A non-Hermitian singular point optical microcavity magnetic field sensor

Abstract

The present invention discloses a non-Hermitian singular point optical microcavity magnetic field sensor. The output end of a wide-spectrum light source is connected to the input end of a magnetic field sensitive unit after passing through a mode spot converter and a one-way isolator in sequence, and the output end of the magnetic field sensitive unit is connected to a micro-spectrometer; the magnetic field sensitive unit includes an input and output waveguide, two identical "8"-shaped waveguide microcavities and a magnetostrictive material layer, and two "8"-shaped waveguide microcavities are coupled and arranged on the same side of the input and output waveguides. The "8"-shaped waveguide microcavity includes a cross-shaped waveguide in the middle and two open ring waveguides. The cross-shaped waveguide is formed by two straight waveguides arranged vertically and orthogonally at their respective midpoints. The two straight waveguides are respectively connected to the two ends of the two open ring waveguides, and a magnetostrictive material layer is arranged under an "8"-shaped waveguide microcavity. The present invention constructs a second-order non-Hermitian system, which takes advantage of the high sensitivity of the non-Hermitian system singular point detection and has the characteristics of small size and easy packaging and integration.

Description

Technical Field

[0001] The invention relates to a magnetic field sensor in the field of integrated optics and magnetic field detection, and in particular to a non-Hermitian singular point optical microcavity magnetic field sensor. Background Art

[0002] Magnetic field sensors are devices that can convert various magnetic fields and their changing quantities into intuitive signal outputs. Magnetic fields are closely related to many aspects of nature and human social life. The magnetic field generated by artificial permanent magnets can be used as a carrier of many kinds of information. Therefore, the tasks of detecting, collecting, storing, converting, and monitoring magnetic fields and the various information contained therein fall on magnetic field sensors. Magnetic field sensors have become an indispensable basic component in information technology and information industry in the information society. At present, people have developed various magnetic field sensors based on various physical, chemical, and biological effects, and have been widely used in various aspects of scientific research, production, and social life, taking on the task of information detection.

[0003] At present, the representative magnetic field detection systems mainly include optical pump magnetometer, fluxgate magnetometer, superconducting quantum interferometer magnetometer and optical fiber magnetic field sensor. Compared with magnetic measurement methods based on other principles, optical magnetic measurement has broad prospects due to its good reliability, compact structure, small size, stability and immunity to electromagnetic interference, but it still has the problem of insufficient accuracy and insufficient sensitivity.

[0004] In recent years, with the in-depth research in the field of micro-nano optics, the research on non-Hermitian optical systems has begun to enter people's field of vision. Unlike traditional Hermitian optical systems, non-Hermitian systems are systems that have energy exchange or gain and loss with the outside world, and their physical quantities can be described by non-Hermitian operators. The essential difference between non-Hermitian systems and Hermitian systems is that non-Hermitian systems have singular points (i.e., exceptional points, hereinafter referred to as singular points). Singular points are degenerate points of non-Hermitian systems. At this point, the real and imaginary parts of the eigenvalues ​​of the system are equal at the same time, the eigenvalues ​​and eigenstates are degenerate at the same time, and the eigenstates can no longer constitute a complete basis vector. There are often abnormal optical phenomena such as phase mutation, energy level crossing, and repulsion near singular points. Therefore, they have important applications in many fields such as unidirectional transmission, loss-induced transparency, and ultra-sensitive sensing. Ultra-sensitive optical sensing based on singular points is currently a research hotspot in the field of non-Hermitian optics. It has different degrees of application in particle detection, temperature sensing, refractive index sensing, and rotation speed measurement. In addition, with the development of micro-nano processing technology, researchers have the ability to build non-Hermitian optical systems on a chip. It has become possible to apply non-Hermitian optical systems in the field of magnetic field detection while maintaining the inherent advantages of optical methods in measuring magnetism and further improving sensitivity. Summary of the invention

[0005] In order to solve the problems in the background technology, the present invention proposes an optical microcavity magnetic field sensor based on non-Hermitian singular points with small size, high precision and easy packaging and integration for non-Hermitian optical systems.

[0006] The magnetic field sensor of the present invention uses a double "8"-shaped waveguide microcavity to construct a non-Hermitian optical system. In the initial state, the coupling coefficient between the two microcavities is adjusted to be at the singular point of the non-Hermitian system. A magnetostrictive material is arranged under the silicon dioxide buffer layer of one of the "8"-shaped waveguide microcavities. When the system is in a magnetic field, the magnetostrictive material is longitudinally expanded by the magnetic field, causing a change in the coupling coefficient between the two microcavities, and causing a change in the output spectrum. By detecting the output spectrum, the external magnetic field information is obtained. The present invention uses the characteristic that the singular point of the non-Hermitian system is sensitive to external perturbations, and further improves the detection sensitivity of the magnetic measurement method.

[0007] The technical solution adopted by the present invention is as follows:

[0008] The present invention comprises a wide-spectrum light source, a pattern spot converter, a unidirectional isolator, a magnetic field sensitive unit and a micro-spectrometer in a packaging shell; the output end of the wide-spectrum light source is connected to the input end of the magnetic field sensitive unit after passing through the pattern spot converter and the unidirectional isolator in sequence, and the output end of the magnetic field sensitive unit is connected to the micro-spectrometer; the wide-spectrum light source, the pattern spot converter, the unidirectional isolator and the micro-spectrometer are all arranged on a lithium niobate thin film layer, a part of the magnetic field sensitive unit is formed by etching the lithium niobate thin film layer, and another part of the magnetic field sensitive unit is arranged under the lithium niobate thin film layer.

[0009] The magnetic field sensitive unit is mainly composed of an input and output waveguide, two identical "8"-shaped waveguide microcavities and a magnetostrictive material layer. The two ends of the input and output waveguide are respectively connected to a one-way isolator and a micro-spectrometer. Two "8"-shaped waveguide microcavities are arranged on the same side of the input and output waveguide. The long axis directions of the two "8"-shaped waveguide microcavities coincide with each other and are located in the same straight line direction perpendicular to the input and output waveguide directions. The two "8"-shaped waveguide microcavities and the "8"-shaped waveguide microcavity close to the input and output waveguide and the input and output waveguide are coupled and connected. The "8"-shaped waveguide microcavity is composed of a cross-shaped waveguide located in the middle and two open-ring waveguides located on both sides. The cross-shaped waveguide is formed by two straight waveguides arranged vertically and orthogonally at their respective midpoints, one end of the two straight waveguides is respectively connected to the two ends of an open-ring waveguide, and the other ends of the two straight waveguides are respectively connected to the two ends of another open-ring waveguide; a magnetostrictive material layer is provided directly below the "8"-shaped waveguide microcavity far away from the input and output waveguides, and no magnetostrictive material layer is provided directly below the "8"-shaped waveguide microcavity close to the input and output waveguides.

[0010] The lithium niobate film layer is arranged on a silicon dioxide buffer layer, and the silicon dioxide buffer layer is arranged on a silicon substrate. The input and output waveguides and the "8"-shaped waveguide microcavity of the magnetic field sensitive unit are both formed by etching the lithium niobate film layer, and the input and output waveguides and the "8"-shaped waveguide microcavity are located on the upper surface of the silicon dioxide buffer layer.

[0011] The magnetostrictive material layer is located below the silicon dioxide buffer layer and above the silicon substrate.

[0012] The broadband light source, the spot converter and the one-way isolator are sequentially arranged along the light path direction, and the broadband light source, the spot converter and the one-way isolator are all located on the upper surface of the silicon dioxide buffer layer.

[0013] The two "8"-shaped waveguide microcavities have the same cavity length and the same resonant frequency.

[0014] Light passes through the input and output waveguides and enters the two "8"-shaped waveguide microcavities through evanescent wave coupling, and the coupling between the two "8"-shaped waveguide microcavities is also completed through evanescent waves [the coupling coefficient is adjusted by controlling the spacing between the input and output waveguides and the "8"-shaped microcavity].

[0015] The magnetostrictive material senses the change in the magnetic field and deforms, driving the "8"-shaped waveguide microcavity directly above it to deform [the "8"-shaped microcavities are misaligned perpendicular to the microcavity plane], thereby affecting the coupling coefficient between the two "8"-shaped waveguide microcavities, so that the light passing through the two "8"-shaped waveguide microcavities is transmitted back to the input and output waveguides to be detected and received by the micro-spectrometer. The magnetic field is detected by analyzing the light signal received by the micro-spectrometer.

[0016] The present invention proposes a non-Hermitian singular point optical microcavity magnetic field sensor. The present invention is beneficial to improving the integration of magnetic field sensors. The present invention utilizes the property that the singular point of a non-Hermitian optical system is sensitive to external perturbations, and further improves the sensitivity of the system while maintaining the advantages of the optical magnetic measurement method, which is expected to solve the problem of insufficient detection sensitivity in optical magnetic measurement. In the design of the sensitive unit structure, an "8"-shaped waveguide microcavity design is adopted, so that light can travel around the microcavity in a circle and have both clockwise and counterclockwise states at the same time, offsetting the influence of the Sagnac effect caused by the rotation of the earth or the rotation of the application environment on the measurement. The present invention has a simple structure and high integration, and is expected to become a new method for optical magnetic measurement.

[0017] Beneficial effects of the present invention:

[0018] In the present invention, all devices are integrated on a silicon substrate, and compared with the optical measurement method of discrete devices, the volume of the magnetic field sensor is reduced, the integration is high, the volume is small, and it is suitable for mass production.

[0019] The present invention constructs a second-order non-Hermitian system, taking advantage of the high sensitivity of the non-Hermitian system singular point detection, and has the characteristics of small size and easy packaging and integration. In addition, two coupled cavities with gain and loss coefficients are constructed, taking advantage of the fact that the singular point of the non-Hermitian system is sensitive to external disturbances, and further improving the sensitivity of the magnetic field sensor while maintaining the original advantages of optical magnetometry.

[0020] The two coupled microcavities constructed in the present invention have an "8"-shaped structure, which in principle eliminates the influence of the Sagnac effect caused by the rotation of the earth and the rotation that may exist in the sensor application environment on the microcavity resonance frequency, eliminates the interference of the gyroscopic effect on the singular points of the non-Hermitian system, and improves the signal-to-noise ratio of the sensor.

[0021] The two straight waveguides in the "8"-shaped waveguide microcavity structure of the present invention are perpendicular to each other, so that light is not coupled into another straight waveguide when transmitted in one straight waveguide, thus ensuring unidirectional transmission of light in the "8"-shaped microcavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of the non-Hermitian optical microcavity magnetic field sensor of the present invention;

[0023] Figure 2 It is a schematic diagram of the structure of the magnetic field sensitive unit in the present invention;

[0024] Figure 3 It is a graph showing the change of the output spectrum with the coupling coefficient between the "8"-shaped waveguide microcavities in the present invention.

[0025] In the figure: 1. broadband light source, 2. pattern spot converter, 3. unidirectional isolator, 4. magnetic field sensitive unit, 5. micro-spectrometer, 6. packaging shell, 7. "8" shaped waveguide microcavity, 8. lithium niobate thin film layer, 41. input and output waveguide, 42. open ring waveguide, 43. straight waveguide, 44. silicon dioxide buffer layer, 45. silicon substrate, 46. magnetostrictive material. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0027]

【like Figure 1As shown, the specifically implemented magnetic field sensor comprises a wide-spectrum light source 1, a pattern spot converter 2, a unidirectional isolator 3, a magnetic field sensitive unit 4 and a miniature spectrometer 5 in a packaging shell 6; the output end of the wide-spectrum light source 1 is connected to the input end of the magnetic field sensitive unit 4 through the pattern spot converter 2 and the unidirectional isolator 3 in sequence, and the output end of the magnetic field sensitive unit 4 is connected to the miniature spectrometer 5; the wide-spectrum light source 1, the pattern spot converter 2, the unidirectional isolator 3 and the miniature spectrometer 5 are all located on the upper surface of the silicon dioxide buffer layer 44, the light transmitting part in the magnetic field sensitive unit 4 is formed by etching the lithium niobate thin film layer 8, and the magnetostrictive material layer 46 for sensing the magnetic field in the magnetic field sensitive unit 4 is arranged below the silicon dioxide buffer layer 44.

[0028]

【like Figure 2 As shown, the magnetic field sensitive unit 4 is mainly composed of an input-output waveguide 41, two identical "8"-shaped waveguide microcavities 7 and a magnetostrictive material layer 46. The input-output waveguide 41 is a straight waveguide, one end of the input-output waveguide 41 serves as the input end of the magnetic field sensitive unit 4, and the other end of the input-output waveguide 41 serves as the output end of the magnetic field sensitive unit 4. The two ends of the input-output waveguide 41 are respectively connected to a unidirectional isolator 3 and a micro-spectrometer 5. Two "8"-shaped waveguide microcavities 7 are arranged [in sequence] on the same side of the input-output waveguide 41. The long axis directions of the two "8"-shaped waveguide microcavities 7 coincide with each other and are located in the same straight line direction perpendicular to the direction of the input-output waveguide 41. The two "8"-shaped waveguide microcavities 7 and the "8"-shaped waveguide microcavity 7 close to the input-output waveguide 41 and the input-output waveguide 41 are coupled and connected.

[0029] The "8"-shaped waveguide microcavity 7 is composed of a cross-shaped waveguide in the middle and two open-ring waveguides 42 on both sides. The cross-shaped waveguide is formed by two straight waveguides 43 arranged vertically and orthogonally at their respective midpoints. One end of the two straight waveguides 43 is respectively connected to the two ends of an open-ring waveguide 42, and the other ends of the two straight waveguides 43 are respectively connected to the two ends of another open-ring waveguide 42; [This makes the two open-ring waveguides 42 arranged symmetrically on both sides of the cross-shaped waveguide, and the line between the midpoints of the two open-ring waveguides 42 is the long axis direction of the "8"-shaped waveguide microcavity 7.] [The "8"-shaped waveguide microcavity is the most important sensitive structure of the magnetic field sensor.]

[0030] A magnetostrictive material layer 46 is provided directly below the "8"-shaped waveguide microcavity 7 far away from the input / output waveguide 41, while no magnetostrictive material layer 46 is provided directly below the "8"-shaped waveguide microcavity 7 close to the input / output waveguide 41 [the magnetostrictive material 46 is used to sense changes in the magnetic field].

[0031] [In this way, a magnetostrictive material 46 is disposed below one of the “8”-shaped waveguide microcavities 7 of the magnetic field sensitive unit 4. The magnetostrictive material 46 is located below the silicon dioxide buffer layer 44 and is in contact with the silicon substrate 45 at the bottom.]

[0032] The lithium niobate thin film layer 8 is arranged on the silicon dioxide buffer layer 44, and the silicon dioxide buffer layer 44 is arranged on the silicon substrate 45. The input and output waveguides 41 and the "8"-shaped waveguide microcavity 7 of the magnetic field sensitive unit 4 [as the light transmitting part] are both formed by etching the lithium niobate thin film layer 8. The input and output waveguides 41 and the "8"-shaped waveguide microcavity 7 are located on the upper surface of the silicon dioxide buffer layer 44.

[0033] The magnetostrictive material layer 46 is located below the silicon dioxide buffer layer 44 and above the silicon substrate 45 [ie, between the silicon dioxide buffer layer 44 and the silicon substrate 45].

[0034] [Except for the area where the magnetic field sensitive unit 4 is located, the rest of the sensor structure is composed of a lithium niobate film layer 8, a silicon dioxide buffer layer 44, and a silicon substrate 45 stacked in sequence from top to bottom. ]

[0035] [During the production process, the lithium niobate film layer 8, the silicon dioxide buffer layer 44, the silicon substrate 45, and the magnetostrictive material layer 46 are first stacked and arranged at corresponding positions, and an area is marked out at the corresponding position on the lithium niobate film layer 8 for arranging the magnetic field sensitive unit 4, and the input and output waveguides 41 and the "8"-shaped waveguide microcavity 7 of the magnetic field sensitive unit 4 are etched in the area, and then the remaining lithium niobate film layer 8 is also etched below the input and output waveguides 41 and the "8"-shaped waveguide microcavity 7, and then the wide-spectrum light source 1, the mode spot converter 2, the one-way isolator 3, and the micro-spectrometer 5 are arranged. ]

[0036] The wide-spectrum light source 1, the spot converter 2, and the one-way isolator 3 are arranged in sequence along the optical path direction, and the wide-spectrum light source 1, the spot converter 2, and the one-way isolator 3 are all located on the upper surface of the silicon dioxide buffer layer 44. [The output end of the one-way isolator 3 is connected to the input end of the magnetic field sensitive unit 4, and the output end of the magnetic field sensitive unit 4 is connected to the input end of the micro-spectrometer 5. ]

[0037] [The light generated by the wide-spectrum light source 1 passes through the pattern spot converter 2 and then enters the input end of the magnetic field sensitive unit 4 through the output end of the one-way isolator 3. The light is output to the micro-spectrometer 5 through the magnetic field sensitive unit 4. The light detected by the micro-spectrometer 5 is analyzed and processed to obtain the transmission-frequency spectrum.

[0038] The one-way isolator 3 is used to isolate the backscattered light in the magnetic field sensitive unit 4.

[0039] The two “8”-shaped waveguide microcavities 7 have the same cavity length and the same resonance frequency.

[0040] [In the "8"-shaped waveguide microcavity, two straight waveguides 43 perpendicular to each other are arranged vertically and orthogonally to form an "8"-shaped structure. The two straight waveguides are perpendicular to each other to ensure that light will not be coupled from one straight waveguide to another straight waveguide when passing through the straight waveguide, so that light will not be coupled during transmission. During the transmission process in the cavity, the light has both clockwise and counterclockwise parts, so as to eliminate the influence of the Sagnac effect caused by the rotation of the earth and other rotations on the cavity resonance frequency. ]

[0041] [One of the two "8"-shaped waveguide microcavities of the magnetic field sensitive unit 4 has loss, and the other has a gain of the same magnitude as the loss, forming a non-Hermitian system.

[0042] The two "8"-shaped waveguide microcavities are coupled to each other through evanescent waves. In the initial state, the distance between the two is precisely adjusted, so that the coupling coefficient and loss coefficient between the two "8"-shaped waveguide microcavities are the same. The coupling coefficient between the "8"-shaped waveguide microcavities matches the introduced gain coefficient and loss coefficient, so that the non-Hermitian system is at the singular point of the non-Hermitian system in the initial state without magnetic field, forming sensitivity to external perturbations.

[0043] Light passes through the input and output waveguides 41 and enters the two "8"-shaped waveguide microcavities 7 by evanescent wave coupling, and the coupling between the two "8"-shaped waveguide microcavities 7 is also completed by evanescent waves.

[0044] [The "8"-shaped waveguide microcavity 7 close to the input / output waveguide 41 is used as the first "8"-shaped waveguide microcavity 7, and the "8"-shaped waveguide microcavity 7 far away from the input / output waveguide 41 is used as the second "8"-shaped waveguide microcavity 7: light is transmitted along the input / output waveguide 41, and after passing through the coupling portion between the first "8"-shaped waveguide microcavity 7 and the input / output waveguide 41, it is first coupled into the first "8"-shaped waveguide microcavity 7 through the evanescent wave, and then transmitted to the first "8"-shaped waveguide microcavity 7 and the second "8"-shaped waveguide microcavity through the unilateral S-shaped waveguide on one side of the first "8"-shaped waveguide microcavity 7. The coupling point between the waveguide microcavities 7 is coupled to the second "8"-shaped waveguide microcavity 7 through the evanescent wave, and then transmitted back to the coupling point between the first "8"-shaped waveguide microcavity 7 and the second "8"-shaped waveguide microcavity 7 through the complete "8"-shaped transmission of the second "8"-shaped waveguide microcavity 7, and then coupled back to the first "8"-shaped waveguide microcavity 7 through the evanescent wave, and then transmitted to the coupling point between the first "8"-shaped waveguide microcavity 7 and the input-output waveguide 41 through the unilateral S-shaped waveguide on the other side of the first "8"-shaped waveguide microcavity 7, and coupled back to the input-output waveguide 41, thereby completing a cyclic transmission process. The above cyclic transmission process is continuously repeated during the light transmission process to realize that the transmission spectrum of the light after passing through the magnetic field sensitive unit 4 is affected by the change of the coupling coefficient of the two "8"-shaped waveguide microcavities 7. 】

[0045] The magnetostrictive material 46 senses the change in the magnetic field and deforms, driving the "8"-shaped waveguide microcavity 7 directly above itself to deform, causing the two "8"-shaped waveguide microcavities 7 to be misaligned in the direction perpendicular to the cavity plane, thereby affecting the coupling coefficient between the two "8"-shaped waveguide microcavities 7, causing the optical signal transmitted back to the input-output waveguide 41 through the two "8"-shaped waveguide microcavities 7 and detected by the micro-spectrometer 5 to change. The optical signal detected and received by the micro-spectrometer 5 is analyzed to realize the detection of the magnetic field.

[0046] [The magnetostrictive material only exists in one of the "8"-shaped waveguide microcavities in the magnetic field sensitive unit, and only the longitudinal length changes under the magnetic field environment. The magnetic field only affects the mutual coupling coefficient of the two "8"-shaped waveguide microcavities. There is no magnetostrictive material in the rest of the magnetic field sensitive unit. The structure from top to bottom is lithium niobate film layer, silicon dioxide buffer layer, and silicon substrate.

[0047] The magnetostrictive material 46 is used to sense the change of magnetic field and expand and contract longitudinally. The two "8"-shaped waveguide microcavity coupling parts are staggered by a certain distance, changing the coupling coefficient between the two, constituting a disturbance to the singular point of the non-Hermitian system, causing the change of the sensor output. When subjected to the magnetic field, the magnetostrictive material 46 changes its length longitudinally, causing the coupling coefficient between the "8"-shaped waveguide microcavities to change, causing the system to deviate from the singular point, causing the change of the resonant output.

[0048] Specifically, the transmission-frequency spectrum output by the micro-spectrometer 5 is processed to obtain the half-maximum full width parameter, and the magnetic field change is obtained according to the corresponding relationship between the half-maximum full width parameter change and the magnetic field change.

[0049] In a specific embodiment, the magnetic field sensitive unit of the singular point optical microcavity magnetic field sensor is designed as follows:

[0050] In this example, the broadband light source 1 adopts an SLD light source with a central wavelength of 1550 nanometers. The radius of the open ring waveguide part 42 of the two "8"-shaped waveguide microcavities is R = 20 microns. Figure 2 From the geometric relationship in , it can be seen that the length of the two perpendicular straight waveguides 43 is 2R = 40 microns. The ratio of the light directly output by the input and output waveguide 41 to the light power coupled into the "8"-shaped waveguide microcavity is 95:5, and the power coupling ratio between the two "8"-shaped waveguide microcavities is also 95:5, that is, 5% of the light is coupled from one "8"-shaped waveguide microcavity into another microcavity.

[0051] The coupling coefficient μ between the input and output waveguide 41 and the “8”-shaped waveguide microcavity 7 is determined as follows:

[0052]

[0053] And the coupling coefficient κ between the two “8”-shaped waveguide microcavities:

[0054]

[0055] Where c is the speed of light in vacuum, n is the refractive index of the waveguide material, and L is the cavity length of the "8"-shaped waveguide microcavity.

[0056] The following two time-domain coupled mode equations of the “8”-shaped waveguide microcavity are established:

[0057]

[0058]

[0059] Wherein, a1 is the energy amplitude in the “8”-shaped waveguide microcavity 7 coupled with the input and output waveguide 41, a2 is the energy amplitude in the “8”-shaped waveguide microcavity 7 with the magnetostrictive material directly below, ω0 is the resonant frequency of the “8”-shaped waveguide microcavity 7, and γ is the gain or loss coefficient of the “8”-shaped waveguide microcavity 7. S in is the optical power coupled from the output end of the unidirectional isolator 3 into the input end of the magnetic field sensitive unit 4, t represents the time parameter, dt in the above equation is the differential with respect to time, and j is an imaginary unit.

[0060] Set the value of the gain or loss coefficient γ = κ so that the system is at a non-Hermitian system singular point in the initial state, Figure 1 The input-output relationship is established as follows: the optical power S output from the output end of the magnetic field sensitive unit 4 out The expression is:

[0061] S out =S in -jμa1

[0062] Then the output spectrum S is calculated out / S in The expression is:

[0063]

[0064] Δω=ω-ω0

[0065] Where Δω is the amount by which the input light frequency deviates from the cavity resonant frequency, and ω represents the input light frequency.

[0066] It can be seen that the output spectrum is closely related to the coupling coefficient κ between the two "8"-shaped waveguide microcavities. In the initial state, the system is at a singular point. When subjected to a magnetic field, the magnetostrictive material layer 46 undergoes a longitudinal length change, and the "8"-shaped waveguide microcavity 7 containing the magnetostrictive material at the bottom will be offset from the other microcavity by a certain distance. Since the coupling between the cavities depends on the action of the evanescent wave, the coupling coefficient k between the two microcavities will change slightly, causing the system to deviate from the singular point, thereby causing a change in the output spectrum.

[0067] like Figure 3 As shown, we can see that the coupling coefficient is 10 -8 The change in ratio will result in a full width at half maximum of 10 7 rad / s change, with high detection sensitivity.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A non-Hermitian singular point optical microcavity magnetic field sensor, characterized in that: The invention comprises a wide-spectrum light source (1), a pattern spot converter (2), a unidirectional isolator (3), a magnetic field sensitive unit (4) and a micro-spectrometer (5) in a packaging shell (6); the output end of the wide-spectrum light source (1) is connected to the input end of the magnetic field sensitive unit (4) after passing through the pattern spot converter (2) and the unidirectional isolator (3) in sequence, and the output end of the magnetic field sensitive unit (4) is connected to the micro-spectrometer (5); the wide-spectrum light source (1), the pattern spot converter (2), the unidirectional isolator (3) and the micro-spectrometer (5) are all arranged on a lithium niobate thin film layer (8); a part of the magnetic field sensitive unit (4) is formed by etching the lithium niobate thin film layer (8), and another part of the magnetic field sensitive unit (4) is arranged below the lithium niobate thin film layer (8); The magnetic field sensitive unit (4) comprises an input / output waveguide (41), two identical "8"-shaped waveguide microcavities (7) and a magnetostrictive material layer (46); two ends of the input / output waveguide (41) are respectively connected to a unidirectional isolator (3) and a micro-spectrometer (5); two "8"-shaped waveguide microcavities (7) are arranged on the same side of the input / output waveguide (41); the long axis directions of the two "8"-shaped waveguide microcavities (7) coincide with each other and are located in the same straight line direction perpendicular to the direction of the input / output waveguide (41); the two "8"-shaped waveguide microcavities (7) and the "8"-shaped waveguide microcavity (7) close to the input / output waveguide (41) and the input / output waveguide (41) are coupled and connected; The "8"-shaped waveguide microcavity (7) is composed of a cross-shaped waveguide located in the middle and two open ring waveguides (42) located on both sides. The cross-shaped waveguide is formed by two straight waveguides (43) arranged vertically and orthogonally at their respective midpoints. One end of the two straight waveguides (43) is respectively connected to the two ends of an open ring waveguide (42), and the other ends of the two straight waveguides (43) are respectively connected to the two ends of another open ring waveguide (42). A magnetostrictive material layer (46) is provided directly below the "8"-shaped waveguide microcavity (7) far from the input and output waveguides (41), and no magnetostrictive material layer (46) is provided directly below the "8"-shaped waveguide microcavity (7) close to the input and output waveguides (41).

2. The non-Hermitian singular point optical microcavity magnetic field sensor according to claim 1, characterized in that: The lithium niobate thin film layer (8) is arranged on a silicon dioxide buffer layer (44), and the silicon dioxide buffer layer (44) is arranged on a silicon substrate (45). The input and output waveguides (41) and the "8"-shaped waveguide microcavity (7) of the magnetic field sensitive unit (4) are both formed by etching the lithium niobate thin film layer (8), and the input and output waveguides (41) and the "8"-shaped waveguide microcavity (7) are located on the upper surface of the silicon dioxide buffer layer (44).

3. The non-Hermitian singular point optical microcavity magnetic field sensor according to claim 2, characterized in that: The magnetostrictive material layer (46) is located below the silicon dioxide buffer layer (44) and above the silicon substrate (45).

4. The non-Hermitian singular point optical microcavity magnetic field sensor according to claim 2, characterized in that: The broadband light source (1), the pattern spot converter (2), and the one-way isolator (3) are arranged in sequence along the light path direction, and the broadband light source (1), the pattern spot converter (2), and the one-way isolator (3) are all located on the upper surface of the silicon dioxide buffer layer (44).

5. The non-Hermitian singular point optical microcavity magnetic field sensor according to claim 1, characterized in that: The two "8"-shaped waveguide microcavities (7) have the same cavity length and the same resonance frequency.

6. The non-Hermitian singular point optical microcavity magnetic field sensor according to claim 1, characterized in that: Light passes through the input and output waveguides (41) and enters the two "8"-shaped waveguide microcavities (7) through evanescent wave coupling, and coupling between the two "8"-shaped waveguide microcavities (7) is also completed through evanescent waves.

7. The non-Hermitian singular point optical microcavity magnetic field sensor according to claim 1, characterized in that: The magnetostrictive material (46) senses the change in the magnetic field and deforms, driving the "8"-shaped waveguide microcavity (7) directly above it to deform, thereby affecting the coupling coefficient between the two "8"-shaped waveguide microcavities (7), so that light passing through the two "8"-shaped waveguide microcavities (7) is transmitted back to the input and output waveguide (41) to be detected and received by the micro-spectrometer (5), and the magnetic field is detected by analyzing the optical signal detected and received by the micro-spectrometer (5).

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