Double-helix polarization modulation and amplification micro-nano waveguide magnetic field sensing device and method

Abstract

The application relates to a double-helix polarization modulation circulating amplification micro-nano waveguide magnetic field sensing device and method, and belongs to the technical fields of magnetic field sensing and optical fiber sensing. The magnetic field sensing device comprises a light source, a circuit control system, a Malus-Zen interference structure based on a circulating amplification system, the circuit control system is used for controlling the light source and the Malus-Zen interference structure based on the circulating amplification system, the Malus-Zen interference structure based on the circulating amplification system comprises a photoelectric detector, a polarization maintaining coupler, a second polarization beam splitter, a fiber delay coil, a double-helix micro-nano waveguide magnetic field probe, a polarization controller, a first polarization beam splitter and an integrated optical element, the application combines the double-helix micro-nano waveguide magnetic field probe and the circulating amplification time sequence control, breaks through key technologies such as controllable circulating times and stable compensation of power fading in a circulating light path, can realize high-performance magnetic field measurement with a sensitivity of 5 pT, and greatly increases the magnetic sensitivity of a weak magnetic sensing system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic field sensing and the technical field of optical fiber sensing, and relates to a double-helix polarization regulation and control circular amplification micro-nano waveguide magnetic field sensing device and method. BACKGROUND

[0002] Weak magnetic field measurement has important application prospects in underwater target detection, geomagnetic matching navigation, power system monitoring, deep space exploration, biomedicine and other fields. Current non-optical measurement methods based on Hall effect, superconducting quantum interference technology, fluxgate technology, electromagnetic induction coil, magnetoresistance effect and optical magnetic field sensors based on optical pumping effect, strain effect of fiber caused by magnetostrictive material and magneto-optic Faraday effect have their own limitations.

[0003] The magnetic field sensor based on the Hall effect has low precision and it is difficult to achieve magnetic measurement with sensitivity better than μT. The superconducting quantum interference magnetometer can achieve magnetic sensitivity less than fT, but it needs a low-temperature environment and the device is difficult to miniaturize; the fluxgate sensor is a relatively mature one, the sensitive unit is composed of high magnetic permeability soft magnetic alloy, excitation coil and signal coil, the sensitivity limit is in the tens of pT, and there is a problem of contradiction between size and sensitivity; the induction coil is the most common magnetic sensor based on electromagnetic induction principle, but it can only measure alternating magnetic field and usually plays an advantage in the frequency band above kHz; the magnetic field sensor made by using the magnetoresistance effect has the characteristics of small size, low power consumption and low cost, but it is difficult to break through the nT level in terms of current precision. The above are non-optical principle magnetic field measurement methods, and the common shortcoming of this kind of sensors is poor anti-electromagnetic interference ability.

[0004] Optically pumped magnetometer is one of the important magnetic field sensors based on optical principle, with fT level sensitivity, which has developed rapidly in recent years and has become a popular sensor to replace superconducting quantum magnetometer, but the measurement bandwidth is difficult to break through kHz, and the probe is difficult to miniaturize; another type of optical magnetic field sensor is the optical fiber magnetic field sensor combining magnetic field detection with optical fiber technology, mainly including three types: the first type is based on M-Z or Sagnac interference structure, which measures the magnetic strain by using double-beam interference structure, and the sensitivity can reach 100 pT, but the environmental stability is poor, which is caused by the environmental stability of the magnetic material itself and the stability of the solid connection between the magnetic material and the optical fiber, and at the same time, due to the low elongation and strain nonlinearity of the magnetostrictive material under weak magnetic field, a large direct current modulation magnetic field needs to be applied to increase the magnetic sensitivity, which is difficult to realize high stability magnetic measurement. The second type is a magnetic field sensor based on magneto-optic Faraday effect, which uses the high magneto-optic deflection coefficient of magneto-optic crystal. When the magnetic field is parallel to the propagation direction of light, the polarization state of linearly polarized light propagating in the crystal produces deflection. The deflection angle is linearly related to the magnetic field size, magneto-optic coefficient and crystal length. The magnetic field is measured by measuring the deflection angle of the polarized light. The main idea to improve the sensitivity is to use high magneto-optic coefficient material and increase the length of the material. At present, YIG (yttrium iron garnet) is a relatively mature material with high magneto-optic coefficient. The magneto-optic coefficient at 1150 nm wavelength is only 328 rad / m / T, and the cost of YIG material is high and the optical loss is large. The magneto-optic coefficient can be greatly improved by doping Bi elements in YIG, but the optical loss of Bi:YIG material is larger, the production is difficult, the cost is higher, and there is no mature product on the market at present. Increasing the length of the sensitive material can improve the sensitivity to a certain extent, but it greatly increases the size of the sensor, which is difficult to realize the pT level miniaturization of the magnetic field measurement, and is not conducive to on-site application. The third type is an optical fiber magnetic field sensor, whose principle is to use optical fiber microstructure combined with magnetic fluid as a magnetic sensitive material to measure the magnetic field. The refractive index of the magnetic fluid changes with the change of the external magnetic field strength, and there is Faraday effect and birefringence effect. Combined with optical method, precise measurement of magnetic field can be realized. However, in actual use, the magnetic field cannot be measured by directly interacting light and magnetic fluid, because the light transmission of magnetic fluid is poor and the transmission loss is large, and reducing the magnetic-optical interaction length limits the magnetic sensitivity of the sensor. Generally, the principle of changing the evanescent field or guided mode of the transmission light in the waveguide by using magnetic fluid is used to measure the magnetic field. The change of external magnetic field changes the refractive index of magnetic fluid, causing the change of effective refractive index of waveguide, leading to the change of intensity or resonance wavelength of transmission light. Optimizing the size and structure of waveguide can change the interaction characteristics of light-magnetic fluid, which can improve the magnetic sensitivity to a certain extent, but it is still difficult to break through 400 pT, and the stability problem caused by temperature is also difficult to solve. SUMMARY

[0005] In view of the problem that current magnetic field sensors are difficult to realize high sensitivity, high stability and small size simultaneously, the application provides a double-helix polarization regulation and control cyclic amplification micro-nano waveguide magnetic field sensor device and method, a double-helix micro-nano waveguide magnetic field probe with a magneto-optical refractive effect is prepared based on a femtosecond laser two-photon polymerization technology, polarization regulation and control cyclic amplification and closed-loop phase detection technologies are combined to improve the magnetic field measurement sensitivity and are used for magnetic field detection, and the designed sensor has the advantages of small size and a system sensitivity better than 5pT.

[0006] In order to achieve the above object, the application adopts the following technical scheme:

[0007] A double-helix polarization regulation and control cyclic amplification micro-nano waveguide magnetic field sensor device, comprising a light source, a circuit control system, a Mach-Zehnder interference structure based on a cyclic amplification system, the circuit control system is used for controlling the light source and the Mach-Zehnder interference structure based on the cyclic amplification system.

[0008] The Mach-Zehnder interference structure based on the cyclic amplification system comprises a photodetector, a polarization maintaining coupler, a second polarization beam splitter, a fiber delay coil, a double-helix micro-nano waveguide magnetic field probe, a polarization controller, a first polarization beam splitter and an integrated optical element.

[0009] The Y1 port of the integrated optical element is connected to the exit end of the light source, the Y2 port of the integrated optical element is connected to the A port of the first polarization beam splitter, the C port of the first polarization beam splitter is connected to the incident port of the polarization controller, the exit port of the polarization controller is connected to the C port of the second polarization beam splitter through the double-helix micro-nano waveguide magnetic field probe and the fiber delay coil in series, the B port of the second polarization beam splitter is connected to the B port of the first polarization beam splitter, the A port of the second polarization beam splitter is connected to the H3 port of the polarization maintaining coupler, the H2 port of the polarization maintaining coupler is connected to the Y3 port of the integrated optical element, and the H1 port of the polarization maintaining coupler is connected to the photodetector.

[0010] Preferably, the circuit control system comprises an analog-to-digital converter, a field programmable logic array, a first digital-to-analog converter and a second digital-to-analog converter, the field programmable logic array is connected to the analog-to-digital converter, the first digital-to-analog converter and the second digital-to-analog converter respectively, the first digital-to-analog converter and the second digital-to-analog converter are connected to the electrodes of the integrated optical element and the electrodes of the polarization controller respectively, and the analog-to-digital converter is connected to the photodetector and a power supply.

[0011] Preferably, the light path between the Y2 port of the integrated optical element and the H3 port of the polarization maintaining coupler constitutes a measurement arm of the Mach-Zehnder interference structure, and the light path between the Y3 port of the integrated optical element and the H2 port of the polarization maintaining coupler constitutes a reference arm of the Mach-Zehnder interference structure.

[0012] Preferably, the double helix micro-nano waveguide magnetic field probe is prepared from magneto-optic refractive polymer material by femtosecond laser two-photon polymerization technology, the magneto-optic refractive polymer material is prepared by doping terbium nanoparticles and polymer, the magnetic sensitivity of the waveguide is improved by the magneto-optic refractive material, the magnetic sensitive waveguide length is increased at a smaller size by the double helix structure, and the magnetic sensitivity of the photonic device is further improved.

[0013] Preferably, the Y1 port of the integrated optical element is used as a linearly polarized light incident port, the Y2 port and the Y3 port are used as linearly polarized light emission ports, and the light incident from the Y1 port is divided into two beams of light inside and emitted from the Y2 port and the Y3 port, respectively.

[0014] Preferably, the first polarization beam splitter and the second polarization beam splitter are based on the principle of evanescent coupling effect, the A port and the B port are used for transmitting vertical linearly polarized light and horizontal linearly polarized light, respectively, and the C port is used for transmitting linearly polarized light in any direction; the vertical linearly polarized light or the horizontal linearly polarized light incident from the A port or the B port can only be emitted from the C port, the vertical linearly polarized light incident from the C port can only be emitted from the B port, and the horizontal linearly polarized light incident from the C port can only be emitted from the A port. In the present application, the B1 and B2 ports of the two polarization beam splitters are welded at 0°.

[0015] Preferably, the H2 port and the H3 port of the polarization maintaining coupler are used as linearly polarized light incident ports, and the H1 port is used as a linearly polarized light emission port; the light of the reference arm and the measurement arm of the Mach-Zehnder interference structure is incident to the polarization maintaining coupler from the H2 port and the H3 port, respectively, and is emitted from the H1 port after interference.

[0016] Preferably, the double helix micro-nano waveguide magnetic field probe has a Taiji structure formed by tangentially connecting two identical spiral structures, wherein a single spiral structure has m concentric semicircular arc units with increasing radii from inside to outside, taking the centers of the two semicircular arc units in the innermost layer as centers, and the opening directions of the concentric semicircular arc units are consistent; the two semicircular arc units in the innermost layer are tangent and have opposite opening directions, and the remaining concentric semicircular arc units are sequentially connected to form a spiral structure; the openings of the outermost peripheries of the two spiral structures are tangential after being respectively elongated by 1 / 4 circular arcs, forming a Taiji double helix structure, and the other two openings are respectively used as input and output ports of the Taiji double helix structure.

[0017] Preferably, the polarization controller is a lithium niobate crystal-based polarization controller, and the optical fiber delay coil is a polarization maintaining optical fiber coil, and the length of the optical fiber delay coil depends on the frequency of the control system.

[0018] The application further discloses a control method of the double-helix polarization regulation and circulation amplification micro-nano waveguide magnetic field sensing device.

[0019] 1) Linearly polarized light with a polarization state in a vertical direction emitted by a light source is split into two parts after being incident on the Y1 port of the integrated optical element, and is emitted from the Y2 port and the Y3 port respectively, and enters the measurement arm end and the reference arm end of the Mach-Zehnder interference optical path respectively, and a voltage is applied to the electrode of the integrated optical element by the circuit control system to modulate the phase of the emitted light of the Y2 port, and the phase difference between the measurement arm optical path and the reference arm optical path is modulated.

[0020] 2) The linearly polarized light entering the measurement arm end of the Mach-Zehnder interference optical path circulates multiple times in the circulation amplification system, and specifically:

[0021] The linearly polarized light with a polarization state in a vertical direction emitted from the Y2 port of the integrated optical element is incident on the A port to the first polarization beam splitter, and then enters the incident end of the polarization controller from the C port, at this time, a voltage is applied to the electrode of the polarization controller by the circuit control system, which is used to convert the polarization state of the light to a horizontal direction, and then the linearly polarized light with a polarization state in a horizontal direction enters the double-helix micro-nano waveguide magnetic field probe and the optical fiber delay coil in sequence from the exit end of the polarization controller, and the linearly polarized light with a polarization state in a horizontal direction emitted from the optical fiber delay coil is incident on the second polarization beam splitter from the C port, and then enters the B port of the first polarization beam splitter from the B port of the second polarization beam splitter, and one circulation amplification is completed; by controlling the voltage applied to the electrode of the polarization controller, the polarization state of the linearly polarized light emitted from the polarization controller is maintained in a horizontal direction, so that the optical signal can be routed multiple times in the optical path to realize multiple amplifications;

[0022] When it is necessary to output signal light, the polarization state of the light is converted to a vertical direction by controlling the voltage applied to the electrode of the polarization controller, and then the linearly polarized light with a polarization state in a vertical direction enters the double-helix micro-nano waveguide magnetic field probe and the optical fiber delay coil in sequence from the exit end of the polarization controller, and the linearly polarized light with a polarization state in a vertical direction emitted from the optical fiber delay coil is incident on the second polarization beam splitter from the C port, and then enters the H3 port of the polarization maintaining coupler from the A port of the second polarization beam splitter.

[0023] 3) The light emitted from the Y3 port of the integrated optical element enters the polarization maintaining coupler from the H2 port, and interferes with the light entering the polarization maintaining coupler from the H3 port, and the interference light signal is emitted from the H1 port and received by the photodetector, the received optical signal is converted into a digital signal, and the measured magnetic field size is obtained after demodulation.

[0024] The application has the following beneficial effects:

[0025] This invention utilizes femtosecond laser two-photon polymerization technology to fabricate a double-helix micro / nano waveguide magnetic field probe with magneto-optical refractive effect. Combined with a cyclic amplification timing control method, it overcomes key technologies such as controllable cycle count and stable compensation for power fading in the cyclic optical path, and constructs a cyclic amplification optical path to obtain a high-sensitivity, high-stability micro / nano photonic device, a polarization-controlled cyclic amplification system, and a high-performance magnetic field measurement system with a sensitivity of 5 pT, forming a miniaturized, high-sensitivity micro / nano photonic weak magnetic sensor. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the principle of the polarization beam splitter used in this invention;

[0027] Figure 2 This is a schematic diagram of the integrated optical element used in this invention;

[0028] Figure 3 This is a schematic diagram of the bias-maintaining coupler used in this invention;

[0029] Figure 4 This is a schematic diagram of the structure of the double-helix micro / nano waveguide magnetic field probe used in this invention.

[0030] Figure 5 This is a schematic diagram of the structure of the double-helix polarization-controlled cyclic amplification micro / nano waveguide magnetic field sensing device of the present invention.

[0031] In the figure: 1 photodetector, 2 polarization-maintaining coupler, 3 second polarization beam splitter, 4 fiber delay coil, 5 double-helix micro / nano waveguide magnetic field probe, 6 polarization controller, 7 first polarization beam splitter, 8 integrated optical element, 9 light source, 10 analog-to-digital converter, 11 field-programmable logic array (FPGA), 12 first digital-to-analog converter, 13 second digital-to-analog converter. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] like Figure 1 As shown, the polarization beam splitter, based on the principle of evanescent coupling, contains three ports (A, B, and C), each connected to a polarizing fiber. Port A can only propagate linearly polarized light with a vertical polarization direction, port B can only propagate linearly polarized light with a horizontal polarization direction, and port C can propagate linearly polarized light in any direction. Polarized light incident from ports A and B can only propagate in the vertical and horizontal polarization directions of port C, respectively. Conversely, vertically polarized light and horizontally polarized light incident from port C can only exit from port A or port B, respectively, ensuring the uniqueness and separability of polarization transmission.

[0034] like Figure 2As shown, the integrated optical element 8 is made of lithium niobate, light is incident from its Y1 port, is split into two beams inside, and is emitted from its Y2 port and Y3 port respectively, and has a phase modulation electrode Z inside for controlling the light emitted from the Y2 port, the voltage of the electrode is provided by the first digital-to-analog converter 12, and the modulation of the phase difference between the measurement light path and the reference light path is realized by voltage regulation to achieve the optimal detection sensitivity.

[0035] As shown in the figure, Figure 3 The polarization maintaining coupler 2 has three ports, H1 port, H2 port and H3 port, the light of the reference arm and the measurement arm of the Mach-Zehnder interference structure is incident into the polarization maintaining coupler 2 from its H2 port and H3 port respectively, and is emitted from its H1 port after interference.

[0036] As shown in the figure, Figure 4 The double helix micro-nano waveguide magnetic field probe 5 as a whole is in the shape of Taiji, which is formed by tangentially connecting two helix structures of the same size, wherein a single helix structure is composed of a series of semicircular arc units in linear relationship, and the cross section of the semicircular arc unit constituting the helix structure adopts a square with a side length of d. The center of a single helix structure is two semicircular arc units C1 and C2 with equal diameters r, the two semicircular arc units C1 and C2 are tangent and the opening directions are opposite. Taking the center O1 of the semicircular arc unit C1 as the center, there are m concentric semicircular arc units except the outermost 1 / 4 circular arc, and the radii from inside to outside are R_i=r / 2+(i-1)×(d+l)(i=1,…,m), the opening directions are the same as C1, and r / 2 is the radius of the semicircular arc unit C1; m=3 is shown in the figure.

[0037] Similarly, taking the center O2 of the semicircular arc unit C2 as the center, there are m concentric semicircular arc units except the outermost 1 / 4 circular arc, and the radii from inside to outside are R_i=r / 2+(i-1)×(d+l)(i=1,…,m), the opening directions are the same as C2.

[0038] The m concentric semicircular arc units with O1 as the center and the m concentric semicircular arc units with O2 as the center are connected two by two to form the entire helix structure, wherein d is the cross-sectional side length of the semicircular arc unit, and l is the spacing between adjacent two semicircular arc units; the outermost periphery of the two helix structures is connected together through two 1 / 4 circular arc structures tangent at point P to form a Taiji-shaped double helix structure; the semicircular arc adjacent to the outermost 1 / 4 circular arc in the corresponding helix structure of the Taiji-shaped double helix structure is the input and output port of the Taiji-shaped double helix structure.

[0039] In this embodiment, the waveguide cross-sectional side length d of each helix structure is about 6μm, the outermost 1 / 4 circular arc diameter of a single helix structure is 1mm, and the waveguide spacing l is 14μm.

[0040] like Figure 5 As shown, a dual-helix polarization-controlled cyclic amplification micro / nano waveguide magnetic field sensing device includes a photodetector 1, a polarization-maintaining coupler 2, a second polarization beamsplitter 3, an optical fiber delay coil 4, a dual-helix micro / nano waveguide magnetic field probe 5, a polarization controller 6, a first polarization beamsplitter 7, an integrated optical element 8, a light source 9, an analog-to-digital converter 10, a field-programmable logic array (FPGA) 11, a first digital-to-analog converter 12, and a second digital-to-analog converter 13. The first polarization beamsplitter 7 and the second polarization beamsplitter 3 each have three optical interfaces: port A, port B, and port C, which are connected to polarizing optical fibers. The integrated optical element 8 includes three optical interfaces: port Y1, port Y2, and port Y3. The polarization-maintaining coupler 2 includes three optical interfaces: port H1, port H2, and port H3. The polarization controller can change or maintain the polarization state of linearly polarized light incident on it by altering the voltage applied to its electrodes. The output end of the light source is connected to the Y1 port of the integrated optical element 8. The Y2 and Y3 ports of the integrated optical element 8 are respectively connected to the A1 port of the first polarization beamsplitter 7 and the H2 port of the polarization-maintaining coupler 2. The H1 and H3 ports of the polarization-maintaining coupler 2 are respectively connected to the A2 port of the photodetector 1 and the second polarization beamsplitter 3. The B ports of the first polarization beamsplitter 7 and the second polarization beamsplitter 3 are connected. One end of the fiber delay coil 4 is connected to the C2 port of the second polarization beamsplitter 3, and the other end is connected to one end of the double-helix micro / nano waveguide magnetic field probe 5. The other end of the double-helix micro / nano waveguide magnetic field probe 5 is connected to one end of the polarization controller 6. The other end of the polarization controller 6 is connected to the C1 port of the first polarization beam splitter 7. The field programmable logic array (FPGA) 11 controls and connects the first digital-to-analog converter 12, the second digital-to-analog converter 13, and the analog-to-digital converter 10. The first digital-to-analog converter 12 and the second digital-to-analog converter 13 are respectively connected to the phase modulation electrode of the integrated optical element 8 and the electrode of the polarization controller 6, providing voltage to them respectively. The analog-to-digital converter 10 is connected to the photodetector 1.

[0041] In one specific embodiment of the present invention, the center wavelength of the light source 1 is 1550nm, and the emitted light is linearly polarized.

[0042] 1) The light emitted from the light source 9 enters through the Y1 port of the integrated optical element 8, and is split into two beams inside it. The beams exit through the Y2 port and the Y3 port, respectively, and enter the measurement arm and reference arm of the Mach-Zehnder interferometer optical path, respectively. The first digital-to-analog converter 12, controlled by the field programmable logic array (FPGA) 11, provides voltage to the phase modulation electrode Z of the integrated optical element 8, modulating the phase of the light emitted from the Y2 port, thereby modulating the phase difference between the measurement optical path and the reference optical path to achieve optimal detection sensitivity.

[0043] 2) The linearly polarized light entering the end of the measurement arm of the Mach-Zehnder interferometer circulates multiple times in the circulating amplification system, specifically:

[0044] (a) Linearly polarized light with a vertical polarization direction emitted from the Y2 end of the integrated optical element 8 is incident on the first polarization beam splitter 7 from the A1 port, is emitted from the C1 port of the first polarization beam splitter 7 to the incident end of the polarization controller 6, at which time the second digital-to-analog converter 13 controlled by the field programmable gate array (FPGA) 11 provides a voltage to the polarization controller 6, converting the polarization state of the light to linearly polarized light with a horizontal polarization direction. This linearly polarized light is emitted from the other end of the polarization controller 6 to one end of the double-helix micro-nano waveguide magnetic field probe 5, is emitted from the other end of the double-helix micro-nano waveguide magnetic field probe 5 to one end of the fiber delay coil 4, is emitted from the other end of the fiber delay coil 4 to the C2 port of the second polarization beam splitter 3, and is finally emitted from the B2 port of the second polarization beam splitter 3 to the B1 port of the first polarization beam splitter 7 to complete one cycle. In subsequent cycles, the polarization state emitted by the polarization controller 6 is kept as linearly polarized light with a horizontal polarization direction;

[0045] (b) Step (a) is repeated n times to achieve multiple rounds of the optical signal in the optical path, circulating through the photonic waveguide to produce a magnetic phase accumulation and improve the magnetic sensitivity of the sensing unit. When the output signal light is needed, the second digital-to-analog converter 13 controlled by the field programmable gate array (FPGA) 11 provides a voltage to the polarization controller 6, converting the polarization state of the light to linearly polarized light with a vertical polarization direction. At this time, the linearly polarized light emitted from the polarization controller 6 is incident on the C2 port of the second polarization beam splitter 3 and is finally emitted from the A2 port of the second polarization beam splitter 3 to the H3 port of the polarization maintaining coupler 2 after passing through the double-helix micro-nano waveguide magnetic field probe 5 and the fiber delay coil 4. At this time, the optical signal makes n+1 rounds in the double-helix micro-nano waveguide magnetic field probe 5, achieving n+1 times improvement in magneto-optical sensitivity;

[0046] 3) During the above propagation process, under the action of an external magnetic field, a magnetic phase difference is generated between the two beams of light transmitted in clockwise and counterclockwise directions in the double-helix micro-nano waveguide magnetic field probe 5. The light emitted from the Y3 port of the integrated optical element 8 enters the H2 port of the polarization maintaining coupler 2, couples and interferes with the light emitted from the H3 port of the circulating amplification system to the H1 port of the polarization maintaining coupler 2, and is emitted from the H1 port of the polarization maintaining coupler 2 to the photodetector 1. The photodetector 1 converts the light into an analog voltage, which is converted into a digital signal by the analog-to-digital converter 10, received and demodulated by the field programmable gate array (FPGA) 11, and the size of the measured magnetic field is obtained.

[0047] The present application introduces the double helix micro-nano waveguide magnetic field probe 5 into the magnetic field deformation optical waveguide device, increases the magneto-optical path difference of the Malus-Zen measurement arm, improves the sensitivity of the device, and obtains a high-sensitivity magnetic field sensor; and introduces the polarization modulation cyclic amplification technology into the magnetic field sensor, so that the circulation number of the transmission light in the sensitive light path is controllable, the amplification multiple can be regulated and controlled as needed, and the magnetic sensitivity of the weak magnetic sensing device is greatly increased.

[0048] The above is only a specific embodiment of the present application. Obviously, the present application is not limited to the above embodiment, and there can be many variations. All variations that can be directly derived or inferred from the disclosure of the present application by those of ordinary skill in the art should be considered as falling within the scope of the present application.

Claims

1. A double-helical polarization-modulated circularly amplified micro-nano waveguide magnetic field sensing device, characterized in that, The application relates to a kind of optical fiber magnetic field sensor, including light source, circuit control system, the Ma-Zeng interference structure based on circulating amplification system, the circuit control system is used for controlling light source and the Ma-Zeng interference structure based on circulating amplification system; The Ma-Zeng interference structure based on circulating amplification system includes a photodetector (1), a polarization maintaining coupler (2), a second polarization beam splitter (3), a fiber delay coil (4), a double helix micro-nano waveguide magnetic field probe (5), a polarization controller (6), a first polarization beam splitter (7) and an integrated optical element (8). The double helix micro-nano waveguide magnetic field probe (5) is in a Taiji-like structure and is formed by tangentially connecting two identical spiral structures, wherein each spiral structure has m concentric semicircular arc units with increasing radii from inside to outside, and the opening directions of the concentric semicircular arc units are consistent; the two semicircular arc units in the innermost layer are tangent and have opposite opening directions, and the remaining concentric semicircular arc units are sequentially connected to form a spiral structure; the openings in the outermost periphery of one spiral structure and the openings in the outermost periphery of the other spiral structure are tangential after being extended by 1 / 4 of a circle, thereby forming a Taiji-like double helix structure, and the other two openings are used as input and output ports of the Taiji-like double helix structure. The light source is connected to the Y1 port of the integrated optical element (8), the Y2 port of the integrated optical element (8) is connected to the A port of the first polarization beam splitter (7), the C port of the first polarization beam splitter (7) is connected to the incident port of the polarization controller (6), the polarization controller (6) is connected to the C port of the second polarization beam splitter (3) through the series connection of the double helix micro-nano waveguide magnetic field probe (5) and the fiber delay coil (4), the B port of the second polarization beam splitter (3) is connected to the B port of the first polarization beam splitter (7), the A port of the second polarization beam splitter (3) is connected to the H3 port of the polarization maintaining coupler (2), the H2 port of the polarization maintaining coupler (2) is connected to the Y3 port of the integrated optical element (8), and the H1 port of the polarization maintaining coupler (2) is connected to the photodetector.

2. The double-helical polarization-manipulated ring-down magnification micro- nanowire magnetic field sensor device of claim 1, wherein, The circuit control system includes an analog-to-digital converter (10), a field programmable logic array (11), a first digital-to-analog converter (12) and a second digital-to-analog converter (13); the field programmable logic array (11) is connected to the analog-to-digital converter (10), the first digital-to-analog converter (12) and the second digital-to-analog converter (13), respectively; the first digital-to-analog converter (12) and the second digital-to-analog converter (13) are connected to the electrodes of the integrated optical element (8) and the electrodes of the polarization controller (6), respectively; and the analog-to-digital converter (10) is connected to the photodetector (1). 3.The dual-helical polarization-tunable loop-amplified micro-nano waveguide magnetic field sensor device according to claim 1, wherein, The optical path between the Y2 port of the integrated optical element (8) and the H3 port of the polarization maintaining coupler (2) constitutes a measurement arm of the Ma-Zeng interference structure, and the optical path between the Y3 port of the integrated optical element (8) and the H2 port of the polarization maintaining coupler (2) constitutes a reference arm of the Ma-Zeng interference structure. 4.The double-helical polarization-manipulated loop-amplified micro-nano waveguide magnetic field sensor device of claim 1, wherein, The double-helix micro-nano waveguide magnetic field probe (5) is prepared from a magneto-optic refractive polymer material by a femtosecond laser two-photon polymerization technology, and the magneto-optic refractive polymer material is prepared by synthesizing terbium nanoparticles and a polymer. 5.The dual-helical polarization-tunable loop-amplified micro-nano waveguide magnetic field sensor device of claim 1, wherein, The Y1 port of the integrated optical element (8) is used as a linearly polarized light incident port, and the Y2 port and the Y3 port are used as linearly polarized light emission ports; the light incident from the Y1 port is divided into two beams of light inside, and the two beams of light are emitted from the Y2 port and the Y3 port, respectively.

6. The double-helical polarization-manipulated ring-down magnification micro- nanowire magnetic field sensor device of claim 1, wherein, The A port and the B port of the first polarization beam splitter (7) and the second polarization beam splitter (3) are used for transmitting linearly polarized light in the vertical direction and linearly polarized light in the horizontal direction, respectively, and the C port is used for transmitting linearly polarized light in any direction; the linearly polarized light in the vertical direction or the linearly polarized light in the horizontal direction incident from the A port or the B port can be emitted only from the C port, the linearly polarized light in the vertical direction incident from the C port can be emitted only from the B port, and the linearly polarized light in the horizontal direction incident from the C port can be emitted only from the A port.

7. The double-helical polarization-manipulated ring-down magnification micro- nanowire magnetic field sensor device of claim 1, wherein, The H2 port and the H3 port of the polarization maintaining coupler (2) are used as linearly polarized light incident ports, and the H1 port is used as a linearly polarized light emission port; the light of the reference arm and the measurement arm of the Mach-Zehnder interference structure is incident from the H2 port and the H3 port to the polarization maintaining coupler (2), respectively, and is emitted from the H1 port after interference. 8.The dual-helical polarization-tunable loop-amplified micro-nano waveguide magnetic field sensor device of claim 1, wherein, The polarization controller (6) is a polarization controller based on a lithium niobate crystal, and the optical fiber delay coil (4) is a polarization maintaining optical fiber coil.

9. A control method for a double helix polarization modulation and cycle amplification micro-nano waveguide magnetic field sensor device according to claim 1, wherein the double helix micro-nano waveguide magnetic field probe (5) in the device is placed in a magnetic field environment to be measured, characterized in that, The application comprises the following steps: 1) the linearly polarized light in the vertical direction emitted from the light source (9) is divided into two beams after being incident from the Y1 port of the integrated optical element (8), and the two beams are emitted from the Y2 port and the Y3 port, respectively, and enter the measurement arm end and the reference arm end of the Mach-Zehnder interference optical path, respectively; the voltage is applied to the electrode of the integrated optical element (8) by the circuit control system to modulate the phase of the light emitted from the Y2 port and modulate the phase difference between the measurement arm optical path and the reference arm optical path; 2) the linearly polarized light entering the measurement arm end of the Mach-Zehnder interference optical path circulates multiple times in the circulating amplification system, and the specific process is as follows: the linearly polarized light in the vertical direction emitted from the Y2 port of the integrated optical element (8) is incident from the A port to the first polarization beam splitter (7), and then enters the incident end of the polarization controller (6) from the C port; at this time, the voltage is applied to the electrode of the polarization controller (6) by the circuit control system to convert the polarization state of the light to the horizontal direction; then the linearly polarized light in the horizontal direction enters the double-helix micro-nano waveguide magnetic field probe (5) and the optical fiber delay coil (4) from the exit end of the polarization controller (6) in sequence; the linearly polarized light in the horizontal direction emitted from the optical fiber delay coil (4) is incident from the C port to the second polarization beam splitter (3), and then enters the B port of the first polarization beam splitter (7) from the B port of the second polarization beam splitter (3), to complete one cycle of amplification; the voltage applied to the electrode of the polarization controller (6) is controlled to maintain the polarization state of the linearly polarized light emitted from the polarization controller (6) in the horizontal direction, so that the optical signal circulates in the optical path multiple times to realize multiple amplifications. ​ When the output signal light is needed, the polarization state of the light is converted to the vertical direction by controlling the voltage applied to the electrodes of the polarization controller (6), then the linearly polarized light in the vertical direction enters the double helix micro-nano waveguide magnetic field probe (5) and the fiber delay coil (4) from the exit end of the polarization controller (6) in turn, the linearly polarized light in the vertical direction from the fiber delay coil (4) enters the second polarization beam splitter (3) from the C port, and then enters the H3 port of the polarization maintaining coupler (2) from the A port of the second polarization beam splitter (3); 3) The light from the Y3 port of the integrated optical element (8) enters the polarization maintaining coupler (2) from the H2 port, interferes with the light entering the polarization maintaining coupler (2) from the H3 port, the interference light signal is emitted from the H1 port and received by the photodetector (1), the received light signal is converted into a digital signal, and the measured magnetic field size is obtained after demodulation.

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