Half-wave voltage measurement method based on electro-optical effect of ferroelectric phase potassium tantalate niobate crystal

Abstract

The invention discloses a half-wave voltage measuring method based on the electro-optical effect of a ferroelectric phase potassium tantalate niobate crystal, and belongs to the field of photoelectric functional materials and devices. The core steps of the measurement method comprise KTN crystal processing and coating, sample directional polarization and half-wave voltage measurement. A KTN crystal sample is processed along the X / Y / Z positive direction of a crystal axis, and is directionally polarized along the Z axis of the crystal optical axis, a driving voltage is applied along the polarization direction, light is transmitted along the X / Y direction, and finally the half-wave voltage is measured. The method provides a complete scheme for measuring the half-wave voltage of the ferroelectric phase KTN crystal material, has the advantages of being simple and convenient in process, good in universality, wide in applicable wave band, safe, efficient and the like, and can provide reference for half-wave voltage measurement and optical performance research of other multi-domain ferroelectric crystals.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic functional materials and devices, and particularly to a method for measuring the half-wave voltage based on the electro-optic effect of ferroelectric potassium tantalate niobate crystals. Background Art

[0002] Ferroelectric crystals are a type of crystals with spontaneous polarization, and the direction of spontaneous polarization can change with the direction of the applied electric field. Ferroelectric crystals usually have properties such as electro-optic, piezoelectric, pyroelectric, and photorefractive, and are widely used in fields such as optical switches, spatial light modulation, and information storage. Among the various ferroelectric crystals discovered so far, potassium tantalate niobate crystals with an ABO3-type perovskite structure are typical ferroelectric crystals.

[0003] Potassium tantalate niobate crystal (KTa 1-x Nb x O3; 0.3 < x < 0.8, hereinafter referred to as KTN) is a solid solution mixed crystal of potassium niobate (KNbO3) and potassium tantalate (KTaO3), and its composition can be adjusted according to the ratio of KNbO3 (KN) and KTaO3 (KT). Potassium tantalate niobate crystal (KTa 1-x Nb x O3) can exist in a paraelectric phase or a ferroelectric phase depending on the composition, and has good quadratic electro-optic and photorefractive properties in the paraelectric phase, and good piezoelectric and linear electro-optic effects in the ferroelectric phase.

[0004] However, the KTN crystal in the ferroelectric phase has a multi-domain structure with a high density of domain walls, and the crystal appears opaque and milky white, and cannot be directly used for optical testing. In traditional measurement methods, the polarization effect of the crystal is not good, and there are residual redundant domain walls, resulting in low crystal transparency and affecting the subsequent measurement of the half-wave voltage of the KTN crystal under crossed polarizers. Summary of the Invention

[0005] Aiming at the above deficiencies of the prior art, the present invention provides a method for measuring the half-wave voltage based on the electro-optic effect of ferroelectric potassium tantalate niobate crystals. The present invention uses a method of first directional polarization and then measuring the half-wave voltage, and successfully finds the optimal spontaneous polarization direction of the KTN crystal, overcoming the defect that the polarization effect of the crystal in the traditional measurement method is not good and affecting the measurement of the half-wave voltage of the KTN crystal.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a method for measuring the half-wave voltage based on the electro-optic effect of ferroelectric potassium tantalate niobate crystals, the ferroelectric potassium tantalate niobate being KTa 1-x Nb x O3 crystal, and the measurement method includes the following steps:

[0007] (1) Processing and coating of KTN crystals: orienting, cutting and polishing the crystals, and then coating the optical polished surface of the crystals parallel to the light transmission direction with a 2-4 μm thick gold, silver or copper metal film layer as an electrode, preferably 3 μm silver metal;

[0008] (2) Sample directional polarization: The crystal is placed in a silicone oil bath and a temperature field and a directional electric field are applied to the crystal to achieve directional polarization of the crystal. The spontaneous polarization direction is along the crystal growth direction.

[0009] (3) Measurement of half-wave voltage: Light is transmitted along the optical axis, and an electric field is applied perpendicular to the direction of light transmission. The detector measures the intensity of the transmitted light to obtain the half-wave voltage value.

[0010] A further improvement of the present scheme is that in step (1), the crystal is oriented by using a microscope to observe the KTN growth stripes against the light on the light-transmitting surface to determine the crystal growth direction, which is defined as the Z direction; taking the crystal orientation physical plane as a reference, the orientation physical plane is respectively parallel and perpendicular to the crystal growth direction, and a cutting tool is used to cut a cubic crystal sample with a side length of 1-10 mm.

[0011] (1) A further improvement of the present scheme, in step (1), the polishing is carried out at 25±2°C and a humidity of 40-80%, using a diamond suspension with a particle size of less than 1 μm to polish the sample surface, and after polishing, the sample obtains a smooth surface with a surface roughness of 1-1.5 nm and a high shape accuracy, a root mean square roughness (RMS) of less than 1 nm, and a parallelism of the upper and lower surfaces of less than 5″. The optical polished surface of the crystal parallel to the light transmission direction is the XY plane, and metal is plated on this surface as an electrode.

[0012] A further improvement of the present solution is that in step (2), a temperature field below the Curie point is applied to the crystal, and the temperature is increased at a rate of 3-10°C / min, preferably 5°C / min.

[0013] A further improvement of the present solution is that the directional electric field applied to the crystal in step (2) is applied along the crystal growth direction, that is, along the Z direction.

[0014] A further improvement of the present scheme is that in step (2), a directional electric field is applied to the crystal at a rate of 200-500 V / min, preferably 300 V / min, and then the crystal is polarized for 20-50 min, preferably 30 min, after the electric field is applied to 1500 V / mm.

[0015] A further improvement of the present scheme is that in step (3), light is passed perpendicularly to the crystal growth direction, and lasers with wavelengths of 633nm, 1030nm, and 1539nm can be used respectively to sequentially incident on a polarizer, a crystal sample, an analyzer, and a detector, and finally the variation of light intensity with voltage is obtained.

[0016] For a further improvement of this solution, in step (3), the detector measures the transmitted light intensity to obtain the value of the half-wave voltage, that is, the half-wave voltage is obtained by measuring the peak value of the light intensity.

[0017] For a further improvement of this solution, the Nb component of the KTa 1-x Nb x O3 crystal is between 0.3 and 0.8, and it is in a tetragonal or orthorhombic phase structure at room temperature.

[0018] The beneficial effects of the present invention are as follows:

[0019] (1) Aiming at the deficiencies of the existing measurement technologies, the present invention provides a method for measuring the half-wave voltage based on the electro-optic effect of ferroelectric potassium tantalate niobate crystals. This method innovatively discovers that the spontaneous polarization of ferroelectric KTN is not random, and the spontaneous polarization along the growth direction is the strongest. The present invention applies an electric field along the Z direction (growth direction), finally realizes the optimal polarization of the KTN sample, and then obtains an optical-grade KTN sample, meeting the requirements of subsequent optical tests, and providing a reference for the measurement of the half-wave voltage and the research of optical properties of other multi-domain ferroelectric crystals.

[0020] (2) The present invention provides a method for measuring the half-wave voltage based on the electro-optic effect of ferroelectric potassium tantalate niobate (KTa 1-x Nb x O3; 0.3 < x < 0.8, abbreviated as KTN) crystals. Its core steps include three parts: KTN crystal processing and coating, sample orientation polarization, and half-wave voltage measurement. The KTN crystal sample is processed along the positive directions of the crystal axes X / Y / Z, oriented and polarized along the crystal optical axis Z axis, a driving voltage is applied along the polarization direction, light passes through in the X / Y direction, and finally the half-wave voltage is measured; the present invention provides a complete solution for the method of measuring the half-wave voltage based on the electro-optic effect of ferroelectric potassium tantalate niobate crystals, with the advantages of simple process, good versatility, wide applicable wavelength range, safety and high efficiency, etc., overcoming the defects in the traditional measurement methods that the polarization effect of the crystal is not good, there are residual redundant domain walls, resulting in low crystal transparency and affecting the subsequent measurement of the half-wave voltage of the KTN crystal under crossed polarizers. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 Structural schematic diagrams of the crystal samples 1-1, 1-2, and 1-3 for directional cutting, the Z direction is the crystal growth direction, and the X and Y directions are perpendicular to the crystal growth direction;

[0023] Figure 2Schematic diagrams of the structures of the crystal samples 2-1, 2-2, and 2-3 for directional cutting, where the Z direction is the crystal growth direction, and the X and Y directions are perpendicular to the crystal growth direction;

[0024] Figure 3 Schematic diagrams of the structures of the crystal samples 3-1, 3-2, and 3-3 for directional cutting, where the Z direction is the crystal growth direction, and the X and Y directions are perpendicular to the crystal growth direction;

[0025] Figure 4 For the directional polarization profile of potassium tantalate niobate crystal (KTa 1-x Nb x O3; 0.3 < x < 0.8, abbreviated as KTN), 1 is the KTN crystal sample, 2 is the pressure needle tip during polarization, and 3 is the silicone oil bath;

[0026] Figure 5 For the measurement result of the square of the voltage - light intensity of sample 1-1;

[0027] Figure 6 For the measurement result of the square of the voltage - light intensity of sample 2-1;

[0028] Figure 7 For the measurement result of the square of the voltage - light intensity of sample 3-1;

[0029] Figure 8 For the schematic diagram of the half - wave voltage test of potassium tantalate niobate crystal (KTa 1-x Nb x O3; 0.3 < x < 0.8, abbreviated as KTN), 1 is the 633nm laser emitter, 2 is the polarizer, 3 is the KTN crystal sample, 4 is the analyzer, 5 is the detector, and V represents the applied external electric field. Detailed implementation manners

[0030] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] The following further describes the present invention in detail with specific embodiments, but the protection scope of the present invention is not limited to the described content.

[0032] Embodiment 1: A method for measuring the half - wave voltage based on the electro - optic effect of ferroelectric potassium tantalate niobate crystal, and the component of the ferroelectric KTN crystal is KTa 0.6 Nb 0.4 O3. The specific steps are as follows:

[0033] (1) Processing and coating: Use a microscope to observe the KTN growth stripes against the light on the light-transmitting surface to determine the crystal growth direction, which is defined as the Z direction, and mark the directional relationship between the growth stripes and the geometric surface. The oriented physical planes are parallel and perpendicular to the crystal growth direction, respectively. A diamond cutting tool is used to orient the crystal to cut a rectangular sample 1-1 with a length, width and height of 3.3mm×2.5mm×1.0mm. The sample obtained by directional cutting is polished using a diamond suspension with a particle size of less than 1μm in an environment of 25±2℃ and a humidity of 40-80%. Then, a magnetron sputtering device is used to plate a silver electrode with a thickness of 3μm on the XY surface of the crystal optical polishing surface perpendicular to the crystal growth direction.

[0034] (2) Sample directional polarization: Figure 4 As shown, the sample was directionally polarized using an SPD high-voltage polarizer. The crystal was placed in a silicone oil bath, the temperature of the silicone oil bath was raised to 25°C at a rate of 5°C / min and kept constant, and an electric field was applied along the crystal growth direction, i.e., in the Z direction, at a rate of 300V / min to 1500V and then polarized for 30min.

[0035] (3) Measurement of half-wave voltage: A laser transmitter with a wavelength of 633nm is used, and the light passes through the polarizer, KTN crystal sample, analyzer and detector in sequence. The polarizer and analyzer are placed vertically, and an external electric field is applied in the Z direction parallel to the crystal growth direction. The light is passed perpendicular to the crystal growth direction, and the light transmission length is 3.3mm. Finally, the detector receives the transmitted light intensity, measures the peak light intensity, and then measures the half-wave voltage value.

[0036] Example 2: The difference from Example 1 is that (1) in the processing coating, the oriented physical planes are respectively parallel and perpendicular to the crystal growth direction, and the crystal is directionally cut by a diamond cutting tool to produce a rectangular sample 1-2 with a length, width and height of 3.3mm×2.5mm×1.0mm. A magnetron sputtering device is used to plate a gold electrode with a thickness of 2μm on the XZ surface of the crystal optical polishing surface parallel to the crystal growth direction.

[0037] (2) During sample directional polarization, the crystal was placed in a silicone oil bath, and the temperature of the silicone oil bath was raised to 25°C at a rate of 3°C / min and kept constant. An electric field was applied perpendicular to the crystal growth direction, i.e., in the Y direction, to 4950 V at a rate of 200 V / min and then polarized for 30 min.

[0038] (3) In the measurement of half-wave voltage, a laser transmitter with a wavelength of 1030nm is used, and the light passes through the polarizer, KTN crystal sample, analyzer and detector in sequence. An electric field is applied in the Y direction perpendicular to the crystal growth direction, and the light is passed parallel to the crystal growth direction, with a light transmission length of 2.5mm. Finally, the detector receives the transmitted light intensity, measures the peak light intensity, and then measures the half-wave voltage value.

[0039] Example 3: The difference from Example 1 is that (1) in the processing coating, the oriented physical planes are respectively parallel and perpendicular to the crystal growth direction, and the crystal is directionally cut by a diamond cutting tool to produce rectangular samples 1-3 with a length, width and height of 3.3mm×2.5mm×1.0mm. A magnetron sputtering device is used to plate a copper electrode with a thickness of 4μm on the optical polished surface YZ of the crystal parallel to the crystal growth direction.

[0040] (2) During sample directional polarization, the crystal was placed in a silicone oil bath, the temperature of the silicone oil bath was raised to 25°C at a rate of 10°C / min and kept constant, an electric field was applied perpendicular to the crystal growth direction, i.e., in the X direction, to 3750 V at a rate of 500 V / min and then polarized for 30 min.

[0041] (3) In the measurement of half-wave voltage, a laser transmitter with a wavelength of 1539nm is used, and the light passes through the polarizer, KTN crystal sample, analyzer and detector in sequence. An electric field is applied in the X direction perpendicular to the crystal growth direction, and the light is passed parallel to the crystal growth direction, with a light transmission length of 3.3mm. Finally, the detector receives the transmitted light intensity, measures the peak light intensity, and then measures the half-wave voltage value.

[0042] In Examples 1-3, the crystals were polarized along the X, Y, and Z directions, respectively. According to the comparison, it was found that the crystal transparency of the sample 1-1 polarized along the Z direction in Example 1 was the highest, which effectively avoided the influence of the domain wall on the light transmission in the subsequent half-wave voltage measurement process. Finally, the half-wave voltage V π =68.934V.

[0043] Embodiment 4: A method for measuring half-wave voltage based on the electro-optical effect of a ferroelectric phase potassium tantalate niobate crystal, wherein the ferroelectric phase KTN crystal component is KTa0.6Nb0.4O3. The specific steps are as follows:

[0044] (1) Processing and coating: Use a microscope to observe the KTN growth stripes against the light on the light-transmitting surface to determine the crystal growth direction, which is defined as the Z direction, and mark the directional relationship between the growth stripes and the geometric surface. The oriented physical surfaces are parallel and perpendicular to the crystal growth direction, respectively. A diamond cutting tool is used to orient the crystal to cut a rectangular sample 2-1 with a length, width and height of 10mm×4.0mm×6.0mm. The sample obtained by directional cutting is polished using a diamond suspension with a particle size of less than 1μm in an environment of 25±2℃ and a humidity of 40-80%. Then, a magnetron sputtering device is used to plate a silver electrode with a thickness of 3μm on the XY surface of the crystal optical polishing surface perpendicular to the crystal growth direction.

[0045] (2) Sample directional polarization: The sample was directional polarized using an SPD high-voltage polarizer. The crystal was placed in a silicone oil bath, and the temperature of the silicone oil bath was raised to 25°C at a rate of 5°C / min and kept constant. An electric field was applied parallel to the crystal growth direction, i.e., in the Z direction, at a rate of 300 V / min to 2550 V and then polarized for 30 min.

[0046] (3) Measurement of half-wave voltage: A laser transmitter with a wavelength of 633nm is used, and the light passes through the polarizer, KTN crystal sample, analyzer and detector in sequence. The polarizer and analyzer are placed vertically, and an electric field is applied in the Z direction parallel to the crystal growth direction. The light is passed perpendicular to the crystal growth direction, and the light transmission length is 10mm. Finally, the detector receives the transmitted light intensity, measures the peak light intensity, and then measures the half-wave voltage value.

[0047] Example 5: The difference from Example 4 is that (1) during the coating processing, the oriented physical planes are respectively parallel and perpendicular to the crystal growth direction, and a diamond cutting tool is used to directionally cut the crystal into a rectangular sample 2-2 with a length, width and height of 10 mm × 4.0 mm × 6.0 mm. A magnetron sputtering device is used to plate a gold electrode with a thickness of 2 μm on the XZ surface of the crystal optical polishing surface parallel to the crystal growth direction.

[0048] (2) During sample directional polarization, the crystal was placed in a silicone oil bath, and the temperature of the silicone oil bath was raised to 25°C at a rate of 3°C / min and kept constant. An electric field was applied perpendicular to the crystal growth direction, i.e., in the Y direction, at a rate of 200 V / min to 6000 V and then polarized for 30 min.

[0049] (3) In the measurement of half-wave voltage, a laser transmitter with a wavelength of 1030nm is used, and the light passes through the polarizer, KTN crystal sample, analyzer and detector in sequence. An electric field is applied in the Y direction perpendicular to the crystal growth direction, and the light is passed parallel to the crystal growth direction, with a light transmission length of 10mm. Finally, the detector receives the transmitted light intensity, measures the peak light intensity, and then measures the half-wave voltage value.

[0050] Example 6: The difference from Example 4 is that (1) during the coating processing, the oriented physical planes are respectively parallel and perpendicular to the crystal growth direction, and a diamond cutting tool is used to directionally cut the crystal into rectangular samples 2-3 with a length, width and height of 10mm×4.0mm×6.0mm. A magnetron sputtering device is used to plate a copper electrode with a thickness of 4μm on the YZ surface of the crystal optical polishing surface parallel to the crystal growth direction.

[0051] (2) During sample directional polarization, the crystal was placed in a silicone oil bath, the temperature of the silicone oil bath was raised to 25°C at a rate of 10°C / min and kept constant, an electric field was applied perpendicular to the crystal growth direction, i.e., in the X direction, to 3450 V at a rate of 500 V / min and then polarized for 30 min.

[0052] (3) In the measurement of half-wave voltage, a laser transmitter with a wavelength of 1539nm is used, and the light passes through the polarizer, KTN crystal sample, analyzer and detector in sequence. An electric field is applied in the X direction perpendicular to the crystal growth direction, and the light is passed parallel to the crystal growth direction, with a light transmission length of 4.0mm. Finally, the detector receives the transmitted light intensity, measures the peak light intensity, and then measures the half-wave voltage value.

[0053] In Examples 4-6, the crystals were polarized along the X, Y, and Z directions, respectively. According to the comparison, it was found that the crystal transparency of Sample 2-1 polarized along the Z direction in Example 4 was the highest, which effectively avoided the influence of the domain wall on the light transmission in the subsequent half-wave voltage measurement process. Finally, the half-wave voltage V was measured. π =66.941V.

[0054] Embodiment 7: A method for measuring half-wave voltage based on the electro-optical effect of a ferroelectric phase potassium tantalate niobate crystal, wherein the ferroelectric phase KTN crystal component is KTa0.6Nb0.4O3. The specific steps are as follows:

[0055] (1) Processing and coating: Use a microscope to observe the KTN growth stripes against the light on the light-transmitting surface to determine the crystal growth direction, which is defined as the Z direction, and mark the directional relationship between the growth stripes and the geometric surface. The oriented physical planes are parallel and perpendicular to the crystal growth direction, respectively. A diamond cutting tool is used to orient the crystal to cut a rectangular sample 3-1 with a length, width and height of 3.5mm×3.5mm×3.5mm. The sample obtained by directional cutting is polished using a diamond suspension with a particle size of less than 1μm in an environment of 25±2℃ and a humidity of 40-80%. Then, a magnetron sputtering device is used to plate a silver electrode with a thickness of 3μm on the XY surface of the crystal optical polishing surface perpendicular to the crystal growth direction.

[0056] (2) Sample directional polarization: The sample was directional polarized using an SPD high-voltage polarizer. The crystal was placed in a silicone oil bath, and the temperature of the silicone oil bath was raised to 25°C at a rate of 5°C / min and kept constant. An electric field was applied along the crystal growth direction, i.e., in the Z direction, at a rate of 300 V / min to 5250 V and then polarized for 30 min.

[0057] (3) Measurement of half-wave voltage: A laser transmitter with a wavelength of 633nm is used, and the light passes through the polarizer, KTN crystal sample, analyzer and detector in sequence. The polarizer and analyzer are placed vertically, and an electric field is applied in the Z direction parallel to the crystal growth direction. The light is passed perpendicular to the crystal growth direction, and the light transmission length is 3.5mm. Finally, the detector receives the transmitted light intensity, measures the peak light intensity, and then measures the half-wave voltage value.

[0058] Example 8: The difference from Example 7 is that (1) in the coating process, the oriented physical planes are parallel and perpendicular to the crystal growth direction, and a diamond cutting tool is used to cut the crystal to obtain a rectangular sample 3-2 with a length, width and height of 3.5 mm × 3.5 mm × 3.5 mm. A magnetron sputtering instrument is used to plate a gold electrode with a thickness of 2 μm on the XZ surface of the crystal optical polishing surface perpendicular to the crystal growth direction.

[0059] (2) During sample directional polarization, the crystal was placed in a silicone oil bath, the temperature of the silicone oil bath was raised to 25°C at a rate of 3°C / min and kept constant, an electric field was applied perpendicular to the crystal growth direction, i.e., in the Y direction, to 5250 V at a rate of 200 V / min and then polarized for 30 min.

[0060] (3) In the measurement of half-wave voltage, a laser transmitter with a wavelength of 1030nm is used, and the light passes through the polarizer, KTN crystal sample, analyzer and detector in sequence. An electric field is applied in the Y direction perpendicular to the crystal growth direction, and light is transmitted parallel to the crystal growth direction, with a light transmission length of 3.5mm. Finally, the detector receives the transmitted light intensity, measures the peak light intensity, and then measures the half-wave voltage value.

[0061] Example 9: The difference from Example 7 is that (1) in the coating process, the oriented physical planes are parallel and perpendicular to the crystal growth direction, and a diamond cutting tool is used to cut the crystal to obtain a rectangular sample 3-3 with a length, width and height of 3.5 mm×3.5 mm×3.5 mm. A copper electrode with a thickness of 4 μm is plated on the optical polished surface YZ of the crystal perpendicular to the crystal growth direction using a magnetron sputtering instrument.

[0062] (2) In the sample directional polarization, the crystal was placed in a silicone oil bath perpendicular to the crystal growth direction, and the temperature of the silicone oil bath was raised to 25°C at a rate of 10°C / min and kept constant, that is, an electric field was applied to 5250 V in the X direction at a rate of 500 V / min and then polarized for 30 min.

[0063] (3) In the measurement of half-wave voltage, a laser transmitter with a wavelength of 1539nm is used, and the light passes through the polarizer, KTN crystal sample, analyzer and detector in sequence. An electric field is applied in the X direction perpendicular to the crystal growth direction, and the light is passed perpendicular to the crystal growth direction, with a light transmission length of 3.5mm. Finally, the detector receives the transmitted light intensity, measures the peak light intensity, and then measures the half-wave voltage value.

[0064] In Examples 7-9, the crystals were polarized along the X, Y, and Z directions, respectively. According to the comparison, it was found that the crystal transparency of the sample 3-1 polarized along the Z direction in Example 7 was the highest, which effectively avoided the influence of the domain wall on the light transmission in the subsequent half-wave voltage measurement process. Finally, the half-wave voltage V π =53.378V.

Claims

1. A half-wave voltage measurement method based on the electro-optical effect of a ferroelectric potassium tantalate niobate crystal, wherein the ferroelectric potassium tantalate niobate is KTa 1-x Nb x O 3 Crystals, It is characterized in that The measurement method includes the following steps: (1) Processing and coating of KTN crystals: Orient, cut and polish the crystals, and then coat the optical polished surface of the crystals parallel to the light transmission direction with a metal film layer as an electrode; (2) Sample directional polarization: The crystal is placed in a silicone oil bath and a temperature field and a directional electric field are applied to the crystal to achieve directional polarization of the crystal. The spontaneous polarization direction is along the crystal growth direction. (3) Measurement of half-wave voltage: Light is transmitted along the optical axis, and an electric field is applied perpendicular to the direction of light transmission. The detector measures the intensity of the transmitted light to obtain the half-wave voltage value.

2. According to the half-wave voltage measurement method based on the electro-optical effect of the ferroelectric phase potassium tantalate niobate crystal according to claim 1, It is characterized in that In the step (1), the crystal is oriented by observing the KTN growth stripes against the light on the light-transmitting surface using a microscope to determine the crystal growth direction, which is defined as the Z direction; taking the crystal orientation physical plane as a reference, the orientation physical plane is parallel and perpendicular to the crystal growth direction respectively, and using a cutting tool to cut a cubic crystal sample with a side length of 1-10 mm.

3. According to the half-wave voltage measurement method based on the electro-optical effect of the ferroelectric phase potassium tantalate niobate crystal according to claim 1, It is characterized in that In the step (1), the polishing is carried out at 25±2° C. and 40-80% humidity using a diamond suspension with a particle size of less than 1 μm to polish the sample surface. The optical polishing surface of the crystal parallel to the light transmission direction is the XY surface, and metal is plated on this surface as an electrode.

4. According to claim 1, the half-wave voltage measurement method based on the electro-optical effect of the ferroelectric phase potassium tantalate niobate crystal, It is characterized in that In the step (2), a temperature field below the Curie point is applied to the crystal, and the temperature is raised to a specified temperature at a rate of 3-10°C / min.

5. According to claim 1, the half-wave voltage measurement method based on the electro-optical effect of the ferroelectric phase potassium tantalate niobate crystal, It is characterized in that In the step (2), the directional electric field is applied to the crystal along the crystal growth direction, that is, along the Z direction.

6. The half-wave voltage measurement method based on the electro-optical effect of the ferroelectric potassium tantalate niobate crystal according to claim 1, It is characterized in that In the step (2), a directional electric field is applied to the crystal at a rate of 200-500 V / min until the electric field reaches 1500 V / mm and then polarized for 30 minutes.

7. The half-wave voltage measurement method based on the electro-optical effect of the ferroelectric potassium tantalate niobate crystal according to claim 1, It is characterized in that In the step (3), light is passed perpendicularly to the crystal growth direction, and lasers with wavelengths of 633nm, 1030nm, and 1539nm are used to sequentially incident on a polarizer, a crystal sample, an analyzer, and a detector, and finally the variation of light intensity with voltage is obtained.

8. The half-wave voltage measurement method based on the electro-optical effect of the ferroelectric potassium tantalate niobate crystal according to claim 1, It is characterized in that In step (3), the detector measures the transmitted light intensity to obtain a half-wave voltage value, that is, the half-wave voltage is obtained by measuring the peak light intensity.

9. The half-wave voltage measurement method based on the electro-optical effect of the ferroelectric potassium tantalate niobate crystal according to claim 1, It is characterized in that The KTa 1-x Nb x O 3 The Nb component of the crystal is between 0.3-0.8, and it has a tetragonal or orthorhombic structure at room temperature.

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