A substrate-free technique for growing bismuth-doped rare-earth iron-garnet bulk crystals

Abstract

The present application relates to a kind of Bi-doped rare earth iron garnet body single crystal growth techniques without substrate, comprising the following steps: raw material preparation, melt preparation, melt is cooled to crystal growth temperature, after melt temperature stabilizes, slowly lower the seed crystal rod installed with seed crystal, with melt, seed crystal rotates at a certain speed;During growth, crystal growth is carried out according to the set variable speed cooling curve, and block crystal is obtained after growing for a period of time;Block crystal is pulled out from melt, and slowly cooled to room temperature, and Bi-doped rare earth iron garnet body single crystal is obtained.The present application obtains large-size block single crystal, gets rid of the dependence of existing Faraday optical rotator growth on substrate, and reduces production cost.The present application can obtain Faraday optical rotator which is thinner than existing product thickness at the same wavelength, further reducing the volume.Moreover, multiple surfaces are simultaneously grown, and larger size crystal is obtained.

Description

Technical Field

[0001] This invention relates to the field of crystal growth technology, and more specifically to a substrate-free Bi-doped rare-earth iron garnet single crystal growth technology. Background Technology

[0002] Faraday rotators, also known as rare-earth iron garnet single-crystal materials, are widely used in the manufacture of isolators in the field of optical communication. In recent years, the rapid development of big data computing, artificial intelligence, and 5G communication has led to a surge in demand for Faraday rotators.

[0003] Due to the non-uniform melting characteristics of rare earth iron garnet, it is mainly obtained through liquid phase epitaxy crystal growth. This involves constructing a supersaturated melt and depositing a film of rare earth iron garnet single crystals onto a substrate. However, the high production cost and low production rate of rare earth iron garnet single crystals are increasingly unable to meet the demands of downstream applications.

[0004] On the one hand, according to the technical requirements for growing garnet crystals using liquid phase epitaxy, the effective component mass ratio of the target crystal in the melt generally needs to be less than 10% to maintain stability during the growth process. Furthermore, the growth rate of rare-earth iron garnet single crystals using liquid phase epitaxy is difficult to exceed 0.5 μm / min, limiting the epitaxial growth speed. On the other hand, for rare-earth iron garnet single crystal materials, epitaxy requires the use of calcium-magnesium-zirconium-doped gadolinium gallium garnet (SGGG) as the substrate material. Currently, the mature SGGG substrate size is 4 inches, and its production cost is high, restricting the development of rare-earth iron garnet single crystals to larger radial dimensions. These factors combined make it difficult to grow large-size, high-mass rare-earth iron garnet single crystals using liquid phase epitaxy. For example, CN112267146A mentions in its background section that liquid phase epitaxy can grow thin films but is not suitable for growing large-size bulk single crystals. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention achieves the growth of bulk rare earth iron garnet single crystals by using a substrate-free method and designing a variable-speed cooling curve that matches the crystal growth rate.

[0006] The technical solution of the present invention is as follows: a substrate-free Bi-doped rare-earth iron garnet single crystal growth technology, comprising the following steps:

[0007] S01, Raw material preparation: Weigh out the powders of bismuth oxide, sodium carbonate, boron oxide, silicon oxide, rare earth oxide, potassium carbonate and iron oxide, mix them evenly, and place them in a platinum crucible. The total mass of rare earth oxide and iron oxide accounts for 7.7wt%~14wt% of the total mass of the raw materials.

[0008] S02, Preparation of melt: Heat the crucible containing the raw material to a melting temperature range of 1200-1600℃ and stir thoroughly to completely melt the raw material; keep it at the temperature for at least 12 hours to homogenize the raw material.

[0009] S03, Growth pretreatment: Cool the melt to the initial crystal growth temperature T0, preferably at a cooling rate of 0.5℃ / min; control the presence of a certain temperature gradient inside the melt by setting the temperature; preferably, the temperature gradient range is 0.3~0.8℃ / cm.

[0010] S04, Crystal Growth: After the melt temperature stabilizes, the seed crystal rod with the seed crystal attached is slowly lowered into contact with the melt, and the seed crystal rotates at a certain speed. During the growth process, the seed crystal continues to rotate, and crystal growth is carried out according to the set variable speed cooling curve. After a period of growth, a bulk crystal is obtained. The bulk crystal is pulled out of the melt and slowly cooled to room temperature. The bulk crystal is a Bi-doped rare earth iron garnet single crystal. Preferably, the rotation speed is 20~60 rpm.

[0011] In some preferred embodiments, the variable-speed cooling curve in step S04 satisfies the cubic equation T=T0-At. 3 -Bt 2 -Ct, where T represents the melt temperature, t is the growth time, T0 represents the initial crystal growth temperature, and coefficients A, B, and C are constants; the value range of coefficient A is 0.00122~0.00482, the value range of coefficient B is 0.0155~0.05, and the value range of coefficient C is 0.127~0.27. Preferably, the range of T0 is between 860℃ and 1060℃.

[0012] Furthermore, the preferred variable-speed cooling curve satisfies one of the following four equations: (1) T = 860 - 0.00122t 3 -0.0155t 2 -0.127t;

[0013] (2) T = 957 - 0.00482t 3 -0.05t 2 -0.228t;

[0014] (3) T = 1025 - 0.00287t 3 -0.033t 2 -0.132t;

[0015] (4) T = 1060 - 0.00346t 3 -0.0423t 2 -0.27t.

[0016] In some preferred embodiments, the rare earth oxide includes at least one of terbium oxide, gadolinium oxide, holmium oxide, and ytterbium oxide.

[0017] In some preferred embodiments, the mass ratio of the raw materials is as follows: bismuth oxide 68%–86.5%wt, sodium carbonate 1%–7%wt, boron oxide 0.05%–4.5%wt, silicon oxide 0.05%–2%wt, potassium carbonate 1%–4.5%wt, iron oxide 7.65%–11%wt, and rare earth oxides 0.05%–3%wt.

[0018] In some preferred embodiments, the chemical formula of the obtained bulk crystal is: Tb x Yb y Bi z Fe 5-n Pt n O 12 , where x=1.6, y=0.2~0.3, z=1.1~1.2, and x+y+z=3, n=0~0.4.

[0019] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0020] 1. This invention provides a substrate-free Bi-doped rare-earth iron garnet bulk single crystal growth technique. Crystal growth is performed according to a set variable-rate cooling curve, which matches the crystal growth rate. Furthermore, after cooling, large-sized hexagonal bulk garnet single crystals can be obtained without acid washing to remove flux impurities. Currently, in the growth process of bulk rare-earth iron garnet, the melt is typically cooled at a constant temperature rate, and the temperature at all locations in the melt must be kept consistent; otherwise, the internal stress of the crystal is high, impurities are easily formed, and the growth rate is low. By adjusting an appropriate cooling rate, the substrate-free technique is achieved. <110> and <211> By adjusting the growth rate of the crystal plane system, high-performance rare-earth iron garnet single crystals were obtained.

[0021] 2. This invention eliminates the dependence of existing Faraday rotator growth on substrates and reduces production costs. Furthermore, it allows for the production of Faraday rotators that are thinner than existing products at the same wavelength (commercially available at approximately 310 μm), further reducing volume.

[0022] 3. This invention uses rare-earth iron garnet crystals as seed crystals, eliminating the difference in thermal expansion coefficients between the substrate material and the grown crystal in liquid-phase epitaxy. For rare-earth iron garnet single crystals, liquid-phase epitaxy requires calcium-magnesium-zirconium-doped gadolinium gallium garnet (SGGG) as the substrate material. However, during the epitaxial growth of rare-earth iron garnet wafers, the difference in lattice constant and thermal expansion coefficient between the wafer and SGGG makes crystal growth difficult.

[0023] 4. This invention uses small-sized rare-earth iron garnet crystals as seed crystals, which are relatively easy to obtain. SGGG is mainly obtained through the Czochralski crystal growth technique, which requires an Ir crucible. Furthermore, due to the requirements for lattice constant, the yield of SGGG is low, resulting in its high price, and the epitaxial growth process is not reusable.

[0024] 5. The growth direction of this invention is mainly... <112> or <110> Variable-speed cooling is employed to ensure that the seed crystal grows at the same rate in all exposed directions. Simultaneously, the effective garnet content in the melt can be increased to over 13%, effectively improving crystal growth efficiency. Currently, commercially available rare-earth iron garnet single crystals can only be grown along SGGG surfaces. <111> A film with a thickness of less than 700 μm is grown in the crystal orientation, and in order to maintain the stability of the growth interface, it is generally necessary to control the effective component mass fraction of melt seed garnet to be less than 10%. The yield is low and gradually cannot keep up with market demand. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the crystal growth process of the present invention.

[0026] Figure 2 This is the temperature control curve for crystal growth in Example 1.

[0027] Figure 3 This is the temperature control curve for crystal growth in Example 2.

[0028] Figure 4 This is a photograph of the bulk crystal obtained in Example 2.

[0029] Figure 5 This is the temperature control curve for crystal growth in Example 3.

[0030] Figure 6 This is a photograph of the bulk crystal obtained in Example 3.

[0031] Figure 7 This is the temperature control curve for crystal growth in Example 4.

[0032] Figure 8 This is a range diagram of the variable speed cooling curve of the present invention.

[0033] Labeling explanations: 1. Lifting rod; 2. Platinum seed crystal clamp; 3. Seed crystal; 4. Platinum crucible; 5. Melt. Detailed Implementation

[0034] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0035] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Furthermore, it should be understood that after reading the disclosure of this invention, those skilled in the art can make various modifications or alterations to the present invention, and these equivalent forms also fall within the scope of protection defined by this invention.

[0036] This invention provides a substrate-free Bi-doped rare-earth iron garnet single crystal growth technique, such as... Figure 1 The process described includes the following steps: Prepared oxides, specifically bismuth oxide, sodium carbonate, boron oxide, silicon oxide, rare earth oxides (terbium oxide, gadolinium oxide, holmium oxide, ytterbium oxide, etc.), potassium carbonate, and iron oxide, are placed in a platinum crucible. To improve the crystal growth rate and increase garnet yield, the effective components of garnet (i.e., rare earth oxides and iron oxide) account for 7.7% and 14% of the total melt mass, respectively. The crucible is heated to melt the oxide raw materials at a temperature range of 1200-1600℃, and the materials are thoroughly stirred at high temperature to ensure complete melting. The mixture is then held at this temperature for at least 12 hours to homogenize the materials. The melt is then cooled to the initial crystal growth temperature T0, which varies between approximately 860℃ and 1060℃ depending on the melt composition.

[0037] To prevent spontaneous nucleation from occurring outside the seed crystal location in the melt, a temperature gradient is maintained within the melt (lowest temperature at the liquid surface) through temperature control. Once the temperature stabilizes, a seed crystal rod (with no special requirements for crystal orientation) with the seed crystal mounted on it (a platinum fitting and crystal connection method are not specified) is slowly lowered into contact with the melt. To enhance the movement of the melt on the seed crystal surface and increase the crystal growth rate, the seed crystal can be rotated at a certain speed. Preferably, the rotation speed of the seed crystal is 20-60 revolutions per minute.

[0038] During growth, the melt temperature is not cooled at a constant rate, but rather at a variable rate. The melt is continuously cooled at a variable rate to maintain stable crystal growth, resulting in differentiated cooling rates at different stages. After a set time, growth ends, and the grown crystal is pulled from the melt and slowly cooled to room temperature. This variable-rate cooling allows for better matching of temperature variations. <110> and <211> By adjusting the growth rate of the later-stage crystals in the crystal plane system, high-performance rare-earth iron garnet single crystals were obtained.

[0039] To facilitate the explanation of the variable-speed cooling method of this invention, t will represent the growth time, and T will represent the melt temperature on day t. The variable-speed cooling curve with respect to the melt temperature T satisfies the cubic equation T = T0 - At. 3 -Bt 2 -Ct, where T represents the melt temperature, t is the growth time, T0 represents the initial crystal growth temperature, and coefficients A, B, and C are constants; the value of coefficient A ranges from 0.00122 to 0.00482, the value of coefficient B ranges from 0.0155 to 0.05, and the value of coefficient C ranges from 0.127 to 0.27. Preferably, the range of T0 is between 860℃ and 1060℃. The unit of t is days, meaning that the melt temperature remains constant for at least 24 hours, but the rate of cooling is not constant, but rather a variable rate of cooling.

[0040] Figure 8 The figures below show the variable-speed cooling curves of different embodiments and the range of the variable-speed cooling curves in the Tt region. The inventors have verified through numerous experiments that... Figure 8 The variable-speed cooling curve range within the Tt region shown (i.e.) Figure 8 The area between the blue and black lines conforms to this invention and can yield large-sized, high-performance rare-earth iron garnet single crystals.

[0041] It should be noted that the growth days shown in the examples are just an example and can be adjusted according to the required single crystal size, and may even exceed 30 days.

[0042] Example 1

[0043] The mass ratio of the raw materials is as follows: bismuth oxide 68%~86.5%wt, sodium carbonate 1%~7%wt, boron oxide 0.05%~4.5%wt, silicon oxide 0.05%~2%wt, rare earth oxides 0.05%~3%wt, potassium carbonate 1%~4.5%wt, and iron oxide 7.65%~11%wt.

[0044] In this embodiment, the rare earth oxides are terbium oxide and ytterbium oxide.

[0045] The prepared raw materials, specifically including bismuth oxide, sodium carbonate, boron oxide, silicon oxide, terbium oxide, potassium carbonate, iron oxide, and ytterbium oxide powder, are placed in a platinum crucible. The combined mass of the rare earth oxides (including ytterbium oxide and terbium oxide) and iron oxide accounts for 7.7% of the total raw material mass, and the total melt mass is 14.75 kg. The crucible is heated to 1400℃ to completely melt the oxide raw materials. The melt is stirred using a platinum stirrer to ensure complete homogenization. The melt is cooled to 860℃ at the liquid surface at a rate of 0.5℃ / min-2℃ / min, while controlling the internal temperature gradient of the melt to approximately 0.3~0.8℃ / cm, preferably 0.5℃ / cm. A jig containing a seed crystal (5mm*5mm*0.5mm plate-shaped bismuth-doped rare earth iron garnet single crystal) is slowly lowered into the furnace. After the temperature stabilizes, the seed crystal is submerged in the melt and rotated unidirectionally at 20 rpm / min. After approximately 16 hours, the exposed crystal faces of the platy garnet were... <110> The crystal planes are covered.

[0046] It should be noted that the present invention uses plate-shaped rare earth iron garnet crystals with the same composition as the melt as seed crystals for liquid phase epitaxial growth, rather than GGG or SGGG substrates.

[0047] The melt then... Figure 2 The growth was carried out at a slow cooling rate for 28 days, with the temperature control equation being: T = 860 - 0.00122t 3 -0.0155t 2 -0.127t, where t represents the growth time in days, and T represents the growth temperature on day t. This temperature curve is... Figure 8 The image is represented by black lines. The final result is a blocky garnet single crystal with a hexagonal shape, approximately 36 mm on each side and 20 mm in height.

[0048] The orientation test revealed that all exposed crystal faces of the bulk single crystal were (110) planes. ICP analysis was used to determine the composition of the crystal, and the chemical formula of the grown crystal was: Tb 1.6 Yb 0.2 Bi 1.2 Fe 4.7 Pt 0.3 O 12 The presence of platinum (Pt) in the crystal is due to a reaction between the raw materials and the platinum crucible.

[0049] The crystal was cut along the (111) plane to a wafer with dimensions of 11*11 mm and a thickness of 0.292 μm. An optical coating was applied to the wafer to obtain a Faraday rotator crystal. Tests were performed at a wavelength of 1310 nm, showing an insertion loss of 0.04 dB, a rotation angle of 45.2°, and an isolation of 41 dB. This fully meets the current requirements for Faraday rotators in isolators.

[0050] Example 2

[0051] The raw materials are in the following mass proportions: bismuth oxide 68%–86.5% wt, sodium carbonate 1%–7% wt, boron oxide 0.05%–4.5% wt, silicon oxide 0.05%–2% wt, rare earth oxides 0.05%–3% wt, potassium carbonate 1%–4.5% wt, and iron oxide 7.65%–11% wt. In this embodiment, the rare earth oxides are terbium oxide and ytterbium oxide.

[0052] The prepared raw materials, specifically including bismuth oxide, sodium carbonate, boron oxide, silicon oxide, terbium oxide, potassium carbonate, iron oxide, and ytterbium oxide powder, were placed in a platinum crucible. The combined mass of iron oxide and rare earth oxides accounted for 10.2% of the total raw material mass, and the total melt mass was 14.74 kg. The crucible was heated to 1400℃ to completely melt the oxide raw materials, and the melt was stirred using a platinum stirrer to ensure complete homogenization. The melt was cooled to 957℃ at the liquid surface at a rate of 0.5℃ / min-2℃ / min, while controlling the internal temperature gradient of the melt to approximately 0.3~0.8℃ / cm, preferably 0.5℃ / cm. A jig containing a seed crystal (a 5mm*5mm*0.5mm plate-shaped bismuth-doped rare earth iron garnet single crystal) was slowly lowered into the furnace. After the temperature stabilized, the seed crystal was submerged in the melt and rotated unidirectionally at 20 rpm / min. After approximately 16 hours, the exposed crystal faces of the platy garnet were... <110> The crystal planes are covered.

[0053] The melt then... Figure 3 The growth was carried out at a slow cooling rate for 15 days, with the temperature control equation being: T = 957 - 0.00482t 3 -0.05t 2 -0.228t, where t represents the growth time in days, and T represents the growth temperature on day t. This temperature curve is... Figure 8 The image is represented by a red line. The final result is a massive garnet single crystal with a hexagonal shape, approximately 22 mm on each side and 15 mm in height. Figure 4 The single-crystal image obtained in this embodiment shows that the desired crystal size has been reached in 15 days, and the growth time can be extended to increase the crystal volume.

[0054] The orientation test revealed that all exposed crystal faces of the bulk single crystal were (110) planes. ICP analysis was used to determine the composition of the crystal, and the chemical formula of the grown crystal was: Tb 1.6 Yb 0.2 Bi 1.2 Fe 4.7 Pt 0.3 O 12The crystal was cut along the (111) plane to a size of 11*11mm and a thickness of 0.293um. An optical coating was applied to the crystal to obtain a Faraday rotator. Tests were performed at a wavelength of 1310nm, and the insertion loss was 0.08dB, the rotation angle was 45.2°, and the isolation was 43dB. This fully meets the current requirements for Faraday rotators in isolators.

[0055] Example 3

[0056] The raw materials are in the following mass proportions: bismuth oxide 68%–86.5% wt, sodium carbonate 1%–7% wt, boron oxide 0.05%–4.5% wt, silicon oxide 0.05%–2% wt, rare earth oxides 0.05%–3% wt, potassium carbonate 1%–4.5% wt, and iron oxide 7.65%–11% wt. In this embodiment, the rare earth oxides are terbium oxide and ytterbium oxide.

[0057] The prepared raw materials, specifically bismuth oxide, sodium carbonate, boron oxide, silicon oxide, terbium oxide, potassium carbonate, iron oxide, and ytterbium oxide powders, were placed in a platinum crucible. The iron oxide and rare earth oxides accounted for 12.2% of the total oxide mass, and the total melt mass was 14.75 kg. The crucible was heated to 1400℃ to completely melt the oxide raw materials, and the melt was stirred using a platinum stirrer to ensure complete homogenization. The melt was cooled to 1025℃ at the liquid surface at a rate of 2℃ / min, while maintaining an internal temperature gradient of approximately 0.5℃ / cm. A jig containing a 5mm*5mm*0.5mm platy bismuth-doped rare earth iron garnet single crystal was slowly introduced into the furnace. After the temperature stabilized, the seed crystal was submerged in the melt and rotated unidirectionally at 20 rpm / min. After approximately 16 hours, the exposed crystal faces of the platy garnet were... <110> Covered by crystal planes. The subsequent melt... Figure 5 The growth was carried out at a slow cooling rate for 29 days, with the temperature control equation being: T = 1025 - 0.00287t 3 -0.033t 2 -0.132t. This temperature curve is at... Figure 8 The green lines represent the final result. The final product was a hexagonal garnet single crystal with a side length of approximately 36.6 mm and a height of approximately 22 mm. Figure 6 This is a single-crystal photograph obtained in this embodiment.

[0058] The orientation test revealed that all exposed crystal faces of the bulk single crystal were (110) planes. ICP analysis was used to determine the composition of the crystal, and the chemical formula of the grown crystal was: Tb 1.6 Yb 0.3 Bi 1.1 Fe 4.7 Pt 0.3 O 12The crystal was cut along the (111) plane to a size of 11*11mm and a thickness of 0.304um. An optical coating was applied to the crystal to obtain a Faraday rotator. Tests were performed at a wavelength of 1310nm, and the insertion loss was 0.07dB, the rotation angle was 44.7°, and the isolation was 42dB. This fully meets the current requirements for Faraday rotators in isolators.

[0059] This invention uses rare-earth iron garnet single crystals as seed crystal materials. By adjusting the proportion of garnet in the melt and controlling the orientation of the exposed crystal faces of the seed crystal, the crystal is made to follow the... <110> or <112> Growth is performed along the crystal orientation (when using SGGG as a substrate, it needs to be along the crystal orientation). <111> (Through temperature and rotation speed control, the crystal orientation is adjusted), and finally, a bulk rare earth iron garnet single crystal material is grown.

[0060] Example 4

[0061] The raw materials are in the following mass proportions: bismuth oxide 68%–86.5% wt, sodium carbonate 1%–7% wt, boron oxide 0.05%–4.5% wt, silicon oxide 0.05%–2% wt, rare earth oxides 0.05%–3% wt, potassium carbonate 1%–4.5% wt, and iron oxide 7.65%–11% wt. In this embodiment, the rare earth oxides are terbium oxide and ytterbium oxide.

[0062] The prepared raw materials, specifically including bismuth oxide, sodium carbonate, boron oxide, silicon oxide, terbium oxide, potassium carbonate, iron oxide, and ytterbium oxide powder, are placed in a platinum crucible. The combined mass of the rare earth oxides and iron oxide accounts for 14% of the total raw material mass, and the total melt mass is 14.73 kg. The crucible is heated to 1400℃ to completely melt the oxide raw materials. The melt is stirred using a platinum stirrer to ensure complete homogenization. The melt is cooled to 1060℃ at the liquid surface at a rate of 0.5℃ / min-2℃ / min, while controlling the internal temperature gradient of the melt to approximately 0.3~0.8℃ / cm, preferably 0.5℃ / cm. A jig containing a seed crystal (5mm*5mm*0.5mm plate-shaped bismuth-doped rare earth iron garnet single crystal) is slowly lowered into the furnace. After the temperature stabilizes, the seed crystal is submerged in the melt and rotated unidirectionally at 20 rpm / min. After approximately 16 hours, the exposed crystal faces of the platy garnet were... <110> The crystal planes are covered.

[0063] The melt then... Figure 7 The growth was carried out at a slow cooling rate for 23 days, with the temperature control equation being: T = 1060 - 0.00346t 3 -0.0423t 2 -0.27t, where t represents the growth time in days, and T represents the growth temperature on day t. This temperature curve is... Figure 8The blue lines represent the points. The final result is a blocky garnet single crystal with a hexagonal shape, approximately 41 mm on each side and 24 mm in height.

[0064] The orientation test revealed that all exposed crystal faces of the bulk single crystal were (110) planes. ICP analysis was used to determine the composition of the crystal, and the chemical formula of the grown crystal was: Tb 1.6 Yb 0.2 Bi 1.2 Fe 4.6 Pt 0.4 O 12 The crystal was cut along the (111) plane to a wafer with dimensions of 11*11mm and a thickness of 0.289um. An optical coating was applied to the wafer to obtain a Faraday rotator crystal. Tested at a wavelength of 1310nm, the crystal showed an insertion loss of 0.07dB, a rotation angle of 44.9°, and an isolation of 41dB. This fully meets the current requirements for Faraday rotators in isolators.

[0065] Table 1 Performance parameters of each embodiment

[0066]

[0067] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0068] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for growing a Bi-doped rare earth iron garnet bulk crystal without a substrate, characterized by, Comprising the following steps: S01, raw material preparation: weigh bismuth oxide, rare earth oxide, iron oxide, sodium carbonate, boron oxide, silicon oxide, potassium carbonate powder and mix them evenly, and put them in a platinum crucible; The sum of the mass of the rare earth oxide and the iron oxide accounts for 7.7% to 14% of the total mass of the raw materials; S02, preparation of the melt: heat the crucible containing the raw materials, the melting temperature range is 1200-1600℃, and fully stir to completely melt the raw materials; homogenize the raw materials by maintaining the temperature for at least 12 hours; S03, growth pretreatment: slowly cool the melt to the initial crystal growth temperature T0; control the temperature gradient inside the melt by setting the temperature; S04, crystal growth: after the melt temperature is stabilized, the seed rod with the seed crystal is slowly lowered to contact the melt, and the seed crystal is rotated at a certain speed; during the growth process, the seed crystal is kept rotating, and the crystal growth is carried out according to the variable speed temperature reduction curve, and a blocky crystal is obtained after a period of growth; the blocky crystal is pulled out of the melt and slowly cooled to room temperature; the blocky crystal is a Bi-doped rare earth iron garnet bulk crystal; the variable speed temperature reduction curve satisfies a cubic equation T = T0-At 3 -Bt 2 -Ct, wherein T represents the melt temperature, t is the growth time, T0 represents the initial growth temperature of the crystal, and the coefficients A, B and C are constants.

2. The Bi-doped rare earth iron garnet bulk crystal growth method without substrate according to claim 1, characterized in that, The coefficient A ranges from 0.00122 to 0.00482, the coefficient B ranges from 0.0155 to 0.05, and the coefficient C ranges from 0.127 to 0.

27.

3. The method of claim 1, wherein the Bi-doped rare earth iron garnet single crystal is grown without a substrate. The range of T0 is 860-1060℃.

4. The method of claim 1, wherein the Bi-doped rare earth iron garnet single crystal is grown without a substrate. The variable-speed cooling curve satisfies one of the following conditions: (1) T = 860 - 0.00122t 3 -0.0155t 2 -0.127t; (2) T = 957 - 0.00482t 3 -0.05t 2 -0.228t; (3) T = 1025 - 0.00287t 3 -0.033t 2 -0.132t; (4) T = 1060 - 0.00346t 3 -0.0423t 2 -0.27t.

5. The Bi-doped rare earth iron garnet bulk crystal growth method without substrate according to claim 1, characterized in that, The mass ratio of the raw materials is: bismuth oxide 68%-86.5%wt, iron oxide 7.65%-11%wt, rare earth oxide 0.05%-3%wt, sodium carbonate 1%-7%wt, boron oxide 0.05%-4.5%wt, silicon oxide 0.05%-2%wt, and potassium carbonate 1%-4.5%wt.

6. The Bi-doped rare earth iron garnet bulk crystal growth method without substrate according to claim 1, characterized in that, The rare earth oxide includes at least one of terbium oxide, gadolinium oxide, holmium oxide, and ytterbium oxide.

7. The Bi-doped rare earth iron garnet bulk crystal growth method without substrate according to claim 1, characterized in that, The temperature gradient in step S03 ranges from 0.3 to 0.8℃ / cm; the cooling speed is 0.5-2℃ / min.

8. The method of claim 1, wherein the Bi-doped rare earth iron garnet single crystal is grown without a substrate. The seed crystal rotation speed in step S04 is 20-60rpm.

Images