Light beam deflection method and device based on secondary electro-optical effect of cerium-nickel double-doped strontium barium niobate crystal

Abstract

The invention relates to the technical field of photoelectric functional crystal materials, and provides a light beam deflection method and device based on the secondary electro-optical effect of a cerium-nickel double-doped strontium barium niobate crystal. The method comprises the following steps: firstly, growing strontium barium niobate (SBN) crystals by adopting a Czochralski method, and realizing doping of cerium and nickel; then, the grown SBN crystal is cut, ground and polished, a double-layer metal electrode is deposited, and an electro-optical deflection device with excellent ohmic contact characteristics is formed through rapid annealing; before use, electron pre-injection is carried out on the crystal; and finally, incident light is incident, and light beam deflection is realized under the action of an external electric field. By optimizing component design and doping regulation, the Curie temperature of the SBN crystal is adjusted to be close to the room temperature, and large-angle light beam deflection is achieved in combination with electron pre-injection; under the voltage of + / -450V, the maximum deflection angle can reach + / -140mrad, and a novel solution is provided for the high-efficiency electro-optical deflection technology.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic functional crystal materials, and specifically to a beam deflection method and device based on the quadratic electro-optic effect of cerium- and nickel-codoped strontium barium niobate crystals. Background Art

[0002] Beam deflection technology has wide applications in fields such as laser processing, optical communication, beam scanning, optical modulation, three-dimensional imaging, lidar, and medical imaging. Currently, beam deflection methods mainly include mechanical scanning methods, acousto-optic deflection methods, and electro-optic deflection methods. The mechanical scanning method mainly relies on the rotation of a mirror or the oscillation of a microelectromechanical system (MEMS) to achieve beam deflection. Although it has a large deflection angle, due to the involvement of mechanical components, it is limited by inertia, vibration, and mechanical wear, and it is difficult to further improve the scanning speed. The acousto-optic deflector controls the beam direction through the periodic refractive index change caused by ultrasonic waves inside the crystal. Its deflection speed is much higher than that of the mechanical scanning method, but the deflection angle is small, and the deflection angle is related to the wavelength of light, resulting in certain limitations in the application range.

[0003] In contrast, the electro-optic deflector changes the refractive index of the material by applying an external electric field, thereby achieving beam deflection, and has advantages such as no mechanical inertia, high-speed response, and low energy consumption. Electro-optic deflection technology mainly relies on the electro-optic effect, including the linear electro-optic effect (Pockels effect) and the quadratic electro-optic effect (Kerr effect). Electro-optic materials based on the Pockels effect, such as lithium niobate, lithium tantalate, and potassium titanyl phosphate, have a linear relationship between the refractive index change and the external electric field, and have a relatively fast response speed, but the electro-optic coefficient is limited, and the deflection angle is small, making it difficult to meet the requirements of large-angle scanning. For electro-optic materials based on the Kerr effect, the refractive index change has a quadratic relationship with the external electric field. Although theoretically a larger deflection angle can be obtained than the Pockels effect, the Kerr coefficients of most materials are small, and usually a relatively high driving voltage is required to achieve effective beam deflection, and the electro-optic effect saturates as the external voltage increases, resulting in that the maximum deflection angle of most quadratic electro-optic crystal materials can usually only reach the μrad level, and the application scenarios are limited. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a beam deflection method and device based on the quadratic electro-optic effect of cerium-nickel co-doped strontium barium niobate (SBN) crystal. By means of composition regulation and cerium (Ce) doping, the present invention prepares an SBN crystal with a Curie point close to room temperature, and enhances its quadratic electro-optic effect by nickel (Ni) doping. By using the method of electron pre-injection under ohmic contact conditions, a space charge electric field with a gradient distribution is formed inside the SBN crystal, and then the precise control of the crystal refractive index gradient is realized by means of the quadratic electro-optic effect of the cubic phase SBN crystal, so as to realize fast, efficient and large-angle beam deflection. The present invention can be widely applied to the fields of optical communication, lidar, medical imaging, laser processing, etc., providing a new solution for the development of optical deflection technology.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a beam deflection method based on the quadratic electro-optic effect of cerium-nickel co-doped strontium barium niobate crystal, comprising the following steps:

[0007] Step 1, crystal growth: grow strontium barium niobate (SBN, Sr x Ba 1- x Nb 2 O 6 ) crystal by the Czochralski Method, and optimize its electro-optic performance by doping Ce 2 O 3 and Ni 2 O 3 . The Sr component of the SBN crystal is preferably x = 0.75, where the Ce doping concentration is 0.8 - 1.2 mol%, used to regulate the Curie point of the crystal to near room temperature, and the Ni doping concentration is 0.01 - 0.05 mol%, used to increase the dielectric constant and enhance the quadratic electro-optic effect.

[0008] Step 2, optical element preparation: cut, grind and polish the grown SBN crystal to prepare a cuboid optical wafer. Each surface of the wafer corresponds to the (100), (010) and (001) crystal planes, and the light-passing surface and the electrode coating surface need to be polished at the optical level. Subsequently, deposit a metal electrode on the (100) or (010) surface of the crystal by magnetron sputtering or ion sputtering technology to obtain an electro-optic deflection device with ohmic contact characteristics.

[0009] Step 3, Beam deflection: The incident light is incident along the

[001] direction. After passing through the polarizer, it is converted into linearly polarized light with the polarization direction parallel to the direction of the applied electric field and then enters the crystal. Before the crystal is used as an electro-optic deflector, electrons need to be pre-injected into the crystal through an applied voltage. After the electrons enter the crystal, they are trapped by the defect states, thereby forming a gradient-distributed electric field inside the crystal and achieving a controllable gradient distribution of the refractive index. In addition, during the use process, the crystal temperature needs to be controlled within the range of 2 - 5 °C above the Curie point, and the temperature control accuracy reaches ±0.1 °C to maintain the stability of the quadratic electro-optic effect and prevent the electro-optic coefficient from fluctuating with temperature and affecting the beam deflection performance. After applying the deflection voltage on the two crystal surfaces coated with electrodes, the space charge gradient electric field inside the crystal induces a refractive index gradient distribution, and beam deflection can be achieved at the crystal output end.

[0010] Further, in the above step 1, since the SBN crystal is usually grown at high temperature in a growth furnace with a nitrogen atmosphere, due to insufficient oxygen, oxygen vacancy defects are easily formed inside the crystal, resulting in the color center effect of the crystal and thus affecting the transmittance. To improve the material quality, the as-grown crystal usually needs to be annealed at high temperature in oxygen to reduce oxygen vacancy defects. The annealing process parameters are as follows: heating rate 100 - 200 °C / h, annealing temperature 1150 - 1250 °C, constant temperature time 12 - 24 hours, cooling rate 50 - 150 °C / h.

[0011] Further, in the above step 2, the ohmic contact electrode adopts a double-layer metal structure. The inner electrode material is selected from Al, Ti or Ag, and its thickness is 50 - 150 nm, which is used to provide good ohmic contact; the outer electrode material is selected from Au or Pt, and its thickness is 100 - 200 nm, which is used to prevent electrode oxidation and improve long-term stability.

[0012] Further, in the above step 2, after the electrode sputtering is completed, the crystal needs to be rapidly annealed (secondary annealing) to improve the contact characteristics between the metal and the crystal. The specific annealing process is as follows: annealing temperature 300 - 500 °C, constant temperature time 5 - 10 minutes, heating time 5 - 30 seconds, and the annealing atmosphere is selected from nitrogen or argon.

[0013] Further, in the above step 3, the working voltage range for electron pre-injection is 400 - 500 V / mm, and the first electron injection time should be greater than or equal to 2 s to ensure the formation of a uniform and stable space charge distribution inside the crystal. Electron pre-injection is performed on the crystal to form a gradient-distributed space charge electric field inside the crystal, thereby achieving a controllable distribution of the refractive index gradient.

[0014] Further, in the above step 3, to accelerate the electron injection process, ultraviolet laser irradiation can be used to increase the rate and depth of electron injection. The wavelength range of the ultraviolet laser is 266 nm to 405 nm, and the optical power density range is 500 mW to 1000 mW / mm 2 .

[0015] The beneficial effects of the present invention are as follows:

[0016] (1) Electro-optic deflection based on gradient refractive index usually relies on a relatively high quadratic electro-optic coefficient of the crystal to achieve. For SBN crystals, only when the crystal is in the cubic phase above the Curie point will it exhibit a significant quadratic electro-optic effect. However, the Curie temperature of SBN crystals is usually much higher than room temperature. Taking the most commonly used SBN:61 (Sr 0.61 Ba 0.39 Nb 2 O 6 ) as an example, its Curie temperature is as high as 80 °C. In practical applications, to utilize its quadratic electro-optic performance, the working temperature must be maintained above 80 °C, which is obviously extremely inconvenient in many application scenarios and limits its wide application.

[0017] To overcome this problem, the present invention adjusts the Curie temperature of the SBN crystal to near room temperature by optimizing the composition design and doping regulation. First, by adjusting the raw material ratio and increasing the Sr content, the Curie temperature of the SBN crystal is reduced to about 56 °C. Subsequently, Ce 3+ doping further reduces the Curie temperature and finally stabilizes it near room temperature, thus meeting the actual application requirements.

[0018] This SBN crystal with a Curie temperature close to room temperature greatly expands the application range of SBN crystals in the field of electro-optic deflection, improves the practicality and convenience of the device, enables it to work efficiently at room temperature, helps reduce power consumption and system complexity, and enhances the stability and reliability of optical devices.

[0019] (2) SBN crystals exhibit the best quadratic electro-optic performance near the Curie point, and the higher the Curie temperature, the more significant the quadratic electro-optic effect. Therefore, although Ce 3+ doping and composition regulation can effectively adjust the Curie temperature of SBN crystals to near room temperature to meet the requirements of room-temperature operation, this process will lead to a decrease in quadratic electro-optic performance, thus affecting the light deflection efficiency.

[0020] To compensate for the loss of quadratic electro-optic performance caused by Curie temperature regulation, the present invention introduces Ni doping and utilizes the doping effect of Ni to enhance the quadratic electro-optic coefficient of SBN crystals. The measured results show that the SBN crystal after Ni doping compared with the undoped SBN:75 (Sr 0.75 Ba0.25 Nb 2 O 6 ) has a quadratic electro-optic coefficient increased by 50%; compared with the SBN:75 crystal doped only with Ce 3+ , its quadratic electro-optic coefficient is doubled, effectively compensating for the decrease in electro-optic performance caused by the Curie point regulation, so that the crystal can still maintain excellent electro-optic modulation ability at room temperature.

[0021] (3) By the method of electron injection, a gradient-distributed electric field is established inside the crystal, thereby inducing a gradient change in the refractive index and achieving precise control of the beam deflection. Compared with the method of forming a gradient electric field through a specific-shaped electrode design or using the component gradient to regulate the refractive index distribution, the method of constructing a gradient refractive index by electron injection adopted in the present invention is simpler and more efficient, and can significantly improve the deflection ability and response speed of the device.

[0022] For the electro-optic deflection device prepared based on the above method, its maximum deflection angle can reach ±140 mrad (about ±8°), and a larger angle can be tried to be achieved by adjusting the device size, voltage, etc. It far exceeds the deflection ability of the existing electro-optic deflection devices, providing a better solution for fields such as optical scanning, optical communication, and lidar. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is the IV characteristic curve of the wafer before and after annealing in Example 1;

[0025] Figure 2 It is the comparison of the dielectric temperature spectra of the double-doped crystal, the single-doped crystal, and the undoped crystal in Example 1;

[0026] Figure 3 It is the change of the quadratic electro-optic coefficient of the SBN crystal in Example 1 with temperature;

[0027] Figure 4 It is the schematic diagram of the SBN crystal electro-optic deflection system device;

[0028] Figure 5 It is the schematic diagram of the electro-optic deflection principle based on the gradient electric field formed by space charge;

[0029] Figure 6 It is the deflection angle of the SBN crystal in Example 1 under different voltages;

[0030] Figure 7 is the dielectric temperature spectrum of the SBN crystal in Example 2;

[0031] Figure 8 is the dielectric temperature spectrum of the SBN crystal in Example 3. Detailed implementation manners

[0032] 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 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.

[0033] Example 1: Electro-optic deflection of Ce,Ni:SBN75 crystal (Ce: 1 mol%, Ni: 0.02 mol%)

[0034] The crystal was grown by the Czochralski method. The experimental raw materials were SrCO with a purity of 4N 3 , BaCO 3 and Nb 2 O 5 powders. The raw materials were proportioned according to the ratio of SrCO 3 :BaCO 3 :Nb 2 O 5 = 0.764:0.236:1. Ce 2 O 3 and Ni 2 O 3 were doped in the raw materials, with the doping amount of Ce element being 1 mol% and the doping amount of Ni element being 0.02 mol%. The raw materials were mixed in a mixer for 48 h to make the powders fully and evenly mixed. In order to remove the moisture and volatile substances in the raw materials, two pre-sinterings were carried out in a muffle furnace. The first pre-sintering temperature was 900 °C for 36 h. Then, the polycrystalline material obtained from the first pre-sintering was ground into powder in an agate crucible and subjected to the second pre-sintering at a temperature of 1300 °C for 36 h. After that, the powder was placed in an iridium crucible and then grown under a nitrogen atmosphere. The pulling speed was 1 mm / h and the rotation speed was 3 / rpm, and a Ce,Ni co-doped Sr 0.75 Ba 0.25 Nb 2 O 6 crystal was prepared.

[0035] Since the SBN crystal is grown in an iridium crucible, nitrogen gas needs to be introduced during the growth process to prevent the oxidation of iridium, which results in a large number of oxygen vacancy defects in the as-grown raw crystal. Therefore, thermal annealing technology is required to eliminate oxygen vacancy defects and improve the crystal transmittance. At the same time, thermal annealing can also release the internal stress of the crystal and improve the structural uniformity. The annealing is carried out using a NBD-LT1700-60IT vertical tube furnace from Nobady Company, and the annealing process parameters are as follows: heating rate 100 °C / h, annealing temperature 1150 °C, holding time 12 hours, cooling rate 150 °C / h. After annealing, the crystal changes from dark blue to light yellow.

[0036] The annealed SBN crystal is cut and polished according to the crystal orientation to process a cuboid optical wafer with dimensions of 1 mm × 3.2 mm × 4 mm. The surfaces of the wafer correspond to the (100), (010), and (001) crystal planes, and the four surfaces of 1×3.2 and 3.2×4 are polished to the optical grade. On two parallel surfaces of 3.2×4 (corresponding to the (100) plane), a 100-nm-thick Ti electrode is first deposited by magnetron sputtering, and then a 100-nm-thick Au electrode is deposited. To ensure good Ohmic contact between the inner Ti electrode and the crystal, after the electrode sputtering is completed, the crystal needs to be subjected to rapid annealing treatment (secondary annealing). The purpose is to enhance the diffusion and interaction between the metal and the crystal, promote the formation of an alloy phase or a diffusion layer at the interface, reduce the barrier height, and make the metal-crystal contact closer to the ideal Ohmic contact. The specific annealing process is as follows: using a RTP rapid annealing furnace from Nobady Company (model NBD-HR1200-110TI), annealing is carried out by passing nitrogen gas (to prevent the oxidation of the metal electrode during annealing). It is heated from room temperature to 400 °C in 5 s, and after holding for 5 min, it starts to cool down. It is set to cool down to room temperature in 20 s. Since there is no active cooling device in direct contact with the crystal, the actual cooling time is usually slightly longer than the set time. The IV characteristic curves before and after annealing are measured and compared using a Keithley electrometer (as Figure 1 shown). The experimental results show that after the rapid annealing treatment, the IV characteristic curve changes from non-linear ( Figure 1 data of circular symbols in Figure 1 ) to linear ( data of square symbols in

[0037] ), proving that the contact performance of the device is significantly optimized and a good Ohmic contact is formed. Figure 2 Figure 2 The variation law of the dielectric constant of the wafer with temperature is measured using an LCR digital bridge, and the results are shown as the data points of triangular symbols in Figure 2The square symbol data) was compared, and the results showed that doping with Ce adjusted the Curie point of the crystal from 56 °C to around 25 °C at room temperature; the dielectric constant of the SBN75 crystal co-doped with Ce and Ni was increased by more than 1 time compared with the SBN75 crystal doped with Ce alone, and was increased by 50% compared with the undoped SBN75 crystal.

[0038] According to the quadratic electro-optic coefficient s ij and the relative dielectric constant ε r relation:

[0039]

[0040] where g ij is the aurora coefficient, which is only related to the wavelength and is independent of the dielectric constant and temperature. It can be seen from the formula that the quadratic electro-optic coefficient is proportional to the dielectric constant. A larger dielectric constant usually indicates that the crystal has a larger quadratic electro-optic coefficient. We used the Mach-Zehnder system to measure the quadratic electro-optic coefficient of the cubic-phase SBN crystal near the Curie point, and the results are as Figure 3 , and the quadratic electro-optic coefficient of the SBN crystal reaches 10 -14 m 2 / V 2 level, but near the Curie point, the quadratic electro-optic coefficient changes rapidly with temperature. We usually control the crystal temperature within the range of 2 - 5 °C above the Curie point during use.

[0041] Using the SBN optical wafer element prepared in the previous step, an electro-optic deflection system was built, and the structure is as Figure 4 shown. The incident light is incident along the

[001] direction of the crystal, and after passing through the polarizer, it is converted into vertically polarized light and then enters the crystal. Before the crystal is used as an electro-optic deflector, electrons need to be pre-injected into the crystal through an external voltage. After the electrons enter the crystal, they are trapped by the defect states, thus forming a gradient-distributed electric field inside the crystal to achieve a controllable gradient distribution of the refractive index. The injection voltage used is 400 V, and the forward voltage and reverse voltage each act for 3 s to ensure the formation of a uniform space charge distribution. To increase the injection depth and injection speed, the injection process uses 405 nm ultraviolet light irradiation of 1000 mW / mm 2 . In addition, a TEC temperature control device is also required to control the crystal at 3 °C above the Curie point, and the temperature control accuracy is ±0.1 °C. Then, after applying a deflection voltage on the two crystal surfaces plated with electrodes, beam deflection can be achieved at the crystal output end.

[0042] The principle of electro-optic deflection is as Figure 5 , the pre-injected electrons are trapped by the defects inside the crystal after entering the crystal, forming relatively stable space charges. Assuming that the defects inside the crystal are uniformly distributed and are uniformly filled with the injected electrons, according to Gauss's law:

[0043]

[0044] Among them, ρ(z) is the space charge density, and ε is the dielectric constant. The electric field intensity formed by the superposition of the electric field formed by the space charge and the applied electric field can be calculated from the formula:

[0045]

[0046] Among them, the first term is the applied electric field, and the second term is the electric field formed by the space charge. It can be seen that the electric field formed by the space charge is distributed in a gradient.

[0047] Under the action of the gradient electric field and the electro-optic effect, a refractive index with a gradient distribution is formed inside the crystal, causing the light beam to deflect. The deflection angle can be expressed as:

[0048]

[0049] Therefore, under the ideal condition of uniform distribution of space charge, the electro-optic deflection angle of SBN should vary linearly with the applied voltage. Figure 6 For the device we used Figure 3 The measured electro-optic deflection angles of the SBN crystal at different voltages. The results show that at low voltages, the change of the deflection angle with the voltage is approximately linear. When the voltage is relatively high, due to the saturation of the electro-optic effect, the growth rate of the deflection angle slows down. The measured maximum deflection angle is ±140 mrad.

[0050] Example 2: Electro-optic deflection of Ce,Ni:SBN75 crystal (Ce: 1.2 mol%, Ni: 0.05 mol%)

[0051] The operation process of this example is the same as that of Example 1, only some process parameters are adjusted. The following content only describes in detail the parts that are different from Example 1.

[0052] The Czochralski method is adopted and by doping Ce 2 O 3 and Ni 2 O 3 A Ce,Ni co-doped Sr 0.75 Ba 0.25 Nb 2 O 6 crystal is prepared. The content of Ce element in the crystal is 1.2 mol%, and the content of Ni element is 0.05 mol%. The as-grown crystal is annealed to reduce oxygen vacancy defects: the heating rate is 160 °C / h, the annealing temperature is 1200 °C, the isothermal time is 18 hours, and the cooling rate is 100 °C / h.

[0053] The annealed SBN crystal was cut and polished according to the crystal orientation to process a cuboid optical wafer with dimensions of 2 mm × 3 mm × 5 mm. The surfaces of the wafer corresponded to the (100), (010), and (001) crystal planes, and the four surfaces of 2×3 and 3×5 were polished to the optical grade. On two parallel surfaces of 3×5 (corresponding to the (100) plane), a 50-nm-thick Ag electrode was first deposited by magnetron sputtering, and then a 200-nm-thick Pt electrode was deposited. Then, the wafer was subjected to rapid thermal annealing: using an RTP rapid thermal annealing furnace, annealing was carried out in a nitrogen atmosphere. It was heated from room temperature to 500 °C in 30 s, held at a constant temperature for 8 min and then started to cool, and was set to cool to room temperature in 30 s. After RTP rapid thermal annealing, a good ohmic contact was formed between the crystal and the electrode.

[0054] The dielectric temperature spectrum of the wafer was measured using a variable-temperature LCR digital bridge, and the results were as Figure 7 , and its Curie temperature was determined to be 19.4 °C. Electrons were pre-injected into the crystal to form a space charge field with a gradient structure. The injection voltage used was 500 V, and the forward voltage and reverse voltage each acted for 2 s to ensure the formation of a uniform space charge distribution. To increase the injection depth and injection speed, the injection process was irradiated with 365-nm ultraviolet light at 700 mW / mm 2 . Then, the crystal was controlled at 2 °C above the Curie point using a TEC temperature control device, and the temperature control accuracy was ±0.1 °C. After applying a deflection voltage on the two crystal planes plated with electrodes, beam deflection could be achieved at the output end of the crystal. It was actually measured that at a deflection voltage of ±820 V, the maximum deflection angle could reach ±95 mrad.

[0055] Example 3: Electro-optic deflection of Ce,Ni:SBN75 crystal (Ce: 0.8 mol%, Ni: 0.01 mol%)

[0056] The operation process of this example was the same as that of Example 1, and only some process parameters were adjusted. The following content will only be described in detail for the parts that are different from Example 1.

[0057] The Czochralski method was used and Ce 2 O 3 and Ni 2 O 3 were doped to prepare a Ce,Ni co-doped Sr 0.75 Ba 0.25 Nb 2 O 6 crystal. The content of Ce element in the crystal was 0.08 mol%, and the content of Ni element was 0.01 mol%. The as-grown crystal was annealed to reduce oxygen vacancy defects: the heating rate was 200 °C / h, the annealing temperature was 1250 °C, the holding time at a constant temperature was 24 hours, and the cooling rate was 50 °C / h.

[0058] The annealed SBN crystal is cut and ground according to the crystal orientation to process a cuboid optical wafer with dimensions of 1.5 mm × 2.5 mm × 6 mm. The surfaces of the wafer correspond to the (100), (010), and (001) crystal planes, and the four surfaces of 1.5 × 2.5 and 2.5 × 6 are polished to the optical grade. On two parallel surfaces of 2.5 × 6 (corresponding to the (100) plane), a 150-nm-thick Al electrode is first deposited by ion sputtering, and then a 150-nm-thick Au electrode is deposited. Then, the wafer is subjected to rapid annealing treatment: using an RTP rapid annealing furnace, annealing is carried out in an argon atmosphere. It is heated from room temperature to 300 °C in 20 s, kept at a constant temperature for 10 min, and then cooled down, with the cooling time set to 30 s to reach room temperature. After RTP rapid annealing, a good ohmic contact is formed between the crystal and the electrode.

[0059] The dielectric temperature spectrum of the wafer is measured using a variable-temperature LCR digital bridge, and the results are as Figure 8 , and its Curie temperature is determined to be 36.1 °C. Electrons are pre-injected into the crystal to form a space charge field with a gradient structure. The injection voltage used is 440 V, and the forward voltage and reverse voltage each act for 3 s to ensure a uniform space charge distribution. To increase the injection depth and injection speed, the injection process is irradiated with 266-nm ultraviolet light at 500 mW / mm 2 . Then, the crystal is controlled at 5 °C above the Curie point using a TEC temperature control device, with a temperature control accuracy of ±0.1 °C. After applying a deflection voltage on the two crystal surfaces with electrodes, beam deflection can be achieved at the output end of the crystal. It is measured that at a deflection voltage of ±650 V, the maximum deflection angle can reach ±115 mrad.

Claims

1. A beam deflection method based on the secondary electro-optical effect of cerium-nickel doped barium strontium niobate crystal, characterized in that: The method comprises the following steps: (1) Crystal growth: Ce and Ni doped SBN crystals were prepared by the Czochralski method and by doping Ce2O3 and Ni2O3, i.e. Sr x Ba 1-x Nb2O6 crystal, wherein the Ce doping concentration is 0.8-1.2 mol%, and the Ni doping concentration is 0.01-0.05 mol%; (2) Preparation of optical elements: The SBN crystal prepared in step (1) is cut, ground and polished to prepare a rectangular optical wafer, wherein each surface of the wafer corresponds to the (100), (010) and (001) crystal planes, wherein the light-transmitting surface and the electrode coating surface need to be polished to an optical grade, and then, a metal electrode is deposited on the surface of the crystal on the (100) or (010) surface of the crystal by magnetron sputtering or ion sputtering technology to obtain an electro-optical deflection device with ohmic contact characteristics; (3) Beam deflection: The incident light is incident along the [001] direction, and is converted into linearly polarized light with a polarization direction parallel to the direction of the external electric field by a linear polarizer, and then incident on the crystal. Before the crystal is used for electro-optical deflection, electrons need to be pre-injected into the crystal through an external voltage. After a deflection voltage is applied to the two crystal planes plated with electrodes, the beam can be deflected at the crystal output end.

2. The light beam deflection method based on the secondary electro-optical effect of cerium-nickel dual-doped barium strontium niobate crystal according to claim 1 is characterized in that: The SBN crystal in step (1) needs to be subjected to high temperature annealing treatment, and the annealing process parameters are as follows: heating rate 100-200°C / h, annealing temperature 1150-1250°C, constant temperature time 12-24 hours, cooling rate 50-150°C / h.

3. The light beam deflection method based on the secondary electro-optical effect of cerium-nickel dual-doped barium strontium niobate crystal according to claim 1 is characterized in that: The electrode of the SBN crystal in step (2) adopts a double-layer metal structure, wherein the inner electrode material is Al, Ti or Ag, and its thickness is 50 to 150 nm; the outer electrode material is Au or Pt, and its thickness is 100 to 200 nm.

4. The light beam deflection method based on the secondary electro-optical effect of cerium-nickel dual-doped barium strontium niobate crystal according to claim 1 is characterized in that: In step (3), after the electrode sputtering is completed, the crystal needs to be rapidly annealed. The specific annealing process is as follows: annealing temperature 300-500°C, constant temperature time 5-10 minutes, heating time 5-30 seconds, annealing atmosphere is nitrogen or argon.

5. The light beam deflection method based on the secondary electro-optical effect of cerium-nickel dual-doped barium strontium niobate crystal according to claim 1 is characterized in that: The electron pre-injection operating voltage in step (3) is in the range of 400 to 500 V / mm, and the first electron injection time is not less than 2 s.

6. The light beam deflection method based on the secondary electro-optical effect of cerium-nickel dual-doped barium strontium niobate crystal according to claim 1 is characterized in that: In step (3), the operating temperature of the crystal must be maintained within a range of 2 to 5°C above the Curie point, and the temperature control accuracy must be ensured to reach ±0.1°C.

7. The light beam deflection method based on the secondary electro-optical effect of cerium-nickel dual-doped barium strontium niobate crystal according to claim 1 is characterized in that: In step (3), ultraviolet laser irradiation is used during the electron injection process, wherein the ultraviolet laser wavelength range is 266nm to 405nm, and the optical power density range is 500mW to 1000mW / mm 2 .

8. An electro-optical deflection device, characterized in that: The method is prepared by adopting step (1) and step (2) described in any one of claims 1 to 3.

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