Aminomethyl ammonium phosphonate compound, birefringent crystal of aminomethyl ammonium phosphonate compound and preparation method and application of birefringent crystal

Abstract

The invention discloses an aminomethyl ammonium phosphonate compound, a birefringent crystal thereof, and a preparation method and application of the birefringent crystal, and belongs to the technical field of crystal materials. The chemical formula of the aminomethyl ammonium phosphonate compound is NH4PO3CH2NH3, and the structural formula of the aminomethyl ammonium phosphonate compound is shown as a formula 1 in the specification. The chemical formula of the birefringent crystal of the aminomethyl ammonium phosphonate compound is NH4PO3CH2NH3, and the birefringent crystal belongs to an orthorhombic crystal system. According to the birefringent crystal of the large-size aminomethyl ammonium phosphonate compound, the crystal blank is oriented according to crystallographic data of the crystal, the crystal is cut according to the required angle, thickness and section size, and the light passing surface of the crystal is polished, so that the birefringent crystal can be used as a birefringent device; the birefringent crystal of the aminomethyl ammonium phosphonate compound has a birefringent index of 0.048 at 546 nm and an ultraviolet absorption edge shorter than 200 nm, and has the advantages that a light-transmitting wave band reaches a deep ultraviolet region, physical and chemical properties are stable, deliquescence is not easy, processing and storage are easy, and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of crystal materials and relates to an aminomethyl ammonium phosphonate compound, a birefringent crystal thereof, and a preparation method and application thereof. Background Art

[0002] Uniaxial and biaxial crystals have optical anisotropy inside the crystal material, which will produce birefringence, and the angle between the refracted light rays, the propagation direction and the polarization state are closely related to the crystal structure. The birefringence of crystals is not only a special natural phenomenon, but also one of the important optical properties of optoelectronic functional crystal materials. By utilizing the linear optical property of crystal birefringence, the polarization state of modulated light can be achieved. Crystals with excellent birefringence properties are widely used in many fields and high-precision scientific research instruments such as optical isolators, Glan prisms, polarization optical devices, circulators, optoelectronic modulators, and laser polarization technology.

[0003] In order to adapt to the development of laser lithography technology towards deep ultraviolet, not only high requirements are put forward for nonlinear optical crystal materials, but also birefringent crystal materials are required to develop towards deep ultraviolet and large birefringence. Taking the current 193nm laser lithography as an example, the birefringent material that can reach 193nm on the market is MgF2 crystal, but its birefringence is very small 0.012@546nm. Due to its small birefringence, the device made from it will be correspondingly large, and the production cost will increase and the convenience of use will be greatly reduced. Other birefringent materials with larger birefringence cannot reach the deep ultraviolet (less than 200nm). In addition, during the lithography process, the laser undergoes repeated refraction, reflection, transmission and other processes, and the polarization state and propagation direction of the laser will seriously affect the lithography effect. It can be seen that birefringent materials play a very important role in practical applications and are also one of the current key devices.

[0004] Therefore, how to develop an aminomethyl ammonium phosphonate compound, a birefringent crystal of the aminomethyl ammonium phosphonate compound and a preparation method thereof, and use the same in the preparation of an optical isolator, a circulator, a beam shifter, an optical polarizer or an optical modulator are problems that need to be solved urgently by those skilled in the art. Summary of the invention

[0005] In view of this, the present invention provides an aminomethyl ammonium phosphonate compound, a birefringent crystal thereof, and a preparation method and application thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] An aminomethyl ammonium phosphonate compound, the chemical formula of the aminomethyl ammonium phosphonate compound is NH4PO3CH2NH3, and the structural formula is shown in Formula 1:

[0008]

[0009] The present invention also provides a method for preparing the above-mentioned aminomethyl ammonium phosphonate compound, comprising the following steps:

[0010] The aminomethylphosphonic acid ammonium compound is prepared by aqueous solution method:

[0011] The N-containing compound and the P-containing compound are mixed uniformly in a molar ratio of N element to P element of 1:1, and water is added dropwise thereto. The mixture is placed in a water bath, and the temperature is increased to 45-55° C. at a heating rate of 5° C. / min, and the mixture is kept warm for 48-72 hours to obtain the above-mentioned aminomethylphosphonic acid ammonium compound;

[0012] Alternatively, the aminomethyl ammonium phosphonate compound may be prepared by a hydrothermal method:

[0013] The N-containing compound and the P-containing compound are mixed uniformly in a molar ratio of N element to P element of 1:1, and are loaded into a hydrothermal kettle, water is dripped into the kettle, and the hydrothermal kettle is sealed and placed in an oven, and the temperature is increased to 100-120° C. at a heating rate of 5-8° C. / h, and the temperature is kept for 40-60 hours to obtain the above-mentioned aminomethyl ammonium phosphonate compound;

[0014] The above-mentioned N-containing compound is (NH4)2CO3, NH4HCO3, NH4F, NH3·H2O, NH4Cl or NH4NO3; the above-mentioned P-containing compound is H2PO3CH2NH2.

[0015] Furthermore, the aminomethyl ammonium phosphonate compound is prepared by an aqueous solution method, and the ratio of the total mass of the N-containing compound and the P-containing compound to the volume of the water dropped is 1g:(5-15)mL; the aminomethyl ammonium phosphonate compound is prepared by a hydrothermal method, and the ratio of the total mass of the N-containing compound and the P-containing compound to the volume of the water dropped is 1g:(2-3)mL.

[0016] The present invention also provides a birefringent crystal of the above-mentioned aminomethyl ammonium phosphonate compound. The chemical formula of the birefringent crystal of the above-mentioned aminomethyl ammonium phosphonate compound is NH4PO3CH2NH3, belongs to the orthorhombic crystal system, has a space group of Pna21, and a unit cell parameter of α=β=γ=90°, the unit cell volume is

[0017] The present invention also provides a method for preparing a birefringent crystal of the above-mentioned aminomethyl ammonium phosphonate compound, comprising the following steps:

[0018] (1) adding the aminomethyl ammonium phosphonate compound to deionized water, then subjecting the mixture to ultrasonic treatment at 50° C. to allow the mixture to be fully mixed and dissolved, and filtering the mixture with filter paper to obtain a mixed solution;

[0019] (2) placing the mixed solution obtained in step (1) in a container and sealing it, placing it in a static environment, piercing the seal with a number of small holes, and leaving it at room temperature for 12-20 days;

[0020] (3) waiting for the mixed solution in step (2) to grow crystal particles at the bottom of the glass container until the size of the crystal particles no longer changes significantly, thereby obtaining seed crystals;

[0021] (4) repeating step (1) to obtain a mixed solution, suspending the seed crystal obtained in step (3) in the mixed solution, and letting it stand and grow at room temperature for 15-30 days to obtain a birefringent crystal of aminomethyl ammonium phosphonate compound;

[0022] Or, comprising the steps of:

[0023] (a) dissolving the aminomethyl ammonium phosphonate compound in deionized water to obtain an incompletely dissolved mixture, and subjecting the incompletely dissolved mixture to ultrasonic treatment at a temperature of 50° C. to fully mix and dissolve the mixture to obtain a mixed solution;

[0024] (b) transferring the mixed solution obtained in step (a) into a high-pressure reactor, and tightening and sealing the high-pressure reactor;

[0025] (c) placing the autoclave in a thermostatic box, heating the temperature to 100-120° C. at a heating rate of 50° C. / h, keeping the temperature for 2-3 days, and then cooling the temperature to room temperature at a cooling rate of 4-6° C. / day to obtain birefringent crystals of aminomethyl ammonium phosphonate compound.

[0026] Furthermore, in step (1), the ratio of the mass of the aminomethyl ammonium phosphonate compound to the volume of deionized water is (10-15) g: (120-200) mL, and the ultrasonic power is 500 W; in step (a), the ratio of the mass of the aminomethyl ammonium phosphonate compound to the volume of deionized water is (3-4) g: (15-30) mL, and the ultrasonic power is 500 W.

[0027] The present invention also provides an application of the birefringent crystal of the aminomethyl ammonium phosphonate compound in the preparation of an optical isolator, a circulator, a beam displacer, an optical polarizer or an optical modulator.

[0028] Furthermore, in an optical polarizer, the birefringent crystal of the aminomethylammonium phosphonate compound is a polarization beam splitting prism.

[0029] Furthermore, in the polarization beam splitter prism, the birefringent crystal of the aminomethyl ammonium phosphonate compound is a Glan prism, a Wollaston prism or a Rochon prism.

[0030] The beneficial effects of the present invention are:

[0031] (1) The present invention is the first to discover the existence of aminomethyl ammonium phosphonate compounds and to achieve the synthesis and preparation of aminomethyl ammonium phosphonate compounds.

[0032] (2) The preparation method of the aminomethyl ammonium phosphonate birefringent crystal of the present invention is adopted to obtain the birefringent crystal of the aminomethyl ammonium phosphonate compound with a size of millimeters. By extending the growth period of the crystal, the birefringent crystal of the aminomethyl ammonium phosphonate compound with a corresponding large size can be obtained. In the growth of the birefringent crystal of the aminomethyl ammonium phosphonate compound, the crystal is easy to grow and transparent without wrapping, and has the advantages of fast growth speed, low cost, and easy to obtain large-sized crystals.

[0033] (3) The large-sized birefringent crystal of the aminomethyl ammonium phosphonate compound is prepared by the method for preparing the birefringent crystal of the aminomethyl ammonium phosphonate compound of the present invention. The crystal blank is oriented according to the crystallographic data of the crystal, the crystal is cut according to the required angle, thickness and cross-sectional size, and the light-transmitting surface of the crystal is polished. The crystal can be used as a birefringent device. The birefringent crystal of the aminomethyl ammonium phosphonate compound has a birefringence index of 0.048 at 546 nm, an ultraviolet absorption edge shorter than 200 nm, a light transmission band reaching the deep ultraviolet region, stable physical and chemical properties, not easy to deliquesce, and easy to process and store. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The XRD spectrum of the aminomethyl ammonium phosphonate compound powder of the present invention is as follows;

[0035] Figure 2 This is a photo of a birefringent crystal of the aminomethyl ammonium phosphonate compound grown according to the present invention;

[0036] Figure 3 is a structural diagram of a birefringent crystal of the aminomethyl ammonium phosphonate compound of the present invention;

[0037] Figure 4 It is a schematic diagram of the wedge-shaped birefringent crystal polarization beam splitter of the present invention;

[0038] Figure 5 Schematic diagram of the optical isolator of the present invention, a is a diagram showing the incident light passing through, b is a diagram showing the incident light blocking;

[0039] Figure 6 Schematic diagram of the beam displacer of the present invention, a is a crystal processing design diagram, b is a crystal spectrogram;

[0040] Figure 4-6 In the figure, 1 is the incident light, 2 is the o light, 3 is the e light, 4 is the optical axis, 5 is the NH4HPO3CH3 crystal, 6 is the light transmission direction, and 7 is the optical axis plane. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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] Example 1

[0043] The aminomethylphosphonic acid ammonium compound is prepared by aqueous solution method:

[0044] Weigh 1 g of (NH4)2CO3 and H2PO3CH2NH2 in a molar ratio of 1:2 and mix them evenly. Put them into a beaker, drop 15 mL of water into it, place it in a water bath, heat it to 55°C at a heating rate of 5°C / min, and keep it warm for 72 hours to obtain an aminomethylphosphonic acid ammonium compound.

[0045] The reaction equation is as follows: (NH4)2CO3+2H2PO3CH2NH2→2NH4PO3CH2NH3+CO2+H2O.

[0046] Example 2

[0047] The aminomethylphosphonic acid ammonium compound is prepared by aqueous solution method:

[0048] Weigh 1 g of NH4NO3 and H2PO3CH2NH2 in a molar ratio of 1:1 and mix them evenly. Put them into a beaker, drop 5 mL of water into it, place it in a water bath, heat it to 52°C at a heating rate of 5°C / min, and keep it warm for 48 hours to obtain an aminomethylphosphonic acid ammonium compound.

[0049] The reaction equation is as follows: NH4NO3+H2PO3CH2NH2→NH4PO3CH2NH3+HNO3.

[0050] Example 3

[0051] The aminomethylphosphonic acid ammonium compound is prepared by aqueous solution method:

[0052] Weigh 1 g of NH4F and H2PO3CH2NH2 in a molar ratio of 1:1 and mix them evenly. Put them into a beaker, drop 10 mL of water into it, place it in a water bath, heat it to 45°C at a heating rate of 5°C / min, and keep it warm for 56 hours to obtain an aminomethylphosphonic acid ammonium compound.

[0053] The reaction equation is as follows: NH4F+H2PO3CH2NH2→NH4PO3CH2NH3+HF.

[0054] Example 4

[0055] The aminomethylphosphonic acid ammonium compound is prepared by aqueous solution method:

[0056] Weigh 1 g of NH4Cl and H2PO3CH2NH2 in a molar ratio of 1:1 and mix them evenly. Put them into a beaker, drop 5 mL of water into it, place it in a water bath, heat it to 55°C at a heating rate of 5°C / min, and keep it warm for 72 hours to obtain an aminomethylphosphonic acid ammonium compound.

[0057] The reaction equation is as follows: NH4Cl+H2PO3CH2NH2→NH4PO3CH2NH3+HCl.

[0058] Example 5

[0059] The aminomethyl ammonium phosphonate compound was prepared by hydrothermal method:

[0060] Weigh 1 g of NH4HCO3 and H2PO3CH2NH2 in a molar ratio of 1:1 and mix them evenly. Put them into a closed hydrothermal kettle, drop 3 mL of water, place them in an oven, heat them to 120°C at a heating rate of 50°C / h, and keep them warm for 40 hours to obtain an aminomethylphosphonic acid ammonium compound.

[0061] The reaction equation is as follows: NH4HCO3+H2PO3CH2NH2→NH4PO3CH2NH3+CO2+H2O.

[0062] Example 6

[0063] The aminomethyl ammonium phosphonate compound was prepared by hydrothermal method:

[0064] Weigh 1 g of NH3·H2O and H2PO3CH2NH2 in a molar ratio of 1:1 and mix them evenly. Put them into a closed hydrothermal kettle, drop 2 mL of water into it, place it in an oven, heat it to 100°C at a heating rate of 50°C / h, and keep it warm for 60 hours to obtain an aminomethylphosphonic acid ammonium compound.

[0065] The reaction equation is as follows: NH3·H2O+H2PO3CH2NH2→NH4PO3CH2NH3+H2O.

[0066] Example 7

[0067] The method for preparing the birefringent crystal of aminomethyl ammonium phosphonate compound comprises the following steps:

[0068] (a) dissolving 3 g of the aminomethyl ammonium phosphonate compound prepared in Example 1 in 15 mL of deionized water to obtain an incompletely dissolved mixture, and subjecting the incompletely dissolved mixture to ultrasonic treatment at a temperature of 50° C. and an ultrasonic power of 500 W to fully mix and dissolve the mixture to obtain a mixed solution;

[0069] (b) transferring the mixed solution obtained in step (a) into a high-pressure reactor, and tightening and sealing the high-pressure reactor;

[0070] (c) placing the autoclave in a thermostatic box, heating the temperature to 100° C. at a heating rate of 50° C. / h, keeping the temperature for 3 days, and then cooling the temperature to room temperature at a cooling rate of 6° C. / day to obtain a birefringent crystal of aminomethylammonium phosphonate compound with a size of 2 mm×2 mm×1 mm.

[0071] Example 8

[0072] The method for preparing the birefringent crystal of aminomethyl ammonium phosphonate compound comprises the following steps:

[0073] (a) 4 g of the aminomethyl ammonium phosphonate compound prepared in Example 2 was dissolved in 20 mL of deionized water to obtain an incompletely dissolved mixture, and the incompletely dissolved mixture was subjected to ultrasonic treatment at a temperature of 50° C. and an ultrasonic power of 500 W to fully mix and dissolve the mixture to obtain a mixed solution;

[0074] (b) transferring the mixed solution obtained in step (a) into a high-pressure reactor, and tightening and sealing the high-pressure reactor;

[0075] (c) The autoclave was placed in a thermostatic box, heated to 105°C at a heating rate of 50°C / h, kept at that temperature for 3 days, and then cooled to room temperature at a cooling rate of 5°C / day to obtain a birefringent crystal of aminomethylammonium phosphonate compound with a size of 3 mm×2 mm×1 mm.

[0076] Example 9

[0077] The method for preparing the birefringent crystal of aminomethyl ammonium phosphonate compound comprises the following steps:

[0078] (a) 4 g of the aminomethyl ammonium phosphonate compound prepared in Example 3 was dissolved in 30 mL of deionized water to obtain an incompletely dissolved mixture, and the incompletely dissolved mixture was subjected to ultrasonic treatment at a temperature of 50° C. and an ultrasonic power of 500 W to fully mix and dissolve the mixture to obtain a mixed solution;

[0079] (b) transferring the mixed solution obtained in step (a) into a high-pressure reactor, and tightening and sealing the high-pressure reactor;

[0080] (c) The autoclave was placed in a thermostatic box, heated to 102° C. at a heating rate of 50° C. / h, kept at that temperature for 2 days, and then cooled to room temperature at a cooling rate of 5° C. / day to obtain a birefringent crystal of aminomethylammonium phosphonate compound with a size of 3 mm×3 mm×2 mm.

[0081] Example 10

[0082] The method for preparing the birefringent crystal of aminomethyl ammonium phosphonate compound comprises the following steps:

[0083] (1) 10 g of the aminomethyl ammonium phosphonate compound prepared in Example 4 was added to 120 mL of deionized water, and then ultrasonically treated at 50° C. with an ultrasonic power of 500 W to fully mix and dissolve the mixture, and filtered with filter paper to obtain a mixed solution;

[0084] (2) placing the mixed solution obtained in step (1) in a container and sealing it, placing it in a static environment, piercing the seal with a number of small holes, and leaving it at room temperature for 15 days;

[0085] (3) waiting for the mixed solution in step (2) to grow crystal particles at the bottom of the glass container until the size of the crystal particles no longer changes significantly, thereby obtaining seed crystals;

[0086] (4) Repeat step (1) to obtain a mixed solution, suspend the seed crystal obtained in step (3) in the mixed solution, and let it stand and grow at room temperature for 24 days to obtain a birefringent crystal of aminomethyl ammonium phosphonate compound with a size of 8 mm×4 mm×2 mm.

[0087] Embodiment 11

[0088] The method for preparing the birefringent crystal of aminomethyl ammonium phosphonate compound comprises the following steps:

[0089] (1) 15 g of the aminomethyl ammonium phosphonate compound prepared in Example 5 was added to 200 mL of deionized water, and then ultrasonic treatment was performed at 50° C. with an ultrasonic power of 500 W to fully mix and dissolve the mixture, and then filtered with filter paper to obtain a mixed solution;

[0090] (2) placing the mixed solution obtained in step (1) in a container and sealing it, placing it in a static environment, piercing the seal with a number of small holes, and leaving it at room temperature for 18 days;

[0091] (3) waiting for the mixed solution in step (2) to grow crystal particles at the bottom of the glass container until the size of the crystal particles no longer changes significantly, thereby obtaining seed crystals;

[0092] (4) Repeat step (1) to obtain a mixed solution, suspend the seed crystal obtained in step (3) in the mixed solution, and let it stand and grow at room temperature for 27 days to obtain a birefringent crystal of aminomethyl ammonium phosphonate compound with a size of 12 mm×5 mm×3 mm.

[0093] Example 12

[0094] The method for preparing the birefringent crystal of aminomethyl ammonium phosphonate compound comprises the following steps:

[0095] (1) 10 g of the aminomethyl ammonium phosphonate compound prepared in Example 6 was added to 200 mL of deionized water, and then ultrasonic treatment was performed at 50° C. with an ultrasonic power of 500 W to fully mix and dissolve the mixture, and then filtered with filter paper to obtain a mixed solution;

[0096] (2) placing the mixed solution obtained in step (1) in a container and sealing it, placing it in a static environment, piercing the seal with a number of small holes, and leaving it at room temperature for 20 days;

[0097] (3) waiting for the mixed solution in step (2) to grow crystal particles at the bottom of the glass container until the size of the crystal particles no longer changes significantly, thereby obtaining seed crystals;

[0098] (4) Repeat step (1) to obtain a mixed solution, suspend the seed crystal obtained in step (3) in the mixed solution, and let it stand and grow at room temperature for 30 days to obtain a birefringent crystal of aminomethyl ammonium phosphonate compound with a size of 22 mm×8 mm×4 mm.

[0099] Embodiment 13

[0100] The birefringent crystals of the aminomethyl ammonium phosphonate compound obtained in Examples 7-12 were used to prepare wedge-shaped birefringent crystal polarization beam splitters (such as Figure 4 As shown), a wedge-shaped birefringent crystal with its optical axis oriented as Figure 4 At room temperature, a beam of natural light can be split into two linearly polarized beams after passing through the crystal. The greater the birefringence, the farther the two beams can be separated, making it easier to separate the beams. The birefringence of aminomethyl ammonium phosphonate at 546nm is 0.048, which is larger than the birefringence of 0.012 of the current commercial MgF2 crystal, and the effect will be more excellent.

[0101] Embodiment 14

[0102] The birefringent crystals of the aminomethyl ammonium phosphonate compounds obtained in Examples 7-12 were used to prepare optical isolators. A Faraday light rotator that rotates the polarization plane of an incident light beam by 45° was placed between a pair of birefringent crystal deflectors that were placed at 45° to each other. This formed an optical isolator that only allowed the forward propagating light beam to pass through the system, while blocking the reverse propagating light beam. Figure 5 a means the incident light beam can pass through, Figure 5 b means the reflected light is blocked.

[0103] Embodiment 15

[0104] The birefringent crystals of the aminomethyl ammonium phosphonate compounds obtained in Examples 7-12 were used to prepare beam displacers. A birefringent crystal was processed so that its optical axis and the edge formed a certain angle (such as Figure 6a), when natural light is incident vertically, it can be divided into two linearly polarized lights with vibration directions perpendicular to each other (as shown in Figure 6 b). They are o light and e light respectively. The greater the birefringence, the farther the two beams can be separated, making it easier to separate the beams.

[0105] The disclosed embodiments are described to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An aminomethylphosphonic acid ammonium compound, characterized in that The chemical formula of the aminomethyl ammonium phosphonate compound is NH4PO3CH2NH3, and the structural formula is shown in Formula 1:

2. A method for preparing the aminomethylphosphonic acid ammonium compound according to claim 1, characterized in that: The steps include: The aminomethylphosphonic acid ammonium compound is prepared by aqueous solution method: The N-containing compound and the P-containing compound are mixed uniformly in a molar ratio of N element to P element of 1:1, and the mixture is added into a beaker, and water is added thereto. The mixture is placed in a water bath, and the temperature is increased to 45-55° C. at a heating rate of 5° C. / min, and the mixture is kept warm for 48-72 hours to obtain the aminomethyl ammonium phosphonate compound; Alternatively, the aminomethyl ammonium phosphonate compound may be prepared by a hydrothermal method: The N-containing compound and the P-containing compound are mixed uniformly in a molar ratio of N element to P element of 1:1, and are loaded into a hydrothermal kettle, water is dripped into the kettle, and the hydrothermal kettle is sealed and placed in an oven, and the temperature is increased to 100-120° C. at a heating rate of 5-8° C. / h, and the temperature is kept for 40-60 hours to obtain the aminomethyl ammonium phosphonate compound; The N-containing compound is (NH4)2CO3, NH4HCO3, NH4F, NH3·H2O, NH4Cl or NH4NO3; the P-containing compound is H2PO3CH2NH2.

3. The method for preparing the aminomethyl ammonium phosphonate compound according to claim 2, wherein: The aminomethyl ammonium phosphonate compound is prepared by an aqueous solution method, and the ratio of the total mass of the N-containing compound and the P-containing compound to the volume of the water dropped is 1g:(5-15)mL; the aminomethyl ammonium phosphonate compound is prepared by a hydrothermal method, and the ratio of the total mass of the N-containing compound and the P-containing compound to the volume of the water dropped is 1g:(1-3)mL.

4. A birefringent crystal of the aminomethyl ammonium phosphonate compound according to claim 1, characterized in that: The chemical formula of the birefringent crystal of the aminomethyl ammonium phosphonate compound is NH4PO3CH2NH3, which belongs to the orthorhombic crystal system, has a space group of Pna21, and a unit cell parameter of α=β=γ=90°, the unit cell volume is 5. A method for preparing a birefringent crystal of the aminomethyl ammonium phosphonate compound according to claim 4, characterized in that: The steps include: (1) adding the aminomethyl ammonium phosphonate compound of claim 1 to deionized water, then subjecting the mixture to ultrasonic treatment at 50° C. to thorough mixing and dissolution, and filtering with filter paper to obtain a mixed solution; (2) placing the mixed solution obtained in step (1) in a container and sealing it, placing it in a static environment, piercing the seal with a number of small holes, and leaving it at room temperature for 12-20 days; (3) waiting for the mixed solution in step (2) to grow crystal particles at the bottom of the glass container until the size of the crystal particles no longer changes significantly, thereby obtaining seed crystals; (4) repeating step (1) to obtain a mixed solution, suspending the seed crystal obtained in step (3) in the mixed solution, and letting it stand and grow at room temperature for 15-30 days to obtain a birefringent crystal of aminomethyl ammonium phosphonate compound; Or, comprising the steps of: (a) dissolving the aminomethyl ammonium phosphonate compound according to claim 1 in deionized water to obtain an incompletely dissolved mixture, and subjecting the incompletely dissolved mixture to ultrasonic treatment at a temperature of 50° C. to fully mix and dissolve the mixture to obtain a mixed solution; (b) transferring the mixed solution obtained in step (a) into a high-pressure reactor, and tightening and sealing the high-pressure reactor; (c) placing the autoclave in a thermostatic box, heating the temperature to 100-120° C. at a heating rate of 50° C. / h, keeping the temperature for 2-3 days, and then cooling the temperature to room temperature at a cooling rate of 4-6° C. / day to obtain birefringent crystals of aminomethyl ammonium phosphonate compound.

6. The method for preparing a birefringent crystal of an aminomethyl ammonium phosphonate compound according to claim 5, characterized in that: In step (1), the ratio of the mass of the aminomethyl ammonium phosphonate compound to the volume of deionized water is (10-15) g: (120-200) mL, and the ultrasonic power is 500 W; in step (a), the ratio of the mass of the aminomethyl ammonium phosphonate compound to the volume of deionized water is (3-4) g: (15-30) mL, and the ultrasonic power is 500 W.

7. Use of the birefringent crystal of the aminomethylammonium phosphonate compound according to claim 4 in the preparation of an optical isolator, a circulator, a beam displacer, an optical polarizer or an optical modulator.

8. Use of the birefringent crystal of the aminomethyl ammonium phosphonate compound according to claim 7 in the preparation of an optical isolator, a circulator, a beam displacer, an optical polarizer or an optical modulator, characterized in that: In an optical polarizer, the birefringent crystal of the aminomethylammonium phosphonate compound is a polarization beam splitter prism.

9. Use of the birefringent crystal of the aminomethyl ammonium phosphonate compound according to claim 8 in the preparation of an optical isolator, a circulator, a beam displacer, an optical polarizer or an optical modulator, characterized in that: In the polarization beam splitter prism, the birefringent crystal of the aminomethyl ammonium phosphonate compound is a Glan prism, a Wollaston prism or a Rochon prism.

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