An ultra-miniature cold atom inertial sensor with extended interference time

Abstract

This invention relates to an ultra-miniature cold atom inertial sensor with extended interference time, comprising a Raman optical path, a cooling optical path, a MOT coil assembly, a detector chip, and an ultra-miniature passive vacuum cavity. The MOT coil assembly is symmetrically arranged around the outer periphery of the ultra-miniature passive vacuum cavity to trap atomic clusters within the cavity using a magnetic field and to adjust the free fall distance of the atomic clusters. The cooling optical path penetrates both the MOT coil assembly and the ultra-miniature passive vacuum cavity to cool, trap, and prepare the atomic clusters. The Raman optical path is vertically incident on the ultra-miniature passive vacuum cavity to manipulate the cooled and trapped cold atomic clusters for interference. The detector chip is positioned adjacent to the ultra-miniature passive vacuum cavity to detect the atomic state signals after interference. This invention reduces the complexity, size, and weight of the sensor. By modulating the magnetic field to change the position of the trapped cold atomic clusters, adjusting the free fall distance of the atomic clusters, and extending the interference distance and time, it improves the accuracy of inertial measurement.

Description

Technical Field

[0001] This invention relates to the field of cold atom inertial measurement technology, and more specifically to an ultra-miniature cold atom inertial sensor with extended interference time. Background Technology

[0002] The cold atom interferometric precision measurement process occurs within a cold atom inertial sensor. A complete cold atom interferometric measurement process consists of atomic cooling and trapping, sub-Doppler cooling, state preparation, Raman interferometry, and fluorescence detection. The inertial parameter to be measured is transmitted to the interferometric measurement process, affecting the phase of the interference fringes. The required inertial parameter value is obtained by solving the interference fringes.

[0003] Cold atom inertial sensors rely on an active dual-axis stabilization platform to maintain the alignment of Raman light with the direction of gravity. The large size and weight of the cold atom inertial sensor itself, along with the increased size and weight of the stabilization platform, make it difficult to adapt to different dynamic environments. The complexity of the cold atom inertial sensor itself reduces the environmental adaptability of the device, limiting the application scenarios of cold atom inertial measurement equipment. The excessively high power consumption reduces the portability of the cold atom inertial sensor, limiting its application areas.

[0004] To address the aforementioned challenges, miniaturization of cold atom inertial sensors has become an inevitable trend. The increasing maturity of MEMS (Micro-Electro-Mechanical Systems) and PIC (Photonic Integrated Circuit) technologies offers new avenues for miniaturization. Utilizing MEMS and PIC technologies simplifies traditional cold atom inertial sensors, reducing system complexity and improving system integration and environmental adaptability. Replacing core components in cold atom inertial sensors with MEMS and PIC components can effectively reduce their size, weight, and power consumption. Furthermore, new materials and processes can help simplify the system while maintaining the performance of each core component, thereby ensuring the accuracy of cold atom inertial measurements.

[0005] Furthermore, the accuracy of cold atom inertial measurements is negatively correlated with the square of the interference time T, i.e., negatively correlated with the interference distance. Taking a cold atom gravimeter as an example, the gravitational change corresponding to a single interference fringe (2π) is λ / (2T). 2 This means that the accuracy is negatively correlated with the square of the interference period T and negatively correlated with the falling distance H. The longer the falling distance, the higher the theoretical measurement accuracy. The advantage of miniaturized cold atom inertial sensors lies in the fact that repeated trapping can greatly shorten the cooling trapping time of atomic clusters, improve the gravity data output rate, and significantly enhance the ability to resist dynamic environments. However, this inevitably leads to a reduction in the falling distance, which in turn reduces the measurement accuracy. How to extend the falling distance without increasing the system complexity is one of the issues that need to be considered in the miniaturization design of cold atom inertial sensing systems. Summary of the Invention

[0006] Based on the above description, the present invention provides an ultra-miniature cold atom inertial sensor with extended interference time to solve the problem of measurement accuracy being limited by the short interference time in miniaturized cold atom inertial sensors.

[0007] The technical solution of this invention to solve the above-mentioned technical problems is as follows: An ultra-miniature cold atom inertial sensor with extended interference time, comprising a chip-type Raman optical path, a chip-type cooling optical path, an MOT coil group, a detector chip, and an ultra-miniature passive vacuum cavity, wherein:

[0008] The MOT coil group is symmetrically arranged on the outer periphery of the ultra-small passive vacuum cavity to trap the atomic clusters in the ultra-small passive vacuum cavity by magnetic field and to adjust the free fall path of the atomic clusters.

[0009] The chip-type cooling optical path runs through the MOT coil group and the ultra-small passive vacuum cavity to cool, trap, and prepare the atomic clusters.

[0010] The chip-type Raman optical path is vertically incident on the ultra-small passive vacuum cavity to manipulate the cooled and trapped cold atom clusters for interference;

[0011] The detection chip is positioned adjacent to the ultra-small passive vacuum cavity to detect the atomic state signal after interference.

[0012] Based on the above technical solution, the present invention can be further improved as follows.

[0013] Preferably, the MOT coil group includes two bias magnetic field coils and two MOT magnetic field coils. The two bias magnetic field coils are arranged coaxially vertically and are correspondingly arranged at the upper and lower ends of the ultra-small passive vacuum cavity. This is used to change the vertical position of the cold atom cluster by adjusting the bias magnetic field, thereby extending the falling distance of the cold atom cluster. The two MOT magnetic field coils are arranged coaxially horizontally, and the ultra-small passive vacuum cavity is located between the two MOT magnetic field coils to rapidly and repeatedly trap the atom cluster. The chip-type cooling optical path horizontally passes through one of the MOT magnetic field coils and enters the ultra-small passive vacuum cavity.

[0014] Preferably, the chip-type cooling optical path includes a cooling light input fiber, a cooling light beam expander collimator chip, a cooling light polarization modulation system, and a grating chip arranged sequentially along the cooling light propagation direction, and the ultra-small passive vacuum cavity is disposed between the cooling light polarization modulation system and the grating chip;

[0015] The cooling light input fiber is used to input cooling light, pump-back light, state preparation light and probe light into the chip-type cooling light path;

[0016] The cooling light beam expander and collimator chip is fixedly connected to the cooling light input fiber and is used to adjust the spot size and collimation of the light input to the chip-type cooling light path to obtain a Gaussian collimated cooling beam.

[0017] The cooling light polarization modulation system is used to adjust the polarization state of the Gaussian collimated cooling beam and to input the Gaussian collimated cooling beam with the adjusted polarization state into the ultra-small passive vacuum cavity along the axis of the MOT magnetic field coil.

[0018] The grating chip is used to convert the Gaussian collimated cooling beam passing through the ultra-small passive vacuum cavity into three first-order diffracted beams, the propagation direction of the three first-order diffracted beams being toward the atomic trapping region of the ultra-small passive vacuum cavity.

[0019] Preferably, the grating chip has three sets of grating structures on the side facing the output end of the cooling light polarization modulation system. The three sets of grating structures are connected end to end to form an equilateral triangle. Each set of grating structures generates a first-order diffraction beam according to the Gaussian collimated cooling beam.

[0020] Preferably, the grating chip is disposed close to the outer wall of the ultra-small passive vacuum cavity.

[0021] Preferably, the cooling light beam expanding and collimating chip includes a first solid waveguide and a first apodization grating connected along the optical path. The first solid waveguide is used to guide the input cooling light, return pump light, state preparation light and probe light to the first apodization grating. The first apodization grating is used to convert the input cooling light, return pump light, state preparation light and probe light into a Gaussian collimated cooling beam.

[0022] Preferably, the chip-type Raman optical path includes a Raman light input fiber, a Raman light beam expander and collimator chip, a Raman light polarization modulation system, and a polarization beam splitter (PBS) arranged sequentially along the light propagation direction, and further includes a first reflecting mirror and a conical reflecting mirror, wherein:

[0023] The Raman light input fiber is used to input Raman light with two different frequency components into the chip-type Raman light path;

[0024] The Raman beam expanding and collimating chip is fixedly connected to the Raman beam input fiber and is used to adjust the spot size and collimation of the input Raman beam to obtain Gaussian collimated Raman beam after beam expansion and collimation.

[0025] The Raman polarization modulation system is used to adjust the Gaussian collimated Raman light to the polarization state required for interference.

[0026] The polarization beam splitter PBS has a transmission output end and a reflection output end, which is used to split the Gaussian collimated Raman light after the polarization state is adjusted into a first Raman light and a second Raman light according to the frequency. The first Raman light and the second Raman light are output from the transmission output end and the reflection output end respectively in a one-to-one correspondence.

[0027] The first reflector is disposed above the ultra-small passive vacuum cavity, so that the first Raman light is reflected and vertically incident on the atomic trapping region of the ultra-small passive vacuum cavity along the central axis of the bias magnetic field coil;

[0028] The conical reflector is positioned below the miniature passive vacuum cavity to reflect the second Raman light and then vertically incident it along the central axis of the bias magnetic field coil into the atomic trapping region of the miniature passive vacuum cavity.

[0029] Preferably, the Raman beam expanding and collimating chip includes a second solid waveguide and a second apodization grating connected along the optical path. The second solid waveguide is used to guide the input Raman light to the second apodization grating, and the second apodization grating is used to convert the input Raman light into Gaussian collimated Raman light.

[0030] Preferably, the detector chip is positioned perpendicular to the chip-type cooling optical path.

[0031] Preferably, the detection chip is a chip-type fluorescent detection lens.

[0032] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: The ultra-miniature cold atom inertial sensor with extended interference time provided by this invention effectively reduces the complexity, size, weight and power consumption of the inertial sensor through the miniaturization and chip-based structure design of key internal components; through reasonable optical path and magnetic field design, rapid and repeated trapping of cold atom clusters is achieved, effectively reducing the time required for cluster trapping and improving the data output rate of cold atom inertial measurement; by modulating the magnetic field to change the position of the trapped cold atom clusters and adjusting the free fall path length of the clusters, the interference distance and interference time of the cold atom clusters are extended, improving the accuracy of inertial measurement within a limited space. Attached Figure Description

[0033] Figure 1a This is a schematic diagram illustrating the principle of an ultra-miniature cold atom inertial sensor with extended interference time, provided by an embodiment of the present invention. Figure 1b This is a schematic diagram of the cooling optical path principle of an ultra-miniature cold atom inertial sensor with extended interference time, provided by an embodiment of the present invention. Figure 1c A schematic diagram of the interference optical path principle of an ultra-miniature cold atom inertial sensor with extended interference time provided in an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of the detection optical path of an ultra-miniature cold atom inertial sensor with extended interference time provided in an embodiment of the present invention;

[0035] Figure 3 A schematic diagram of a scheme for repeated trapping and interference time extension of an ultra-small cold atom inertial sensor provided in an embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of the beam expander and collimator chip structure provided in an embodiment of the present invention.

[0037] The attached diagram lists the components represented by each number as follows:

[0038] 1. Raman light input fiber; 2. Raman light beam expander and collimator chip; 3. Raman light polarization modulation system; 4. Polarization beam splitter prism (PBS); 5. First reflector; 6. MOT coil group; 7. Ultra-miniature passive vacuum cavity; 8. Grating chip; 9. Conical reflector; 10. Cooled light input fiber; 11. Cooled light beam expander and collimator chip; 12. Cooled light polarization modulation system; 13. Detector chip; 60. First bias magnetic field coil; 61. Second bias magnetic field coil; 62. First MOT magnetic field coil; 63. Second MOT magnetic field coil; 64. MOT center position; 65. End point of free fall of atomic cluster; 66. Highest position of MOT trapped atomic cluster; 110. First solid waveguide; 111. First apodization grating; 20. Second solid waveguide; 21. Second apodization grating. Detailed Implementation

[0039] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0041] It is understood that spatial relation terms such as "below," "under," "below," "below," "above," "over," etc., can be used here to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as "below" or "under" or "below" of other elements or features will be oriented "over" of other elements or features. Therefore, the exemplary terms "below" and "under" can include both upper and lower orientations. Furthermore, the device may also include other orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptive terms used herein will be interpreted accordingly.

[0042] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediary element. In the following embodiments, "connection" should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have the transmission of electrical signals or data between them.

[0043] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0044] Currently, cold atom inertial sensors are large in size, weight, and power consumption. Maintaining high-precision cold atom inertial measurements on dynamic carriers is costly. Typically, a two-axis stabilization platform with greater load-bearing capacity and better dynamic performance is needed to maintain the attitude stability of the inertial sensor, which undoubtedly limits the application scenarios of cold atom inertial sensors. The high complexity also results in poor adaptability to dynamic environments and poor portability of cold atom inertial sensors, further limiting their application scenarios.

[0045] To solve the above problems, such as Figures 1a-1c As shown, this embodiment of the invention provides an ultra-miniature cold atom inertial sensor with extended interference time, including a chip-type Raman optical path, a chip-type cooling optical path, an MOT coil group 6, a detector chip 13, and an ultra-miniature passive vacuum cavity 7. The chip-type cooling optical path is as follows: Figure 1b As shown by the arrow, the chip-type Raman optical path is as follows: Figure 1c As shown by the arrow, where:

[0046] The MOT coil group 6 is symmetrically arranged on the outer periphery of the ultra-small passive vacuum cavity 7 to trap atomic groups in the ultra-small passive vacuum cavity 7 by magnetic field and to adjust the free fall stroke of the atomic groups; the ultra-small passive vacuum cavity 7 is preferably a miniaturized passive vacuum glass cavity containing alkali metal vapor as the atomic source for interferometric measurement.

[0047] like Figure 1b As shown, the chip-type cooling optical path passes through the MOT coil group 6 and the ultra-small passive vacuum cavity 7 to cool, trap, and prepare the atomic clusters.

[0048] like Figure 1c As shown, the chip-type Raman optical path is vertically incident on the ultra-small passive vacuum cavity 7 to manipulate the cold atom clusters after cooling and trapping to interfere, thereby realizing precise measurement of gravitational acceleration.

[0049] like Figure 2 As shown, the detector chip 13 is disposed adjacent to the ultra-small passive vacuum cavity 7 to detect the atomic state signal after interference, such as fluorescence signal.

[0050] Understandably, based on the deficiencies in the background technology, this embodiment of the invention proposes an ultra-miniature cold atom inertial sensor with extended interference time.

[0051] The primary objective of this invention is to design an ultra-miniature cold atom gravimeter based on MEMS and PIC technologies. By utilizing a chip magneto-optical trap (MOT), a beam-expanding and collimating optical path based on an apodization grating chip 8, and passive glass cavity technology, an ultra-small cold atom inertial sensor is designed. This effectively reduces the complexity, size, weight, and power consumption of the cold atom inertial sensor, enhances its dynamic environmental adaptability, improves the inertial data output rate, and maximizes the interference time within a limited volume to ensure the accuracy of cold atom inertial measurements.

[0052] A secondary objective of this invention is to develop general miniaturization techniques applicable to the field of cold atom inertial measurement, which can be extended to different cold atom inertial measurement systems to achieve miniaturization and integration of inertial sensors, transforming laboratory devices into engineered portable instruments.

[0053] When this cold atom inertial sensor is working, it uses methods such as... Figure 1bThe cooling light provided by the chip-type cooling optical path causes alkali metal atoms in the ultra-miniature passive vacuum cavity 7 to form optical clusters, concentrating the atoms within a specific region. Combined with the magneto-optical trap formed by the MOT coil group 6, the atoms are bound within the preset atomic confinement region by an inward force, preventing escape. The MOT coil group 6 allows for both the confinement of atomic clusters and the modulation of their magnetic field bias by adjusting the coil current, thereby enabling the adjustment of the free-fall trajectory of the atomic clusters. By cooling and confining the atoms through the chip-type cooling optical path and the magneto-optical trap formed by the MOT coils, a cold atomic cluster with adjustable trajectory is obtained. Then, two Raman beams of different frequencies in the chip-type Raman optical path act on the cold atomic cluster from two opposite directions. The two frequencies of Raman beams work together to manipulate the atomic cluster, achieving the interferometric measurement process. The detection chip 13 detects the fluorescence signal of the cold atomic cluster to calculate the physical quantity to be measured, such as gravitational acceleration.

[0054] This invention effectively reduces the complexity, size, weight, and power consumption of inertial sensors through a compact internal sensor structure design; it achieves rapid and repeated trapping of cold atom clusters through reasonable optical path and magnetic field design, effectively reducing the time required for cluster trapping and improving the data output rate of cold atom inertial measurements; by modulating the magnetic field to change the position of the trapped cold atom clusters, adjusting the free fall path length of the clusters, and extending the interference distance and interference time of the cold atom clusters, the accuracy of inertial measurements is improved within a limited space.

[0055] Based on the above technical solution, this embodiment can be further improved as follows.

[0056] Figure 1b This demonstrates the optical path principle of the cooling light in one possible implementation. (Combined with...) Figure 1b and Figure 3 As shown, the chip-type cooling optical path includes a cooling light input fiber 10, a cooling light beam expander collimator chip 11, a cooling light polarization modulation system 12, and a grating chip 8 arranged sequentially along the cooling light propagation direction. The ultra-small passive vacuum cavity 7 is disposed between the cooling light polarization modulation system 12 and the grating chip 8.

[0057] The cooling light input fiber 10 is used to input cooling light, pump back light, state preparation light and probe light into the chip-type cooling light optical path; wherein, the cooling light is used to cool the atomic cluster, the pump back light is used to assist in cooling the trapped atoms, the state preparation light is used to prepare the state of the atomic cluster, and the probe light is used to detect the atomic state after the interference is completed;

[0058] The cooling light beam expanding and collimating chip 11 is fixedly connected to the cooling light input fiber 10 and is used to adjust the spot size and collimation of the light input to the chip-type cooling light path to obtain a Gaussian collimated cooling beam, which becomes a cooling light that can be used to trap cold atom clusters.

[0059] The cooling light polarization modulation system 12 is used to adjust the polarization state of the Gaussian collimated cooling beam, for example, to modulate the polarization state to the circularly polarized light required for cold atom cooling and trapping, and to input the Gaussian collimated cooling beam after adjusting the polarization state into the ultra-small passive vacuum cavity 7 along the axial direction of the MOT magnetic field coil.

[0060] The grating chip 8 is used to convert the Gaussian collimated cooling beam passing through the ultra-miniature passive vacuum cavity 7 into three first-order diffracted beams, the propagation direction of which is towards the atomic trapping region of the ultra-miniature passive vacuum cavity 7. Figure 1b As shown by the arrow, the atoms are cooled and trapped by a Gaussian collimated cooling beam and three first-order diffraction beams generated by the grating chip 8.

[0061] Understandably, the shared optical path for cooling light, pump-back light, state preparation light, and probe light reduces the number of input optical paths for the inertial sensor, effectively lowering its size, weight, and power consumption. The grating chip 8, combined with the MOT coil group 6, simplifies the existing six-beam spatial MOT to requiring only one input beam (one cooling light input optical path), significantly reducing system complexity. The cooling light beam expander and collimator chip 11, while reducing the complexity of the optical path system, also effectively reduces the size and weight of the inertial sensor.

[0062] like Figure 2 The diagram illustrates the structure of the grating chip 8 in one possible implementation. Combined with... Figure 1b and Figure 2 As shown, the grating chip 8 has three sets of grating structures on the side facing the output end of the cooling light polarization modulation system 12. The three sets of grating structures are connected end to end to form an equilateral triangle. Each set of grating structures generates a first-order diffracted beam according to the Gaussian collimated cooling beam. Generating diffracted light through the structure on the grating surface is a conventional technique in this field, and its working principle will not be described in detail here. In this embodiment, the grating chip 8 generates a diffracted beam tending towards the center of the atom trapping region by setting three sets of grating structures. Combined with the Gaussian collimated cooling beam and the MOT coil group 6, it can achieve a better cooling and trapping effect for cold atom clusters.

[0063] As shown in the figure, in order to further achieve the miniaturization of the device structure, the grating chip 8 is set close to the outer wall of the ultra-small passive vacuum cavity 7.

[0064] like Figure 4As shown, the cooling light beam expanding and collimating chip 11 includes a first solid waveguide 110 and a first apodization grating 111 connected along the optical path. The first solid waveguide 110 is used to guide the input cooling light, return pump light, state preparation light and probe light to the first apodization grating 111. The first apodization grating 111 is used to convert the input cooling light, return pump light, state preparation light and probe light into a Gaussian collimated cooling beam.

[0065] Figure 3 This illustrates the specific composition of the MOT coil group 6 in one possible implementation and its relationship with the ultra-miniature passive vacuum cavity 7 and the chip-type cooling optical path. For example... Figure 3 As shown, the MOT coil group 6 includes two bias magnetic field coils (first bias magnetic field coil 60 and second bias magnetic field coil 61) and two MOT magnetic field coils (first MOT magnetic field coil 63 and second MOT magnetic field coil 62). Figure 3 Taking a specific perspective as an example, the first bias magnetic field coil 60 and the second bias magnetic field coil 61 are arranged coaxially vertically. The ultra-miniature passive vacuum cavity 7 is arranged coaxially vertically between the first bias magnetic field coil 60 and the second bias magnetic field coil 61. The first bias magnetic field coil 60 is arranged at the upper end of the ultra-miniature passive vacuum cavity 7, and the second bias magnetic field coil 61 is arranged at the lower end of the ultra-miniature passive vacuum cavity 7. The first MOT magnetic field coil 63 and the second MOT magnetic field coil 62 are respectively arranged at the upper and lower ends of the ultra-miniature passive vacuum cavity 7 and are coaxially arranged with the cooling optical path. The vertical position of the cold atom cluster in the magnetic field can be changed by adjusting the bias magnetic field between the first MOT magnetic field coil 63 and the second MOT magnetic field coil 62, thereby extending the falling distance of the cold atom cluster. The first MOT magnetic field coil 63 and the second MOT magnetic field coil 62 are arranged coaxially horizontally, and the ultra-miniature passive vacuum cavity 7 is located between the first MOT magnetic field coil 63 and the second MOT magnetic field coil 62. The chip-type cooling optical path passes laterally through one of the MOT magnetic field coils along the axial direction and is incident on the ultra-small passive vacuum cavity 7, acting on the atomic clusters in the ultra-small passive vacuum cavity 7 for rapid and repeated trapping of atomic clusters.

[0066] Normally, atomic groups are trapped in Figure 3 The center position of MOT shown is 64, free fall to Figure 3 The atomic cluster is shown at position 65, the endpoint of its free fall. After detection, the chip-type cooling optical path and the MOT magnetic field are immediately activated. By modulating the MOT magnetic field, most of the atomic cluster can be re-trapped at the MOT center position 64, reducing the atomic cluster loading time and increasing the gravity data output rate. By modulating the bias magnetic field, the atomic cluster can be lifted to... Figure 3The highest position of the MOT-trapped atomic cluster shown is 66, which undoubtedly increases the distance the atomic cluster falls freely within a limited space, increases the interference time, and improves the accuracy of gravity measurement.

[0067] In one possible implementation, such as Figure 1c As shown, the chip-type Raman optical path includes a Raman light input fiber 1, a Raman light beam expander and collimator chip 2, a Raman light polarization modulation system 3, and a polarization beam splitter PBS 4 arranged sequentially along the light propagation direction. It also includes a first reflecting mirror 5 and a conical reflecting mirror 9, wherein:

[0068] The Raman light input fiber 1 is used to input Raman light with two different frequency components into the chip-type Raman light path;

[0069] The Raman beam expanding and collimating chip 2 is fixedly connected to the Raman beam input fiber 1 and is used to adjust the spot size and collimation of the input Raman beam in order to obtain the Gaussian collimated Raman beam after beam expansion and collimation.

[0070] The Raman polarization modulation system 3 is used to adjust the Gaussian collimated Raman light to the polarization state required for interference.

[0071] The polarization beam splitter PBS4 has a transmission output end and a reflection output end, which is used to split the Gaussian collimated Raman light after the polarization state is adjusted into a first Raman light and a second Raman light according to the frequency. The first Raman light is output from the transmission output end, and the second Raman light is output from the reflection output end.

[0072] The first reflector 5 is disposed above the ultra-small passive vacuum cavity 7 to reflect the first Raman light and cause the reflected first Raman light to pass through the center of the first bias magnetic field coil 60 and be vertically incident on the atomic trapping region of the ultra-small passive vacuum cavity 7 along the central axis of the first bias magnetic field coil 60, acting on the cold atom cluster from top to bottom.

[0073] The conical mirror 9 is positioned below the reflection output end of the polarizing beam splitter PBS4 and the ultra-miniature passive vacuum cavity 7. It is used to allow the second Raman light to be reflected by the conical mirror 9, pass through the second bias magnetic field coil 61 from bottom to top, and be vertically incident on the atomic trapping region of the ultra-miniature passive vacuum cavity 7 along the central axis of the bias magnetic field coil, acting on the cold atomic clusters from bottom to top.

[0074] Understandably, two Raman light components with different frequencies are input into the sensor through Raman light input fiber 1. After passing through Raman light beam expanding and collimating chip 2, they are transformed into Gaussian collimated light spots and output. Then, through Raman light polarization modulation system 3, the Raman light is modulated to the polarization required for interference. After being split by polarization beam splitter prism PBS4, the first Raman light of frequency 1 is transmitted and then reflected by the first reflector 5 before acting on the cold atom cluster. The second Raman light of frequency 2 is reflected and transmitted downwards, then reflected by conical reflector 9 before being transmitted upwards, and finally acting on the cold atom cluster. The two Raman light frequencies work together to manipulate the atom cluster, realizing the interferometric measurement process.

[0075] In one possible implementation, the Raman beam expanding and collimating chip 2 includes a second solid waveguide 20 and a second apodization grating 21 connected along the optical path. The second solid waveguide 20 is used to guide the input Raman light to the second apodization grating 21, and the second apodization grating 21 is used to convert the input Raman light into Gaussian collimated Raman light.

[0076] In one possible implementation, such as Figure 2 As shown, the detector chip 13 is positioned perpendicular to the chip-type cooling optical path and aligned with the atomic cooling trapping region of the ultra-small passive vacuum cavity 7. For example, if the vertical direction is taken as the Z-axis and the direction in which the chip-type cooling optical path enters the ultra-small passive vacuum cavity 7 is taken as the X-axis, then the detection axis of the detector chip 13 is the Y-axis, and the X, Y, and Z directions are perpendicular to each other.

[0077] Preferably, the detection chip 13 is a chip-type fluorescence detection lens. The chip-type fluorescence detection lens is placed as close as possible to the miniaturized passive vacuum glass cavity, which collects as much fluorescence signal as possible while reducing the volume of the fluorescence detection part and the size and weight of the inertial sensor.

[0078] The present invention provides an ultra-miniature cold atom inertial sensor with extended interference time, which has the following advantages:

[0079] (1) By using on-chip MOT, chip-based optical path design, miniaturized passive vacuum glass cavity, chip-based fluorescence detection lens and compact sensor internal structure design, the complexity, size, weight and power consumption of inertial sensors are effectively reduced.

[0080] (2) By designing a reasonable MOT magnetic field and bias magnetic field, rapid and repeated trapping of cold atom clusters is achieved, which effectively reduces the time required for trapping atom clusters and improves the data output rate of cold atom measurement inertial quantities;

[0081] (3) By modulating the bias magnetic field, the position of the trapped cold atom cluster is changed, the interference distance and interference time of the cold atom cluster are extended, and the accuracy of inertial measurement is improved in a limited space.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A miniature cold atom inertial sensor with extended interference time, characterized in that, It includes a chip-based Raman optical path, a chip-based cooling optical path, an MOT coil assembly, a detector chip, and an ultra-miniature passive vacuum cavity, among which: The MOT coil group is symmetrically arranged on the outer periphery of the ultra-small passive vacuum cavity to trap the atomic clusters in the ultra-small passive vacuum cavity by magnetic field and to adjust the free fall path of the atomic clusters. The chip-type cooling optical path runs through the MOT coil group and the ultra-small passive vacuum cavity to cool, trap, and prepare the atomic clusters. The chip-type Raman optical path is vertically incident on the ultra-small passive vacuum cavity to manipulate the cooled and trapped cold atom clusters for interference; The detection chip is positioned adjacent to the ultra-small passive vacuum cavity to detect the atomic state signal after interference; The MOT coil group includes two bias magnetic field coils and two MOT magnetic field coils. The two bias magnetic field coils are arranged coaxially vertically and are correspondingly arranged at the upper and lower ends of the ultra-small passive vacuum cavity. This is used to change the vertical position of the cold atom cluster by adjusting the bias magnetic field, thereby extending the falling distance of the cold atom cluster. The two MOT magnetic field coils are arranged coaxially horizontally, and the ultra-small passive vacuum cavity is located between the two MOT magnetic field coils to rapidly and repeatedly trap the atom cluster. The chip-type cooling optical path horizontally passes through one of the MOT magnetic field coils and enters the ultra-small passive vacuum cavity.

2. The ultra-miniature cold atom inertial sensor with extended interference time according to claim 1, characterized in that, The chip-type cooling optical path includes a cooling light input fiber, a cooling light beam expander collimator chip, a cooling light polarization modulation system, and a grating chip arranged sequentially along the cooling light propagation direction. The ultra-small passive vacuum cavity is disposed between the cooling light polarization modulation system and the grating chip. The cooling light input fiber is used to input cooling light, pump-back light, state preparation light and probe light into the chip-type cooling light path; The cooling light beam expander and collimator chip is fixedly connected to the cooling light input fiber and is used to adjust the spot size and collimation of the light input into the chip-type cooling light path to obtain a Gaussian collimated cooling beam. The cooling light polarization modulation system is used to adjust the polarization state of the Gaussian collimated cooling beam and to input the Gaussian collimated cooling beam with the adjusted polarization state into the ultra-small passive vacuum cavity along the axis of the MOT magnetic field coil. The grating chip is used to convert the Gaussian collimated cooling beam passing through the ultra-small passive vacuum cavity into three first-order diffracted beams, the propagation direction of the three first-order diffracted beams being toward the atomic trapping region of the ultra-small passive vacuum cavity.

3. The ultra-miniature cold atom inertial sensor with extended interference time according to claim 2, characterized in that, On the grating chip, three sets of grating structures are provided on the side facing the output end of the cooling light polarization modulation system. The three sets of grating structures are connected end to end to form an equilateral triangle. Each set of grating structures generates a first-order diffraction beam according to the Gaussian collimated cooling beam.

4. A miniature cold atom inertial sensor with extended interference time according to claim 2 or 3, characterized in that, The grating chip is positioned close to the outer wall of the ultra-small passive vacuum cavity.

5. The ultra-miniature cold atom inertial sensor with extended interference time according to claim 2, characterized in that, The cooling light beam expanding and collimating chip includes a first solid waveguide and a first apodization grating connected along the optical path. The first solid waveguide is used to guide the input cooling light, return pump light, state preparation light and probe light to the first apodization grating. The first apodization grating is used to convert the input cooling light, return pump light, state preparation light and probe light into a Gaussian collimated cooling beam.

6. The ultra-miniature cold atom inertial sensor with extended interference time according to claim 1, characterized in that, The chip-type Raman optical path includes, sequentially arranged along the light propagation direction, a Raman light input fiber, a Raman light beam expander and collimator chip, a Raman light polarization modulation system, and a polarization beam splitter (PBS), and also includes a first reflecting mirror and a conical reflecting mirror, wherein: The Raman light input fiber is used to input Raman light with two different frequency components into the chip-type Raman light path; The Raman beam expanding and collimating chip is fixedly connected to the Raman beam input fiber and is used to adjust the spot size and collimation of the input Raman beam to obtain Gaussian collimated Raman beam after beam expansion and collimation. The Raman polarization modulation system is used to adjust the Gaussian collimated Raman light to the polarization state required for interference. The polarization beam splitter PBS has a transmission output end and a reflection output end, which is used to split the Gaussian collimated Raman light after the polarization state is adjusted into a first Raman light and a second Raman light according to the frequency. The first Raman light and the second Raman light are output from the transmission output end and the reflection output end respectively in a one-to-one correspondence. The first reflector is disposed above the ultra-small passive vacuum cavity, so that the first Raman light is reflected and vertically incident on the atomic trapping region of the ultra-small passive vacuum cavity along the central axis of the bias magnetic field coil; The conical reflector is positioned below the miniature passive vacuum cavity to reflect the second Raman light and then vertically incident it along the central axis of the bias magnetic field coil into the atomic trapping region of the miniature passive vacuum cavity.

7. The ultra-miniature cold atom inertial sensor with extended interference time according to claim 6, characterized in that, The Raman beam expanding and collimating chip includes a second solid waveguide and a second apodization grating connected along the optical path. The second solid waveguide is used to guide the input Raman light to the second apodization grating, and the second apodization grating is used to convert the input Raman light into Gaussian collimated Raman light.

8. The ultra-miniature cold atom inertial sensor with extended interference time according to claim 1, characterized in that, The detection chip is positioned perpendicular to the chip-type cooling optical path.

9. A miniature cold atom inertial sensor with extended interference time according to claim 1 or 8, characterized in that, The detection chip is a chip-type fluorescent detection lens.

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