A polydimethylsiloxane optical cavity direct current magnetic field sensing system

Abstract

The application discloses a polydimethylsiloxane optical cavity direct-current magnetic field sensing system, and belongs to the optical field, wherein a signal output by a tunable laser is sent to an input end of a polarization controller; an output end of the polarization controller is connected with a fiber taper; the fiber taper is coupled with a polydimethylsiloxane optical cavity in a sensing unit, and after the coupling, a signal output by the fiber taper is sent to an input end of a detector; an output end of the detector is connected with an input end of a beam splitter, three signals output by the beam splitter are sent to a servo controller, an oscilloscope and an electrical spectrum analyzer respectively; an output end of the servo controller is connected with an input end of the oscilloscope in one way and connected with a regulation and control input end of the tunable laser in another way. The application can measure the direct-current magnetic field by using singular points existing in the sensing system, has high sensitivity, and can remotely detect the magnetic field information.

Description

Technical Field

[0001] This invention belongs to the field of optics, specifically relating to a polydimethylsiloxane optical cavity DC magnetic field sensing system. Background Technology

[0002] Magnetic field sensors have a wide range of applications and are of significant value in fields such as medicine and defense. Optical magnetic field sensing systems have attracted widespread attention due to their advantages such as high speed and resistance to electromagnetic interference. Currently, there are many implementation schemes for using optical cavities for magnetic field sensing, but schemes combining them with microwave systems are still rare. Ferromagnetic resonance in such systems is easier to implement than mechanical mode tuning, and it exhibits a significant advantage in sensitivity. Therefore, based on the idea of ​​ferromagnetic resonance-assisted magnetic field sensing, a scheme is further proposed for high-sensitivity sensing using an open-loop cavity and ferromagnetic resonance in a dissipative coupling state. This sensing system can achieve high-precision DC magnetic field measurement and can be applied to the detection of weak DC magnetic fields in the future, possessing advantages such as interconnectivity with microwave systems, high speed, and high precision. Summary of the Invention

[0003] This invention utilizes the dissipative coupling state of ferromagnetic resonance and microwave cavity to propose a DC magnetic field sensing system using a polydimethylsiloxane (PDMS) optical cavity. Specifically, it involves an optical resonant system composed of a PDMS optical cavity and an optical fiber taper, capable of exciting ferromagnetic resonance microstrip lines in yttrium iron garnet (YIG), an open-loop cavity that achieves dissipative coupling with the ferromagnetic resonance, and other necessary detection equipment to construct a magnetic field sensing system that can be used in the field of DC magnetic field detection.

[0004] A polydimethylsiloxane optical cavity DC magnetic field sensing system includes a tunable laser, a polarization controller, an optical fiber taper, a sensing unit, a detector, a beam splitter, a servo controller, an oscilloscope, and an electrical spectrum analyzer. The sensing unit includes a multi-layer sensing structure—PDMS optical cavity, YIG, gadolinium gallium garnet (GGG), microstrip line, dielectric, split-ring resonator (SRR), and excitation sources—microwave source and DC magnet.

[0005] The signal output from the tunable laser is fed into the input of a polarization controller; the output of the polarization controller is connected to a fiber taper; the fiber taper is coupled to the PDMS optical cavity in the sensing unit, and the output signal from the fiber taper is fed into the input of a detector; the output of the detector is connected to the input of a beam splitter, and the three signals output by the beam splitter are fed into a servo controller, an oscilloscope, and an electrical spectrum analyzer; one output of the servo controller is connected to the input of the oscilloscope, and the other is connected to the control input of the tunable laser. The servo controller is used to lock the wavelength of the tunable laser at a specific mode of the cavity.

[0006] The sensing unit comprises a multi-layered sensing structure and excitation sources (microwave source and DC magnet). The sensing structure has a multi-layered stacked structure, consisting of an SRR, dielectric, microstrip line, GGG, YIG, and PDMS optical cavity from bottom to top. The microstrip line input is connected to the microwave source output, generating a microwave magnetic field that acts on the YIG located on the GGG substrate. The microwave magnetic field and the DC magnetic field generated by the DC magnet jointly excite ferromagnetic resonance in the YIG. The ferromagnetic resonance in the YIG can also drive deformation of the PDMS cavity above. The PDMS optical cavity and the fiber taper can be coupled together through evanescent waves within the fiber taper. Therefore, the deformation of the PDMS optical cavity caused by the effects of other parts of the system can be detected by the optical field and converted into an electrical signal by the detector. The parameter changes of the SRR located below the dielectric can cause the SRR and the ferromagnetic resonance in the YIG to be dissipatively coupled. After confirming the dissipative coupling state, the magnetic field strength generated by the DC magnet can be adjusted to place it at a singular point. After the system is adjusted to the specified state, if there is a DC magnetic field signal to be measured, the electrical spectrum analyzer will show that a single frequency component splits into two frequency components. The difference between these two frequencies can be used to characterize the intensity of the DC magnetic field signal to be measured.

[0007] Optical fibers are used to connect the tunable laser to the polarization controller, the polarization controller to the fiber taper, and the fiber taper to the detector; electrical cables are used to connect the detector to the beam splitter, the beam splitter to the electrical spectrum analyzer, the beam splitter to the oscilloscope, the beam splitter to the servo controller, the servo controller to the oscilloscope, the servo controller to the tunable laser, and the microwave source to the microstrip line.

[0008] Preferably, the open-ring cavity SRR is compatible with micro-nano fabrication processes, and its specific dimensions can be designed according to the actual required resonant frequency.

[0009] Ideally, the YIG should be placed at the center of the microwave magnetic field generated by the microstrip line to ensure successful excitation of ferromagnetic resonance.

[0010] Preferably, the structural parameters of the SRR should ensure that it can be in a dissipative coupling state with the ferromagnetic resonance in the YIG.

[0011] Preferably, the ferromagnetic resonance mode in YIG is in a dissipative coupling state with SRR. By adjusting the signal intensity generated by the DC magnet, the system is placed at a singular point in the dissipative coupling state, so as to perform high-sensitivity DC magnetic field sensing.

[0012] Preferably, the PDMS optical cavity should be located at the geometric center above the YIG to ensure that the force generated by the YIG can effectively act on the PDMS optical cavity.

[0013] Preferably, the tunable laser has a wavelength of 630nm to ensure low-loss transmission of the optical signal within the PDMS cavity.

[0014] Preferably, the polarization state of the polarization controller should ensure the highest optical quality factor of the optical mode.

[0015] The beneficial effects of this invention are as follows: In the sensing system of this invention, when the open annular cavity and ferromagnetic resonance are in dissipative coupling, the system parameters can be adjusted to place it at a singular point. At this point, high-precision DC magnetic field sensing sensitivity can be obtained. The singular point in the sensing system allows for the measurement of DC magnetic fields with high sensitivity. Furthermore, this system can interact with microwave systems, is easily integrated with fiber optic systems, and enables remote detection of magnetic field information. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the system of the present invention;

[0017] Figure 2 This is a schematic diagram of the sensing structure in the sensing unit. Detailed Implementation

[0018] The following specific embodiments further illustrate the essential features and significant advancements of the present invention, but the scope of the present invention is not limited to the following embodiments:

[0019] Specific implementation method one: as follows Figure 1As shown, the polydimethylsiloxane optical cavity DC magnetic field sensing system described in this embodiment includes a tunable laser 1, a polarization controller 2, an optical fiber taper 3, a sensing unit 4, a detector 5, a beam splitter 6, a servo controller 7, an oscilloscope 8, and an electrical spectrum analyzer 9; the sensing unit includes a multi-layer sensing structure—PDMS optical cavity 10, YIG 11, GGG 12, microstrip line 13, dielectric 14, SRR 15, and an excitation source—microwave source 16 and DC magnet 17. The signal output from the tunable laser 1 is fed into the input terminal of the polarization controller 2; the output terminal of the polarization controller 2 is connected to the fiber taper 3; the fiber taper 3 is coupled to the PDMS optical cavity 10 in the sensing unit 4, and the output signal from the fiber taper 3 after coupling is fed into the input terminal of the detector 5; the output terminal of the detector 5 is connected to the input terminal of the beam splitter 6, and the three signals output by the beam splitter 6 are fed into the servo controller 7, the oscilloscope 8, and the electrical spectrum analyzer 9; one output terminal of the servo controller 7 is fed into the input terminal of the oscilloscope 8, and the other is fed into the control input port of the tunable laser 1. The servo controller 7 is used to lock the wavelength of the tunable laser 1 at a specific mode of the PDMS optical cavity 10.

[0020] The tunable laser 1 is connected to the polarization controller 2, the polarization controller 2 to the fiber taper 3, and the fiber taper 3 to the detector 5 using optical fibers; the detector 5 is connected to the beam splitter 6, the beam splitter 6 to the electrical spectrum analyzer 9, the beam splitter 6 to the oscilloscope 8, the beam splitter 6 to the servo controller 7, the servo controller 7 to the oscilloscope 8, the servo controller 7 to the tunable laser 1, the microwave source 16 to the microstrip line 13 using electrical cables.

[0021] Specific Implementation Method Two: Combining Figure 1 and Figure 2This embodiment is a supplement to the DC magnetic field sensing system of a polydimethylsiloxane optical cavity described in Embodiment 1. The sensing unit 4 includes a multi-layered stacked sensing structure and an excitation source (microwave source 16 and DC magnet 17). The sensing structure has a multi-layered stacked structure, from bottom to top: SRR 15, dielectric 14, microstrip line 13, GGG 12, YIG 11, and PDMS optical cavity 10. The input end of microstrip line 13 is connected to the output end of microwave source 16, generating a microwave magnetic field that acts on YIG 11 located on the GGG 12 substrate. The microwave magnetic field and the DC magnetic field generated by DC magnet 17 jointly excite ferromagnetic resonance in YIG 11. The ferromagnetic resonance in YIG 11 can also drive deformation of the PDMS optical cavity 10 above. The PDMS optical cavity 10 and fiber taper 3 can be coupled together through evanescent waves within fiber taper 3. Therefore, the deformation of the PDMS optical cavity 10 caused by the effects of other parts of the system can be detected by the optical field and converted into an electrical signal by detector 5. The parameter variation of SRR15, located below medium 14, can cause SRR15 to be dissipatively coupled with the ferromagnetic resonance in YIG11. After confirming the dissipative coupling state, the magnetic field strength generated by DC magnet 17 can be adjusted to place it at a singular point. After the system is adjusted to the specified state, if the DC magnetic field signal to be measured exists, the electrical spectrum analyzer 9 will show that a single frequency component splits into two frequency components. The difference between these two frequencies can be used to characterize the strength of the DC magnetic field signal to be measured.

[0022] Specific implementation method three: Combining Figure 1 This embodiment is a supplement to the DC magnetic field sensing system for a polydimethylsiloxane optical cavity described in Embodiment 1. The servo controller 7 is used to lock the light output from the tunable laser 1 to a specific wavelength of a certain optical mode in the PDMS optical cavity 10. After observing the transmission spectrum of the PDMS optical cavity 10 on the oscilloscope 8, a specific optical mode in the PDMS optical cavity 10 can be selected, and the wavelength locking is achieved using the thermal effect of the auxiliary cavity assisted by the servo controller 7, so as to perform subsequent magnetic field performance calibration and measurement. During locking, the servo controller 7 receives the signal from the detector 5, and by adjusting its parameters, it can output a feedback voltage signal to the tunable laser 1 to achieve locking. Simultaneously, the servo controller 7 can output an error signal to the oscilloscope 8 to monitor the locking effect. Electrical cables are used to connect the servo controller 7 to the tunable laser 1, the servo controller 7 to the oscilloscope 8, and the servo controller 7 to the detector 5.

[0023] Specific implementation method four: Combination Figure 1This embodiment is a supplement to the DC magnetic field sensing system for a polydimethylsiloxane optical cavity described in Embodiment 1. A microwave source 16 generates a microwave magnetic field through a microstrip line 13, which, together with the DC magnetic field generated by a DC magnet 17, excites ferromagnetic resonance in the YIG11. In the experiment, the direction of the DC magnetic field generated by the DC magnet 17 must be perpendicular to the direction of the magnetic field in the microwave magnetic field to excite the ferromagnetic resonance. The ferromagnetic resonance in the YIG11 acts on the PDMS optical cavity 10 through magnetostriction, causing deformation of the PDMS optical cavity. The structural parameters of the SRR15 ensure that it can dissipately couple with the ferromagnetic resonance in the YIG11; by adjusting the field strength generated by the DC magnet 17, it can be positioned at a singularity of dissipative coupling. When a DC magnetic field to be measured is present, the PDMS optical cavity 10 is driven, and the light field transmitted within the PDMS optical cavity 10 is also modulated. By monitoring the changes in the signal on the electrical spectrum analyzer 9 caused by the output light field, the change in the intensity of the DC magnetic field signal to be measured can be demodulated. If a DC magnetic field signal to be measured is present, a single frequency component can be seen to split into two frequency components on the electrical spectrum analyzer 9. The difference between these two frequencies can be used to characterize the intensity of the DC magnetic field signal to be measured.

[0024] Specific Implementation Method Five: Combining Figure 2 This embodiment is a supplement to the polydimethylsiloxane optical cavity DC magnetic field sensing system described in Embodiment 1. The parameters of the SRR15 structure are designed to ensure dissipative coupling with the ferromagnetic resonance generated in YIG11. The SRR15 is made of copper and features a hollow structure, as shown in the diagram. Figure 2 As shown in the darker areas, the specific dimensions are: a = 5mm, b = 3.8mm, c = 0.4mm, and the structural thickness is 35μm. Microstrip line 13 must meet a 50-ohm impedance matching condition, for example, a width of 0.57mm, a length of 40mm, and a thickness of 35μm. The YIG thickness is 25μm. The dielectric dimensions are 50mm in length, 25mm in width, and 0.64mm in thickness, with a relative permittivity of 10. The length and width dimensions of the multilayer stacked structure can be selected as needed, such as 50mm in length and 25mm in width.

Claims

1. A polydimethylsiloxane optical cavity DC magnetic field sensing system, characterized in that: The sensing system includes a tunable laser (1), a polarization controller (2), a fiber taper (3), a sensing unit (4), a detector (5), a beam splitter (6), a servo controller (7), an oscilloscope (8), and an electrical spectrum analyzer (9); The signal output from the tunable laser (1) is sent to the input of the polarization controller (2); the output of the polarization controller (2) is connected to the fiber taper (3); the fiber taper (3) is coupled to the polydimethylsiloxane PDMS optical cavity (10) in the sensing unit (4), and the output signal of the fiber taper (3) after coupling is sent to the input of the detector (5); the output of the detector (5) is connected to the input of the beam splitter (6), and the three signals output by the beam splitter (6) are sent to the servo controller (7), the oscilloscope (8), and the electrical spectrum analyzer (9); one output of the servo controller (7) is sent to the input of the oscilloscope (8), and the other output is sent to the control input port of the tunable laser (1); the servo controller (7) locks the wavelength of the tunable laser (1) at a specific mode of the PDMS optical cavity (10); The sensing unit (4) includes a multi-layer sensing structure, a microwave source (16), and a DC magnet (17). The sensing structure has a multi-layer stacked structure, which consists of an open ring cavity SRR (15), a dielectric (14), a microstrip line (13), a gadolinium gallium garnet (GGG) (12), a yttrium iron garnet (YIG) (11), and a PDMS optical cavity (10) from bottom to top. The input end of the microstrip line (13) is connected to the output end of the microwave source (16) to generate a microwave magnetic field, which acts on the YIG (11) located on the GGG (12) substrate. The microwave magnetic field and the DC magnetic field generated by the DC magnet (17) together excite ferromagnetic resonance in the YIG (11). The YIG (11) is placed at the center of the microwave magnetic field generated by the microstrip line (13) to ensure successful excitation of ferromagnetic resonance. The PDMS optical cavity (10) is located at the geometric center above the YIG (11) to ensure that the force generated by the YIG (11) acts on the PDMS optical cavity (10). The ferromagnetic resonance in YIG(11) drives the deformation of the PDMS optical cavity (10) above. The PDMS optical cavity (10) and the fiber taper (3) are coupled together through the evanescent wave in the fiber taper (3). The deformation of the PDMS optical cavity (10) is detected by the optical field and converted into an electrical signal by the detector (5). The SRR (15) located below the medium (14) causes the SRR (15) and the ferromagnetic resonance in YIG(11) to be in dissipative coupling. After the dissipative coupling state is confirmed, the magnetic field strength generated by the DC magnet (17) is adjusted to place it at the singular point. If there is a DC magnetic field signal to be measured, the single frequency component is split into two frequency components on the electrical spectrum analyzer (9). The difference between these two frequency components represents the strength of the DC magnetic field signal to be measured. SRR(15) adopts a hollow structure. The hollow part is an open square rectangular annular cavity. The outer side of the rectangle is 5mm long and the inner side is 3.8mm long. A 0.4mm long opening is made in the middle of one side to obtain the dissipative coupling of ferromagnetic resonance in SRR(15) and YIG(11). The selection of singularities in dissipative coupling states is achieved by adjusting the strength of the DC magnet; The tunable laser (1) is connected to the polarization controller (2), the polarization controller (2) is connected to the fiber taper (3), and the fiber taper (3) is connected to the detector (5) using optical fibers. The detector (5) is connected to the beam splitter (6), the beam splitter (6) is connected to the electrical spectrum analyzer (9), the beam splitter (6) is connected to the oscilloscope (8), the beam splitter (6) is connected to the servo controller (7), the servo controller (7) is connected to the oscilloscope (8), the servo controller (7) is connected to the tunable laser (1), and the microwave source (16) is connected to the microstrip line (13) using electrical cables.

2. The polydimethylsiloxane optical cavity DC magnetic field sensing system according to claim 1, characterized in that: The microstrip line (13) has a width of 0.57 mm, a length of 40 mm, and a thickness of 35 μm to meet the impedance matching condition of 50 ohms.

3. The polydimethylsiloxane optical cavity DC magnetic field sensing system according to claim 1, characterized in that: The thickness of the YIG(11) is 25 μm.

4. The polydimethylsiloxane optical cavity DC magnetic field sensing system according to claim 1, characterized in that: The medium (14) has a length of 50 mm, a width of 25 mm, a thickness of 0.64 mm, and a relative permittivity of 10.

5. The polydimethylsiloxane optical cavity DC magnetic field sensing system according to claim 1, characterized in that: The tunable laser (1) has a wavelength of 630nm, which ensures low-loss transmission of optical signals within the PDMS optical cavity (10).

6. The polydimethylsiloxane optical cavity DC magnetic field sensing system according to claim 1, characterized in that: The DC magnetic field generated by the DC magnet (17) is perpendicular to the direction of the microwave magnetic field generated by the microwave source (16) through the microstrip line (13), thereby exciting ferromagnetic resonance.

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