Large momentum transfer atom interferometer and method based on hollow-core optical fiber guidance

Abstract

The invention relates to a large momentum transfer atom interferometer and method based on hollow-core optical fiber guidance, and belongs to the technical field of measurement. Comprising a first optical path assembly for transmitting a first Bragg light beam, a second optical path assembly for transmitting a dipole light beam, a third optical path assembly for transmitting a detection light beam, a fourth optical path assembly for transmitting a second Bragg light beam, a fifth optical path assembly for transmitting a correlation cooling light beam, a hollow-core optical fiber and a photoelectric detector, the fifth light path assembly outputs three groups of mutually orthogonal correlation cooling light beams which are intersected and overlapped right above the hollow-core optical fiber, the light output ends of the first, second and third light path assemblies are led to the lower end of the hollow-core optical fiber, the light output end of the fourth light path assembly is led to the upper end of the hollow-core optical fiber, and the upper end of the hollow-core optical fiber is led to the light input end of the photoelectric detector. The high-order Bragg diffraction process based on hollow-core optical fiber guidance is adopted, the size of a required light field is small, the light power is small, and the development requirement of a compact atom interferometer in the future is better met.

Description

Technical Field

[0001] The present invention belongs to the technical field of measurement, and particularly relates to a large momentum transfer atomic interferometer and method based on hollow fiber guiding. Background Art

[0002] Atomic interferometers can accurately measure the hyperfine structure constant, verify Einstein's equivalence principle, and achieve ultra-high-precision inertial measurement, which is driving the leap of measurement science from the classical limit to the quantum benchmark. In recent years, the atomic coherent beam splitting technology based on large momentum transfer has received extensive attention and developed rapidly. This technology can significantly increase the interference area of atomic interference measurement and the scale factor and short-term sensitivity by increasing the momentum transfer of cold atomic matter waves on the interference path (the existing Raman transition type atomic interferometer corresponds to two-photon momentum transfer ), and has development advantages in fields such as gravitational wave detection and dark matter search.

[0003] So far, all publicly demonstrated large momentum transfer atomic interferometers are mostly constructed based on Bragg diffraction of free space optical lattices. In the above Bragg diffraction process, the momentum transfer obtained by cold atomic matter waves is related to the Bragg diffraction order n, which is However, with the increase of the Bragg diffraction order, the two-photon Rabi frequency (or light intensity) required for atoms to be in the Bragg transition state also increases significantly, and the optical power of the corresponding Bragg beam also increases accordingly.

[0004] Therefore, the limited laser power will severely limit the development potential of large momentum transfer atomic interferometers based on free space optical lattices. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a large momentum transfer atomic interferometer and method based on hollow fiber guiding to solve or improve the defects existing in the prior art.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention provides a large momentum transfer atomic interferometer based on a hollow-core fiber guiding, which includes a first optical path component for transmitting a first Bragg beam, a second optical path component for transmitting a dipole beam, a third optical path component for transmitting a probe beam, a fourth optical path component for transmitting a second Bragg beam, a fifth optical path component for transmitting a counter-propagating cooling beam, a hollow-core fiber, and a photodetector. The hollow-core fiber is vertically arranged in a vacuum chamber. The light output end of the fifth optical path component leads to the vacuum chamber and can overlap three sets of mutually orthogonal counter-propagating cooling beams directly above the hollow-core fiber. The light output ends of the first optical path component, the second optical path component, and the third optical path component lead to the lower end of the hollow-core fiber. The light output end of the fourth optical path component leads to the upper end of the hollow-core fiber. The upper end of the hollow-core fiber leads to the light input end of the photodetector.

[0007] Preferably, the first optical path component includes a first single-mode polarization-maintaining fiber, a first fiber collimator, and a first half-wave plate arranged in sequence along the light transmission direction. The light output end of the first single-mode polarization-maintaining fiber is connected to the light input end of the first fiber collimator. The first single-mode polarization-maintaining fiber is used for inputting the first Bragg beam. The first fiber collimator is used for collimating the first Bragg beam and outputting it. The first half-wave plate is used for changing the polarization direction of the first Bragg beam.

[0008] Preferably, the second optical path component includes a second single-mode polarization-maintaining fiber, a second fiber collimator, and a second half-wave plate arranged in sequence along the light transmission direction. The light output end of the second single-mode polarization-maintaining fiber is connected to the light input end of the second fiber collimator. The second single-mode polarization-maintaining fiber is used for inputting the dipole beam. The second fiber collimator is used for collimating the dipole beam and outputting it. The second half-wave plate is used for changing the polarization direction of the dipole beam.

[0009] Preferably, the third optical path component includes a third single-mode polarization-maintaining fiber, a third fiber collimator, and a third half-wave plate arranged in sequence along the light transmission direction. The light output end of the third single-mode polarization-maintaining fiber is connected to the light input end of the third fiber collimator. The third single-mode polarization-maintaining fiber is used for inputting the probe beam. The third fiber collimator is used for collimating the probe beam and outputting it. The third half-wave plate is used for changing the polarization direction of the probe beam.

[0010] Preferably, a first polarization beam splitter prism is jointly arranged in the output directions of the first optical path component and the second optical path component, and a non-polarizing beam splitter prism is jointly arranged in the output directions of the third optical path component and the first polarization beam splitter prism.

[0011] Preferably, a plane mirror and a first achromatic cemented lens are sequentially arranged in the output direction of the non-polarizing beam splitting prism. The plane mirror is used to reflect the light beam, and the first achromatic cemented lens is used to focus and couple the first Bragg beam, the dipole beam, and the probe beam into the hollow fiber, and collimate the second Bragg beam emitted from the lower end of the hollow fiber at the same time.

[0012] Preferably, the fourth optical path component includes a fourth single-mode polarization-maintaining fiber, a fourth fiber collimator, and a fourth half-wave plate arranged in sequence along the light transmission direction. The light output end of the fourth single-mode polarization-maintaining fiber is connected to the light input end of the fourth fiber collimator. The fourth single-mode polarization-maintaining fiber is used to transmit the second Bragg beam, the fourth fiber collimator is used to collimate the second Bragg beam and output it, and the fourth half-wave plate is used to change the polarization direction of the second Bragg beam.

[0013] Preferably, a second polarizing beam splitting prism, a band-pass filter, and a second achromatic cemented lens are sequentially arranged in the output direction of the fourth optical path component. The band-pass filter is used to block the transmission of the dipole beam, and the second achromatic cemented lens is used to focus and couple the second Bragg beam into the hollow fiber, and collimate the first Bragg beam, the dipole beam, and the probe beam emitted from the upper end of the hollow fiber at the same time.

[0014] Preferably, the hollow fiber is a bare fiber after the coating layer is stripped.

[0015] Preferably, the photodetector is a silicon avalanche photodetector.

[0016] Preferably, the vacuum degree of the vacuum chamber is less than 10 -8 Pa.

[0017] The present invention also provides a large momentum transfer atomic interference method based on hollow fiber guiding. Using the large momentum transfer atomic interferometer based on hollow fiber guiding, the method includes the following steps: S1. Cooling and trapping cold atom clusters from the background high-speed atomic gas in the vacuum chamber by using three groups of counter-propagating cooling beams transmitted by the fifth optical path component; S2. Using the dipole beam transmitted by the second optical path component to form a far-detuned optical dipole trap. Some of the cold atoms in the cold atom cluster are confined in the far-detuned optical dipole trap and are guided into the hollow fiber under the assistance of the gravity field; S3. Using the first Bragg beam transmitted by the first optical path component and the second Bragg beam transmitted by the fourth optical path component to form a group of Bragg beams, and forming a periodically distributed optical lattice in the hollow fiber. The cold atom matter wave in the hollow fiber obtains a large momentum transfer during the high-order Bragg diffraction process based on the optical lattice; S4. Coherently operate using three groups of Bragg beams of π / 2 - π - π / 2 successively, causing the cold atom matter wave to split, reflect, and recombine on the interference path, thus forming a Mach - Zehnder interferometer; S5. Use a photodetector to detect the optical power signal of the probe beam transmitted by the third optical path component after being absorbed by the cold atoms in the hollow fiber, obtain the atomic population probability, and then calculate the atomic interference phase shift containing the acceleration information to be measured; under different evolution time conditions, by scanning the chirp rate of the Bragg beam, multiple interference fringes are obtained; according to the chirp rate corresponding to the coincidence of the interference fringes, the acceleration to be measured is calculated.

[0018] Compared with the prior art (the Bragg diffraction scheme based on free - space optical lattice), the present invention has the following beneficial effects: (1) The present invention uses the dipole beam transmitted by the second optical path component to form a far - detuned optical dipole trap. The cold atoms are guided into the hollow fiber through the far - detuned optical dipole trap. The cold atoms are strongly confined by the guiding light field inside the hollow fiber, which can effectively overcome the influence of the carrier acceleration in the non - measurement direction and has outstanding advantages in dynamic environments and vector measurement scenarios; (2) The present invention uses the Bragg beam transmitted by the second optical path component and the Bragg beam transmitted by the fourth optical path component to be coupled into the hollow fiber from both ends, which can form a periodically distributed optical lattice inside the hollow fiber. The cold atom matter wave will undergo a high - order Bragg diffraction process under the action of the optical lattice. Compared with the Bragg diffraction scheme based on free - space optical lattice, coupling the Bragg beam into the hollow fiber can significantly reduce its mode field diameter from dozens of millimeters in free space to dozens of micrometers. Therefore, under the condition of the same Bragg diffraction order, the optical power required by the present invention will be reduced by about 6 orders of magnitude; under the condition of optical power constraint, the present invention can achieve a higher - order Bragg diffraction process, greatly increasing the momentum transfer of the cold atom matter wave and significantly improving the scale factor and short - term sensitivity of atomic interference measurement. (3) Using the interferometer and interference method of the present invention, the experimental scenario of strong photon - atom interaction can be compressed to the order of dozens of micrometers, which better meets the development requirements of future compact atomic interferometers. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is a schematic structural diagram of an embodiment of the present invention.

[0021] Markings in the figure: 1. First single-mode polarization-maintaining optical fiber; 2. First fiber collimator; 3. First Bragg beam; 4. First half-wave plate; 5. First polarization beam splitter prism; 6. Second half-wave plate; 7. Dipole beam; 8. Second fiber collimator; 9. Second single-mode polarization-maintaining optical fiber; 10. Non-polarizing beam splitter prism; 11. Third half-wave plate; 12. Probe beam; 13. Third fiber collimator; 14. Third single-mode polarization-maintaining optical fiber; 15. Plane mirror; 16. First achromatic cemented lens; 17. Hollow-core optical fiber; 17-1. Cross-section of the hollow-core optical fiber; 18. Cold atom cloud; 19. Counter-propagating cooling beam; 20. Second achromatic cemented lens; 21. Band-pass filter; 22. Second polarization beam splitter prism; 23. Fourth half-wave plate; 24. Second Bragg beam; 25. Fourth fiber collimator; 26. Fourth single-mode polarization-maintaining optical fiber; 27. Photoelectric detector; 28. Vacuum chamber. Specific implementation mode

[0022] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. To make the above features and advantages of the present invention more obvious and understandable, specific embodiments are hereby given and detailed descriptions are made below in conjunction with the accompanying drawings.

[0023] As Figure 1 shown, an embodiment of the present invention provides a large-momentum-transfer atom interferometer based on the guidance of a hollow-core optical fiber 17, including a first optical path component for transmitting a first Bragg beam 3, a second optical path component for transmitting a dipole beam 7, a third optical path component for transmitting a probe beam 12, a fourth optical path component for transmitting a second Bragg beam 24, a fifth optical path component for transmitting a counter-propagating cooling beam 19, a hollow-core optical fiber 17, and a photoelectric detector 27. The hollow-core optical fiber 17 is vertically arranged in a vacuum chamber 28. The light output end of the fifth optical path component leads to the inside of the vacuum chamber 28 and can overlap three sets of mutually orthogonal counter-propagating cooling beams 19 (only two sets of them are schematically shown in the plane projection) directly above the hollow-core optical fiber 17. The light output ends of the first optical path component, the second optical path component, and the third optical path component lead to the lower end of the hollow-core optical fiber 17. The light output end of the fourth optical path component leads to the upper end of the hollow-core optical fiber 17. The upper end of the hollow-core optical fiber leads to the light input end of the photoelectric detector 27.

[0024] The working process of this embodiment is as follows: (1) Cooling process: The counter-propagating cooling light beam 19 is used to cool and trap the cold atom cloud 18 from the background high-speed atomic gas in the vacuum chamber 28. The cold atom cloud 18 is located above the upper end of the hollow-core fiber 17 and at the center of the overlapping region of the counter-propagating cooling light beam 19; (2) Loading process: The dipole light beam 7 transmitted by the second optical path component is used to form a far-detuned optical dipole trap. The far-detuned optical dipole trap provides confinement for the cold atom cloud 18 in the radial direction of the hollow-core fiber 17 to suppress atomic diffusion. Under the assistance of the gravitational field, the cold atom cloud 18 freely falls along the axial direction of the hollow-core fiber 17. The part of the cold atoms in the cold atom cloud 18 that spatially overlaps with the far-detuned optical dipole trap will be guided into the hollow-core fiber 17; (3) Large momentum transfer process: The first Bragg light beam 3 transmitted by the first optical path component and the second Bragg light beam 24 transmitted by the fourth optical path component propagate in opposite directions in the hollow-core fiber 17 to form a periodically distributed optical lattice. The cold atom matter wave of the cold atom cloud 18 undergoes a high-order Bragg diffraction process under the action of the first Bragg light beam 3 and the second Bragg light beam 24 (i.e., under the action of the optical lattice) to obtain a large momentum transfer. The order of the Bragg diffraction process is determined by the optical powers of the first Bragg light beam 3 and the second Bragg light beam 24; (4) Interference process: The first Bragg light beam 3 transmitted by the first optical path component and the second Bragg light beam 24 transmitted by the fourth optical path component form a set of Bragg light beams. After undergoing the coherent operations of three groups of Bragg light beams of π / 2 - π - π / 2 in sequence, the cold atom matter wave is split, reflected, and combined on the interference path to form a Mach-Zehnder interferometer; (5) Detection process: Detect the optical power signal of the detection light beam 12 transmitted by the third optical path component passing through the hollow-core fiber 17.

[0025] In this embodiment, a first polarization beam splitter prism 5 is disposed in the common output direction of the first optical path assembly and the second optical path assembly. The first polarization beam splitter prism 5 is configured to split incident light into two beams of light with polarization directions parallel or perpendicular to the incident plane, namely, P light and S light. The P light is the transmitted light emitted from the first polarization beam splitter prism 5, and the S light is the reflected light emitted from the first polarization beam splitter prism 5. The operating wavelength range of the first polarization beam splitter prism 5 covers the wavelengths of the first Bragg beam 3 and the dipole beam 7. By rotating the first half-wave plate 4 and the second half-wave plate 6, the first Bragg beam 3 and the dipole beam 7 are respectively adjusted to P light and S light, so as to achieve the combination of the first Bragg beam 3 and the dipole beam 7 after they are incident from both sides of the first polarization beam splitter prism 5; A non-polarizing beam splitter prism 10 is disposed in the common output direction of the third optical path assembly and the first polarization beam splitter prism 5. The non-polarizing beam splitter prism 10 is insensitive to the polarization of incident light. The operating wavelength range of the non-polarizing beam splitter prism 10 covers the wavelengths of the first Bragg beam 3, the dipole beam 7, and the probe beam 12. After being combined by the first polarization beam splitter prism 5, the first Bragg beam 3 and the dipole beam 7 are perpendicularly incident on the center of the first side surface of the non-polarizing beam splitter prism 10. The non-polarizing beam splitter prism 10 is configured to spatially split incident light into reflected light and transmitted light according to a specific splitting ratio. For example, after the incident light (such as the probe beam 12) passes through the non-polarizing beam splitter prism 10, the splitting ratio of its reflected light and transmitted light is 10:90.

[0026] In this embodiment, a plane mirror 15 and a first achromatic cemented lens 16 are sequentially disposed in the output direction of the non-polarizing beam splitter prism 10. The plane mirror 15 is configured to reflect the beam of light. The first achromatic cemented lens 16 is configured to focus and couple the first Bragg beam 3, the dipole beam 7, and the probe beam 12 into the hollow-core optical fiber 17, and collimate the second Bragg beam 24 emitted from the lower end of the hollow-core optical fiber 17 at the same time. Wherein, the operating wavelength range of the first achromatic cemented lens 16 covers the wavelengths of the first Bragg beam 3, the dipole beam 7, and the probe beam 12; After being combined by the non-polarizing beam splitter prism 10, the first Bragg beam 3, the dipole beam 7, and the probe beam 12 are reflected by the plane mirror 15 and then incident on the center of the first achromatic cemented lens 16; The first Bragg beam 3, the dipole beam 7, and the probe beam 12 are focused by the first achromatic cemented lens 16 to the lower end of the hollow-core optical fiber 17, and the corresponding beam energy is coupled into the hollow-core optical fiber 17.

[0027] In this embodiment, the first optical path component includes a first single-mode polarization-maintaining fiber 1, a first fiber collimator 2, and a first half-wave plate 4 arranged in sequence along the optical transmission direction. The optical output end of the first single-mode polarization-maintaining fiber 1 is connected to the optical input end of the first fiber collimator 2. The first single-mode polarization-maintaining fiber 1 is used to input a first Bragg beam 3. The first fiber collimator 2 is used to collimate the first Bragg beam 3 and output it. The first half-wave plate 4 is used to change the polarization direction of the first Bragg beam 3. Among them, the first Bragg beam 3 is a linearly polarized light, and the wavelength of the first Bragg beam 3 is in the red-detuned condition compared to the specific transition energy level of the atoms in the cold atom group 18. The working wavelength of the first half-wave plate 4 is the same as the wavelength of the first Bragg beam 3. The first Bragg beam 3 is perpendicularly incident on the center of the first side surface of the first polarization beam splitter prism 5 after passing through the first half-wave plate 4. By adjusting the slow axis direction of the first half-wave plate 4, the first Bragg beam 3 is changed into a P light with a polarization direction parallel to the incident plane and is transmitted through the first polarization beam splitter prism 5.

[0028] In this embodiment, the second optical path component includes a second single-mode polarization-maintaining fiber 9, a second fiber collimator 8, and a second half-wave plate 6 arranged in sequence along the optical transmission direction. The optical output end of the second single-mode polarization-maintaining fiber 9 is connected to the optical input end of the second fiber collimator 8. The second single-mode polarization-maintaining fiber 9 is used to input a dipole beam 7. The second fiber collimator 8 is used to collimate the dipole beam 7 and output it. The second half-wave plate 6 is used to change the polarization direction of the dipole beam 7. Among them, the dipole beam 7 is a linearly polarized light, and the wavelength of the dipole beam 7 is in the far red-detuned condition compared to the specific transition energy level of the atoms in the cold atom group 18, that is, it is shifted towards the red light direction. The working wavelength of the second half-wave plate 6 is the same as the wavelength of the dipole beam 7. The dipole beam 7 is perpendicularly incident on the center of the second side surface of the first polarization beam splitter prism 5 after passing through the second half-wave plate 6. By adjusting the slow axis direction of the second half-wave plate 6, the dipole beam 7 is changed into an S light with a polarization direction perpendicular to the incident plane and is reflected by the first polarization beam splitter prism 5.

[0029] In this embodiment, the third optical path component includes a third single-mode polarization-maintaining fiber 14, a third fiber collimator 13, and a third half-wave plate 11 that are arranged in sequence along the optical transmission direction. The optical output end of the third single-mode polarization-maintaining fiber 14 is connected to the optical input end of the third fiber collimator 13. The third single-mode polarization-maintaining fiber 14 is used to input the probe beam 12. The third fiber collimator 13 is used to collimate the probe beam 12 and output it. The third half-wave plate 11 is used to change the polarization direction of the probe beam 12. Among them, the probe beam 12 is a linearly polarized light, and the wavelength of the probe beam 12 satisfies the near-resonance condition with the specific transition energy level of the atoms in the cold atom cloud 18. The working wavelength of the third half-wave plate 11 is the same as the wavelength of the probe beam 12. The probe beam 12 is perpendicularly incident on the center of the second side surface of the non-polarizing beam splitter prism 10 after passing through the third half-wave plate 11. By adjusting the slow axis direction of the third half-wave plate 11, the probe beam 12 is changed into a P light with a polarization direction parallel to the incident plane, and is transmitted through the second polarization beam splitter prism 22 and enters the photodetector 27.

[0030] In this embodiment, a second polarization beam splitter prism 22, a band-pass filter 21, and a second achromatic doublet lens 20 are sequentially arranged in the output direction of the fourth optical path component. The band-pass filter 21 is used to block the transmission of the dipole beam 7. The second achromatic doublet lens 20 is used to focus and couple the second Bragg beam 24 into the hollow fiber 17, and at the same time collimate the first Bragg beam 3, the dipole beam 7, and the probe beam 12 emitted from the upper end of the hollow fiber 17. Among them, the stop band range of the band-pass filter 21 covers the wavelength of the dipole beam 7, and the pass band range covers the wavelengths of the first Bragg beam 3, the probe beam 12, and the second Bragg beam 24. The working wavelength range of the second achromatic doublet lens 20 covers the wavelengths of the first Bragg beam 3, the dipole beam 7, the probe beam 12, and the second Bragg beam 24.

[0031] In this embodiment, the fourth optical path component includes a fourth single-mode polarization-maintaining fiber 26, a fourth fiber collimator 25, and a fourth half-wave plate 23 that are arranged in sequence along the optical transmission direction. The optical output end of the fourth single-mode polarization-maintaining fiber 26 is connected to the optical input end of the fourth fiber collimator 25. The fourth single-mode polarization-maintaining fiber 26 is used to transmit the second Bragg beam 24. The fourth fiber collimator 25 is used to collimate the second Bragg beam 24 and output it. The fourth half-wave plate 23 is used to change the polarization direction of the second Bragg beam 24. Among them, the second Bragg beam 24 is a linearly polarized light, and the wavelength of the second Bragg beam 24 is in a red-detuned condition compared to the specific transition energy level of atoms in the cold atom group 18. The operating wavelength of the fourth half-wave plate 23 is the same as the wavelength of the second Bragg beam 24. The second Bragg beam 24 is perpendicularly incident on the center of the first side face of the second polarization beam splitter prism 22 after passing through the fourth half-wave plate 23. By adjusting the slow axis direction of the fourth half-wave plate 23, the second Bragg beam 24 is changed into an S light whose polarization direction is perpendicular to the incident plane. After being reflected by the second polarization beam splitter prism 22, it is incident on the center of the band-pass filter 21 and undergoes transmission. The transmitted second Bragg beam 24 is focused to the upper end of the hollow fiber 17 by the second achromatic cemented lens 20, and the corresponding beam energy is coupled into the hollow fiber 17.

[0032] In this embodiment, the number of the fifth optical path components is three groups, and its specific structure is prior art. For example, the fifth optical path component includes a fifth single-mode polarization-maintaining fiber and a fifth fiber collimator that are arranged in sequence along the optical transmission direction. The fifth single-mode polarization-maintaining fiber is used to transmit the counter-propagating cooling beam 19, and the fifth fiber collimator is used to collimate the counter-propagating cooling beam 19 and output it. Three groups of counter-propagating cooling beams 19 that are mutually orthogonal are formed in the vacuum chamber 28 by the three groups of fifth optical path components, and they intersect and overlap directly above the hollow fiber 17.

[0033] In this embodiment, the photodetector 27 is preferably but not limited to a silicon avalanche photodetector. The probe beam 12 is transmitted through the second polarization beam splitter prism 22 and is incident on the silicon avalanche photodetector. The silicon avalanche photodetector is used to measure the optical power signal of the probe beam 12 after being absorbed by the atoms in the hollow fiber 17. The optical power signal of the probe beam 12 after being absorbed by the atoms in the hollow fiber 17 reflects the atomic population probability.

[0034] In this embodiment, the hollow fiber 17 is a bare fiber after the coating layer is stripped. The hollow fiber 17 is also called an anti-resonant hollow photonic crystal fiber, and all half-wave plates are also called half-wave plates. The vacuum degree of the vacuum chamber 28 is less than 10 -8 Pa, which can reduce the influence of environmental disturbances on the interferometer.

[0035] In this embodiment, the counter-propagating cooling beam 19 is a circularly polarized light, and the wavelength of the counter-propagating cooling beam 19 is in a red-detuned condition with respect to a specific atomic transition energy level.

[0036] This embodiment also provides a large momentum transfer atomic interference method based on the guiding of a hollow-core fiber 17. Using the large momentum transfer atomic interferometer based on the guiding of the hollow-core fiber 17, the method includes the following steps: S1. Cooling and trapping a cold atom cloud 18 from the background high-speed atomic gas in the vacuum chamber 28 by using three groups of counter-propagating cooling beams 19 transmitted by a fifth optical path component (after the rubidium atom dispenser in the vacuum chamber is energized and heated, it can continuously release high-speed atomic gas, providing an atomic source for the preparation of a cold atom cloud; where "high-speed" thermodynamically characterizes the average kinetic energy of atoms). S2. Using the dipole beam 7 transmitted by a second optical path component to form a far-detuned optical dipole trap. Some cold atoms of the cold atom cloud 18 are confined in the far-detuned optical dipole trap and are guided into the hollow-core fiber 17 under the assistance of the gravitational field. S3. Using the first Bragg beam 3 transmitted by a first optical path component and the second Bragg beam 24 transmitted by a fourth optical path component to form a group of Bragg beams, and forming a periodically distributed optical lattice in the hollow-core fiber 17; the cold atom matter wave in the hollow-core fiber 17 obtains a large momentum transfer during the high-order Bragg diffraction process based on the optical lattice. S4. Successively using the coherent operation of three groups of π / 2 - π - π / 2 Bragg beams to split, reflect, and combine the cold atom matter wave on the interference path, constituting a Mach-Zehnder interferometer. S5. Using a photodetector 27 to detect the optical power signal of the probe beam 12 transmitted by a third optical path component after being absorbed by the cold atoms in the hollow-core fiber 17, obtaining the atomic population probability, and further calculating the atomic interference phase shift containing the acceleration information to be measured; under different evolution time conditions, by scanning the chirp rate of the Bragg beam, multiple interference fringes are obtained; according to the chirp rate corresponding to the coincidence of the interference fringes, the acceleration to be measured is calculated.

[0037] The advantages of this embodiment are as follows: (1) The present invention uses the dipole beam 7 transmitted by a second optical path component to form a far-detuned optical dipole trap, and radially confines atoms in the hollow-core fiber 17 through the far-detuned optical dipole trap: The far-detuned optical dipole trap can overcome the carrier acceleration in the non-measurement direction, and then trap the cold atom cloud 18 in the potential well. The maximum carrier acceleration it can overcome is a max = U0k B / (ω m m a ). Where, U0 is the potential well depth of the far-detuned optical dipole trap, k Brepresents the Boltzmann constant, ω m is the mode field radius of the hollow-core fiber 17, m a is the atomic mass; Exemplarily, for 87 Rb atoms, when the mode field diameter of the hollow-core fiber 17 is 20 μm, the maximum carrier acceleration that can be overcome by a potential well depth of 100 μK is approximately 1000 m / s 2 ; (2) Compared with the Bragg diffraction scheme based on free-space optical lattices, the present invention requires less optical power under the condition of the same Bragg diffraction order: The momentum transfer obtained by an atom during the nth-order Bragg diffraction is where is the reduced Planck constant, and k is the wave vector of the Bragg beam. In order to achieve a higher momentum transfer during atomic coherent beam splitting operations and further increase the scaling factor and improve the short-term sensitivity, it is necessary to introduce higher-order Bragg diffraction processes; However, as the Bragg diffraction order increases, the two-photon Rabi frequency (or optical intensity) required for the atom to be in the Bragg transition state also increases significantly, and the optical power of the corresponding Bragg beam also increases accordingly. Compared with the Bragg diffraction scheme based on free-space optical lattices, coupling the Bragg beam into the hollow-core fiber 17 can significantly reduce its mode field diameter from dozens of millimeters in free space to dozens of micrometers. The optical fields of the Bragg beams in free space and the hollow-core fiber 17 are approximately Gaussian distributions, and the relationship between the central optical intensity I and the optical power P is: where ω is the mode field radius. Therefore, under the condition of the same Bragg diffraction order, the large momentum transfer atomic interferometer based on the guidance of the hollow-core fiber 17 proposed by the present invention requires approximately six orders of magnitude less optical power than the existing Bragg diffraction scheme based on free-space optical lattices.

[0038] In practical applications, atoms in the initial state |p0> sequentially experience beam splitting, reflection, and beam combination processes under the action of three groups of π / 2-π-π / 2 Bragg beams, thereby constructing a Mach-Zehnder interferometer, which can be used to measure inertial information such as acceleration and gravity. Under the ideal condition of not considering the influence of the gravity gradient and angular velocity in the inertial field on the atomic interference phase shift, the population probability P of the atom finally in the f state is: where C is the interference fringe contrast, and 2n(k eff ·a m -πα)T 2 is the atomic interference phase shift, and a mThe acceleration to be measured is \(a\), the chirp rate of the Bragg beam is \(\alpha\), and the time interval (or evolution time) between the three groups of Bragg beams is \(T\). By detecting the optical power signal of the probe beam 12 after passing through the atoms absorbed in the hollow-core fiber 17, the atomic population probability \(P\) in the state can be obtained, and then the atomic interference phase shift including the acceleration \(a\) to be measured can be calculated. Under different evolution times \(T\), multiple interference fringes are obtained by scanning the chirp rate of the Bragg beam. According to the chirp rate \(\alpha_0\) corresponding to the coincidence of the interference fringes, the acceleration \(a\) to be measured can be calculated as f \(a=\pi\alpha_0 / k\). m m m In addition, the terms "first", "second", "third", and "fourth" are used for descriptive purposes only and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", "third", and "fourth" may explicitly or implicitly include one or more of such features.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements for some of the technical features. However, such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0040] ​

Claims

1. A large-momentum-transfer atomic interferometer based on hollow-core fiber guiding, characterized in that It includes a first optical path component for transmitting a first Bragg beam, a second optical path component for transmitting a dipole beam, a third optical path component for transmitting a probe beam, a fourth optical path component for transmitting a second Bragg beam, a fifth optical path component for transmitting counterpropagating cooling beams, a hollow-core fiber, and a photodetector. The hollow-core fiber is vertically disposed in a vacuum chamber. The light output end of the fifth optical path component leads to the vacuum chamber and can intersect and overlap three groups of counterpropagating cooling beams that are mutually orthogonal directly above the hollow-core fiber. The light output ends of the first optical path component, the second optical path component, and the third optical path component lead to the lower end of the hollow-core fiber. The light output end of the fourth optical path component leads to the upper end of the hollow-core fiber. The upper end of the hollow-core fiber leads to the light input end of the photodetector.

2. The large-momentum-transfer atomic interferometer based on hollow-core fiber guiding according to claim 1, wherein The first optical path component includes a first single-mode polarization-maintaining fiber, a first fiber collimator, and a first half-wave plate sequentially arranged along the light transmission direction. The light output end of the first single-mode polarization-maintaining fiber is connected to the light input end of the first fiber collimator. The first single-mode polarization-maintaining fiber is used to input the first Bragg beam. The first fiber collimator is used to collimate the first Bragg beam and output it. The first half-wave plate is used to change the polarization direction of the first Bragg beam.

3. The large-momentum-transfer atomic interferometer based on hollow-core fiber guiding according to claim 1, wherein The second optical path component includes a second single-mode polarization-maintaining fiber, a second fiber collimator, and a second half-wave plate sequentially arranged along the light transmission direction. The light output end of the second single-mode polarization-maintaining fiber is connected to the light input end of the second fiber collimator. The second single-mode polarization-maintaining fiber is used to input the dipole beam. The second fiber collimator is used to collimate the dipole beam and output it. The second half-wave plate is used to change the polarization direction of the dipole beam.

4. The large-momentum-transfer atomic interferometer based on a hollow-core fiber guiding according to claim 1, wherein The third optical path component includes a third single-mode polarization-maintaining fiber, a third fiber collimator, and a third half-wave plate sequentially arranged along the light transmission direction. The light output end of the third single-mode polarization-maintaining fiber is connected to the light input end of the third fiber collimator. The third single-mode polarization-maintaining fiber is used to input the probe beam. The third fiber collimator is used to collimate the probe beam and output it. The third half-wave plate is used to change the polarization direction of the probe beam.

5. The large-momentum-transfer atomic interferometer based on hollow-core fiber guiding according to claim 1, wherein A first polarization beam splitter prism is jointly arranged in the output directions of the first optical path component and the second optical path component. A non-polarizing beam splitter prism is jointly arranged in the output directions of the third optical path component and the first polarization beam splitter prism.

6. The large momentum transfer atomic interferometer based on hollow-core fiber guiding according to claim 5, wherein A plane mirror and a first achromatic cemented lens are sequentially arranged in the output direction of the non-polarizing beam splitter prism. The plane mirror is used to reflect the beam. The first achromatic cemented lens is used to focus and couple the first Bragg beam, the dipole beam, and the probe beam into the hollow-core fiber, and at the same time collimate the second Bragg beam emitted from the lower end of the hollow-core fiber.

7. The large-momentum-transfer atomic interferometer based on hollow-core fiber guiding according to claim 1, wherein The fourth optical path component includes a fourth single-mode polarization-maintaining fiber, a fourth fiber collimator, and a fourth half-wave plate, which are arranged in sequence along the optical transmission direction. The optical output end of the fourth single-mode polarization-maintaining fiber is connected to the optical input end of the fourth fiber collimator. The fourth single-mode polarization-maintaining fiber is used to transmit the second Bragg beam. The fourth fiber collimator is used to collimate the second Bragg beam and output it. The fourth half-wave plate is used to change the polarization direction of the second Bragg beam.

8. The large-momentum-transfer atomic interferometer based on hollow-core fiber guiding according to claim 1, wherein A second polarization beam splitter prism, a band-pass filter, and a second achromatic cemented lens are sequentially arranged in the output direction of the fourth optical path component. The band-pass filter is used to block the transmission of the dipole beam. The second achromatic cemented lens is used to focus the second Bragg beam and couple it into the hollow-core fiber, and at the same time collimate the first Bragg beam, the dipole beam, and the probe beam emitted from the upper end of the hollow-core fiber.

9. The large-momentum-transfer atomic interferometer based on hollow-core fiber guiding according to claim 1, characterized in that, The hollow-core optical fiber is a bare fiber after the coating layer is removed, the photodetector is a silicon avalanche photodetector, and the vacuum degree of the vacuum chamber is less than 10 -8 Pa.

10. A large-momentum-transfer atomic interference method based on the guidance of hollow-core optical fiber, using the large-momentum-transfer atomic interferometer based on the guidance of hollow-core optical fiber as described in claim 1, characterized in that, It includes the following steps: S1. Cooling and trapping a cold atom group from the background high-speed atomic gas in the vacuum chamber by using three groups of counter-propagating cooling beams transmitted by the fifth optical path component; S2. Forming a far-detuned optical dipole trap by using the dipole beam transmitted by the second optical path component. Part of the cold atoms in the cold atom group are confined in the far-detuned optical dipole trap and are guided into the hollow-core fiber under the assistance of the gravity field; S3. Using the first Bragg beam transmitted by the first optical path component and the second Bragg beam transmitted by the fourth optical path component to form a group of Bragg beams, and forming a periodically distributed optical lattice in the hollow-core fiber. The cold atom matter wave in the hollow-core fiber obtains a large momentum transfer during the high-order Bragg diffraction process based on the optical lattice; S4. Successively using the coherent operation of three groups of π / 2-π-π / 2 Bragg beams to split, reflect, and combine the cold atom matter wave on the interference path to form a Mach-Zehnder interferometer; S5. Using a photodetector to detect the optical power signal of the probe beam transmitted by the third optical path component after being absorbed by the cold atoms in the hollow-core fiber, obtaining the atomic population probability, and further calculating the atomic interference phase shift containing the acceleration information to be measured; under different evolution time conditions, by scanning the chirp rate of the Bragg beam, multiple interference fringes are obtained; according to the chirp rate corresponding to the coincidence of the interference fringes, the acceleration to be measured is calculated.

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