterned electrodes corresponding to the domain structure to be fabricated are fabricated on both surfaces of the substrate at the same time, and the projections of the electrode patterns are completely consistent. ;The pattern electrode on the +Z surface of the substrate is connected to high voltage, and the pattern electrode on the -Z surface is grounded; the voltage of the electric pulse is selected according to the material and thickness of the substrate, in the range of tens to tens of thousands of volts; the electric pulse is applied between the two electrodes , preparing a ferroelectric superlattice; the patterned electrodes include periodic, non-periodic, quasi-periodic, double-periodic, one-dimensional, two-dimensional and other patterned electrode structures. The invention prepares the ferroelectric superlattice by applying the electric pulse higher than the coercive field. The invention enhances the suppression effect of the non-electrode region on the lateral extension of the electric domain through the patterned electrodes on both sides, and can realize the preparation of the ferroelectric superlattice with a small period and a thick substrate.

Description

A kind of preparation method of ferroelectric superlattice

technical field

The invention relates to a method for preparing a superlattice, especially a ferroelectric superlattice preparation technology, more specifically, it relates to a method for preparing a ferroelectric superlattice with a double-sided pattern electrode polarization method, which can enhance the constraint on ferroelectric domain inversion , to optimize the consistency of the domain structure on both sides of the substrate.

Background technique

Since the invention of laser, the use of nonlinear response to manipulate light has become the most important branch of nonlinear optics. It has been widely used in quantum electronics, laser physics and other disciplines to solve a series of scientific and engineering problems. For nonlinear interactions, the highest efficiency is achieved only when the phases are matched. In general media, due to the dispersion of light, the momentum conservation cannot be satisfied automatically (called wave vector mismatch), so the nonlinear frequency conversion efficiency is very low. There are usually two methods to compensate the phase difference: birefringence phase matching (BPM) and quasi-phase matching (QPM). BPM uses the anisotropy of the refractive index of the crystal to achieve matching of light wave vectors at different frequencies. This method is limited by the birefringence properties of the crystal, and the wavelength range that can be matched is very narrow. And QPM is to compensate the wave vector mismatch in the nonlinear process by changing the sign of the nonlinear coefficient of the material in the crystal and introducing the reciprocal lattice vector to satisfy the momentum conservation condition. Its advantages are: the laser wave vector and the energy flow are in the same direction, and there is no problem of "walking" of the energy flow due to birefringence matching; at the same time, the size and structure of the modulation area can be designed according to requirements, and it can be used in the entire light transmission band of the crystal. achieve phase matching. Based on level matching, people design and manufacture a series of frequency conversion devices such as frequency multiplication, sum frequency, difference frequency, and parametric oscillation. In order to improve the performance of devices, many nonlinear materials have been studied, including lithium niobate, lithium tantalate, gallium arsenide, etc., and the nonlinear susceptibility modulation technology of many nonlinear materials at the micron and nanometer scales has been developed. Materials with artificially modulated nonlinear susceptibility are called optical superlattices. At the same time, due to the excellent piezoelectric, electroacoustic, and electro-optic properties of ferroelectric materials such as lithium niobate and lithium tantalate, after the introduction of artificial modulation of nonlinear polarizability, it has a wide range of applications in optics, acoustics, and electricity. It also has characteristics that traditional materials do not have, and can be used to make devices such as acoustic filters and ultrasonic transducers with excellent performance. Therefore, optical superlattices based on such materials are collectively called ferroelectric superlattices or dielectric supercrystals. grid.

At present, the main way to prepare ferroelectric superlattice is electric field polarization technology. Materials such as lithium niobate, lithium tantalate, and KTP have spontaneous polarization P _s , and have ferroelectricity below the Curie temperature. When an electric field higher than the coercive field is applied to the crystal, the direction of its spontaneous polarization will change, accompanied by a nonlinear susceptibility change. For lithium niobate, KTP, etc., there are only two spontaneous polarization directions of +Z and -Z in the crystal. When the electric field is polarized, the change of the spontaneous polarization direction corresponds to the change of the nonlinear coefficient. The sudden change of polarized wave phase π compensates for the phase mismatch in the frequency conversion process. The domain direction modulation enables the phase mismatch to be always compensated, thus resulting in an efficient frequency conversion effect. Its conversion efficiency is also related to the laser interaction length. The electric field polarization technology uses photolithography and other micro-processing techniques to make electrodes, which is conducive to the preparation of large-area, high-precision, and efficient ferroelectric superlattices, and has been widely studied.

At present, the commonly used electric field polarization method is that the sample is first monodomainized, z-cut, and the thickness is on the order of millimeters. After polishing and cleaning, it is then photoetched, and a metal electrode is plated on one side, and an insulating medium is filled in the gap between the metal electrodes. The other side is conductive with electrolyte, and then a certain pulse voltage is applied between the two sides to reverse the ferroelectric domain in the area covered by the electrode. Usually, the metal electrode corresponding to the domain structure will be plated on the side that is easy to form flip nucleation, such as the +Z side of lithium niobate and the -Z side of KTP. The other side is the electrolyte. Filling the gap of the metal electrode with an insulating medium to prevent the charge flow can constrain the expansion of the flipping domain, while the charge flow on the other side is not restricted by the insulating region. When high voltage is applied, electric domains start to be generated from the side with patterned electrodes, and continue to grow when high voltage is applied, and electric domains penetrate to the other side. Therefore, the morphology and ratio of the positive and negative domains on the front and back sides of ferroelectric superlattices prepared by this method are usually different. Domains appear as triangles due to the influence of the lattice structure. Theoretically, during the QPM frequency conversion process, the ratio of positive and negative electric domains determines the energy conversion efficiency. Therefore, using this method to prepare a superlattice, the energy conversion efficiency on both sides of the crystal is inconsistent, which affects the available thickness of the crystal. At the same time, the inconsistency in the lateral expansion speed of the ± Z _Z plane domain also makes it difficult to prepare a small-period superlattice. These problems restrict the application of ferroelectric superlattice in high-power laser output, frequency conversion of ultraviolet and visible light bands, high-performance acoustic filters, ultrasonic transducers, etc., so new technical means are needed to improve the performance of ferroelectric superlattice. Preparation quality.

Contents of the invention

The purpose of the invention is to improve the uniformity of the ±z plane domain structure when the substrate is polarized. An electrode structure corresponding to the domain structure is proposed on the ±z plane of the substrate at the same time, and the confinement of charges can be realized on both sides, which can improve the consistency of the domain structure of the ±z plane. It is beneficial to the preparation of thick substrates and small-period superlattices.

The technical solution of the present invention is, the preparation method of the ferroelectric superlattice, using the ferroelectric material as the substrate, simultaneously fabricating patterned electrodes corresponding to the domain structure to be fabricated on the ±Z two surfaces of the substrate, and the electrode pattern The projection is completely consistent; the pattern electrode on the +Z surface of the substrate is connected to high voltage, and the pattern electrode on the -Z surface is grounded; the voltage of the electric pulse is selected according to the material and thickness of the substrate, ranging from tens to tens of thousands of volts; the electric pulse is applied to A ferroelectric superlattice is prepared between the two electrodes; the patterned electrodes include periodic, non-periodic, quasi-periodic, double-periodic, one-dimensional, two-dimensional and other patterned electrode structures.

Further, the electrodes may be metal materials such as aluminum, nickel, chromium, or other conductive substances such as electrolyte solutions or molten salts.

Further, an insulating medium can be filled between the electrode patterns according to the magnitude of the voltage or the line width of the structure; the insulating medium can be a dielectric material such as photoresist, epoxy resin, and silicon dioxide.

Further, an appropriate electric pulse time is selected and applied to the patterned electrodes to polarize the ferroelectric superlattice, and the single electric pulse time is usually several milliseconds to several seconds. When polarizing, only one long pulse can be applied, or multiple short pulses can be applied, which is related to the pattern area to be polarized and the substrate material.

Further, the method for making the patterned electrode includes micromachining methods such as photolithography, coating, etching, stripping, and polishing.

The ferroelectric materials include but are not limited to lithium niobate (CLN) with the same composition, lithium tantalate (CLT) with the same composition, lithium tantalate with stoichiometric ratio (SLT), lithium niobate with stoichiometric ratio (SLN), magnesium-doped Lithium tantalate (MgO:LT), magnesium-doped lithium niobate (MgO:LN), potassium dihydrogen phosphate (KDP), potassium titanium hydrogen phosphate (KTP) and other ferroelectric materials.

The substrate may be a film substrate with a thickness of several hundred nanometers to several tens of micrometers, or a bulk substrate with a thickness of several hundred micrometers to several centimeters. The substrate is of any size and can be several inches in diameter or micron in size.

Further, the present invention can carry out grating electrode polarization on both sides of the ridge-shaped ferroelectric crystal on the dielectric material substrate such as silicon dioxide or indium tin oxide (ITO), and the two sides of the ridge-shaped ferroelectric crystal are +z and -z respectively. On the z plane, grating electrodes are prepared on the substrate and on the side of the ridge ferroelectric crystal and are connected to each other. The electrodes on both sides of the crystal are insulated from each other and the electrode pattern is symmetrical about the central plane of the ridge crystal.

The beneficial effect of the present invention is that the present invention prepares ferroelectric superlattice by using the method of making electrodes corresponding to the domain structure on both sides. By enhancing the confinement effect of the insulating medium on domain inversion, the uniformity of the domain structure is improved. The method of the present invention is beneficial to the preparation of ferroelectric superlattices with thick substrates, and is also conducive to the preparation of micron or submicron electric domains and other small periodic ferroelectrics. High-quality fabrication of electric superlattices, especially small-period ferroelectric superlattices.

Description of drawings

Fig. 1 body block and film substrate schematic diagram of the present invention; Among Fig. 1 (a) body block circular substrate, diameter 1-10cm, thickness is 0.3-3mm common; (b) body block is rectangular, length and width are 5 -50mm; and (c), (d) in the thin film substrate, a is the silicon dioxide material substrate, and b is the ferroelectric thin film material.

The electrode structure schematic diagram of Fig. 2 the present invention; Among Fig. 2 (a) (b) (c) (d) corresponding insulating medium 1 (colorless), insulating medium 2 (gray) can be the schematic diagram of same kind or different material, The black is the electrode;

The schematic diagram of the polarization circuit of the present invention in Fig. 3;

Figure 4 Schematic diagram of electric field polarization domain dynamics model;

Figure 5. Structural diagram of ferroelectric superlattice domain structure of one-dimensional 4.2μm periodic CLT with polarized double-sided electrodes of 0.5mm thickness;

Fig. 6 SLT ferroelectric superlattice domain structure with 2mm thick one-dimensional 30μm periodic SLT polarized by double-sided electrodes;

Figure 7. Domain structure diagram of 0.5mm thick two-dimensional 7.42μm periodic CLN ferroelectric superlattice polarized by double-sided electrodes;

Fig. 8 Schematic diagram of the electrode structure of a 500nm-thick ridge-shaped ferroelectric film sample electrode polarized by double-sided electrodes.

Detailed ways

There are corresponding pattern structures on both sides of the substrate, for example with the same period. Ferroelectric optical superlattice double-sided patterned electrode polarization, using ferroelectric material as the substrate, fabricating electrodes corresponding to the domain structure to be prepared on the ±z plane of the ferroelectric material, and then applying electric pulses to realize ferroelectric domain inversion. Ferroelectric materials include lithium niobate, lithium tantalate, KTP and other ferroelectric materials. The substrate can be a 0.3-3mm thick bulk substrate made of the above-mentioned ferroelectric material. The bulk substrate is usually z-cut, and the ±z surface is optically or acoustically polished; it can also be on other substrate layers (SiO2 _, etc.) The ferroelectric thin film substrate with a thickness of hundreds of nanometers to tens of microns on the surface can be a z-cut planar structure or a ridge-shaped substrate, as shown in Figure 1. When making electrodes, mature micro-processing technologies such as photolithography, coating, etching, and embossing are used, and the specific electrode pattern preparation process is designed according to electrode preparation requirements. The electrode design can be one-dimensional, two-dimensional and other required structural forms. Usually, the frequency doubling of green light requires a one-dimensional structure with a design cycle of 6-8um. For example, photoresist is used to make electrode patterns corresponding to each other on the ±z plane of the crystal. Then the electrode structure can be made as a mask or directly transfer the designed pattern to the photoresist by electron beam exposure, ultraviolet direct writing, etc. (the thickness of the photoresist is usually about 1um to 10um), and then develop, Coating, etching and other processes to complete the production of electrode patterns. The electrode can be metal or conductive solution, and it is mainly divided into two manufacturing methods, the electrode is covered with insulating material and the electrode is covered with insulating material. The electrode fabrication methods on both sides of the substrate can be combined arbitrarily according to actual needs, as shown in Figure 2, the insulating media 1 and 2 in the figure can be the same or different materials. When metal electrodes are used, their thickness is typically between 100 and 500 nanometers. After making the double-sided electrodes, apply electric pulses between the electrodes, and use the signal generator to generate electric pulses. The specific polarization circuit is shown in Figure 3. The +z side is connected to high voltage, and the -z side is connected to low voltage. The voltage is the same as The crystal coercive field is related to the thickness of the substrate. When the polarization voltage is high, the electric pulse signal is amplified by a voltage amplifier. For example, the coercive field of lithium niobate is 21kV, and the pulse voltage is 1.1kV to polarize lithium niobate with a thickness of 0.5mm, which is usually slightly higher than the coercive field. The time of electric pulse application is related to the substrate material and the area of the polarized region. The polarization electric quantity is calculated by the following formula, Q=2P _s A, where P _s is the spontaneous polarization, lithium niobate P _s =0.7μC/mm ² , and A is the area of the flipped domain. The pulse width of a single polarizing electrical pulse is usually between a few milliseconds and a few seconds. Generally, for a ferroelectric material substrate with low conductivity, record the current in the circuit during the polarization process, calculate the electric quantity Q=∫idt=2P _s A, and apply one or more electric pulses until the total electric quantity reaches the calculated value After the preparation of the ferroelectric superlattice is completed, the current can be detected by instruments such as oscilloscopes and galvanometers. In order to prevent spontaneous depolarization of the crystal after polarization, after applying each electric pulse, it is necessary to continue to maintain the voltage at about half of the polarization voltage for 100ms. For ferroelectric materials with high conductivity, the applied electric quantity is judged according to the specific material.

According to the domain dynamics model of electric field polarization at room temperature, domain inversion can be divided into six stages: domain nucleation, tip growth, tip growth to the other side, reversed domain merging under the electrode, and domain expansion to the outside of the electrode. Inversion domain stabilization (V.Shur et al Ferroelectrics Vol.221, pp157-167, 1999; and Vol.236, pp129-144, 2001), as shown in Figure 4. The actual electric field inside the crystal is the main factor affecting these six processes. The actual electric field E _loc in the crystal is determined by the external electric field E _ex , the depolarization field P _s is spontaneous polarization, the external shielding field E _escr of the crystal (generated by surface adsorption charges), and the bulk shielding field E _bscr (charges inside the crystal) are jointly determined (take a one-dimensional periodic structure as an example).

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; loc</span>}}<span\; class="notranslate">\; ~</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; ext</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&Delta;x</span>}}{\mathrm{<span\; class="notranslate">\; \&Lambda;</span>}}$

It can be seen that the suppression of domain inversion by the insulating medium is inversely proportional to the crystal thickness d, which makes us have certain limitations when using this method to polarize thicker samples. Use the double-sided electrode polarization method, that is, prepare patterned electrodes on both sides of the superlattice matrix material, the electrode morphology is symmetrical to the domain structure to be prepared, and cover the insulating medium, apply a high voltage electric field, so that the electrode covers the domain domain Flip to obtain the ferroelectric superlattice that needs to be prepared.

In this case, both sides of the substrate are covered by periodic insulating dielectrics. Similarly, the electric field inside the crystal is analyzed using the plate capacitor model. We have:

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; loc</span>}}<span\; class="notranslate">\; ~</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; ext</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&Delta;x</span>}}{\mathrm{<span\; class="notranslate">\; \&Lambda;</span>}}$

Compared with the two formulas, the constraint of the insulating medium on the domain flip is doubled by this method, which is not only conducive to the preparation of thicker samples, but also helps to improve the polarization quality when preparing small-period samples.

Example 1

The crystal material is made of 0.5mm thick Z-cut lithium tantalate (CLT) with the same composition ratio, and the ±z surface is optically polished. The electrode structure is shown in Figure 1. A one-dimensional periodic Al electrode with a period of 4.2 μm was fabricated on the +Z and -Z surfaces of the crystal at the same time, and the thickness of the Al electrode was 200 nm. A single Al electrode grating is 1 μm wide and 5 mm long. The grating area has a total length of 10 mm and a width of 5 mm. The space between the Al electrodes is filled with epoxy resin. Q=2P _s A, where P _s is spontaneous polarization, and lithium tantalate P _s =0.5 μC/mm ² , the total electricity required for polarization is calculated to be 25 μC. Add 12kV pulse high voltage, the electric pulse width is 20ms. A 10kΩ sampling resistor is connected in series in the polarization circuit, and the potential difference at both ends of the sampling resistor is recorded with an oscilloscope to obtain the current waveform, and the total amount of polarized charge is calculated, and the polarization is completed when it reaches 25 μC. The lithium tantalate optical superlattice prepared by double-sided electrode method is shown in Figure 5.

Example 2

The crystal material is 2mm thick Z-cut stoichiometric lithium tantalate (SLT), with ±z-plane optical grade polishing. The electrode structure is shown in Figure 2. First, photoresist patterns with a period of 30um are obtained by photolithography on the +Z and -Z surfaces of the crystal respectively. The pattern is mirror-symmetrical about the substrate, and then coated with an Al film to produce a one-dimensional Al film with a period of 30μm. For electrodes, a single Al electrode grating is 5 mm long and 15 μm wide, and the total size of the electrode area is 5 mm long and 5 mm wide. The photoresist is an insulating layer, which insulates the Al electrodes on the crystal surface from each other. The calculated polarization requires a total charge of 25 μC. Add 500V pulse high voltage, the electric pulse width is 20ms. The ammeter is connected in series in the polarization circuit, the current signal collected by the ammeter is recorded by a computer, the total amount of polarization charge is calculated from the current, and the polarization is completed when it reaches 25μC. The stoichiometric lithium tantalate optical superlattice prepared by this method is shown in Fig. 6.

Example 3

The crystal material is made of lithium niobate (CLN) with a thickness of 0.5mm, and the ±z surface is optically polished. The electrode structure is shown in Figure 2(b). The +Z and -Z planes of the crystal were photolithographically etched and Al was plated to form a two-dimensional tetragonal Al electrode structure with a period of 7.42 μm. The electrodes were mirror-symmetrical about the substrate, and the Al electrodes 200nm thick. A single Al electrode is 2 μm wide and 2 μm long. The electrode area has a total length of 10 mm and a width of 10 mm. Q=2P _s A, where P _s is spontaneous polarization, and lithium niobate P _s =0.7 μC/mm ² , the total electricity required for polarization is calculated to be 50 μC. Add 11kV pulse high voltage, the electric pulse width is 20ms. A 10kΩ sampling resistor is connected in series in the polarization circuit, and the potential difference at both ends of the sampling resistor is recorded with an oscilloscope to obtain the current waveform, and the total amount of polarization charge is calculated, and the polarization is completed when it reaches 50 μC. The stoichiometric lithium niobate optical superlattice prepared by this method is shown in Fig. 7.

Example 4

The crystal material is a ridge-shaped lithium niobate film (CLN) bonded on a silicon dioxide substrate with a thickness of 0.5 mm. The electrode structure is shown in Figure 8, a is a silicon dioxide substrate with a thickness of 0.5 mm, and b is a ridge-shaped lithium niobate film with a thickness of 500 nm and a width of 4 μm. First, on the silicon dioxide substrate and the two sides of the ridge-shaped lithium niobate crystal, that is, the +Z surface and the -Z surface, the fabrication cycle is 6.95 μm Al grating electrode, and the length of a single Al grating electrode is 4 mm. 1 μm wide, the dimensions of the grating electrode regions on both sides of the ridge-shaped lithium niobate crystal are 10 mm long and 4 mm wide. The photoresist is an insulating layer, which insulates the Al electrodes on both sides of the ridge crystal from each other. The calculated polarization requires a total charge of 2×10 ^-3 μC. Add 100V pulse high voltage, the electric pulse width is 2ms. A weak ammeter is connected in series in the polarization circuit, and the current signal collected by the ammeter is recorded by a computer, and the total amount of polarization charge is calculated from the current, and the polarization is completed when it reaches 2×10 ^-3 μC.

Claims (7)

1. A ferroelectric superlattice preparation method is characterized in that it is a substrate with a ferroelectric material, and the pattern electrodes corresponding to the domain structure that needs to be made are made simultaneously on both faces of the substrate, and the projection of the electrode pattern is completely Matching; the pattern electrode on the +Z surface of the substrate is connected to high voltage, and the pattern electrode on the -Z surface is grounded; the voltage of the electric pulse is selected according to the material and thickness of the substrate, in the range of tens to tens of thousands of volts; the electric pulse is applied to the two electrodes In between, a ferroelectric superlattice is prepared; the patterned electrodes include periodic, non-periodic, quasi-periodic, double-periodic, one-dimensional, two-dimensional and other patterned electrode structures. 2. ferroelectric superlattice preparation method according to claim 1, is characterized in that between electrode patterns, fills insulating medium by voltage size or structure line width; insulating medium can be photoresist, epoxy resin or silicon dioxide Dielectric material; and the electrodes on both sides and the insulating medium can be a combination of different materials respectively. 3. The ferroelectric superlattice preparation method according to claim 1, characterized in that the appropriate electric pulse time is selected to be applied to the pattern electrode to polarize the ferroelectric superlattice, and the single electric pulse time is usually from several milliseconds to several seconds; only one long pulse or multiple short pulses are applied during polarization, which is related to the pattern area to be polarized and the substrate material. 4. ferroelectric superlattice preparation method according to claim 1, it is characterized in that electrode is the solution or molten salt conductive substance of aluminum, nickel, chromium metal material, electrolyte; The method for making patterned electrode comprises photolithography, coating, Etch, lift off, polish micromachining methods. 5. ferroelectric superlattice preparation method according to claim 1 is characterized in that described ferroelectric material comprises lithium niobate (CLN), lithium tantalate (CLT), stoichiometric ratio lithium tantalate (SLT) , stoichiometric lithium niobate (SLN), magnesium-doped lithium tantalate (MgO:LT), magnesium-doped lithium niobate (MgO:LN), potassium dihydrogen phosphate (KDP), potassium titanium hydrogen phosphate (KTP) ferroelectric Material. 6. The ferroelectric superlattice preparation method according to claim 1, characterized in that said substrate is a film substrate with a thickness of several hundred nanometers to tens of microns, and is a film substrate with a thickness of several hundred microns to several centimeters. Bulk substrate. 7. ferroelectric superlattice preparation method according to claim 1 is characterized in that the ridge ferroelectric crystal both sides on silicon dioxide or indium tin oxide (ITO) dielectric material substrate carries out grating electrode polarization, The two sides of the ridge-shaped ferroelectric crystal are +Z and -Z planes respectively. The grating electrodes are prepared on the substrate and the side of the ridge-shaped ferroelectric crystal. The grating electrodes are connected to each other on the substrate, and the grating electrodes on the two sides of the crystal are connected to each other. Insulating and symmetrical about the center plane of the ridge crystal.