Optical magnetic field sensor based on YIG crystal

Abstract

The invention discloses an optical magnetic field sensor based on a YIG crystal, belongs to the technical field of magnetic field measurement, and solves the problem of how to design a YIG crystal optical magnetic field sensor with high response linearity and small measurement waveform distortion. A first optical fiber collimator of the sensor is tightly connected with a first polaroid, the first polaroid is tightly connected with a cylindrical YIG crystal, the cylindrical YIG crystal is tightly connected with a second polaroid, and the second polaroid is tightly connected with a second optical fiber collimator; the cylindrical YIG crystal is sleeved with the cylindrical YIG crystal, the cylindrical YIG crystal and the cylindrical YIG crystal are coaxial, the inner diameter of the cylindrical YIG crystal is equal to the diameter of the cylindrical YIG crystal, and the length of the cylindrical YIG crystal is equal to the length of the cylindrical YIG crystal; the Gaussian diameter of an emergent light beam of the first optical fiber collimator is equal to the diameter of the cylindrical YIG crystal; the response waveform distortion of the sensor is reduced, and the linearity of a response characteristic curve is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic field measurement and relates to an optical magnetic field sensor based on YIG crystal. Background Art

[0002] Magnetic field measurement technology is a basic technology in electrical engineering. Optical magnetic field sensors have the advantages of high insulation strength, anti-electromagnetic interference, and wide measurement bandwidth. They have obvious advantages in magnetic field measurement scenarios where there are strong electric fields, strong electromagnetic interference, and wide-bandwidth signals to be measured.

[0003] YIG (yttrium iron garnet) crystal is a ferrimagnetic magneto-optical crystal with a large Faraday rotation angle and good light transmission performance, and has broad application prospects in the field of optical magnetic field measurement. However, for cylindrical YIG crystals, its magnetization characteristics cause the magneto-optical response curve to show obvious nonlinearity when the crystal aspect ratio is high; and due to the influence of the magnetic domain structure, when the Gaussian diameter of the detection beam in the sensor is significantly smaller than the crystal diameter, the sensor's response waveform will be significantly distorted. Therefore, it is of great significance to design a YIG crystal optical magnetic field sensor with high response linearity and small measurement waveform distortion. Summary of the invention

[0004] The technical solution of the present invention is used to solve the problem of how to design a YIG crystal optical magnetic field sensor with high response linearity and small measurement waveform distortion.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] The present invention provides an optical magnetic field sensor based on a YIG crystal, wherein the output end of a first optical fiber collimator (11) of the sensor is closely connected to one side of a first polarizer (12), the other side of the first polarizer (12) is closely connected to the input end of a cylindrical YIG crystal (13), the output end of the cylindrical YIG crystal (13) is closely connected to one side of a second polarizer (15), the other side of the second polarizer (15) is closely connected to the input end of a second optical fiber collimator (16); The ring-shaped YIG crystal (14) is sleeved on the outside of the cylindrical YIG crystal (13); the ring-shaped cylindrical YIG crystal (14) and the cylindrical YIG crystal (13) are coaxial; the inner diameter of the ring-shaped cylindrical YIG crystal (14) is equal to the diameter of the cylindrical YIG crystal (13); the length of the ring-shaped cylindrical YIG crystal (14) is equal to the length of the cylindrical YIG crystal (13); and the Gaussian diameter of the light beam emitted by the first optical fiber collimator (11) is equal to the diameter of the cylindrical YIG crystal (13).

[0007] Preferably, the included angle between the first polarizer (12) and the second polarizer (15) in the transmission direction is 45°.

[0008] Preferably, the surface of the annular columnar YIG crystal (14) is coated with a light absorbing coating.

[0009] Preferably, the input end of the first fiber collimator (11) is connected to a fiber laser.

[0010] Preferably, the output end of the second optical fiber collimator (16) is connected to a photodetector.

[0011] Preferably, the input end of the first fiber collimator (11) is connected to the fiber laser, and the output end of the second fiber collimator (16) is connected to the photodetector.

[0012] The advantages of the present invention are:

[0013] The present invention can satisfy the requirement that the Gaussian diameter of the light beam is close to the diameter of the cylindrical YIG crystal under a smaller light beam Gaussian diameter, so that the response waveform of the sensor does not show obvious distortion; at the same time, the response characteristic curve of the sensor is regulated by installing an outer ring-shaped YIG crystal, thereby improving the linearity of the response characteristic curve. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a perspective view of the structure of an optical magnetic field sensor based on a YIG crystal according to the first embodiment of the present invention;

[0015] Figure 2 is a structural side perspective view of an optical magnetic field sensor based on a YIG crystal according to a first embodiment of the present invention;

[0016] Figure 3 is a structural side view of an optical magnetic field sensor based on a YIG crystal according to the first embodiment of the present invention;

[0017] Figure 4 is a magneto-optical response characteristic curve diagram of the optical magnetic field sensor based on the YIG crystal according to the first embodiment of the present invention;

[0018] The symbols in the accompanying drawings are explained as follows:

[0019] 11---the first optical fiber collimator, 12---the first polarizer, 13---cylindrical YIG crystal, 14---ring cylindrical

[0020] YIG crystal, 15---the second polarizer, 16---the second optical fiber collimator. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments:

[0023] Embodiment 1

[0024] like Figures 1 to 3 As shown, the optical magnetic field sensor based on YIG crystal in the embodiment of the present invention comprises: a first optical fiber collimator (11), a first polarizer (12), a cylindrical YIG crystal (13), a ring-shaped cylindrical YIG crystal (14), a second polarizer (15), and a second optical fiber collimator (16);

[0025] The input end of the first fiber collimator (11) is connected to the fiber laser via an optical fiber, the output end of the first fiber collimator (11) is closely connected to one side of a first polarizer (12), the other side of the first polarizer (12) is closely connected to the input end of a cylindrical YIG crystal (13), the output end of the cylindrical YIG crystal (13) is closely connected to one side of a second polarizer (15), the other side of the second polarizer (15) is closely connected to the input end of a second fiber collimator (16), and the output end of the second fiber collimator (16) is connected to a photodetector via an optical fiber; The annular cylindrical YIG crystal (14) is sleeved on the outside of the cylindrical YIG crystal (13), the annular cylindrical YIG crystal (14) and the cylindrical YIG crystal (13) are coaxial, the inner diameter of the annular cylindrical YIG crystal (14) is equal to the diameter of the cylindrical YIG crystal (13), and the length of the annular cylindrical YIG crystal (14) is equal to the length of the cylindrical YIG crystal (13); the Gaussian diameter of the light beam emitted by the first optical fiber collimator (11) is equal to the diameter of the cylindrical YIG crystal (13), so that the response waveform of the sensor does not show obvious distortion.

[0026] Preferably, the included angle between the first polarizer (12) and the second polarizer (15) in the transmission direction is 45°.

[0027] The sensor works as follows:

[0028] In this embodiment, the wavelength of the incident light is 1310 nm. After the light beam is emitted through the first optical fiber collimator (11), the light beam emitted from the first optical fiber collimator (11) is approximately parallel light with a Gaussian diameter of 1 mm. The light beam then passes through a first polarizer (12) with a size of 3 mm*3 mm*0.2 mm to form linearly polarized light. The linearly polarized light enters a cylindrical YIG crystal (13) with a diameter of 1 mm and a length of 2.5 mm, and the polarization direction rotation angle of the linearly polarized light caused by the Faraday effect in the cylindrical YIG crystal (13) is proportional to the component of the magnetic field parallel to the light transmission direction. After the linear polarized light is rotated in polarization direction by a cylindrical YIG crystal (13), it is transmitted through a second polarizer (15) having a size of 3 mm*3 mm*0.2 mm and enters a second optical fiber collimator (16); the annular cylindrical YIG crystal (14) has an outer diameter of 5 mm, an inner diameter of 1 mm, a length of 2.5 mm, and a light-absorbing coating is coated on the surface; after the annular cylindrical YIG crystal (14) is sleeved on the outside of the cylindrical YIG crystal (13), the magnetization intensity distribution of the cylindrical YIG crystal (13) and the annular cylindrical YIG crystal (14) is equivalent to that of a cylindrical YIG crystal having a diameter of 5 mm and a length of 2.5 mm.

[0029] The magnetization in the inner cylindrical YIG crystal (13) used in this embodiment is affected by the outer annular cylindrical YIG crystal (14), and the two are equivalent to a low aspect ratio cylindrical YIG crystal, thereby improving the linearity of the magneto-optical response characteristic curve; the equivalent aspect ratio D1 of the cylindrical YIG crystal (13) and the annular cylindrical YIG crystal (14) is: 2.5mm / 5mm=0.5; if a cylindrical YIG crystal with a diameter of 1mm and a length of 2.5mm is directly used, its aspect ratio D2 is: 2.5mm / 1mm=2.5. Obviously, D1 is only 1 / 5 of D2, so a more highly linear response characteristic can be obtained.

[0030] like Figure 4 As shown, it is a magneto-optical response characteristic curve diagram of the optical magnetic field sensor based on the YIG crystal according to an embodiment of the present invention. It can be seen from the figure that the linearity of the sensor response curve is significantly improved after the circular cylindrical YIG crystal (14) is installed.

[0031] In order to improve the linearity of the response characteristic curve of the sensor, it is necessary to reduce the aspect ratio of the YIG crystal; in order to suppress the distortion in the response waveform, it is necessary to ensure that the Gaussian diameter of the light beam is close to the diameter of the cylindrical YIG crystal, but it is very difficult to increase the Gaussian diameter of the light beam; the present invention can ensure that the Gaussian diameter of the light beam is close to the diameter of the cylindrical YIG crystal under a smaller Gaussian diameter of the light beam, so that the response waveform of the sensor does not show obvious distortion; at the same time, the response characteristic curve of the sensor is regulated by installing an outer ring-shaped YIG crystal, thereby improving the linearity of the response curve.

[0032] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical magnetic field sensor based on YIG crystal, characterized in that: The output end of the first optical fiber collimator (11) is closely connected to one side of the first polarizer (12), the other side of the first polarizer (12) is closely connected to the input end of the cylindrical YIG crystal (13), the output end of the cylindrical YIG crystal (13) is closely connected to one side of the second polarizer (15), and the other side of the second polarizer (15) is closely connected to the input end of the second optical fiber collimator (16); the annular cylindrical YIG crystal (14) is sleeved on the outside of the cylindrical YIG crystal (13), the annular cylindrical YIG crystal (14) and the cylindrical YIG crystal (13) are coaxial, the inner diameter of the annular cylindrical YIG crystal (14) is equal to the diameter of the cylindrical YIG crystal (13), and the length of the annular cylindrical YIG crystal (14) is equal to the length of the cylindrical YIG crystal (13); the Gaussian diameter of the light beam emitted by the first optical fiber collimator (11) is equal to the diameter of the cylindrical YIG crystal (13).

2. The optical magnetic field sensor based on YIG crystal according to claim 1, characterized in that: The included angle between the first polarizer (12) and the second polarizer (15) in the vibration transmission direction is 45°.

3. The optical magnetic field sensor based on YIG crystal according to claim 1, characterized in that: The surface of the annular columnar YIG crystal (14) is coated with a light absorbing coating.

4. The optical magnetic field sensor based on YIG crystal according to any one of claims 1 to 3, characterized in that: The input end of the first optical fiber collimator (11) is connected to the optical fiber laser.

5. The optical magnetic field sensor based on YIG crystal according to any one of claims 1 to 3, characterized in that: The output end of the second optical fiber collimator (16) is connected to the photoelectric detector.

6. The optical magnetic field sensor based on YIG crystal according to any one of claims 1 to 3, characterized in that: The input end of the first optical fiber collimator (11) is connected to the optical fiber laser, and the output end of the second optical fiber collimator (16) is connected to the photoelectric detector.

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