Device and method for laser crystal growth based on seed crystal reentry method

Abstract

The invention discloses a device and a method for laser crystal growth based on a seed crystal reentry method. The device comprises a furnace body and a control system, the lifting mechanism is arranged in the furnace body and is fixedly connected with the top of the furnace body; the lifting mechanism is connected with a seed crystal support, a rotating mechanism is arranged on the seed crystal support, and a torque detection device is arranged on the rotating mechanism; the seed crystal support is used for loading seed crystals; a crucible is arranged under the seed crystal, a plurality of heating units are arranged around the crucible, a rotating magnetic field generator is also arranged around the crucible, and a cooling system is arranged around the rotating magnetic field generator. According to the device and method for laser crystal growth based on the seed crystal reentry method, the eddy current phenomenon in the laser crystal growth process is effectively restrained by accurately controlling the intensity and frequency of the rotating magnetic field and optimizing magnetic field distribution.

Description

Technical Field

[0001] The present invention relates to the technical field of single crystal growth, and in particular to a device and method for laser crystal growth based on a seed crystal re-entry method. Background Art

[0002] As an important part of modern optics and laser technology, the performance of laser crystals directly affects the output quality and application effect of lasers. The seed crystal re-entry method is a commonly used laser crystal growth technology. By introducing seed crystals into the molten raw materials, the crystals are induced to grow in a specific direction. However, the traditional seed crystal re-entry method has problems such as slow growth rate, uneven crystal quality, and high thermal stress, which limits the large-scale production and application of laser crystals.

[0003] In the prior art, laser crystal growth devices based on the seed crystal re-entry method are prone to produce eddies in the melt. This is because the temperature gradient will cause a buoyancy effect inside the melt, causing the fluid to move in a vertical direction. This movement deflects or interacts with the mainstream direction, thereby inducing eddies, which will not only affect the uniform growth of the crystal, but may also lead to a decrease in crystal quality. In addition, the generation of eddies is also affected by factors such as density differences and external forces. Especially in the growth process of rare earth-doped crystals, the concentration difference of rare earth ions will further aggravate the formation of eddies.

[0004] The formation of eddy currents can cause impurities and bubbles in the melt to be drawn into the crystal, affecting the purity and quality of the crystal. It can also lead to uneven temperature distribution in the melt, affecting the growth rate and shape of the crystal. The greater the temperature gradient, the more obvious the eddy current phenomenon.

[0005] Therefore, it is necessary to improve an apparatus and method for laser crystal growth based on the seed crystal re-entry method in the prior art to solve the above problems. Summary of the invention

[0006] The present invention overcomes the shortcomings of the prior art and provides a device and method for laser crystal growth based on a seed crystal re-entry method, aiming to solve the problem of eddy current phenomenon caused by temperature gradient inside the melt during laser crystal growth in the prior art.

[0007] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a device for laser crystal growth based on seed crystal re-entry method, comprising: a furnace body and a control system, characterized in that;

[0008] A lifting mechanism is arranged in the furnace body, and the lifting mechanism is fixedly connected to the top of the furnace body;

[0009] The lifting mechanism is connected to a seed crystal holder, a rotating mechanism is provided on the seed crystal holder, and a torque detection device is provided on the rotating mechanism; the seed crystal holder is used to load the seed crystal;

[0010] A crucible is arranged directly below the seed crystal, a plurality of heating units are arranged around the crucible, a rotating magnetic field generator is also arranged around the crucible, and a cooling system is arranged around the rotating magnetic field generator.

[0011] In a preferred embodiment of the present invention, the heating unit is divided into a plurality of regions for independent control, and each region can be set with a different heating power and temperature, so as to form a desired temperature gradient in the crucible.

[0012] In a preferred embodiment of the present invention, the number of the heating units arranged in the area requiring a higher temperature is 1-2 more than that of the heating units arranged in the area requiring a lower temperature.

[0013] In a preferred embodiment of the present invention, the magnetic field frequency of the rotating magnetic field generator is 10-20 Hz, and the magnetic field strength is 0.5-1.5T.

[0014] In a preferred embodiment of the present invention, the crucible adopts a conical structure, and the diameter of the top of the crucible is 2-4 mm larger than that of the bottom.

[0015] In a preferred embodiment of the present invention, optionally, the bottom of the crucible has a slight depression.

[0016] In a preferred embodiment of the present invention, the control system is electrically connected to the lifting mechanism, the rotating mechanism, the torque detection device, the heating unit, the rotating magnetic field generator and the cooling system.

[0017] In a preferred embodiment of the present invention, the gas in the furnace body is a protective gas, including argon and helium.

[0018] The present invention provides a method for growing laser crystals based on a seed crystal re-entry method, comprising:

[0019] S1. Loading the seed crystal on the seed crystal holder and placing the melt into the crucible;

[0020] S2, start the heating unit, adjust the temperature in the crucible according to the temperature gradient distribution, so that the melt forms a stable gradient temperature distribution;

[0021] S3, the lifting mechanism controls the seed crystal holder to descend, and when the seed crystal contacts the melt surface, the torque detection device detects the change in the torque of the seed crystal holder to achieve seed crystal positioning;

[0022] S4, starting the rotating magnetic field generator to generate a rotating magnetic field, adjusting the intensity and frequency of the magnetic field, optimizing the convection and heat transfer process in the melt, and inhibiting the formation of eddy currents;

[0023] S5. Under the action of the rotating magnetic field, the control system monitors the crystal growth, temperature gradient distribution and parameters of the rotating magnetic field in real time to ensure the quality and growth rate of the crystal;

[0024] S6. When the crystal growth is completed, the heating unit and the rotating magnetic field generator are stopped, the crystal is lifted out of the melt, and post-processed to obtain a laser crystal.

[0025] In a preferred embodiment of the present invention, the seed crystal positioning method includes:

[0026] During the process of the seed crystal holder loaded with the seed crystal descending, the control system controls the rotating mechanism to drive the seed crystal holder to rotate, and obtains the torque information output by the rotating mechanism to the seed crystal holder in real time;

[0027] The torque output by the driving member is monitored in real time by a torque detection device to determine whether the seed crystal has contacted the liquid surface of the raw material melt;

[0028] The torque change rate can be calculated based on the acquired torque information. When the torque change rate is greater than the preset change rate, it can be determined that the lower surface of the seed crystal has contacted the liquid surface of the raw material melt.

[0029] For any two adjacent time points i and i+1, the torque change ΔT i It can be calculated as ΔT i =T i+1 -T i , where T i and T i+1 is the torque at time point i; the torque change rate R i It can be calculated as the torque change divided by the time interval Where Δt is the time interval;

[0030] Preset a torque change rate threshold R th , if the torque change rate R at a certain time point is found i Greater than the preset threshold R th , it can be judged that the lower surface of the seed crystal has contacted the liquid surface of the raw material melt; the threshold range of the torque change rate is 0.1-10N·m / s

[0031] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0032] (1) The present invention provides a device and method for laser crystal growth based on the seed crystal re-entry method, which effectively suppresses the eddy current phenomenon in the laser crystal growth process by accurately controlling the intensity and frequency of the rotating magnetic field and optimizing the magnetic field distribution. By introducing a rotating magnetic field with a frequency of 10-20Hz and an intensity of 0.5-1.5T, the convection and heat transfer process in the melt is optimized, and the formation of eddy currents is effectively suppressed; combined with the conical crucible design, the top diameter is 2-4mm larger than the bottom, which reduces the accumulation of the melt at the bottom, avoids large liquid flow, and promotes the uniform growth of the crystal; at the same time, the torque detection device is used to monitor the torque change of the seed crystal holder in real time, so as to achieve accurate seed crystal positioning and ensure the stability of crystal growth.

[0033] (2) The present invention combines a rotating magnetic field generator with a heating unit. The stirring effect of the rotating magnetic field in the melt interacts with the temperature gradient formed by the heating unit. The rotating magnetic field stirs the melt through the Lorentz force, reducing the natural convection and eddy currents caused by the temperature gradient, while the heating unit accurately controls the temperature distribution of the melt. The combination of the two achieves fine regulation of the flow state of the melt. It not only suppresses the formation of eddy currents, but also optimizes the temperature distribution of the melt, providing favorable conditions for the uniform growth of crystals. Compared with the prior art, the quality and growth rate of the crystals are further improved.

[0034] (3) The present invention further reduces the eddy current effect of the melt by combining the optimized crucible shape with the rotating magnetic field. The conical crucible or the crucible with a slightly concave bottom design reduces the accumulation of the melt at the bottom and the tendency of eddy currents to form. The rotating magnetic field further suppresses the eddy currents through its stirring effect. The combination of the two makes the flow in the melt more uniform and stable, which not only improves the growth uniformity of the crystal, but also reduces the defects and impurities in the crystal, further improving the optical properties of the crystal.

[0035] (4) The present invention provides a cooling system around the rotating magnetic field generator, which solves the problem of heat generated under long-term high-power operation. The stable magnetic field strength and frequency ensure the effective control of the rotating magnetic field on the melt, promoting the high-quality growth of crystals. This combination ensures the long-term stable operation of the device, improves production efficiency and product quality. Compared with the prior art, the reliability and durability of the system are further enhanced.

[0036] (5) The present invention realizes precise control of seed crystal positioning through the combination of the seed crystal holder and the torque detection device. The seed crystal holder is loaded with the seed crystal and lowered to contact the melt surface. The torque detection device monitors the change of the torque of the seed crystal holder in real time, so as to accurately determine the position of the seed crystal. The correct position of the seed crystal in the melt is ensured, and crystal growth defects caused by improper seed crystal position are avoided. At the same time, the high sensitivity of the torque detection device also improves the accuracy of seed crystal positioning, laying a foundation for high-quality crystal growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 is a structural diagram of a preferred embodiment of the present invention;

[0039] Figure 2 is a method flow chart of a preferred embodiment of the present invention;

[0040] In the figure: 1. lifting mechanism; 2. rotating mechanism; 3. seed crystal holder; 4. torque detection device; 5. control system; 6. melt; 7. crucible; 8. heating unit; 9. rotating magnetic field generator; 10. cooling system; 11. furnace body. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0043] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, "multiple" means two or more.

[0044] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0045] Application Overview:

[0046] In the process of laser crystal growth based on the seed crystal reentry method, the generation of eddy currents is a phenomenon that cannot be ignored. The eddy currents are mainly caused by the temperature gradient inside the melt. This temperature gradient leads to uneven distribution of fluid density, which in turn triggers the buoyancy effect, causing the fluid to form a rotational motion in space. The existence of eddy currents not only affects the flow state of the melt, but may also draw impurities and bubbles into the crystal, leading to instability and defect formation during crystal growth.

[0047] In order to overcome the adverse effects of eddy currents on the growth of laser crystals in the prior art, this application introduces a rotating magnetic field technology. The rotating magnetic field can achieve precise control of the melt temperature gradient by changing the convection and heat transfer process in the melt, thereby reducing the formation of eddy currents. The application of a rotating magnetic field can not only suppress eddy currents, but also optimize the flow state of the melt and improve the growth rate and uniformity of the crystal.

[0048] The present application proposes a device and method for laser crystal growth based on a seed crystal re-entry method, aiming to effectively suppress eddy currents during the growth of laser crystals by precisely controlling the intensity and frequency of a rotating magnetic field and optimizing the magnetic field distribution.

[0049] Exemplary methods:

[0050] like Figure 1 and Figure 2 As shown, a method for laser crystal growth based on seed crystal re-entry method comprises the steps of:

[0051] S1. Loading the seed crystal on the seed crystal holder and placing the melt into the crucible;

[0052] S2, start the heating unit, adjust the temperature in the crucible according to the temperature gradient distribution, so that the melt forms a stable gradient temperature distribution;

[0053] S3, the lifting mechanism controls the seed crystal holder to descend, and when the seed crystal contacts the melt surface, the torque detection device detects the change in the torque of the seed crystal holder to achieve seed crystal positioning;

[0054] S4, starting the rotating magnetic field generator to generate a rotating magnetic field, adjusting the intensity and frequency of the magnetic field, optimizing the convection and heat transfer process in the melt, and inhibiting the formation of eddy currents;

[0055] S5. Under the action of the rotating magnetic field, the control system monitors the crystal growth, temperature gradient distribution and parameters of the rotating magnetic field in real time to ensure the quality and growth rate of the crystal;

[0056] S6. When the crystal growth is completed, the heating unit and the rotating magnetic field generator are stopped, the crystal is lifted out of the melt, and post-processed to obtain a laser crystal.

[0057] The seed crystal holder is made of high-purity, high-temperature-resistant, and corrosion-resistant materials, such as platinum or high-purity ceramics, which can ensure the stability and durability of the seed crystal holder in a high-temperature environment;

[0058] The seed crystal tray is used to load the seed crystal. The seed crystal tray is located below the lifting mechanism and is directly connected to the lifting mechanism. A rotating mechanism is provided on the seed crystal tray. The lifting mechanism is used to drive the seed crystal tray to rise and fall. The rotating mechanism is responsible for driving the seed crystal tray and then rotating the seed crystal to adjust the position of the seed crystal and offset the torque change. The seed crystal tray is located directly above the crucible. When the lifting mechanism is working, the seed crystal tray will descend to make the seed crystal contact the melt surface.

[0059] The lifting mechanism is fixedly connected to the top of the furnace body to ensure its stability.

[0060] The torque detection device is integrated on the seed crystal holder to monitor the torque change of the seed crystal holder in real time;

[0061] The seed crystal is positioned by the above device, and the seed crystal positioning method includes:

[0062] During the process of the seed crystal holder loaded with the seed crystal descending, the control system controls the rotating mechanism to drive the seed crystal holder to rotate, and obtains the torque output by the rotating mechanism to the seed crystal holder in real time;

[0063] Before the seed crystal contacts the liquid surface of the melt, the resistance to the rotation of the seed crystal holder mainly comes from the gas in the furnace. At this time, the torque output by the rotating mechanism is small and basically remains unchanged. The gas in the furnace is a protective gas, including argon and helium. Inert gas has stable chemical properties and is not easy to react with other substances, thus avoiding the oxidation reaction of the melt, which leads to a decrease in the purity of the crystal and affects the optical quality of the crystal.

[0064] When the seed crystal contacts the liquid surface, the raw material melt will provide a strong viscous force to the seed crystal. In order to maintain the uniform rotation of the seed crystal holder, the rotating mechanism needs to output a larger torque to the seed crystal holder to balance the viscous force.

[0065] By monitoring the torque output by the driving member in real time through the torque detection device, a sudden change in the torque can be observed, thereby judging whether the seed crystal has contacted the liquid surface of the raw material melt.

[0066] Furthermore, the torque change rate can be calculated based on the acquired torque information. When the torque change rate is greater than a preset change rate, it can be determined that the lower surface of the seed crystal has contacted the liquid surface of the raw material melt.

[0067] Specifically, for any two adjacent time points i and i+1, the torque change ΔT i It can be calculated as ΔT i =T i+1 -T i , where T i and T i+1 is the torque at time point i; the torque change rate R i It can be calculated as the torque change divided by the time interval Where Δt is the time interval;

[0068] Preset a torque change rate threshold R th , if the torque change rate R at a certain time point is found i Greater than the preset threshold R th , it can be judged that the lower surface of the seed crystal has contacted the liquid surface of the raw material melt;

[0069] Specifically, the threshold range of the torque change rate is 0.1-10N·m / s;

[0070] This method is highly sensitive and can accurately determine the position of the seed crystal relative to the liquid level of the raw material melt, so as to make necessary adjustments to ensure the smooth progress of the crystal growth process.

[0071] In order to achieve gradient temperature, the heating unit is divided into multiple zones for independent control. Different heating power and temperature can be set for each zone, thus forming the required temperature gradient in the crucible.

[0072] The layout of the heating units takes into account the need for temperature gradient, with more heating units arranged in areas where higher temperatures are required and fewer heating units arranged in areas where lower temperatures are required;

[0073] A high-precision temperature controller is used to accurately control the temperature of each heating area. The temperature controller can adjust the heating power according to the temperature gradient curve preset by the control system to ensure that the temperature distribution inside the melt meets the process requirements.

[0074] Since the re-entry of the seed crystal requires setting a temperature gradient, and the temperature gradient will cause convection of the melt, when there is a temperature difference in different areas of the melt, the melt in the high-temperature area will expand and become lighter, while the melt in the low-temperature area will shrink and become heavier. This density difference will cause the melt to flow upward or downward, forming natural convection. As the temperature gradient increases, the convection intensity will also increase, and eventually develop into a vortex.

[0075] Due to the need to prepare laser crystals, taking yellow and green lasers as examples, in order to improve the quality of crystal frequency doubling, rare earth ions need to be heavily doped in the melt; during the growth of rare earth-doped crystals, different components have different melting points and densities, resulting in uneven distribution of components in the melt; the solubility of rare earth ions changes with temperature, forming a concentration gradient in the melt, which causes density differences and thus induces convection;

[0076] The combination of temperature gradient and rare earth ion concentration gradient will cause eddy currents in the melt. The eddy currents make the melt material supply uneven and directional, thus making the crystal morphology characteristics at different positions different. The eddy currents will also cause uneven distribution of solutes in the melt, making the growth rate of the crystal in each direction different during the growth process, thus affecting the final shape of the crystal.

[0077] In order to solve the above problems, a rotating magnetic field is introduced; the rotating magnetic field generator is located around the crucible; the control system is responsible for controlling the power supply to provide a stable current or voltage to the rotating magnetic field generator to generate the required magnetic field strength, and the rotating magnetic field is generated by adjusting the arrangement of the coils and the direction of the current; under long-term high-power operation, the rotating magnetic field generator will generate a lot of heat. In order to avoid damage to the device or performance degradation, a cooling system is set around the rotating magnetic field generator;

[0078] Specifically, in Tb 3+ Taking CYA crystal as an example, the rotating magnetic field can produce a stirring effect in the melt, but at the same time it will not induce strong eddy currents. Compared with traditional mechanical stirring, the rotating magnetic field can stir the melt more evenly; the stirring effect of the rotating magnetic field is achieved through the Lorentz force of the magnetic field on the charged particles in the melt. The charged particles are acted upon by the force in the magnetic field, thereby changing their motion trajectory and achieving the effect of stirring the melt; Tb3+ The distribution of ions in the melt is affected by the rotating magnetic field, which promotes the 3+ Energy transfer between ions and matrix. Specifically, the magnetic field frequency is 10-20 Hz and the intensity is 0.5-1.5T.

[0079] In order to further reduce the eddy effect of the melt and optimize the structure of the crucible, a conical crucible or a crucible with a slightly concave bottom is used to reduce the accumulation of the melt at the bottom and avoid the formation of a large liquid flow; the cone shape can help the melt to better contact the seed crystal and promote the uniform growth of the crystal.

[0080] When the two are combined, the optimized crucible shape reduces the tendency of natural convection and eddy current generation, while the rotating magnetic field further suppresses the formation of eddy currents through its stirring effect. This dual effect makes the flow in the melt more uniform and stable, which is conducive to the uniform growth of crystals.

[0081] Specifically, a crucible with a slight taper has a top diameter 2-4 mm larger than the bottom diameter.

[0082] The design of a slightly concave bottom is not required for all crucibles. For example, when the melt fluidity is good and the crystal growth rate is slow, there is no need to specially design a concave bottom.

[0083] In the actual crystal growth process, the seed crystal needs to be re-entered, and the descending speed is 5-20mm / h; the ascending speed is 10-25mm / h, and the ascending speed is higher than the descending speed; the rotation speed is 5-15r / min.

[0084] Embodiment 1

[0085] A method for growing laser crystals based on a seed crystal re-entry method, comprising the steps of:

[0086] Select high purity Tb 3+ :CYA raw material, put it into a ceramic crucible, the crucible is designed with a slightly concave bottom, and the top diameter is 3mm larger than the bottom;

[0087] The seed crystal is loaded on a seed crystal holder made of platinum, which is equipped with a rotating mechanism and a torque detection device. The seed crystal holder is located below the lifting mechanism and is directly connected to the lifting mechanism.

[0088] Start the heating unit, which is divided into multiple zones and controlled independently according to Tb 3+ : According to the growth requirements of CYA crystal, the temperature gradient curve is preset, and the power of each heating area is precisely adjusted through a high-precision temperature controller;

[0089] The lifting mechanism starts to work, controlling the seed crystal holder to slowly descend at a speed of 5mm / h. During the descent process, the control system controls the rotating mechanism to drive the seed crystal holder to rotate at a speed of 5r / min;

[0090] The torque detection device monitors the torque output by the rotating mechanism in real time. Before the seed crystal contacts the melt surface, the torque remains small and basically unchanged. When the seed crystal contacts the liquid surface, the torque suddenly increases due to the viscosity of the melt. By calculating the torque change rate, when the torque change rate is greater than the preset threshold value of 0.5N·m / s, the control system determines that the seed crystal has contacted the melt surface and stops the seed crystal holder from descending.

[0091] Start the rotating magnetic field generator to generate a rotating magnetic field, and adjust the frequency of the magnetic field to 15 Hz and the intensity to 1 T to optimize the convection and heat transfer process in the melt and inhibit the formation of eddy currents;

[0092] Under the action of the rotating magnetic field, the control system monitors the crystal growth, temperature gradient distribution and parameters of the rotating magnetic field in real time;

[0093] When the crystal growth is completed, the heating unit and the rotating magnetic field generator are stopped; the lifting mechanism raises the seed crystal holder at a speed of 15 mm / h to lift the crystal from the melt; the extracted crystal is cleaned, cut, polished and other post-processing steps to obtain high-quality Tb3+:CYA laser crystal.

[0094] Embodiment 2

[0095] A method for growing laser crystals based on a seed crystal re-entry method, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0096] The frequency of the magnetic field is 10 Hz;

[0097] Embodiment 3

[0098] A method for growing laser crystals based on a seed crystal re-entry method, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0099] The frequency of the magnetic field is 20 Hz;

[0100] Embodiment 4

[0101] A method for growing laser crystals based on a seed crystal re-entry method, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0102] The strength of the magnetic field is 0.5T;

[0103] Embodiment 5

[0104] A method for growing laser crystals based on a seed crystal re-entry method, the same points as those in the second embodiment are not described in detail, and the difference between this embodiment and the second embodiment is that;

[0105] The strength of the magnetic field is 0.5T;

[0106] Embodiment 6

[0107] A method for growing laser crystals based on a seed crystal re-entry method, the same points as those in the third embodiment are not described in detail, and the difference between this embodiment and the third embodiment is that;

[0108] The strength of the magnetic field is 0.5T;

[0109] Embodiment 7

[0110] A method for growing laser crystals based on a seed crystal re-entry method, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0111] The strength of the magnetic field is 1.5T;

[0112] Embodiment 8

[0113] A method for growing laser crystals based on a seed crystal re-entry method, the same points as those in the second embodiment are not described in detail, and the difference between this embodiment and the second embodiment is that;

[0114] The strength of the magnetic field is 1.5T;

[0115] Embodiment 9

[0116] A method for growing laser crystals based on a seed crystal re-entry method, the same points as those in the third embodiment are not described in detail, and the difference between this embodiment and the third embodiment is that;

[0117] The strength of the magnetic field is 1.5T;

[0118] Embodiment 10

[0119] A method for growing laser crystals based on a seed crystal re-entry method, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0120] The top diameter is 2mm larger than the bottom diameter;

[0121] Embodiment 11

[0122] A method for growing laser crystals based on a seed crystal re-entry method, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0123] The top diameter is 4mm larger than the bottom diameter

[0124] Comparative Example 1

[0125] A method for growing laser crystals based on a seed crystal re-entry method, the same points as those in Example 1 are not described in detail, and the difference between this comparative example and Example 1 is that;

[0126] No rotating magnetic field is applied;

[0127] Comparative Example 2

[0128] A method for growing laser crystals based on a seed crystal re-entry method, the similarities with the first and fourth embodiments are not repeated here, and the difference between this comparative example and the first embodiment is that;

[0129] The crucible structure remains unchanged, and the upper and lower diameters are the same;

[0130] Experimental Example 1

[0131] This experimental example is based on Examples 1 to 11, combined with Comparative Examples 1 and 2, to perform optical inspection on the obtained laser crystal, detect light absorption and transmittance, and perform optical evaluation on the prepared crystal;

[0132] Table 1 Optical data

[0133]

[0134]

[0135] In Example 1, a rotating magnetic field with a frequency of 15 Hz and an intensity of 1 T was used. This parameter setting effectively suppressed the formation of eddy currents. The introduction of the rotating magnetic field effectively suppressed the eddy currents and reduced the involvement of impurities and bubbles, thereby improving the optical quality of the crystal. A conical crucible design with a top diameter 3 mm larger than the bottom was adopted to reduce the accumulation of the melt at the bottom, avoid the formation of a large liquid flow, and help reduce the tendency of natural convection and eddy currents. At the same time, the conical design helps the melt to better contact the seed crystal and promotes the uniform growth of the crystal.

[0136] By precisely controlling the intensity and frequency of the rotating magnetic field, combined with an optimized crucible design, the formation of eddy currents can be effectively suppressed and the flow state of the melt can be optimized, thereby significantly improving the growth rate and uniformity of the laser crystal, and ultimately obtaining high-quality laser crystals.

[0137] The above is based on the ideal embodiment of the present invention. Through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A device for laser crystal growth based on a seed crystal re-entry method, comprising: The furnace body and control system are characterized by: A lifting mechanism is arranged in the furnace body, and the lifting mechanism is fixedly connected to the top of the furnace body; The lifting mechanism is connected to a seed crystal holder, a rotating mechanism is provided on the seed crystal holder, and a torque detection device is provided on the rotating mechanism; the seed crystal holder is used to load the seed crystal; A crucible is arranged directly below the seed crystal, a plurality of heating units are arranged around the crucible, a rotating magnetic field generator is also arranged around the crucible, and a cooling system is arranged around the rotating magnetic field generator.

2. The device for laser crystal growth based on the seed crystal re-entry method according to claim 1, characterized in that: The heating unit is divided into a plurality of zones for independent control, and each zone can be set with a different heating power and temperature, thereby forming a desired temperature gradient in the crucible.

3. The device for laser crystal growth based on seed crystal re-entry method according to claim 1, characterized in that: The number of the heating units arranged in the area requiring a higher temperature is 1-2 more than that in the area requiring a lower temperature.

4. The device for laser crystal growth based on seed crystal re-entry method according to claim 1, characterized in that: The magnetic field frequency of the rotating magnetic field generator is 10-20 Hz, and the magnetic field strength is 0.5-1.5T.

5. The device for laser crystal growth based on seed crystal re-entry method according to claim 1, characterized in that: The crucible adopts a conical structure, and the diameter of the top of the crucible is 2-4 mm larger than that of the bottom.

6. The device for laser crystal growth based on seed crystal re-entry method according to claim 1, characterized in that: Optionally, the bottom of the crucible is slightly concave.

7. The device for laser crystal growth based on seed crystal re-entry method according to claim 1, characterized in that: The control system is electrically connected to the lifting mechanism, the rotating mechanism, the torque detection device, the heating unit, the rotating magnetic field generator and the cooling system.

8. The device for laser crystal growth based on seed crystal re-entry method according to claim 1, characterized in that: The gas in the furnace is protective gas, including argon and helium.

9. A method for growing laser crystals based on a seed crystal re-entry method, a device for growing laser crystals based on a seed crystal re-entry method according to any one of claims 1 to 8, characterized in that: S1. Loading the seed crystal on the seed crystal holder and placing the melt into the crucible; S2, start the heating unit, adjust the temperature in the crucible according to the temperature gradient distribution, so that the melt forms a stable gradient temperature distribution; S3, the lifting mechanism controls the seed crystal holder to descend, and when the seed crystal contacts the melt surface, the torque detection device detects the change in the torque of the seed crystal holder to achieve seed crystal positioning; S4, starting the rotating magnetic field generator to generate a rotating magnetic field, adjusting the intensity and frequency of the magnetic field, optimizing the convection and heat transfer process in the melt, and inhibiting the formation of eddy currents; S5. Under the action of the rotating magnetic field, the control system monitors the crystal growth, temperature gradient distribution and parameters of the rotating magnetic field in real time to ensure the quality and growth rate of the crystal; S6. When the crystal growth is completed, the heating unit and the rotating magnetic field generator are stopped, the crystal is lifted out of the melt, and post-processed to obtain a laser crystal.

10. The method for laser crystal growth based on seed crystal re-entry method according to claim 9, characterized in that: Seed crystal positioning methods include: During the process of the seed crystal holder loaded with the seed crystal descending, the control system controls the rotating mechanism to drive the seed crystal holder to rotate, and obtains the torque information output by the rotating mechanism to the seed crystal holder in real time; The torque output by the driving member is monitored in real time by a torque detection device to determine whether the seed crystal has contacted the liquid surface of the raw material melt; The torque change rate can be calculated based on the acquired torque information. When the torque change rate is greater than the preset change rate, it can be determined that the lower surface of the seed crystal has contacted the liquid surface of the raw material melt. For any two adjacent time points i and i+1, the torque change ΔT i It can be calculated as ΔT i =T i+1 -T i , where T i and T i+1 is the torque at time point i; the torque change rate R i It can be calculated as the torque change divided by the time interval Where Δt is the time interval; Preset a torque change rate threshold R th , if the torque change rate R at a certain time point is found i Greater than the preset threshold R th , it can be determined that the lower surface of the seed crystal has contacted the liquid surface of the raw material melt; the threshold range of the torque change rate is 0.1-10N·m / s.

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