Parallel point-contact periodic electrode pattern for ktp crystal, periodic polarization device and method

Abstract

The application discloses a parallel point contact periodic electrode pattern of a KTP crystal, a periodic polarization device and a method. The parallel point contact periodic electrode pattern of the KTP crystal comprises a first electrode and a second electrode, and the first electrode and the second electrode are arranged on opposite surfaces of the KTP crystal respectively. The first electrode comprises a plurality of frame electrodes arranged side by side at intervals. The second electrode is a metal electrode. The frame electrode comprises a first half-circle electrode part, a second half-circle electrode part and a strip electrode part. The first half-circle electrode part is electrically connected with the second half-circle electrode part through the strip electrode part comprising a plurality of strip electrodes which are spaced apart at equal intervals. The periodic polarization device based on the parallel point contact periodic electrode pattern of the KTP crystal is used for high-voltage pulse polarization of the KTP crystal through an external pulse voltage, polarization parameters are set, the domain inversion degree of the KTP crystal is judged, and then the KTP crystal is continuously polarized through an external low-voltage direct current, so that the inversion domain of the KTP crystal is effectively controlled, and the wafer conversion efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of nonlinear optical crystal device technology, and more specifically to parallel point-contact periodic electrode patterns, periodic polarization devices and methods for KTP crystals. Background Technology

[0002] Periodically polarized crystals are created by artificially reversing the periodic polarization of the domains within a ferroelectric crystal, forming a structure with alternating directions and uniform spacing. This periodic modulation of the nonlinear coefficients compensates for phase mismatch caused by refractive index dispersion, maximizing the utilization of the maximum nonlinear optical coefficient and ultimately achieving near-perfect phase-matched frequency conversion efficiency. Periodically polarized crystals can achieve efficient wavelength conversion across the crystal's transmission range using quasi-phase-matching techniques such as frequency doubling, sum-frequency conversion, difference-frequency conversion, parametric transformation, and parametric oscillation. Therefore, they can be widely used in fields such as lasers and quantum information technology.

[0003] Based on photolithographic periodic electrode patterns, the periodic reversal of the ferroelectric domains inside the KTP crystal is a commonly used method for preparing PPKTP crystals by applying a high-voltage pulse exceeding the crystal's coercive field to the spontaneous polarization direction.

[0004] The domain inversion process is generally divided into five stages: domain inversion nucleation, longitudinal growth, merging of adjacent domains, lateral expansion, and formation of a stable domain structure. In the periodic polarization process, the lateral expansion stage often determines the quality of the periodic domain structure, and the main factors affecting the lateral expansion stage are the choice of electric field magnitude and the uniformity of its distribution.

[0005] There are currently two fabrication schemes for PPKTP devices. The first is to increase the crystal resistivity at -100℃ for polarization, and the second is to use Rb... + -K + The exchange forms a periodic surface resistivity difference for polarization at room temperature. In both schemes, the coercive field of KTP exceeds the coercive field of conventional KTP crystals by 2 kV / mm, with the former being approximately 12 kV / mm and the latter approximately 3.4 kV / mm. Therefore, an electric field similar to or even higher than the coercive field is required. Furthermore, after completing the first three stages of domain reversal using a high-voltage pulse exceeding the coercive field, both schemes continue to use the same high-voltage pulse for the last two stages (i.e., lateral expansion and the formation of a stable domain structure) of periodic polarization. The excessively high voltage greatly increases the difficulty of controlling the last two stages of domain reversal, resulting in significant differences in the periodic domain morphology of the +Z and -Z planes of the PPKTP device obtained by the first scheme. The domain width of the -Z plane is smaller than that of the +Z plane, and the domain walls of the -Z plane exhibit obvious bending (i.e., extremely low domain wall straightness). The second scheme cannot stably obtain PPKTP devices.

[0006] In addition, the electrode patterns commonly used in the fabrication of periodically polarized KTP crystals are grating electrode patterns that are triggered by a single line and cover the entire crystal surface. This can cause uneven electric field distribution between the electrode edge and the center region to some extent. To address this issue, the existing solution is to use KCl solution to cover the entire grating electrode for electric field loading. However, this requires a fixture with excellent sealing properties and the process is relatively cumbersome. At the same time, it requires a high degree of integrity of the insulating layer between the grating electrodes. Otherwise, domain inversion will occur in the designed non-inversion region, affecting the periodic polarization results.

[0007] Therefore, how to achieve the longitudinal through-and lateral uniform expansion of the inverted domains of KTP crystals, while obtaining periodic domain morphologies with no significant difference between the +Z and -Z planes, and ultimately realize the preparation of high-quality PPKTP crystals, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] In view of this, the present invention provides a parallel point-contact periodic electrode pattern, a periodic polarization device and method for KTP crystals to solve some of the technical problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] The parallel point-contact periodic electrode pattern of the KTP crystal includes a first electrode and a second electrode, which are respectively disposed on the -Z plane and the +Z plane of the KTP crystal substrate.

[0011] The first electrode includes several frame-shaped electrodes arranged side by side at intervals;

[0012] The second electrode is a metal electrode;

[0013] The frame electrode includes a first semi-circular electrode portion, a second semi-circular electrode portion, and a strip electrode portion. The strip electrode portion is located between the first semi-circular electrode portion and the second semi-circular electrode portion. The first semi-circular electrode portion is electrically connected to the second semi-circular electrode portion through the strip electrode portion.

[0014] Both the first and second semicircular electrode sections are composed of a semicircle with radius r and a rectangle with length and width of 2r and r respectively.

[0015] The strip electrode section includes multiple strip electrodes, with equal-width gaps between adjacent strip electrodes.

[0016] Preferably, the spacing between adjacent frame electrodes arranged side by side is equal to the width of the gap between adjacent strip electrodes.

[0017] Preferably, the edges of each frame electrode of the first electrode and the edge of the KTP crystal have uniform gaps of equal width.

[0018] Preferably, the gaps in the first electrode are filled with photoresist.

[0019] Preferably, each strip electrode in the strip electrode section is parallel to the Y-direction of the KTP crystal.

[0020] Preferably, the ratio of the width of a single strip electrode in the strip electrode section to the width of the equal-width gap between adjacent strip electrodes is 1:5 to 1:1, and the width of a single strip electrode is 1 to 200 μm;

[0021] The semi-circular radius r of the first and second semi-circular electrode portions is 0.5 mm to 1 mm;

[0022] The thickness of the first and second electrodes is 50–500 nm;

[0023] The substrate thickness of KTP crystal is 0.5mm to 1mm;

[0024] The width of the uniform gap between the edges of each frame electrode of the first electrode and the edge of the KTP crystal is 0.5 to 2 mm.

[0025] The thickness of the photoresist filling is 0.5-5μm.

[0026] The periodic polarization device of the KTP crystal, based on the parallel point-contact periodic electrode pattern of the KTP crystal, includes a signal generator, a high-voltage amplifier, a KTP crystal with the parallel point-contact periodic electrode pattern, and an oscilloscope.

[0027] One end of the signal generator is connected to the frame-shaped electrodes and resistor R2, which are arranged side by side at intervals, via a high-voltage amplifier. The second electrode of the KTP crystal is connected in series with resistor R1 and then connected to the other end of the signal generator. Resistors R2 and R3 are connected in series and then connected to the other end of the signal generator.

[0028] The signal generator emits arbitrary waveform pulses, which are amplified by a high-voltage amplifier and output as high voltage. These pulses are then applied to a KTP crystal with a parallel point-contact periodic electrode pattern via probes that correspond one-to-one with the spaced-apart frame electrodes. An oscilloscope is connected to the two ends of resistors R1 and R3 via voltage differential probes to monitor the voltage waveforms of resistors R1 and R3, thereby enabling the monitoring of the applied voltage and current flowing through the KTP crystal during polarization.

[0029] A periodic polarization method for KTP crystals, based on the periodic polarization device of the KTP crystal, includes:

[0030] The signal generator emits arbitrary waveform pulses, which are amplified by a high-voltage amplifier and output high voltage. The high voltage is then applied to a KTP crystal with a parallel point-contact periodic electrode pattern by probes that correspond one-to-one with the spaced side-by-side frame electrodes.

[0031] Set the output high voltage pulse parameters, i.e., polarization parameters, which include pulse voltage, pulse width, relaxation time, and number of pulses;

[0032] Based on the set pulse width, piezoelectric constant, and current flowing through the KTP crystal, calculate the required polarization area, charge amount, polarization time, and number of high-voltage pulses when the piezoelectric constant is 2, and complete the high-voltage pulse voltage application.

[0033] To test the actual piezoelectric constant of the KTP crystal, a DC voltage value is set and applied to the first and second electrodes of the KTP crystal to polarize it. After each application of DC voltage, it is determined whether the KTP crystal has completed periodic polarization. If it has not yet completed periodic polarization, this step is repeated until the periodic polarization of the KTP crystal is completed.

[0034] Preferably, the condition for determining whether periodic polarization has been completed after each application of DC voltage is as follows:

[0035] -0.2≤d″ 33 ≤0.2

[0036] Among them, d″ 33 The actual piezoelectric constant d is measured after each DC voltage application. 33 Value; if the condition is met, the DC voltage loading will end.

[0037] Preferably, when the piezoelectric constant d 33 When = 2, the area required for polarization is:

[0038]

[0039] Where, d′ 33 The initial d measured by KTP crystal 33 Value, S0 is d 33 The area required for polarization when = 0;

[0040] The charge required for KTP crystal polarization is:

[0041] Q = P s ·S

[0042] Among them, P s Let S be the spontaneous polarization intensity of the KTP crystal, and S be the d. 33 The area required for polarization when = 2;

[0043] The input charge of the polarization circuit is:

[0044] Q=∫Idt

[0045] Where I is the measured real-time current through R1, i.e. the real-time current through the KTP crystal, and t is the time the current is applied to the KTP crystal.

[0046] Based on the voltage waveform of R1 monitored by the oscilloscope when a high-voltage pulse voltage is applied, calculate the voltage d of the KTP crystal after high-voltage pulse polarization. 33 The time t required when = 2;

[0047] Calculate the required number of pulses based on the selected pulse width and time t.

[0048] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a parallel point-contact periodic electrode pattern, a periodic polarization device, and a method for KTP crystals. By designing the parallel point-contact periodic electrode pattern, the nucleation rate of the inverted domains and the uniformity of the electric field distribution can be improved. Furthermore, low-field polarization is applied in the last two stages of KTP crystal domain inversion, which suppresses and terminates the lateral expansion of ferroelectric domains during the inversion process. This significantly reduces or even eliminates the difference in morphology between the +Z and -Z plane periodic domains, improves the flatness of the domain walls, and enhances the quality of the periodic inverted domains on the +Z and -Z planes of the KTP crystal. This makes the width of the inverted domains on both Z planes approach the theoretical value, thereby achieving effective control over the inverted domains of the KTP crystal, improving the optical conversion efficiency of the wafer, and showing good application prospects. Moreover, the present invention is simple to operate, and the polarization method is easy to implement. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0050] Figure 1 The attached figure is a schematic diagram of the parallel point-contact periodic electrode pattern structure of the KTP crystal provided by the present invention.

[0051] Figure 2 The attached figure is a top view of the parallel point-contact periodic electrode structure provided by the present invention;

[0052] Figure 3 The attached figure is a schematic diagram of the frame-type electrode structure provided by the present invention;

[0053] Figure 4 The attached figure is a schematic diagram of the periodic polarization device for the KTP crystal provided by the present invention;

[0054] Figure 5 The attached figure is a schematic diagram of an optical micrograph of the +Z plane of the periodic inversion domain structure prepared according to an embodiment of the present invention;

[0055] Figure 6 The attached figure is a schematic diagram of a Z-plane optical micrograph of the periodic inversion domain structure prepared according to an embodiment of the present invention;

[0056] Wherein, 201-first electrode, 202-KTP crystal, 203-second electrode, 301-edge of the first electrode and edge region of the KTP crystal, 302-frame electrode, 303-spacing between adjacent frame electrodes, 401-semi-circular portion of the first and second semi-circular electrode portions, 402-rectangular portion of the first and second semi-circular electrode portions, 403-strip electrode, 404-equal-width gap between adjacent strip electrodes. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] This invention discloses a parallel point-contact periodic electrode pattern for KTP crystals, such as... Figures 1-3 As shown, it includes a first electrode and a second electrode. The first electrode 201 and the second electrode 203 are respectively disposed on the -Z plane and the +Z plane of the KTP crystal 202. The first electrode 201 and the second electrode 203 are uniformly distributed on the opposite surfaces of the KTP crystal 202.

[0059] The first electrode 201 includes a plurality of frame-shaped electrodes 302 arranged side by side at intervals;

[0060] The second electrode 203 is a metal electrode;

[0061] The frame electrode 302 includes a first semi-circular electrode portion, a second semi-circular electrode portion, and a strip electrode portion. The strip electrode portion is located between the first semi-circular electrode portion and the second semi-circular electrode portion. The first semi-circular electrode portion is electrically connected to the second semi-circular electrode portion through the strip electrode portion.

[0062] Both the first and second semi-circular electrode sections are composed of a semicircle 401 with radius r and a rectangle 402 with length and width of 2r and r respectively.

[0063] The strip electrode section includes multiple strip electrodes 403, with equal-width gaps 404 between adjacent strip electrodes 403.

[0064] To further implement the above technical solution, the spacing 303 between adjacent frame electrodes 302 arranged side by side is equal to the equal-width gap 404 between adjacent strip electrodes 403.

[0065] To further implement the above technical solution, the edges of each frame electrode 302 of the first electrode 201 and the edge of the KTP crystal 202 are connected by a uniform gap 301 of equal width, which serves as a buffer area between the edge of the first electrode and the edge of the crystal, thus avoiding creepage during polarization.

[0066] To further implement the above technical solution, the gaps in the first electrode are all filled with photoresist, including equal-width gaps between adjacent strip electrodes 403, intervals between adjacent frame electrodes 302, and equal-width uniform gaps between the edges of each frame electrode 302 of the first electrode 201 and the edges of the KTP crystal 202.

[0067] To further implement the above technical solution, each strip electrode 403 of the strip electrode section is parallel to the Y direction of the KTP crystal 202.

[0068] To further implement the above technical solution, the ratio of the width of a single strip electrode 403 in the strip electrode section to the width of the equal-width gap 404 between adjacent strip electrodes 403 is 1:5 to 1:1, and the width of a single strip electrode 403 is 1 to 200 μm.

[0069] The radius r of the semicircular electrode section 401 of the first and second semicircular electrode sections is 0.5 mm to 1 mm;

[0070] The thickness of the first electrode 201 and the second electrode 203 is 50-500 nm;

[0071] The substrate thickness of KTP crystal 202 is 0.5mm to 1mm;

[0072] The width of the uniform gap 301 between the edge of each frame electrode 302 of the first electrode 201 and the edge of the KTP crystal 202 is 0.5 to 2 mm.

[0073] The thickness of the photoresist filling is 0.5-5μm.

[0074] Periodic polarization devices for KTP crystals, such as Figure 4 The parallel point-contact periodic electrode pattern based on KTP crystal includes a signal generator, a high-voltage amplifier, a KTP crystal with a parallel point-contact periodic electrode pattern, and an oscilloscope.

[0075] One end of the signal generator is connected to the frame-shaped electrode 302 and resistor R2, which are arranged side by side at intervals, via a high-voltage amplifier. The second electrode 203 of the KTP crystal is connected to the other end of the signal generator after being connected in series with resistor R1. Resistors R2 and R3 are connected in series to the other end of the signal generator.

[0076] The signal generator emits arbitrary waveform pulses, which are amplified by a high-voltage amplifier and output as high voltage. These pulses are then applied to a KTP crystal with a parallel point-contact periodic electrode pattern via probes that correspond one-to-one with the spaced-alternate frame electrodes 302. An oscilloscope is connected to the two ends of resistors R1 and R3 via voltage differential probes to monitor the voltage waveforms of resistors R1 and R3, thereby enabling the monitoring of the applied voltage and current flowing through the KTP crystal during polarization.

[0077] In this embodiment, the pulse voltage or DC voltage is applied uniformly to each strip electrode 403 through point contact via the semicircular portion 401 and the rectangular portion 402 of the first and second semicircular electrode portions, thereby forming a uniform longitudinal electric field in the KTP crystal 202 and achieving uniform domain inversion.

[0078] A periodic polarization method for KTP crystals, based on a periodic polarization device for KTP crystals, includes:

[0079] The signal generator emits arbitrary waveform pulses, which are amplified by a high-voltage amplifier and output high voltage. The high voltage is applied to the KTP crystal with a parallel point-contact periodic electrode pattern through probes that correspond one-to-one with and are connected in parallel to the frame-type electrodes 302 arranged at intervals.

[0080] Set the output high voltage pulse parameters, i.e., polarization parameters, which include pulse voltage, pulse width, relaxation time, and number of pulses;

[0081] Based on the set pulse width, piezoelectric constant, and current flowing through the KTP crystal, calculate the required polarization area, charge amount, polarization time, and number of high-voltage pulses when the piezoelectric constant is 2, and complete the high-voltage pulse voltage application.

[0082] To test the actual piezoelectric constant of the KTP crystal, a DC voltage value is set and applied to the first and second electrodes of the KTP crystal to polarize it. After each application of DC voltage, it is determined whether the KTP crystal has completed periodic polarization. If it has not yet completed periodic polarization, this step is repeated until the periodic polarization of the KTP crystal is completed.

[0083] To further implement the above technical solution, the condition for determining whether periodic polarization has been completed after each DC voltage application is as follows:

[0084] -0.2≤d″ 33 ≤0.2

[0085] Among them, d″ 33 The actual piezoelectric constant d is measured after each DC voltage application. 33 Value; if the condition is met, the DC voltage loading will end.

[0086] To further implement the above technical solution, when the piezoelectric constant d 33 When = 2, the area required for polarization is:

[0087]

[0088] Where, d′ 33 The initial d measured by KTP crystal 33 Value, S0 is d 33 The area required for polarization when = 0;

[0089] The charge required for KTP crystal polarization is:

[0090] Q = P s ·S

[0091] Among them, P s Let S be the spontaneous polarization intensity of the KTP crystal, and S be the d. 33 The area required for polarization when = 2;

[0092] The input charge of the polarization circuit is:

[0093] Q=∫Idt

[0094] Where I is the measured real-time current through R1, i.e. the real-time current through the KTP crystal, and t is the time the current is applied to the KTP crystal.

[0095] Based on the voltage waveform of R1 monitored by the oscilloscope when a high-voltage pulse voltage is applied, calculate the voltage d of the KTP crystal after high-voltage pulse polarization. 33 The time t required when = 2;

[0096] Calculate the required number of pulses based on the selected pulse width and time t.

[0097] To further implement the above technical solution, the peak pulse voltage is ≥ the coercive field of the KTP crystal;

[0098] The relaxation time is 0.1–100 ms;

[0099] The pulse width is 0.01–100 ms;

[0100] The DC voltage range is 50V to 300V.

[0101] In another embodiment, the KTP crystal 202 has a thickness of 1 mm, and its length and width can be cut into any size as required; the width of the edge region 301 of the first electrode is 1 mm, and the spacing between each frame electrode is 23 μm; the radius of the semi-circular portion 401 of the frame electrode with the semi-circular electrode portion of the first electrode is 1 mm, the length and width of the rectangular portion 402 with the first and second semi-circular electrode portions are 2 mm and 1 mm, respectively, the width of each strip electrode 403 and the equal-width gap 404 of the strip electrode portion of the frame electrode is 23 μm, and the equal-width gap 404 is filled with photoresist with a thickness of 1 μm; the second electrode 203 has the same material as the first electrode 201, and aluminum is selected as the electrode material, and it is uniformly covered on the opposite surface of the KTP crystal 202 by semiconductor photolithography, and the thickness of the first electrode and the second electrode is 100 nm.

[0102] pass Figure 4 The periodic polarization device of the KTP crystal shown controls the polarization conditions of the electrode line group between the first electrode 201 and the second electrode 203. The polarization conditions mainly include pulse voltage, pulse width, relaxation time, and number of pulses, so as to realize the polarization reversal of the KTP crystal material 202 between the first electrode 201 and the second electrode 203, thereby forming a periodic domain structure inside the KTP crystal material 202.

[0103] The specific polarization conditions are as follows: pulse voltage is 2.01kV, pulse width is 1.6ms, relaxation time is 20ms, and number of pulses is ≥1.

[0104] Based on the set pulse width, piezoelectric constant, and KTP crystal current, calculate the required polarization area, charge required for polarization, time required for polarization, and number of high-voltage pulses required when the piezoelectric constant is 2, and complete the high-voltage pulse voltage application.

[0105] The actual piezoelectric constant of the KTP crystal was tested. A DC voltage of 100V was applied to the first electrode 201 and the second electrode 203 of the KTP crystal to polarize it. After each application of the DC voltage, it was determined whether the KTP crystal had completed periodic polarization. If not, this step was repeated until the periodic polarization of the KTP crystal was complete. The +Z and -Z planes of the prepared periodic inversion domain structure were shown below. Figure 5 and Figure 6 As shown.

[0106] This invention improves the quality of KTP crystal inversion domains by regulating the domain wall expansion in the last two stages of domain inversion, making the duty cycle of the inverted domains close to 50%, thereby improving optical conversion efficiency and achieving more effective utilization of KTP crystals.

[0107] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0108] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A parallel point-contact periodic electrode pattern for a KTP crystal, characterized in that, It includes a first electrode and a second electrode, which are respectively disposed on the -Z plane and the +Z plane of the KTP crystal substrate; The first electrode includes several frame-shaped electrodes arranged side by side at intervals; The second electrode is a metal electrode; The frame electrode includes a first semi-circular electrode portion, a second semi-circular electrode portion, and a strip electrode portion. The strip electrode portion is located between the first semi-circular electrode portion and the second semi-circular electrode portion. The first semi-circular electrode portion is electrically connected to the second semi-circular electrode portion through the strip electrode portion. Both the first and second semicircular electrode sections are composed of a semicircle with radius r and a rectangle with length and width of 2r and r respectively. The strip electrode section includes multiple strip electrodes, with equal-width gaps between adjacent strip electrodes.

2. The parallel point-contact periodic electrode pattern of the KTP crystal according to claim 1, characterized in that, The spacing between adjacent frame electrodes arranged side by side is equal to the equal-width gap between adjacent strip electrodes.

3. The parallel point-contact periodic electrode pattern of the KTP crystal according to claim 1, characterized in that, The edges of each frame electrode of the first electrode and the edge of the KTP crystal have uniform gaps of equal width.

4. The parallel point-contact periodic electrode pattern of the KTP crystal according to claim 1, characterized in that, The gaps in the first electrode are all filled with photoresist.

5. The parallel point-contact periodic electrode pattern of the KTP crystal according to claim 1, characterized in that, Each strip electrode in the strip electrode section is parallel to the Y-axis of the KTP crystal.

6. The parallel point-contact periodic electrode pattern of the KTP crystal according to claim 3 or 4, characterized in that, The ratio of the width of a single strip electrode in the strip electrode section to the width of the equal-width gap between adjacent strip electrodes is 1:5 to 1:1, and the width of a single strip electrode is 1 to 200 μm. The semi-circular radius r of the first and second semi-circular electrode portions is 0.5mm~1mm; The thickness of the first and second electrodes is 50~500 nm; The substrate thickness of KTP crystal is 0.5mm~1mm; The width of the uniform gap between the edge of each frame electrode of the first electrode and the edge of the KTP crystal is 0.5~2mm. The thickness of the photoresist filling is 0.5-5μm.

7. A periodic polarization device for KTP crystals, characterized in that, Based on the parallel point-contact periodic electrode pattern of the KTP crystal according to any one of claims 1-6, it includes a signal generator, a high-voltage amplifier, a KTP crystal with the parallel point-contact periodic electrode pattern, and an oscilloscope. One end of the signal generator is connected to the frame-shaped electrodes and resistor R2, which are arranged side by side at intervals, via a high-voltage amplifier. The second electrode of the KTP crystal is connected in series with resistor R1 and then connected to the other end of the signal generator. Resistors R2 and R3 are connected in series and then connected to the other end of the signal generator. The signal generator emits arbitrary waveform pulses, which are amplified by a high-voltage amplifier and output as high voltage. These pulses are then applied to a KTP crystal with a parallel point-contact periodic electrode pattern via probes that correspond one-to-one with the spaced-apart frame electrodes. An oscilloscope is connected to the two ends of resistors R1 and R3 via voltage differential probes to monitor the voltage waveforms of resistors R1 and R3, thereby enabling the monitoring of the applied voltage and current flowing through the KTP crystal during polarization.

8. A periodic polarization method for KTP crystals, characterized in that, The periodic polarization device based on the KTP crystal according to claim 7 includes: The signal generator emits arbitrary waveform pulses, which are amplified by a high-voltage amplifier and output high voltage. The high voltage is then applied to a KTP crystal with a parallel point-contact periodic electrode pattern by probes that correspond one-to-one with the spaced side-by-side frame electrodes. Set the output high voltage pulse parameters, i.e., polarization parameters, which include pulse voltage, pulse width, relaxation time, and number of pulses; Based on the set pulse width, piezoelectric constant, and current flowing through the KTP crystal, calculate the required polarization area, charge amount, polarization time, and number of high-voltage pulses when the piezoelectric constant is 2, and complete the high-voltage pulse voltage application. To test the actual piezoelectric constant of the KTP crystal, a DC voltage value is set and applied to the first and second electrodes of the KTP crystal to polarize it. After each application of DC voltage, it is determined whether the KTP crystal has completed periodic polarization. If it has not yet completed periodic polarization, this step is repeated until the periodic polarization of the KTP crystal is completed.

9. The periodic polarization method for KTP crystal according to claim 8, characterized in that, After each DC voltage is applied, the condition for determining whether periodic polarization is complete is as follows: ； in, The actual piezoelectric constant d is measured after each DC voltage application. 33 Value; if the condition is met, the DC voltage loading will end.

10. The periodic polarization method for KTP crystal according to claim 8, characterized in that, When the piezoelectric constant d 33 When = 2, the area required for polarization is: ； in, The initial d measured by KTP crystal 33 value, For d 33 The area required for polarization when =0; The charge required for KTP crystal polarization is: Q=P s ·S Among them, P s Let S be the spontaneous polarization intensity of the KTP crystal, and d be the value of d. 33 The area required for polarization when =2; The input charge of the polarization circuit is: Q=ʃIdt Where I is the measured real-time current through R1, i.e. the real-time current through the KTP crystal, and t is the time the current is applied to the KTP crystal. Based on the voltage waveform of R1 monitored by the oscilloscope when a high-voltage pulse voltage is applied, calculate the voltage d of the KTP crystal after high-voltage pulse polarization. 33 Time required when =2 ; Based on the selected pulse width and time Calculate the number of pulses required to be applied.

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