A Faraday rotatable plate and its preparation method

Abstract

This invention discloses a Faraday rotatable film and its preparation method, relating to the field of optical materials technology. The method includes the following steps: heating a mixture of multiple elemental oxides to a preset temperature to melt the oxides into a molten liquid; cooling the molten liquid to a predetermined temperature to make it supersaturated; completely immersing a substrate in the supersaturated molten liquid at a preset angle to a horizontal plane; rotating the substrate to generate a Bi garnet film; and removing the substrate. This invention maintains the substrate at a 45° angle to the molten liquid surface, ensuring complete immersion. During rotation, the molten liquid becomes more uniform, allowing qualified Bi garnet films to grow on both sides of the substrate, thus improving film growth efficiency and reducing substrate consumption. Furthermore, the addition of multiple elemental oxides optimizes the lattice constant and temperature coefficient of Bi garnet, solving the problem of film cracking.

Description

Technical Field

[0001] This invention relates to the field of optical materials technology, and in particular to a Faraday rotator plate and its preparation method. Background Technology

[0002] Faraday rotators are crucial components in the fabrication of passive optical communication devices such as optical isolators and optical circulators. Optical isolators are primarily used in 5G communication systems, including communication between base stations and switching centers, data centers, communication backbone networks, and lidar for autonomous driving.

[0003] An optical isolator is a two-port device that allows optical signals to travel from one port to the other, while attenuating the signal traveling from the second port back to the first. Therefore, an optical isolator can be added after a light source to prevent reflected light from entering the source and maintain its stability. Each laser source in lidar or 10Gb / s high-speed optical communication requires an optical isolator.

[0004] An optical circulator is a non-reciprocal device with multiple inputs and outputs that allows optical signals to be transmitted only along a predetermined port sequence. For example, light can travel from port 1 to port 2, and from port 2 to port 3, while other paths are blocked. Optical circulators are used in applications requiring fiber optic multiplexing, such as OADM and sensing.

[0005] To achieve non-reciprocity of light in optical isolators and optical circulators, Faraday rotators are required; one isolator is needed, while four are needed for the optical circulator. This is due to the presence of yttrium iron garnet (YIG(Y3Fe5O3)). 12 Single crystals exhibit low light absorption and high non-reciprocal magneto-optical rotation in the near-infrared band, making them ideal for fabricating Faraday rotation sheets. Bi ions doped into YIG, as well as bismuth garnet containing rare earth ions, exhibit a large Faraday rotation coefficient and low light absorption coefficient in the near-infrared region. The rotation coefficient in this region is an order of magnitude larger than that of pure YIG, and it can achieve self-biased magnetization, meaning that after the magneto-optical film is magnetized, it can maintain its magnetization state even when the external magnetic field is removed. Therefore, this bismuth garnet becomes an ideal material for fabricating Faraday rotation sheets.

[0006] Currently, Faraday rotatable wafers are generally grown using top-immersion liquid phase epitaxy. The main equipment is a liquid phase epitaxy furnace. Various metal oxides are mixed and placed in a platinum crucible, heated to approximately 1000°C, where the oxides melt into a high-temperature molten liquid. This molten liquid is then cooled to become a supersaturated molten liquid, and then... Figure 2 As shown, a garnet substrate is mounted on a rotating rod, and then... Figure 3As shown, the substrate is lowered to the surface of the supersaturated melt by rotating the rod and the substrate is rotated. Bi garnet film begins to grow on the lower surface of the substrate. When the required thickness is reached, the rotating rod is raised, the substrate with Bi garnet grown is removed, the substrate is polished off, and the remaining part is the required Faraday rotatable sheet.

[0007] However, since the substrate is placed horizontally, if the entire substrate is immersed in the molten liquid, there will be significant differences in concentration and temperature between the molten liquid near the upper and lower surfaces of the substrate. The resulting film growth on the upper and lower surfaces will be inconsistent, and the stress generated will cause the film to crack, thus reducing the yield rate of Faraday rotation sheets. Therefore, only one Faraday rotation sheet can be grown on the surface of the molten liquid, which halves the efficiency and substrate utilization rate. Summary of the Invention

[0008] The purpose of this invention is to provide a Faraday rotatable sheet and its preparation method. The preparation method of the Faraday rotatable sheet provided by this invention reduces the concentration and temperature differences of the attachments on the upper and lower surfaces of the substrate and the stress of the thin film grown on the upper and lower surfaces of the substrate, avoiding the problem of thin film cracking caused by excessive stress, and effectively improving the production efficiency and yield of Faraday rotatable sheets.

[0009] To achieve the above objectives, the present invention provides the following solution:

[0010] A method for preparing a Faraday rotatable plate includes the following steps:

[0011] The oxide mixture is heated to a first temperature and held at that temperature to obtain an oxide melt.

[0012] The oxide melt is cooled to a second temperature to obtain a supersaturated melt.

[0013] The substrate is immersed in the supersaturated melt; the plane of the substrate forms a 45° angle with the surface of the supersaturated melt.

[0014] Rotating the substrate generates a Bi garnet film;

[0015] Remove the substrate to obtain a Faraday rotatable plate.

[0016] Preferably, the oxide mixture includes: Tb2O3, Gd2O3, B2O3, Fe2O3, PbO, Bi2O3 and Al2O3.

[0017] Preferably, the mass ratio of Tb2O3, Gd2O3, B2O3, Fe2O3, PbO, Bi2O3 and Al2O3 is 1:(1.078~1.096):(7.456~7.476):(25.809~25.841):(212.571~212.771):(146.076~146.216):(0.796~0.806).

[0018] Preferably, the substrate is (CaGd)3(ZrMgGa)5O 12 .

[0019] Preferably, the first temperature is 1099℃~1101℃, and the heat preservation time is 34min~36min.

[0020] Preferably, the cooling rate is 99–101 °C / hr, and the second temperature is 849 °C–851 °C.

[0021] Preferably, the substrate rotates at a speed of 10 rpm, and the rotation time of the substrate is the same as the growth time of the Bi garnet film.

[0022] Preferably, the method for removing the substrate is as follows: cut the substrate in half lengthwise and then grind it off.

[0023] The present invention also provides a Faraday rotation plate prepared by the above preparation method, wherein the composition of the Faraday rotation plate is Bi. 1.13 Gd 1.14 Tb 0.70 Pb 0.03 Fe 4.95 Pt 0.01 Al 0.04 O 12 .

[0024] Preferably, the rotation angle of the Faraday rotator is 45°, the insertion loss is 0.05dB, and the Faraday rotation coefficient is 0.1115 / um.

[0025] According to specific embodiments provided by the present invention, the following technical effects are disclosed:

[0026] This invention provides a Faraday rotatable sheet and its preparation method. The method involves immersing the substrate completely in the molten liquid at a 45° angle, reducing the concentration and temperature differences in the molten liquid near the upper and lower surfaces of the substrate. During rotation, the molten liquid becomes more uniform, allowing qualified Bi garnet films to grow on both sides of the substrate, thus improving film growth efficiency and reducing substrate consumption. Furthermore, the addition of various elemental oxides optimizes the lattice constant and temperature coefficient of Bi garnet, reducing stress in the film and solving the problem of film cracking. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart illustrating a method for improving the yield and efficiency of manufacturing Faraday rotator plates, as provided in an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the structure of a device for fabricating a Faraday rotator in the prior art.

[0030] Figure 3 This is a schematic diagram of the fabrication of a Faraday rotator in the prior art.

[0031] Figure 4 This is a schematic diagram of the apparatus for manufacturing a Faraday rotator plate provided in an embodiment of the present invention.

[0032] Figure 5 This is a schematic diagram illustrating the fabrication of the Faraday rotator plate provided in an embodiment of the present invention.

[0033] ①-Substrate, ②-High-temperature molten metal, ③-Rotating rod Detailed Implementation

[0034] This invention provides a method for preparing a Faraday rotatable plate, comprising the following steps:

[0035] S1: Heat the oxide mixture to a first temperature and hold it thereto obtain an oxide solution;

[0036] S2: Cool the oxide solution to a second temperature to obtain a supersaturated solution;

[0037] S3: Immerse the substrate in the supersaturated solution; the plane of the substrate forms a 45° angle with the surface of the supersaturated solution;

[0038] S4: Rotate the substrate to generate a Bi garnet film;

[0039] S5: Remove the substrate to obtain a Faraday rotatable plate.

[0040] The present invention heats an oxide mixture to a first temperature and holds it thereon to obtain an oxide solution.

[0041] In this invention, the oxide mixture comprises Tb₂O₃, Gd₂O₃, B₂O₃, Fe₂O₃, PbO, Bi₂O₃, and Al₂O₃; the mass ratio of Tb₂O₃, Gd₂O₃, B₂O₃, Fe₂O₃, PbO, Bi₂O₃, and Al₂O₃ is 1:(1.078~1.096):(7.456~7.476):(25.809~25.841):(212.571~212.771):(146.07) The preferred ratio is 1: (1.082–1.092): (7.461–7.471): (25.819–25.831): (212.621–212.721): (146.116–146.176): (0.798–0.804), and the most preferred ratio is 1: 1.087: 7.466: 25.825: 212.671: 146.146: 0.801. This invention optimizes the lattice constant and temperature coefficient of Bi garnet by adding various elemental oxides, reducing the stress generated in the film and solving the problem of film cracking.

[0042] In this invention, the first temperature is preferably 1099℃~1101℃, more preferably 1100℃; the heat preservation time is preferably 34min~36min, more preferably 35min.

[0043] In this invention, it is preferable to stir the solution after the heat preservation is completed. The stirring time is preferably 14-16 minutes, more preferably 15 minutes. This invention makes the solution more homogeneous through stirring.

[0044] The oxide melt is obtained, and the present invention cools the oxide melt to a second temperature to obtain a supersaturated melt.

[0045] In this invention, the cooling rate is preferably 99–101 °C / hr, more preferably 100 °C / hr, and the second temperature is preferably 849 °C–851 °C, more preferably 850 °C. This invention cools the oxide melt to make it a supersaturated melt.

[0046] After obtaining the supersaturated melt, the present invention immerses the substrate in the supersaturated melt.

[0047] In this invention, the substrate plane forms a 45° angle with the supersaturated melt surface; the substrate is preferably Gd3(ScGa)5O. 12 Sm3(ScGa)5O 12 La3(ScGa)5O 12 Or (CaGd)3(ZrMgGa)5O 12 More preferably, it is (CaGd)3(ZrMgGa)5O12 In this invention, the substrate is preferably preheated in a preheating zone before being immersed in the saturated melt. The preheating temperature is preferably 800-1000°C, more preferably 880-920°C, and the preheating time is preferably 5-30 min, more preferably 10-20 min, and most preferably 15 min.

[0048] This invention immerses the substrate completely in the molten liquid at a 45° angle, reducing the concentration and temperature differences in the molten liquid near the upper and lower surfaces of the substrate. During rotation, the molten liquid becomes more uniform, allowing qualified Bi garnet films to be grown on both sides of the substrate, thus improving film growth efficiency and reducing substrate consumption.

[0049] In this invention, the substrate is immersed in the supersaturated melt, and then the substrate is rotated to generate a Bi garnet film.

[0050] In this invention, the substrate rotation rate is preferably 1–100 rpm, more preferably 5–20 rpm, and most preferably 10 rpm; the substrate rotation time is preferably 30–60 h, more preferably 40–50 h. The substrate rotation time in this invention is the same as the growth time of the Bi garnet film.

[0051] After obtaining a Bi garnet film, the present invention removes the substrate to obtain a Faraday rotatable sheet.

[0052] In this invention, the preferred method for removing the substrate is to cut the substrate in half and grind it off.

[0053] The present invention obtains two Bi garnet sheets after removing the substrate, and grinds a single Bi garnet sheet until its Faraday rotation angle is 45°.

[0054] Preferably, the method for removing the substrate is to cut the substrate in half from the middle and grind off the substrate.

[0055] The present invention also provides a Faraday rotation plate prepared by the above preparation method, wherein the composition of the Faraday rotation plate is Bi. 1.05～1.21 Gd 1.07～1.21 Tb 0.66～0.74 Pb 0.03 Fe 4.85～5.05 Pt 0.01 Al 0.03～0.05 O 12 The optimal choice is: Bi 1.13 Gd 1.1 4Tb 0.70 Pb 0.03 Fe 4.95 Pt 0.01 Al 0.04 O 12 .

[0056] Preferably, the rotation angle of the Faraday rotator is 45°, the insertion loss is 0.05dB, and the Faraday rotation coefficient is 0.115° / µm.

[0057] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0058] The purpose of this invention is to provide a method that can improve the yield and efficiency of manufacturing Faraday rotatable wafers, and to solve the problem in the prior art that the difference in concentration and temperature of the melt near the upper and lower surfaces of the substrate caused by the horizontal immersion of the substrate into the melt, resulting in inconsistent film growth on the upper and lower surfaces, and the stress generated by this causes the film to crack, thus reducing the yield and efficiency of manufacturing Faraday rotatable wafers.

[0059] Based on the above analysis of the prior art, the embodiments of the present invention provide the following technical solutions:

[0060] Example 1:

[0061] 1. Ingredients:

[0062] The following oxides were weighed using an analytical balance: 5.643g Tb2O3, 6.134g Gd2O3, 42.131g B2O3, 145.73g Fe2O3, 1200.1g PbO, 824.7g Bi2O3, and 4.520g Al2O3.

[0063] 2. Loading:

[0064] The weighed oxides are poured into the platinum crucible in order of increasing quantity from largest to smallest.

[0065] 3. Feeding:

[0066] Place the platinum crucible containing oxides into the liquid phase epitaxial furnace.

[0067] 4. Heating:

[0068] Start the liquid phase epitaxial furnace heating program, heat the platinum crucible, and hold at 1100℃ for 35 minutes to melt the oxide mixture into a molten liquid.

[0069] 5. Stir:

[0070] Lower the rotating rod with the stirring clamp and stir the melt for 15 minutes to make it more uniform. After stirring, raise the rotating rod and remove the stirring clamp.

[0071] 6. Cooling down:

[0072] The temperature is lowered to 850°C at a rate of 100°C / hr, at which point a stable supersaturated melt is formed in the crucible.

[0073] 7. Mounting the substrate:

[0074] like Figure 4 Place a 3-inch (CaGd)3(ZrMgGa)5O12 substrate under the rotating rod, making the substrate 45° with the horizontal plane, and lower the rotating rod to preheat in the preheating zone for 15 minutes.

[0075] 8. Growth:

[0076] like Figure 5 The rotating rod is lowered further to fully immerse the substrate in the molten metal, and the substrate is rotated. The Bi garnet film begins to grow, and after 30 hours, the film growth is complete. The rotating rod is then raised, and the substrate with grown Bi garnet is removed after 30 minutes in the preheating zone.

[0077] 9. Grinding:

[0078] The substrate was cut in half using wire cutting, and the substrate was then ground away to obtain two 3-inch Bi garnet Faraday rotation slices. Their thickness was measured to be 513 μm. The individual Bi garnet slices were then ground until their Faraday rotation angle reached 45°.

[0079] 10. Measurement:

[0080] Using X-ray scanning electron microscopy, the composition of Bi garnet was determined to be Bi. 1.13 Gd 1.14 Tb 0.70 Pb 0.03 Fe 4.95 Pt 0.01 Al 0.0 4O 12 .

[0081] Using an optical measurement system, the insertion loss was measured to be 0.05 dB and the Faraday rotation coefficient to be 0.115° / μm. This basically meets the requirements for fabricating an optical isolator.

[0082] Existing methods for fabricating Faraday rotatable sheets can only grow one layer on the surface of the molten metal, halving both efficiency and substrate utilization. This invention allows for the growth of Faraday rotatable sheets on both sides of the substrate, doubling efficiency and halving substrate utilization, thus reducing the cost of fabricating Faraday rotatable sheets.

[0083] This invention selects multiple element oxides to add, optimizes the lattice constant and temperature coefficient of Bi garnet, solves the problem of thin film cracking, and improves the yield rate of Faraday rotation sheet fabrication.

[0084] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0085] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method of producing a Faraday rotator, characterized by, Includes the following steps: The oxide mixture is heated to a first temperature and held at that temperature to obtain an oxide solution. The oxide solution is cooled to a second temperature to obtain a supersaturated solution; The substrate is immersed in the supersaturated solution; The plane of the substrate forms a 45° angle with the surface of the supersaturated solution. Rotating the substrate generates a Bi garnet film; Remove the substrate to obtain a Faraday rotatable sheet; The oxide mixture includes: Tb2O3, Gd2O3, B2O3, Fe2O3, PbO, Bi2O3 and AI2O3; The mass ratio of Tb₂O₃, Gd₂O₃, B₂O₃, Fe₂O₃, PbO, Bi₂O₃, and Al₂O₃ is 1: (1.078~1.096): (7.456~7.476): (25.809~25.841): (212.571~212.771): (146.076~146.216): (0.796~0.806). The substrate is Gd3(ScGa)5O 12 Sm3(ScGa)5O 12 La3(ScGa)5O 12 Or (CaGd)3(ZrMgGa)5O 12 ; The first temperature is 1099℃~1101℃, and the heat preservation time is 34min~36min; The cooling rate is 99~101℃ / hr, and the second temperature is 849℃~851℃; The substrate rotates at a speed of 10 rpm, and the rotation time of the substrate is the same as the growth time of the Bi garnet film. The method for removing the substrate is as follows: cut the substrate in half from the middle and grind off the substrate. The Faraday rotator has a rotation angle of 45°, an insertion loss of 0.05dB, and a Faraday rotation coefficient of 0.115 / µm.

2. A Faraday rotator plate produced by the production method according to claim 1, characterized in that The Faraday rotator has a composition of Bi 1.05~1.21 Gd 1.07~1.21 Tb 0.66~0.74 Pb 0.03 Fe 4.85~5.05 Pt 0.01 A1 0.03~0.05 O 12 .

Images