A low-scandium-doped terbium-gallium-garnet magneto-optical crystal without radial stripes and a preparation method thereof

Abstract

This invention relates to a scandium-terbium-gallium garnet magneto-optical crystal without radial stripes and its preparation method. The Tb3Sc crystal was grown using the Czochralski method. x Ga 5‑x O 12 The magneto-optical crystal (where x = 0.05–0.3) belongs to the cubic crystal system and has the space group Ia–3d. This method utilizes a small amount of Sc... 3+ Partial Ga doping 3+ This helps suppress the formation of spiral dislocation-related defects, enabling the growth of high-quality terbium gallium garnet magneto-optical crystals without radial stripes. Low-concentration Sc 3+ The doping strategy has shown excellent results in addressing the radial stripe defect in TGG crystals and improving their key performance characteristics, providing a practical new approach for the fabrication of core materials for magneto-optical devices. This crystal material is expected to find practical applications in magneto-optical devices such as magneto-optical isolators, magneto-optical circulators, and magneto-optical modulators.

Description

Technical Field

[0001] This invention belongs to the field of magneto-optical materials and crystal growth technology, specifically relating to a low-doped scandium-terbium-gallium garnet magneto-optical crystal without radial stripes and its preparation method. Background Technology

[0002] With the rapid development of high-power solid-state lasers, fiber lasers, and ultrafast laser processing technologies, laser technology is increasingly widely used in industrial fields such as precision manufacturing, semiconductor processing, display panel cutting, new energy battery manufacturing, aerospace, and defense equipment. Especially in high-power, high-beam-quality, and high-stability laser systems, optical devices face higher requirements for thermal stability, resistance to laser damage, and polarization control performance. Magneto-optical materials, as core functional materials for realizing the Faraday rotation effect, are a crucial foundation for fabricating key devices such as optical isolators, magneto-optical switches, and laser feedback suppressors.

[0003] Among magneto-optical materials, magneto-optical glass, as an amorphous magneto-optical material, exhibits high transmittance in the visible-near-infrared band, is isotropic, and is easily fabricated into large-size products. However, the relatively low Verde constant of magneto-optical glass hinders device miniaturization. Furthermore, magneto-optical glass has poor thermal conductivity and a low laser damage threshold, making it unsuitable for high-power laser systems. Currently, the main commercially available crystalline magneto-optical material in the visible-near-infrared band is terbium gallium garnet (TGG) crystal.

[0004] Terbium gallium garnet (Tb3Ga5O) 12 TGG crystal is an excellent magneto-optical crystal, belonging to the cubic crystal system with a space group of Ia-3d and lattice parameters a=b=c=1.235nm, where Tb 3+ Ions occupy dodecahedral sites in the crystal, Ga 3+ Ions occupy octahedral and tetrahedral sites in the crystal, respectively. TGG crystals possess excellent properties such as a large Verdet constant, low optical loss, high thermal conductivity, and high optical damage threshold, and exhibit excellent transmittance in the 400-1500 nm wavelength range (excluding 475-500 nm). Although terbium aluminum garnet (TAG) has a higher Verdet constant than TGG, its non-uniform melting characteristics have prevented the acquisition of practically usable TAG single crystals. Therefore, TGG crystals have become one of the unique and attractive materials for Faraday devices, and are widely used in various Faraday devices such as fiber lasers, Ti:sapphire tunable lasers, ultrafast lasers, and seed-implanted lasers.

[0005] TGG is the most widely used paramagnetic magneto-optical crystal. However, radial stripe defects extending from the crystal center outwards are frequently observed in TGG crystals. These defects cause light scattering and reduce the optical quality of the TGG crystal.

[0006] Regarding the causes of radial stripe defects, existing research suggests they are related to compositional deviations, stress concentrations, and dislocation evolution during the growth process, particularly the scattering of light by the stress field associated with helical dislocations. On the other hand, the high-temperature growth of TGG melt carries the risk of Ga2O3 volatilization, which may cause the melt composition to continuously deviate from the ideal stoichiometric ratio, thereby inducing compositional inhomogeneity and defects.

[0007] Therefore, exploring a preparation method that can effectively suppress or eliminate radial stripe defects and improve crystal optical uniformity and overall performance while maintaining the advantages of the TGG system's pullable growth is key to obtaining higher power level applications for this material. Summary of the Invention

[0008] The purpose of this invention is to provide a low-scandium-terbium-gallium garnet magneto-optical crystal without radial stripes applicable to the visible-near-infrared band, and its preparation method. This magneto-optical crystal possesses excellent optical and magnetic properties, which is beneficial for producing superior magneto-optical performance. Furthermore, this magneto-optical crystal is a uniformly molten compound with a growth temperature of 1400~1500℃, and can be grown using the mid-frequency induction pulling method. This process is simple, has a short cycle time, and enables large-scale, low-cost mass production.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A scandium-terbium-gallium garnet magneto-optical crystal with no radial stripes, the crystal having the chemical formula Tb3Sc x Ga 5- x O 12 Where x = 0.05~0.3; belongs to the cubic crystal system, space group Ia-3d; the crystal does not exhibit radial stripe structure extending outward from the center along the growth direction when observed under strong white light transmission illumination.

[0010] A method for preparing a scandium-terbium-gallium garnet magneto-optical crystal without radial stripes includes the following specific steps: (1) Synthesis of polycrystalline raw materials: according to the synthesis of Tb3Sc x Ga 5-x O 12 (x=0.05~0.3) Accurately weigh Tb4O7, Sc2O3 and Ga2O3 (purity 99.99%) raw materials according to stoichiometric ratio, mix them evenly and compress them into tablets; pre-sinter the tablets at 1400 ℃ for 12 h, cool them and grind them and compress them into tablets again; then sinter them at 1600 ℃ for 24 h, and cool them to room temperature in the furnace to obtain polycrystalline raw materials.

[0011] (2) Single crystal growth: An iridium crucible is used as the container for crystal growth. The synthesized polycrystalline raw material is placed into the container and then placed in a single crystal pulling furnace. Single crystal pulling is carried out in an inert gas atmosphere (such as N2, Ar, etc.). The growth temperature is 1400-1500℃, the growth rate is 0.3-1.5mm / h, and the crystal rotation speed is 3-10r / min. The changes in the crystal growth ring and growth trend are observed through the quartz observation window on the single crystal pulling furnace. The rise and fall of the potential and its rate of change are adjusted by a Eurometer to control the crystal growth morphology.

[0012] (3) Crystal annealing: After the crystal growth is completed, the crystal is lifted and removed from the melt. The crystal height is adjusted so that it is 1-3 mm above the surface of the melt. Then, it is slowly annealed to room temperature at a cooling rate of 5-80℃ / h to obtain cubic Tb3Sc. x Ga 5- x O 12 Magneto-optical crystal.

[0013] Applications: The terbium gallium garnet magneto-optical crystals without radial stripes, after orientation, cutting, polishing and coating, are expected to be used in devices such as magneto-optical isolators, magneto-optical circulators and magneto-optical modulators.

[0014] The beneficial effects of this invention are as follows: This invention can obtain a low-scandium-terbium-gallium garnet magneto-optical crystal with high optical quality and excellent magneto-optical properties. This magneto-optical crystal exhibits good light transmission and magneto-optical properties in the visible-near-infrared region. Tested using a Faraday magneto-optical effect testing system, the magneto-optical crystal Tb3Sc of this invention... x Ga 5-x O 12 The Verdet constant is 40.6 rad / T·m (1064 nm), which is superior to that of commercially available terbium gallium garnet (TGG) crystals. Furthermore, the magneto-optical crystal of this invention is a uniformly fused compound, with a growth temperature of 1400-1500℃, and can be grown using the mid-frequency induction pulling method. This growth process is simple, has a short cycle time, and enables large-scale, low-cost mass production. Attached Figure Description

[0015] Figure 1 For Tb3Sc x Ga 5-x O 12 Crystal photograph; Figure 2 For Tb3Sc x Ga 5-x O 12 XRD pattern of crystalline powder; Figure 3 This is a schematic diagram of the Faraday magneto-optical effect testing system for the present invention. Figure 4 It is Tb3Sc x Ga 5-x O 12 Comparison of optimizations of the crystal (right) and the TGG crystal (left) on radial stripe defects. Detailed Implementation

[0016] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto. Example 1

[0017] Press Tb3Sc 0.1 Ga 4.9 O 12 Accurately weighed Tb4O7, Sc2O3, and Ga2O3 (99.99%) were mixed and ground evenly in a corundum mortar. After pressing into tablets, the mixture was calcined in a muffle furnace at 1400℃ for 12 hours. After cooling, it was ground again and pressed into tablets. Subsequently, it was sintered at 1600℃ for 24 hours and cooled to room temperature in the furnace to obtain polycrystalline raw materials. A φ50×40mm sample was used. 3 An iridium crucible was used as the container for crystal growth. The synthesized polycrystalline powder was loaded into the container and placed in a Czochralski furnace for single-crystal pulling under an inert atmosphere. The growth temperature was 1500℃, the growth rate was 1.5 mm / h, and the crystal rotation speed was 3 r / min. During growth, the changes in the crystal growth ring and trend were observed through a quartz observation window. The potential rise and fall and its rate of change were adjusted using a Eurometer to control the crystal growth morphology. After growth, the crystal was lifted and detached from the melt, and its height was adjusted to be 3 mm above the melt surface. Then, a cooling program was set, and the crystal was slowly annealed to room temperature at a cooling rate of 30~50℃ / h, yielding a Tb3Sc crystal with dimensions of 18 mm × 20 mm (constant diameter portion). 0.1 Ga 4.9 O 12 Crystal ( Figure 1 ).

[0018] X-ray powder diffraction was used to analyze the Tb3Sc prepared in Example 1. 0.1 Ga 4.9 O 12 Phase analysis of crystalline powders Figure 2 The XRD pattern of the grown crystal is shown. The results indicate that the grown crystal belongs to the cubic crystal system, space group Ia-3d, and no other impurity phases are present. Tb3Sc 0.1 Ga 4.9 O 12 After orientation, cutting, and polishing, the crystal is subjected to extinction testing using a Faraday magneto-optical effect testing system. Figure 3The Faraday rotation angle of the crystal was tested, and its Verdet constant was 41.4 rad / T·m (1064 nm), which is higher than that of the currently commercially available terbium gallium garnet (TGG) magneto-optical crystal.

[0019] Comparative Example 1 Undoped terbium gallium garnet magneto-optical crystal Tb3Ga5O 12 (TGG) and its defects and properties: Under the same characterization conditions, undoped TGG crystals showed obvious radial stripe defects under strong transmitted light illumination; while in Example 1, no obvious radial stripes were observed under the same observation conditions. Figure 4 Extinction method in Faraday magneto-optical effect testing system ( Figure 3 The Faraday rotation angle of the crystal was tested, and its Verdet constant was 40.0 rad / T·m (1064 nm).

[0020] For ease of comparison, the relevant sample formulations and performance of the embodiments of the present invention are summarized in Table 1.

[0021] Table 1. Comparison of composition, macroscopic defects, and core properties of different terbium gallium garnets.

[0022] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-doped scandium-terbium-gallium garnet magneto-optical crystal without radial stripes, characterized in that: Its chemical formula is Tb3Sc x Ga 5- x O 12 , where x = 0.05~0.3, belongs to the cubic crystal system, and the space group is Ia-3d.

2. The method for preparing a scandium-terbium-gallium garnet magneto-optical crystal according to claim 1, characterized in that: Single crystal growth was performed using the Czochralski method.

3. The preparation method according to claim 2, characterized in that, Includes the following steps: (1) Polycrystalline raw material synthesis: Tb4O7, Sc2O3 and Ga2O3 raw materials were weighed according to the stoichiometric ratio, mixed evenly and pressed into tablets, pre-sintered at 1400℃ for 12h, cooled and ground and pressed into tablets again; then sintered at 1600℃ for 24h, cooled to room temperature in the furnace to obtain polycrystalline raw materials. (2) Single crystal growth: Polycrystalline raw materials are pulled into single crystals in an inert gas atmosphere, and the growth temperature is controlled at 1400-1500℃, the growth rate is 0.3-1.5mm / h, and the crystal rotation speed is 3-10r / min. (3) Crystal annealing: After the crystal growth is completed, the melt is removed and annealed to room temperature at a rate of 5 to 80 °C / h to obtain the low-doped scandium terbium gallium garnet magneto-optical crystal.

4. The application of the scandium-terbium-gallium garnet magneto-optical crystal according to claim 1, characterized in that: Used to fabricate magneto-optical isolators, magneto-optical circulators, magneto-optical switches, and magneto-optical modulators in the visible-near-infrared region.

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