Atomic spin polarization gradient suppression method based on annular beam pumping

Abstract

An atomic spin polarization gradient suppression method based on annular light beam pumping uses the characteristics of large external light field intensity, small internal light field intensity and the like of an annular light beam to realize rapid polarization of atoms which are depolarized due to bubble wall collision around an atomic gas chamber wall so as to compensate a polarization gradient caused by bubble wall collision. The method is characterized in that a phase distribution diagram of an annular light beam is designed according to the size and the structure of an air chamber, a Gaussian beam is shaped into the annular light beam through a spatial light modulator, and the generated annular light beam is used for atomic spin ensemble polarization. Comprising the following steps: performing center alignment on an annular light beam and a square gas chamber, and performing vertical incidence, so that the annular light beam polarizes alkali metal atoms and inert gas in the gas chamber; and measuring longitudinal relaxation of electron spin and nuclear spin, and evaluating an atomic spin polarization gradient suppression result.

Description

Technical Field

[0001] This invention relates to the field of atomic spin inertial measurement technology, and in particular to an atomic spin polarization gradient suppression method based on ring beam pumping. By shaping a Gaussian beam into a ring beam, efficient polarization of atoms around the gas chamber wall is achieved, compensating for depolarization caused by bubble wall collision relaxation, thereby suppressing the polarization gradient, improving the polarization uniformity of the atomic spin ensemble, and helping to improve the long-term stability of the atomic spin inertial measurement system. Background Technology

[0002] With the development of quantum precision measurement and sensing technology, quantum effect-based sensors have begun to be widely used in precision measurement fields, such as magnetic field sensing and inertial sensing. Atomic spin angular velocity measuring instruments based on spin-exchange relaxation-free (SERF) technology are expected to become the next generation of high-precision inertial measurement sensors. For modern inertial sensing and navigation systems, the long-term stability of atomic spin angular velocity measuring instruments is an important indicator. In miniaturized atomic spin gyroscopes, the efficient polarization of alkali metal atom spins and inert gas atom spins is the decisive factor determining the long-term stability of the atomic spin ensemble. Due to the reduced gas chamber volume, the diffusion effect of atoms causes relaxation of atoms near the gas chamber wall, thereby inducing polarization gradients between alkali metal atoms and inert gas atoms. Summary of the Invention

[0003] This invention addresses the deficiencies or shortcomings of existing technologies by providing an atomic spin polarization gradient suppression method based on ring beam pumping. Utilizing the characteristics of a ring beam, such as high external light field intensity and low internal light field intensity, it can rapidly polarize atoms around the atomic gas chamber wall that have depolarized due to bubble wall collisions, thereby suppressing the polarization gradient and improving the long-term stability of miniaturized atomic spin angular velocity measuring instruments.

[0004] The technical solution of the present invention is as follows:

[0005] A method for suppressing atomic spin polarization gradients based on ring beam pumping is characterized by shaping a Gaussian beam into a ring beam on the pumping optical path before the gas chamber. The cross-section of the ring beam covers the cross-section of the cavity of the gas chamber. The central region of the cross-section of the ring beam has a smaller optical field intensity, while the peripheral region has a larger optical field intensity. The ring beam is used to polarize alkali metal atoms and inert gases in the gas chamber. The larger optical field intensity is configured to rapidly polarize atoms around the gas chamber wall that have depolarized due to bubble wall collisions, thereby suppressing atomic spin polarization gradients.

[0006] Includes the following steps:

[0007] Step 1: The polarization gradient caused by bubble wall collisions under Gaussian beam pumping is determined through simulation and experiment. The polarization distribution of the atomic ensemble is adjusted according to the polarization gradient, and a ring beam is designed to compensate for the polarization gradient.

[0008] Step 2: Design the phase distribution diagram of the annular beam based on the size and structure of the air chamber, and determine the optical parameters of the spot size and phase distribution corresponding to the optimal annular beam;

[0009] Step 3: Shape the Gaussian beam into a ring beam using a spatial light modulator, including loading the phase distribution map of the ring beam into the spatial light modulator, applying a voltage to the spatial light modulator to change the phase distribution of the Gaussian beam, thereby shaping it into the desired ring beam.

[0010] Step 4: Use the generated ring beam for atomic spin ensemble polarization, including centering the ring beam with the square gas cell and incident perpendicularly, so that the ring beam polarizes the alkali metal atoms and inert gas in the gas cell.

[0011] Step 5: Measure the longitudinal relaxation of electron spin and nuclear spin, and evaluate the results of atomic spin polarization gradient suppression. This includes varying the gas chamber temperature, switching the pump light, and using the free induction decay method to evaluate the electron spin and nuclear spin relaxation at different atomic number densities. At the same time, compare the electron spin and nuclear spin relaxation under Gaussian beam pumping, and then evaluate the results of atomic spin polarization gradient suppression brought about by the ring beam.

[0012] Step 4 includes:

[0013]

[0014] Where P e R represents the steady-state electron spin longitudinal polarizability. op R is the optical pump rate. rel denoted as the total longitudinal relaxation rate of the electron spin.

[0015] Step 4 includes:

[0016]

[0017] Where P n For steady-state nuclear spin longitudinal polarizability, The spin exchange rate between electron spin and nuclear spin. The longitudinal total relaxation rate of the nuclear spin.

[0018] Step 1 includes: When the system is working normally, due to the characteristics of the ring beam having a large external light field intensity and a small internal light field intensity, the pump rate of the part with a large light field intensity is large, and therefore the steady-state polarization is also large. The part with the strong light intensity of the ring beam is exactly around the gas chamber wall, that is, the region where the polarization gradient caused by the collision of the bubble wall exists.

[0019] Step 5 includes:

[0020]

[0021] in Let be the longitudinal relaxation rate of the electron. This refers to the relaxation of electrons due to collisions with the bubble walls. This refers to the spin-disrupting collisional relaxation of electrons.

[0022] Step 5 includes: in the electron spin longitudinal relaxation mechanism, the total relaxation rate of electrons is tested by the S-curve method, the influence of electron pump rate is removed by the switch pump light method, the longitudinal relaxation time is tested and fitted under different atomic number densities, and the relaxation terms related to atomic number density are removed. The relaxation terms include spin exchange relaxation and spin destruction relaxation, thereby approximately evaluating the magnitude of electron spin bubble wall collision relaxation.

[0023] Step 5 includes:

[0024]

[0025] in For nuclear spin-breaking collision relaxation, The bubble wall collision relaxation of nuclear spin. For electric quadrupole moment relaxation, For spin-exchange collision relaxation, This is magnetic field gradient relaxation.

[0026] Step 5 includes: In the longitudinal relaxation mechanism of nuclear spin, bubble wall collision relaxation and electric quadrupole moment relaxation are the dominant terms. The nuclear spin and electron spin can be decoupled by applying a main magnetic field signal or a large magnetic field signal Bz along the z-axis. The nuclear spin free induction decay (FID) signal under Bz is tested. This FID signal reflects the longitudinal relaxation time of the nuclear spin. By testing and fitting the longitudinal relaxation time under different atomic number densities, the magnitude of nuclear spin bubble wall collision relaxation can be approximately evaluated.

[0027] The technical effects of this invention are as follows: This invention provides an atomic spin polarization gradient suppression method based on a ring beam pump. Utilizing the characteristics of a ring beam—high external light field intensity and low internal light field intensity—it can rapidly polarize atoms around the atomic gas chamber wall that have depolarized due to bubble wall collisions, thereby compensating for the polarization gradient caused by bubble wall collisions. This is beneficial for improving the long-term stability of miniaturized atomic spin angular velocity measuring instruments. The invention is characterized by designing a phase distribution diagram of the ring beam according to the size and structure of the gas chamber; shaping the Gaussian beam into a ring beam using a spatial light modulator; and using the generated ring beam for atomic spin ensemble polarization. This includes center-aligning the ring beam with a square gas chamber and incident perpendicularly, causing the ring beam to polarize the alkali metal atoms and inert gas in the gas chamber; measuring the longitudinal relaxation of electron spin and nuclear spin; and evaluating the atomic spin polarization gradient suppression results. This method can be used in quantum precision measurement research based on spin-coupled ensembles, such as the SERF atomic spin inertial measurement system. Attached Figure Description

[0028] Figure 1 This is a schematic flowchart illustrating the implementation of an atomic spin polarization gradient suppression method based on ring beam pumping according to the present invention. Figure 1 The process includes: Step 1, determining the polarization gradient caused by bubble wall collisions under Gaussian beam pumping through simulation and experiments, and based on this result, adjusting the atomic ensemble polarization distribution to design a ring beam for compensating for the polarization gradient; Step 2, designing the phase distribution map of the ring beam according to the size and structure of the gas cell, and determining the optimal spot size, phase distribution, and other optical parameters of the ring beam under this structured gas cell; Step 3, shaping the Gaussian beam into a ring beam using a spatial light modulator, including loading the ring beam phase distribution map determined in the previous step into the spatial light modulator, and applying a voltage to the spatial light modulator to change the phase distribution of the Gaussian beam. This shapes the beam into the desired ring beam. Step 4 involves using the generated ring beam for atomic spin ensemble polarization, including centering the ring beam with the square gas cell and incident perpendicularly, so that the ring beam polarizes the alkali metal atoms and inert gas in the gas cell. Step 5 involves measuring the longitudinal relaxation of electron spin and nuclear spin, and evaluating the results of atomic spin polarization gradient suppression. This includes methods such as varying the gas cell temperature, switching the pump light, and free induction decay to evaluate the electron spin and nuclear spin relaxation at different atomic number densities. At the same time, the electron spin and nuclear spin relaxation under Gaussian beam pumping is compared to evaluate the results of atomic spin polarization gradient suppression. Detailed Implementation

[0029] The following is in conjunction with the attached diagram ( Figure 1 The invention will be described in the following sections and examples.

[0030] Figure 1 This is a schematic flowchart illustrating the implementation of an atomic spin polarization gradient suppression method based on ring beam pumping according to the present invention. (Reference) Figure 1 As shown, an atomic spin polarization gradient suppression method based on ring beam pumping includes shaping a Gaussian beam into a ring beam on the pump optical path before entering the gas chamber. The cross-section of the ring beam covers the cross-section of the cavity of the gas chamber. The central region of the cross-section of the ring beam has a smaller optical field intensity, while the peripheral region has a larger optical field intensity. The ring beam is used to polarize alkali metal atoms and inert gases in the gas chamber. The larger optical field intensity is configured to rapidly polarize atoms around the gas chamber wall that have depolarized due to bubble wall collisions, thereby suppressing the atomic spin polarization gradient.

[0031] The process includes the following steps: Step 1, determining the polarization gradient caused by bubble wall collisions under Gaussian beam pumping through simulation and experiments, and designing a ring beam to compensate for the polarization gradient by adjusting the atomic ensemble polarization distribution according to the polarization gradient; Step 2, designing the ring beam phase distribution diagram based on the gas cell size and structure, and determining the optical parameters of the optimal ring beam's spot size and phase distribution; Step 3, shaping the Gaussian beam into a ring beam using a spatial light modulator, including loading the ring beam phase distribution diagram into the spatial light modulator, applying voltage to the spatial light modulator to change the phase distribution of the Gaussian beam, thereby shaping it into the desired ring beam. The required ring beam; Step 4, use the generated ring beam for atomic spin ensemble polarization, including centering the ring beam with the square gas cell and incident perpendicularly, so that the ring beam polarizes the alkali metal atoms and inert gas in the gas cell; Step 5, measure the longitudinal relaxation of electron spin and nuclear spin, and evaluate the atomic spin polarization gradient suppression results, including varying the gas cell temperature, switching the pump light, and using the free induction decay method to evaluate the electron spin and nuclear spin relaxation at different atomic number densities, while comparing the electron spin and nuclear spin relaxation under Gaussian beam pumping, and then evaluating the atomic spin polarization gradient suppression results brought by the ring beam.

[0032] Step 4 includes:

[0033]

[0034] Where P e R represents the steady-state electron spin longitudinal polarizability. op R is the optical pump rate. rel denoted as the total longitudinal relaxation rate of the electron spin.

[0035] Step 4 includes:

[0036]

[0037] Where P n For steady-state nuclear spin longitudinal polarizability, The spin exchange rate between electron spin and nuclear spin. The longitudinal total relaxation rate of the nuclear spin.

[0038] Step 1 includes: When the system is working normally, due to the characteristics of the ring beam having a large external light field intensity and a small internal light field intensity, the pump rate of the part with a large light field intensity is large, and therefore the steady-state polarization is also large. The part with the strong light intensity of the ring beam is exactly around the gas chamber wall, that is, the region where the polarization gradient caused by the collision of the bubble wall exists.

[0039] Step 5 includes:

[0040]

[0041] in Let be the longitudinal relaxation rate of the electron. This refers to the relaxation of electrons due to collisions with the bubble walls. This refers to the spin-disrupting collisional relaxation of electrons.

[0042] Step 5 includes: In the electron spin longitudinal relaxation mechanism, the total relaxation rate of electrons can be tested by the S-curve method, the switch pump light method can remove the influence of electron pump rate, the longitudinal relaxation time is tested and fitted under different atomic number densities, and relaxation terms related to atomic number density, such as spin exchange relaxation and spin destruction relaxation, can be removed, thereby approximately evaluating the magnitude of electron spin bubble wall collision relaxation.

[0043] Step 5 includes:

[0044]

[0045] in For nuclear spin-breaking collision relaxation, The bubble wall collision relaxation of nuclear spin. For electric quadrupole moment relaxation, For spin-exchange collision relaxation, This is magnetic field gradient relaxation.

[0046] Step 5 includes: In the longitudinal relaxation mechanism of nuclear spin, bubble wall collision relaxation and electric quadrupole moment relaxation are the dominant terms. The nuclear spin and electron spin can be decoupled by applying a main magnetic field signal or a large magnetic field signal Bz along the z-axis. The nuclear spin FID signal (FID, Free Induction Decay) under Bz is tested. This signal can reflect the longitudinal relaxation time of the nuclear spin. By testing and fitting the longitudinal relaxation time under different atomic number densities, the magnitude of nuclear spin bubble wall collision relaxation can be approximately evaluated.

[0047] A method for suppressing atomic spin polarization gradients based on ring beam pumping is proposed. This method utilizes the high intensity of the outer light field and the low intensity of the inner light field of the ring beam to efficiently polarize atoms around the gas chamber wall that are depolarized due to bubble wall collisions, thereby suppressing the atomic spin polarization gradient. Specifically, the polarization gradient caused by bubble wall collisions under Gaussian beam pumping is determined based on simulations and experiments. Based on this result, the atomic ensemble polarization distribution is adjusted, and a ring beam is designed to compensate for the polarization gradient. The phase distribution map of the ring beam is designed according to the size and structure of the gas chamber. The Gaussian beam is shaped into a ring beam using a spatial light modulator. The generated ring beam is used for atomic spin ensemble polarization, including centering the ring beam with the square gas chamber and subjecting it perpendicularly, so that the ring beam polarizes the alkali metal atoms and inert gas in the gas chamber. The longitudinal relaxation of electron spin and nuclear spin is measured, and the results of atomic spin polarization gradient suppression are evaluated.

[0048] A method for suppressing atomic spin polarization gradients based on ring beam pumping includes the following steps:

[0049] Step 1: The polarization gradient caused by bubble wall collisions under Gaussian beam pumping is determined through simulation and experiment. Based on the result, the polarization distribution of the atomic ensemble is adjusted to design a ring beam to compensate for the polarization gradient.

[0050] Step 2: Based on the size and structure of the air chamber, design the phase distribution diagram of the annular beam. It is necessary to determine the optimal spot size, phase distribution, and other optical parameters of the annular beam under this air chamber structure.

[0051] Step 3: Shape the Gaussian beam into a ring beam using a spatial light modulator. This includes loading the ring beam phase distribution map determined in the previous step into the spatial light modulator, applying a voltage to the spatial light modulator to change the phase distribution of the Gaussian beam, thereby shaping it into the desired ring beam.

[0052] Step 4: Use the generated ring beam for atomic spin ensemble polarization, including centering the ring beam with the square gas cell and incident perpendicularly, so that the ring beam polarizes the alkali metal atoms and inert gas in the gas cell.

[0053] Step 5: Measure the longitudinal relaxation of electron spin and nuclear spin, and evaluate the results of atomic spin polarization gradient suppression. This includes methods such as varying the gas chamber temperature, switching the pump light, and free induction decay to evaluate the electron spin and nuclear spin relaxation at different atomic number densities. At the same time, compare the electron spin and nuclear spin relaxation under Gaussian beam pumping to further evaluate the results of atomic spin polarization gradient suppression.

[0054] This invention discloses an atomic spin polarization gradient suppression method based on ring beam pumping. By shaping a traditional Gaussian beam into a ring beam and polarizing the spin ensemble of alkali metal atoms and inert gas atoms, and taking advantage of the high external light field intensity and low internal light field intensity of the ring beam, the atomic spins around the gas chamber wall that are depolarized due to bubble wall collisions can be polarized by increasing the pump rate. This compensates for bubble wall collision relaxation and suppresses the polarization gradient. At the same time, this method is beneficial to improving the polarizability of electron spin and nuclear spin, thereby further improving the long-term stability of miniaturized atomic spin gyroscopes.

[0055] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, and / or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A method for suppressing atomic spin polarization gradients based on ring beam pumping, characterized in that, The method involves shaping a Gaussian beam into a ring beam on the pump optical path before entering the gas chamber. The cross-section of the ring beam covers the cross-section of the cavity of the gas chamber. The central region of the cross-section of the ring beam has a smaller optical field intensity, while the peripheral region has a larger optical field intensity. The ring beam is used to polarize the alkali metal atoms and inert gas in the gas chamber. The larger optical field intensity is configured to rapidly polarize atoms around the gas chamber wall that have depolarized due to bubble wall collisions, thereby suppressing the atomic spin polarization gradient.

2. The atomic spin polarization gradient suppression method based on ring beam pumping according to claim 1, characterized in that, Includes the following steps: Step 1: The polarization gradient caused by bubble wall collisions under Gaussian beam pumping is determined through simulation and experiment. The polarization distribution of the atomic ensemble is adjusted according to the polarization gradient, and a ring beam is designed to compensate for the polarization gradient. Step 2: Design the phase distribution diagram of the annular beam based on the size and structure of the air chamber, and determine the optical parameters of the spot size and phase distribution corresponding to the optimal annular beam; Step 3: Shape the Gaussian beam into a ring beam using a spatial light modulator, including loading the phase distribution map of the ring beam into the spatial light modulator, applying a voltage to the spatial light modulator to change the phase distribution of the Gaussian beam, thereby shaping it into the desired ring beam. Step 4: Use the generated ring beam for atomic spin ensemble polarization, including centering the ring beam with the square gas cell and incident perpendicularly, so that the ring beam polarizes the alkali metal atoms and inert gas in the gas cell. Step 5: Measure the longitudinal relaxation of electron spin and nuclear spin, and evaluate the results of atomic spin polarization gradient suppression. This includes varying the gas chamber temperature, switching the pump light, and using the free induction decay method to evaluate the electron spin and nuclear spin relaxation at different atomic number densities. At the same time, compare the electron spin and nuclear spin relaxation under Gaussian beam pumping, and then evaluate the results of atomic spin polarization gradient suppression brought about by the ring beam.

3. The atomic spin polarization gradient suppression method based on ring beam pumping according to claim 2, characterized in that, Step 4 includes: Where P e R represents the steady-state electron spin longitudinal polarizability. op R is the optical pump rate. rel denoted as the total longitudinal relaxation rate of the electron spin.

4. The atomic spin polarization gradient suppression method based on ring beam pumping according to claim 2, characterized in that, Step 4 includes: Where P n For steady-state nuclear spin longitudinal polarizability, The spin exchange rate between electron spin and nuclear spin. The longitudinal total relaxation rate of the nuclear spin.

5. The atomic spin polarization gradient suppression method based on ring beam pumping according to claim 2, characterized in that, Step 1 includes: When the system is working normally, due to the characteristics of the ring beam having a large external light field intensity and a small internal light field intensity, the pump rate of the part with a large light field intensity is large, and therefore the steady-state polarization is also large. The part with the strong light intensity of the ring beam is exactly around the gas chamber wall, that is, the region where the polarization gradient caused by the collision of the bubble wall exists.

6. The atomic spin polarization gradient suppression method based on ring beam pumping according to claim 2, characterized in that, Step 5 includes: in Let be the longitudinal relaxation rate of the electron. This refers to the relaxation of electrons due to collisions with the bubble walls. This refers to the spin-disrupting collisional relaxation of electrons.

7. The atomic spin polarization gradient suppression method based on ring beam pumping according to claim 2, characterized in that, Step 5 includes: in the electron spin longitudinal relaxation mechanism, the total relaxation rate of electrons is tested by the S-curve method, the influence of electron pump rate is removed by the switch pump light method, the longitudinal relaxation time is tested and fitted under different atomic number densities, and the relaxation terms related to atomic number density are removed. The relaxation terms include spin exchange relaxation and spin destruction relaxation, thereby approximately evaluating the magnitude of electron spin bubble wall collision relaxation.

8. The atomic spin polarization gradient suppression method based on ring beam pumping according to claim 2, characterized in that, Step 5 includes: in For nuclear spin-breaking collision relaxation, The bubble wall collision relaxation of nuclear spin. For electric quadrupole moment relaxation, For spin-exchange collision relaxation, This is magnetic field gradient relaxation.

9. The atomic spin polarization gradient suppression method based on ring beam pumping according to claim 2, characterized in that, Step 5 includes: In the longitudinal relaxation mechanism of nuclear spin, bubble wall collision relaxation and electric quadrupole moment relaxation are the dominant terms. The nuclear spin and electron spin can be decoupled by applying a main magnetic field signal or a large magnetic field signal Bz along the z-axis. The nuclear spin free induction decay (FID) signal under Bz is tested. This FID signal reflects the longitudinal relaxation time of the nuclear spin. By testing and fitting the longitudinal relaxation time under different atomic number densities, the magnitude of nuclear spin bubble wall collision relaxation can be approximately evaluated.

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