Subminiature cold atom inertial sensor with prolonged interference time

Abstract

The invention relates to a subminiature cold atom inertial sensor with prolonged interference time, which comprises a Raman light path, a cooling light path, MOT coil groups, a detection chip and a subminiature passive vacuum cavity, and is characterized in that the MOT coil groups are symmetrically arranged on the periphery of the subminiature passive vacuum cavity so as to trap atomic groups in the subminiature passive vacuum cavity through a magnetic field; the free falling stroke of the atomic group is adjusted; the light path of the cooling light penetrates through the MOT coil assembly and the ultra-small passive vacuum cavity so as to cool, trap and prepare atomic groups; a Raman light path vertically enters the ultra-small passive vacuum cavity so as to control the cooled and imprisoned cold atomic group to interfere; and the detection chip is arranged adjacent to the subminiature passive vacuum cavity so as to detect the interfered atomic state signal. According to the invention, the complexity, volume and weight of the sensor are reduced, the position for trapping the cold atomic group is changed by modulating the magnetic field, the free falling stroke length of the atomic group is adjusted, the interference distance and interference time of the cold atomic group are prolonged, and the precision of inertial measurement is improved.

Description

Technical Field

[0001] The invention relates to the technical field of cold atom inertial measurement, and in particular to an ultra-small cold atom inertial sensor with extended interference time. Background Art

[0002] The cold atom interferometry precision measurement process takes place in the cold atom inertial sensor. Atomic cooling and trapping, sub-Doppler cooling, state preparation, Raman interferometry, and fluorescence detection constitute a complete cold atom interferometry measurement process. 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] At present, the cold atom inertial sensor with the highest degree of engineering is the cold atom absolute gravimeter. The French company Muquans has launched the AQG series of cold atom absolute gravimeters with measurement accuracy comparable to that of traditional laser interferometer absolute gravimeters, and has achieved continuous measurement of absolute gravity on the top of a volcano in Italy. Several research groups in the United States, France and China have also carried out the development of dynamic cold atom gravimeters, and have achieved absolute gravity measurement on dynamic carriers such as ships, aircraft and vehicles. However, the cold atom inertial sensor relies on an active dual-axis stabilization platform to keep the direction of Raman light consistent with the direction of gravity. The volume and weight of the cold atom inertial sensor itself are too large, and the volume and weight of the stabilization platform also increase accordingly, making it difficult to adapt to different dynamic environments; the complexity of the cold atom inertial sensor itself reduces the environmental adaptability of the device and limits the use scenarios of cold atom inertial measurement equipment; excessive power consumption reduces the portability of the cold atom inertial sensor and limits the application field of the cold atom inertial sensor.

[0004] In order to solve the above problems, miniaturization of cold atom inertial sensors has become an inevitable trend. With the increasing maturity of micro-electromechanical (MEMS) technology and photonic integrated PIC technology, new ideas have been provided for the miniaturization of cold atom inertial sensors. MEMS and PIC technologies can be used to simplify traditional cold atom inertial sensors, reduce system complexity, and improve system integration and environmental adaptability. MEMS and PIC components can be used to replace the core components in cold atom inertial sensors, which can effectively reduce the volume, weight and power consumption of cold atom inertial sensors. New materials and new processes can help us simplify the system while ensuring the performance of each core component, thereby ensuring the accuracy of cold atom inertial measurement.

[0005] In addition, the accuracy of cold atom inertial measurement is negatively correlated with the square of the interference time T, that is, negatively correlated with the interference distance. Taking the cold atom gravimeter as an example, the gravity change value corresponding to a single interference fringe (2π) of the cold atom gravimeter is λ / (2T 2), which is negatively correlated with the square of the interference period T and the falling distance H. The longer the falling distance, the higher the theoretical measurement accuracy. The advantage of miniaturized cold atom inertial sensors is that repeated trapping can greatly shorten the cooling trapping time of atomic groups, improve the output rate of gravity data, and significantly enhance the ability to resist dynamic environments. However, it will inevitably cause a decrease in the falling distance, and the measurement accuracy will decrease accordingly. How to extend the falling distance without increasing the complexity of the system is also one of the issues that need to be considered in the miniaturization design of cold atom inertial sensor systems. Summary of the invention

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

[0007] The technical solution of the present invention to solve the above technical problems is as follows: an ultra-small cold atom inertial sensor with extended interference time, comprising a chip-type Raman optical path, a chip-type cooling optical path, a MOT coil group, a detection chip and an ultra-small passive vacuum cavity, wherein: The MOT coil group is symmetrically arranged on the periphery of the ultra-small passive vacuum cavity to trap the atomic groups in the ultra-small passive vacuum cavity through a magnetic field and adjust the free fall stroke of the atomic groups; The chip-type cooling light path runs through the MOT coil group and the ultra-small passive vacuum cavity to cool, trap and prepare the atomic group; The chip-type Raman light path is incident vertically on the ultra-small passive vacuum cavity to manipulate the cold atomic groups after cooling and trapping to perform interference; The detection chip is arranged adjacent to the ultra-small passive vacuum chamber to detect the atomic state signal after interference.

[0008] Based on the above technical solution, the present invention can also be improved as follows.

[0009] Preferably, the MOT coil group includes two bias magnetic field coils and two MOT magnetic field coils, the two bias magnetic field coils are coaxially arranged vertically, and the two bias magnetic field coils are arranged one by one at the upper and lower ends of the ultra-small passive vacuum cavity, and are used to change the vertical position of the cold atomic clusters by adjusting the bias magnetic field to extend the falling distance of the cold atomic clusters; the two MOT magnetic field coils are coaxially arranged horizontally, and the ultra-small passive vacuum cavity is arranged between the two MOT magnetic field coils to quickly and repeatedly trap the atomic clusters; the chip-type cooling light path passes through one of the MOT magnetic field coils horizontally and is incident on the ultra-small passive vacuum cavity.

[0010] Preferably, the chip-type cooling light optical path comprises a cooling light input optical fiber, a cooling light beam expansion and collimation chip, a cooling light polarization modulation system and a grating chip which are sequentially arranged along the propagation direction of the cooling light, and the ultra-small passive vacuum cavity is arranged between the cooling light polarization modulation system and the grating chip; The cooling light input optical fiber is used to input cooling light, back-pumping light, state preparation light and detection light into the chip-type cooling light optical path; The cooling light beam expansion and collimation chip is fixedly connected to the cooling light input optical 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 light beam; The cooling light polarization modulation system is used to adjust the polarization state of the Gaussian collimated cooling light beam, and input the Gaussian collimated cooling light beam after the polarization state is adjusted into the ultra-small passive vacuum cavity along the axial direction of the MOT magnetic field coil; The grating chip is used to convert the Gaussian collimated cooling light beam passing through the ultra-small passive vacuum cavity into three beams of first-order diffraction light, and the propagation direction of the three beams of first-order diffraction light is toward the atomic trapping region of the ultra-small passive vacuum cavity.

[0011] Preferably, three groups of grating structures are provided on the grating chip on a side facing the output end of the cooling light polarization modulation system, the three groups of grating structures are connected end to end to form an equilateral triangle, and each group of grating structures generates a beam of first-order diffraction light according to the Gaussian collimated cooling light beam.

[0012] Preferably, the grating chip is arranged in close contact with the outer wall of the ultra-small passive vacuum chamber.

[0013] Preferably, the cooling light beam expansion and collimation chip comprises a first solid waveguide and a first apodization grating connected along an optical path, wherein the first solid waveguide is used to guide the input cooling light, back-pumping light, state preparation light and detection light to the first apodization grating, and the first apodization grating is used to convert the input cooling light, back-pumping light, state preparation light and detection light into a Gaussian collimated cooling light beam.

[0014] Preferably, the chip-type Raman light path includes a Raman light input optical fiber, a Raman light beam expansion and collimation chip, a Raman light polarization modulation system, a polarization beam splitter prism PBS, and a first reflector and a conical reflector, wherein: The Raman light input optical fiber is used to input Raman lights of two different frequency components into the chip-type Raman light path; The Raman light beam expansion and collimation chip is fixedly connected to the Raman light input optical fiber, and is used to adjust the spot size and collimation of the input Raman light to obtain Gaussian collimated Raman light after beam expansion and collimation; The Raman light polarization modulation system is used to adjust the Gaussian collimated Raman light to the polarization state required for interference; The polarization beam splitter prism PBS has a transmission output end and a reflection output end, and is used to separate the Gaussian collimated Raman light after adjusting the polarization state into a first Raman light and a second Raman light according to the frequency, and the first Raman light and the second Raman light are outputted 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, and is used to allow the first Raman light to be reflected and then 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 arranged below the ultra-small passive vacuum cavity, and is used to make the second Raman light, after being reflected, vertically incident on the atomic trapping region of the ultra-small passive vacuum cavity along the central axis of the bias magnetic field coil.

[0015] Preferably, the Raman light beam expansion and collimation chip comprises 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.

[0016] Preferably, the detection chip is arranged perpendicular to the chip-type cooling light path.

[0017] Preferably, the detection chip is a chip-type fluorescence detection lens.

[0018] Compared with the prior art, the technical solution of the present application has the following beneficial technical effects: the ultra-small cold atom inertial sensor with extended interference time provided by the present invention effectively reduces the complexity, volume, weight and power consumption of the inertial sensor through the miniaturization of key components inside the sensor and the chip-based structural design; through reasonable optical path and magnetic field design, the rapid and repeated trapping of cold atomic clusters is achieved, which effectively reduces the time required for the trapping of atomic clusters and improves the data output rate of cold atom measurement of inertial quantities; by modulating the magnetic field to change the position of the trapped cold atomic clusters and adjust the free fall travel length of the atomic clusters, the interference distance and interference time of the cold atomic clusters are extended, thereby improving the accuracy of inertial measurement within a limited space. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1a A schematic diagram of the principle of an ultra-small cold atom inertial sensor with extended interference time provided by an embodiment of the present invention, Figure 1b A schematic diagram of the cooling optical path principle of an ultra-small 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-small cold atom inertial sensor with extended interference time provided by an embodiment of the present invention; Figure 2 A schematic diagram of a detection optical path of an ultra-small cold atom inertial sensor with extended interference time provided by an embodiment of the present invention; Figure 3 A schematic diagram of a repeated trapping and interference time extension scheme of an ultra-small cold atom inertial sensor with extended interference time provided by an embodiment of the present invention; Figure 4 A schematic diagram of the structure of a beam expansion and collimation chip provided in an embodiment of the present invention.

[0020] In the accompanying drawings, the components represented by the reference numerals are listed as follows: 1. Raman light input fiber, 2. Raman light beam expansion and collimation chip, 3. Raman light polarization modulation system, 4. Polarization beam splitter prism PBS, 5. First reflector, 6. MOT coil group, 7. Ultra-small passive vacuum cavity, 8. Grating chip, 9. Conical reflector, 10. Cooling light input fiber, 11. Cooling light beam expansion and collimation chip, 12. Cooling light polarization modulation system, 13. Detection 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. Free fall end position of atomic cluster, 66. Highest position of MOT trapped atomic cluster, 110. First solid waveguide, 111. First apodized grating, 20. Second solid waveguide, 21. Second apodized grating. DETAILED DESCRIPTION

[0021] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0023] It will be appreciated that spatial relationship terms such as "under", "beneath", "below", "under", "above", "above", etc., may be used herein to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that in addition to the orientations shown in the figures, spatial relationship terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, the element or feature described as "under other elements" or "under it" or "under it" will be oriented as "on" the other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0024] It should be noted that when an 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 intermediate element. The "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0025] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" etc. specify the presence of stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0026] At present, cold atom inertial sensors are large in size, weight and power consumption. The cost of maintaining high-precision inertial measurement of cold atoms on dynamic carriers is high. Usually, a two-axis stabilized platform with heavier load-bearing capacity and better dynamic performance is required to maintain the posture stability of the inertial sensor, which undoubtedly limits the application scenarios of cold atom inertial sensors. The higher complexity leads to the poor adaptability of cold atom inertial sensors to dynamic environments and poor portability, which limits the application scenarios of cold atom inertial sensors.

[0027] In order to solve the above problems, Figure 1a~Figure 1c As shown, the embodiment of the present invention provides an ultra-small cold atom inertial sensor with extended interference time, including a chip-type Raman optical path, a chip-type cooling optical path, a MOT coil group 6, a detection chip 13 and an ultra-small passive vacuum cavity 7. The chip-type cooling optical path is as shown in FIG. Figure 1b As shown by the arrows, the chip-type Raman light path is as follows Figure 1c As shown by the arrows, where: The MOT coil group 6 is symmetrically arranged on the periphery of the ultra-small passive vacuum chamber 7 to trap the atomic groups in the ultra-small passive vacuum chamber 7 through a magnetic field and to adjust the free fall stroke of the atomic groups; the ultra-small passive vacuum chamber 7 preferably adopts a miniaturized passive vacuum glass cavity, which contains alkali metal vapor as an atomic source for interference measurement; like Figure 1b As shown, the chip-type cooling light path passes through the MOT coil group 6 and the ultra-small passive vacuum chamber 7 to cool, trap and prepare the atomic clusters; like Figure 1c As shown, the chip-type Raman light path is vertically incident on the ultra-small passive vacuum cavity 7 to manipulate the cold atomic groups after cooling and trapping to interfere, thereby realizing precise measurement of gravitational acceleration; like Figure 2 As shown, the detection chip 13 is disposed adjacent to the ultra-small passive vacuum chamber 7 to detect the atomic state signal after interference, such as a fluorescence signal.

[0028] It can be understood that, based on the defects in the background technology, the embodiment of the present invention proposes an ultra-small cold atom inertial sensor with extended interference time.

[0029] The primary purpose of the present invention is to design an ultra-small cold atom gravimeter solution based on MEMS technology and PIC technology, and to design an ultra-small cold atom inertial sensor by using a chip magneto-optical trap MOT, a beam expansion collimation optical path based on apodization grating chip 8, and passive glass cavity technology, so as to effectively reduce the complexity, volume, weight and power consumption of the cold atom inertial sensor, enhance the dynamic environment adaptability of the cold atom inertial sensor, improve the inertial data output rate, and at the same time increase the interference time as much as possible within a limited volume to ensure the accuracy of cold atom inertial measurement.

[0030] A secondary purpose of the present invention is to develop general miniaturization technologies that can be applied to the field of cold atom inertial measurement. These technologies can be extended and applied to different cold atom inertial measurement systems to achieve the miniaturization and integration of inertial sensors and transform laboratory devices into engineered portable instruments.

[0031] When the cold atomic inertial sensor is working, Figure 1bThe cooling light provided by the chip-type cooling light path shown causes the alkali metal atoms in the ultra-small passive vacuum cavity 7 to form an optically cohesive group, and gathers the atoms in a certain area; combined with the magnetic potential well formed by the MOT coil group 6, the atoms are bound in the preset atomic confinement area by the inward force and do not escape. The setting of the MOT coil group 6 allows it to not only confine the atomic group, but also modulate its magnetic field bias by adjusting the current of the coil, thereby achieving the free fall stroke adjustment of the atomic group. The atoms are cooled and confined by the chip-type cooling light path and the magnetic optical trap formed by the MOT coil to obtain a cold atomic group with adjustable stroke. Then, two Raman lights of different frequencies in the chip-type Raman light path act on the cold atomic group from two opposite directions, and the two frequencies of Raman light jointly manipulate the atomic group to achieve an interference measurement process. The detection chip 13 detects the fluorescence signal of the cold atomic group, which is used to resolve the physical quantity to be measured, such as gravitational acceleration.

[0032] The present invention effectively reduces the complexity, volume, weight and power consumption of the inertial sensor through a compact sensor internal structure design; realizes rapid and repeated trapping of cold atomic clusters through reasonable optical path and magnetic field design, effectively reduces the time required for atomic cluster trapping, and improves the data output rate of cold atom measurement inertial quantity; modulates the magnetic field to change the position of the trapped cold atomic clusters, adjusts the free fall travel length of the atomic clusters, and extends the interference distance and interference time of the cold atomic clusters, thereby improving the accuracy of inertial measurement within a limited space.

[0033] Based on the above technical solution, this embodiment can also be improved as follows.

[0034] Figure 1b The optical path principle of cooling light in one possible implementation is shown. Figure 1b and Figure 3 As shown, the chip-type cooling light optical path includes a cooling light input optical fiber 10, a cooling light beam expansion and collimation chip 11, a cooling light polarization modulation system 12 and a grating chip 8 which are sequentially arranged along the propagation direction of the cooling light, and the ultra-small passive vacuum cavity 7 is arranged between the cooling light polarization modulation system 12 and the grating chip 8; The cooling light input optical fiber 10 is used to input cooling light, pumping light, state preparation light and detection light into the chip-type cooling light optical path; wherein the cooling light is used to cool the atomic group, the pumping light is used to assist in cooling the trapped atoms, the state preparation light is used to perform state preparation on the atomic group, and the detection light is used to detect the atomic state after the interference is completed; The cooling light beam expansion and collimation chip 11 is fixedly connected to the cooling light input optical fiber 10, and is used to adjust the spot size and collimation of the light input into the chip-type cooling light path, so as to obtain a Gaussian collimated cooling light beam, which becomes cooling light that can be used to trap cold atomic groups; The cooling light polarization modulation system 12 is used to adjust the polarization state of the Gaussian collimated cooling light beam, for example, to modulate the polarization state into circularly polarized light required for cold atom cooling and trapping, and to input the Gaussian collimated cooling light beam after adjusting the polarization state into the ultra-small passive vacuum cavity 7 along the axial direction of the MOT magnetic field coil; The grating chip 8 is used to convert the Gaussian collimated cooling light beam passing through the ultra-small passive vacuum cavity 7 into three beams of first-order diffraction light, and the propagation direction of the three beams of first-order diffraction light is toward the atomic trapping region of the ultra-small passive vacuum cavity 7. Figure 1b As shown by the arrows, the cooling and trapping of atoms is achieved by a Gaussian collimated cooling beam and three first-order diffraction lights generated by the grating chip 8.

[0035] It can be understood that the cooling light, pumping light, state preparation light and detection light share the same optical path, which reduces the number of input optical paths of the inertial sensor and effectively reduces the volume, weight and power consumption of the inertial sensor. The grating chip 8 is combined with the MOT coil group 6 to simplify the six-beam spatial MOT of the prior art to only one beam of input light (one cooling light input optical path), which greatly reduces the complexity of the system. The cooling light beam expansion and collimation chip 11 reduces the complexity of the optical path system while effectively reducing the volume and weight of the inertial sensor.

[0036] like Figure 2 FIG. 8 shows a possible structure of the grating chip 8 in one embodiment. Figure 1b and Figure 2 As shown, on the grating chip 8, three groups of grating structures are provided on one side facing the output end of the cooling light polarization modulation system 12, and the three groups of grating structures are connected end to end to form an equilateral triangle, and each group of grating structures generates a beam of first-order diffraction light according to the Gaussian collimated cooling light beam. Generating diffracted light through the structure of the grating surface is a conventional technical means in this field, and its working principle is not described here. The grating chip 8 of this embodiment generates a diffraction beam tending to the center of the atomic trapping area by setting three groups of grating structures, which, combined with the Gaussian collimated cooling beam and the MOT coil group 6, can achieve a better cooling and trapping effect of cold atomic groups.

[0037] As shown in the figure, in order to further realize the structural miniaturization of the device, the grating chip 8 is arranged close to the outer wall of the ultra-small passive vacuum chamber 7.

[0038] like Figure 4As shown, the cooling light beam expansion and collimation chip 11 includes a first solid waveguide 110 and a first apodization grating 111 connected along an optical path, wherein the first solid waveguide 110 is used to guide the input cooling light, back-pumping light, state preparation light and detection light to the first apodization grating 111, and the first apodization grating 111 is used to convert the input cooling light, back-pumping light, state preparation light and detection light into a Gaussian collimated cooling light beam.

[0039] Figure 3 The specific composition of the MOT coil assembly 6 in a possible implementation manner and its coordination relationship with the ultra-small passive vacuum cavity 7 and the chip-type cooling light path are shown. Figure 3 As shown, the MOT coil assembly 6 includes two bias magnetic field coils (a first bias magnetic field coil 60 and a second bias magnetic field coil 61) and two MOT magnetic field coils (a first MOT magnetic field coil 63 and a second MOT magnetic field coil 62). Figure 3 Taking the perspective of as an example, the first bias magnetic field coil 60 and the second bias magnetic field coil 61 are arranged coaxially in the vertical direction, and the ultra-small passive vacuum chamber 7 is coaxially arranged 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-small passive vacuum chamber 7, and the second bias magnetic field coil 61 is arranged at the lower end of the ultra-small passive vacuum chamber 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-small passive vacuum chamber 7 and are coaxially arranged with the cooling light path. The vertical position of the cold atomic group 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 to extend the falling distance of the cold atomic group. The first MOT magnetic field coil 63 and the second MOT magnetic field coil 62 are coaxially arranged in the horizontal direction, and the ultra-small passive vacuum chamber 7 is arranged between the first MOT magnetic field coil 63 and the second MOT magnetic field coil 62. The chip-type cooling light path passes through one of the MOT magnetic field coils laterally along the axial direction of the MOT magnetic field coil 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 the atomic clusters.

[0040] Typically, atoms are trapped in Figure 3 The MOT center position shown is 64, free falling to Figure 3 The free fall end position of the atom cluster shown is 65. After the detection is completed, the chip cooling light path and the MOT magnetic field are immediately turned on. By modulating the MOT magnetic field, most of the atom clusters can be re-trapped at the MOT center position 64, reducing the atom cluster loading time and improving the gravity data output rate. By modulating the bias magnetic field, the atom cluster can be lifted to Figure 3The highest position of the MOT trapped atom cluster is 66, which can undoubtedly increase the free-falling distance of the atom cluster within a limited space, increase the interference time, and improve the accuracy of gravity measurement.

[0041] In one possible implementation, Figure 1c As shown, the chip-type Raman light path includes a Raman light input optical fiber 1, a Raman light beam expansion and collimation chip 2, a Raman light polarization modulation system 3, a polarization beam splitter prism PBS4, and a first reflector 5 and a conical reflector 9, which are sequentially arranged along the light propagation direction. The Raman light input optical fiber 1 is used to input Raman lights of two different frequency components into the chip-type Raman light path; The Raman light beam expansion and collimation chip 2 is fixedly connected to the Raman light input optical fiber 1, and is used to adjust the spot size and collimation of the input Raman light to obtain Gaussian collimated Raman light after beam expansion and collimation; The Raman light polarization modulation system 3 is used to adjust the Gaussian collimated Raman light to the polarization state required for interference; The polarization beam splitter prism PBS4 has a transmission output end and a reflection output end, and is used to separate the Gaussian collimated Raman light after adjusting the polarization state into a first Raman light and a second Raman light according to the frequency, wherein the first Raman light is output from the transmission output end, and the second Raman light is output from the reflection output end; The first reflector 5 is disposed above the ultra-small passive vacuum cavity 7, and is used to reflect the first Raman light, and make the reflected first Raman light pass through the center of the first bias magnetic field coil 60, and vertically enter the atomic trapping region of the ultra-small passive vacuum cavity 7 along the central axis of the first bias magnetic field coil 60, and act on the cold atomic group from top to bottom; The conical reflector 9 is arranged at the reflection output end of the polarization splitter prism PBS4 and below the ultra-small passive vacuum cavity 7, and is used to make the second Raman light pass through the second bias magnetic field coil 61 from bottom to top after being reflected by the conical reflector 9, and vertically enter the atomic trapping region of the ultra-small passive vacuum cavity 7 along the central axis of the bias magnetic field coil, and act on the cold atomic clusters from bottom to top.

[0042] It can be understood that two Raman lights of different frequency components are input into the sensor through the Raman light input optical fiber 1, and are converted into Gaussian collimated light spots after passing through the Raman light beam expansion and collimation chip 2. The Raman lights are then modulated into the polarization required for interference through the Raman light polarization modulation system 3, and are split by the polarization beam splitter prism PBS4. The first Raman light of frequency 1 is transmitted, and then acts on the cold atomic cluster after being reflected by the first reflector 5. The second Raman light of frequency 2 is transmitted downward after reflection, and then transmitted upward after being reflected by the conical reflector 9, and finally acts on the cold atomic cluster. The two frequencies of Raman light jointly manipulate the atomic cluster to realize the interference measurement process.

[0043] In one possible embodiment, the Raman light beam expansion and collimation 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.

[0044] In one possible implementation, Figure 2 As shown, the detection chip 13 is perpendicular to the chip-type cooling light path and is aligned with the atomic cooling trapping area of ​​the ultra-small passive vacuum chamber 7. For example, the vertical direction is the Z direction, the direction in which the chip-type cooling light path is incident on the ultra-small passive vacuum chamber 7 is the X direction, and the detection axis of the detection chip 13 is the Y direction, and the X direction, Y direction, and Z direction are perpendicular to each other.

[0045] Preferably, the detection chip 13 is a chip-type fluorescence detection lens. The chip fluorescence detection lens is as close as possible to the miniaturized passive vacuum glass cavity, which can collect as many fluorescence signals as possible while reducing the volume of the fluorescence detection part and the volume and weight of the inertial sensor.

[0046] The ultra-small cold atom inertial sensor with extended interference time provided by the present invention has the following advantages: (1) The complexity, volume, weight and power consumption of inertial sensors are effectively reduced through on-chip MOT, chip-based optical path design, miniaturized passive vacuum glass cavity, chip-based fluorescence detection lens and compact sensor internal structure design; (2) Through the reasonable design of MOT magnetic field and bias magnetic field, the rapid repeated trapping of cold atomic clusters is achieved, which effectively reduces the time required for atomic cluster trapping and improves the data output rate of cold atom inertial measurement; (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 within a limited space.

[0047] 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultra-small cold atom inertial sensor with extended interference time, characterized in that: It includes a chip-type Raman optical path, a chip-type cooling optical path, a MOT coil group, a detection chip and an ultra-small passive vacuum cavity, wherein: The MOT coil group is symmetrically arranged on the periphery of the ultra-small passive vacuum cavity to trap the atomic groups in the ultra-small passive vacuum cavity through a magnetic field and adjust the free fall stroke of the atomic groups; The chip-type cooling light path runs through the MOT coil group and the ultra-small passive vacuum cavity to cool, trap and prepare the atomic group; The chip-type Raman light path is incident vertically on the ultra-small passive vacuum cavity to manipulate the cold atomic groups after cooling and trapping to perform interference; The detection chip is arranged adjacent to the ultra-small passive vacuum chamber to detect the atomic state signal after interference.

2. The ultra-small cold atom inertial sensor with extended interference time according to claim 1, characterized in that: The MOT coil group includes two bias magnetic field coils and two MOT magnetic field coils. The two bias magnetic field coils are coaxially arranged vertically, and the two bias magnetic field coils are arranged one by one at the upper and lower ends of the ultra-small passive vacuum cavity, so as to change the vertical position of the cold atomic clusters by adjusting the bias magnetic field to extend the falling distance of the cold atomic clusters; the two MOT magnetic field coils are coaxially arranged horizontally, and the ultra-small passive vacuum cavity is arranged between the two MOT magnetic field coils to quickly and repeatedly trap the atomic clusters; the chip-type cooling light path horizontally passes through one of the MOT magnetic field coils and is incident on the ultra-small passive vacuum cavity.

3. The ultra-small cold atom inertial sensor with extended interference time according to claim 2, characterized in that: The chip-type cooling light optical path comprises a cooling light input optical fiber, a cooling light beam expansion and collimation chip, a cooling light polarization modulation system and a grating chip which are sequentially arranged along the propagation direction of the cooling light, and the ultra-small passive vacuum cavity is arranged between the cooling light polarization modulation system and the grating chip; The cooling light input optical fiber is used to input cooling light, back-pumping light, state preparation light and detection light into the chip-type cooling light optical path; The cooling light beam expansion and collimation chip is fixedly connected to the cooling light input optical 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 light beam; The cooling light polarization modulation system is used to adjust the polarization state of the Gaussian collimated cooling light beam, and input the Gaussian collimated cooling light beam after the polarization state is adjusted into the ultra-small passive vacuum cavity along the axial direction of the MOT magnetic field coil; The grating chip is used to convert the Gaussian collimated cooling light beam passing through the ultra-small passive vacuum cavity into three beams of first-order diffraction light, and the propagation direction of the three beams of first-order diffraction light is toward the atomic trapping region of the ultra-small passive vacuum cavity.

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

5. The ultra-small cold atom inertial sensor with extended interference time according to claim 3 or 4, characterized in that: The grating chip is arranged closely against the outer wall of the ultra-small passive vacuum chamber.

6. The ultra-small cold atom inertial sensor with extended interference time according to claim 3, characterized in that: The cooling light beam expansion and collimation chip comprises a first solid waveguide and a first apodization grating connected along an optical path, wherein the first solid waveguide is used to guide input cooling light, back-pumping light, state preparation light and detection light to the first apodization grating, and the first apodization grating is used to convert the input cooling light, back-pumping light, state preparation light and detection light into a Gaussian collimated cooling light beam.

7. The ultra-small cold atom inertial sensor with extended interference time according to claim 2, characterized in that: The chip-type Raman light path includes a Raman light input optical fiber, a Raman light beam expansion and collimation chip, a Raman light polarization modulation system, a polarization beam splitter prism PBS, and a first reflector and a conical reflector, wherein: The Raman light input optical fiber is used to input Raman lights of two different frequency components into the chip-type Raman light path; The Raman light beam expansion and collimation chip is fixedly connected to the Raman light input optical fiber, and is used to adjust the spot size and collimation of the input Raman light to obtain Gaussian collimated Raman light after beam expansion and collimation; The Raman light polarization modulation system is used to adjust the Gaussian collimated Raman light to the polarization state required for interference; The polarization beam splitter prism PBS has a transmission output end and a reflection output end, and is used to separate the Gaussian collimated Raman light after adjusting the polarization state into a first Raman light and a second Raman light according to the frequency, and the first Raman light and the second Raman light are outputted 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, and is used to allow the first Raman light to be reflected and then 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 arranged below the ultra-small passive vacuum cavity, and is used to make the second Raman light, after being reflected, vertically incident on the atomic trapping region of the ultra-small passive vacuum cavity along the central axis of the bias magnetic field coil.

8. The ultra-small cold atom inertial sensor with extended interference time according to claim 7, characterized in that: The Raman light beam expansion and collimation chip comprises a second solid waveguide and a second apodization grating connected along an optical path, wherein 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.

9. The ultra-small cold atom inertial sensor with extended interference time according to claim 1, characterized in that: The detection chip is arranged perpendicular to the chip-type cooling light path.

10. The ultra-small cold atom inertial sensor with extended interference time according to claim 1 or 9, characterized in that: The detection chip is a chip-type fluorescence detection lens.

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