CN109752671B - A Stable Control System for Optical Frequency Shift of Atomic Magnetometer - Google Patents
A Stable Control System for Optical Frequency Shift of Atomic Magnetometer Download PDFInfo
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Abstract
本发明属于原子磁强计技术领域，具体涉及一种原子磁强计光频移的稳定控制系统；检测光模块产生的两束检测光分别与驱动光模块产生的两束驱动光中的一束在原子气室内部交汇，两束检测光分别提取两束驱动光抽运的原子气室内原子的进动信息，实现独立的磁场测量；两束检测光经过光电转换后分别输入锁相放大器A和锁相放大器B进行信号处理，锁相放大器A和锁相放大器B的输出信号经过比例和积分环节后，依据锁相放大器A的输出信号设置DDS的输出频率，DDS驱动激励线圈，将原子气室内原子锁定在共振点；DDS输出频率实时锁定在原子的进动频率上，实现外磁场的测量；锁相放大器B的输出信号与设定值比较后，控制驱动光模块，实现光频移的稳定控制。
The invention belongs to the technical field of atomic magnetometers, and in particular relates to a stable control system for optical frequency shift of atomic magnetometers; Intersection inside the atomic gas chamber, the two beams of detection light respectively extract the precession information of the atoms in the atomic gas chamber pumped by the two beams of driving light to realize independent magnetic field measurement; the two beams of detection light are respectively input into the lock-in amplifier A and The lock-in amplifier B performs signal processing. After the output signals of the lock-in amplifier A and the lock-in amplifier B go through the proportional and integral links, the output frequency of the DDS is set according to the output signal of the lock-in amplifier A, and the DDS drives the excitation coil. The atoms are locked at the resonance point; the DDS output frequency is locked at the precession frequency of the atoms in real time to realize the measurement of the external magnetic field; after the output signal of the lock-in amplifier B is compared with the set value, it controls the driving optical module to achieve the stability of the optical frequency shift control.
Description
Technical Field
The invention belongs to the technical field of atomic magnetometers, and particularly relates to a stable control system for optical frequency shift of an atomic magnetometer.
Background
In recent years, atomic magnetometers have been rapidly developed by virtue of the advantages of high sensitivity, small volume, low power consumption and the like, and have been widely applied to numerous hot spot fields. Taking magnetic anomaly latency as an example, an atomic magnetometer is required to have high sensitivity and high stability, and therefore, stable control of an atomic magnetometer noise source is required. The pumping light polarization atom is adopted as the premise of the work of the atomic magnetometer, the pumping light irradiates an atom air chamber to enable the atom to feel a false magnetic field, and equivalently, a system measurement error is introduced, namely light frequency shift:
in the formula, BLSIs a shift of light frequency reElectron radius, c the speed of light, phi the photon flux,
Is a degree of circular polarization, gammaeIs the electron gyromagnetic ratio, V (V-V)0) Is linear in spectrum, and is related to atomic density and optical frequency.
Formula (1) indicates that: the optical frequency shift varies with the pump optical frequency, optical intensity, polarization characteristics, and atomic density, and fluctuations in any of these parameters will cause perturbations in the optical frequency shift.
Atoms respond to optical frequency shift and a real external magnetic field simultaneously, precess according to vector superposition of the optical frequency shift and the real external magnetic field, and convert optical frequency shift noise into magnetic field measurement noise:
in the formula (I), the compound is shown in the specification,
is a real external magnetic field,
Is the magnetic field experienced by the atom.
Optical frequency shift noise is one of the major noise sources that currently restrict the stability of atomic magnetometers, and therefore needs to be stably controlled.
At present, the means for inhibiting the optical frequency shift mainly depends on filling a large amount of buffer gas to reduce the sensitivity of the magnetometer to the optical frequency shift. However, a large amount of buffer gas can widen the magnetic resonance line width, and the sensitivity of the magnetometer is reduced, so that the control method cannot meet the application requirements of magnetic anomaly detection on high sensitivity and high stability of the atomic magnetometer.
Disclosure of Invention
In view of the above prior art, an object of the present invention is to provide a stable control system for optical frequency shift of an atomic magnetometer, which solves the problem of inaccurate measurement and control of optical frequency shift, and improves the control accuracy of optical frequency shift.
In order to achieve the above object, the present invention adopts the following technical solutions.
The invention relates to a stable control system of optical frequency shift of an atomic magnetometer, which comprises a driving optical module, a detection optical module, an atomic air chamber, an exciting coil, a phase-locked amplifier A, a phase-locked amplifier B and a frequency synthesizer DDS;
the driving light module generates two beams of left-handed circular polarization driving light and right-handed circular polarization driving light with the same light intensity to enter the atomic gas chamber;
the detection light module generates two beams of linear polarization detection light with the same frequency and the same polarization state to enter the atomic gas chamber;
adjusting the driving optical module and the detection optical module to enable two beams of detection light generated by the detection optical module to respectively intersect with one beam of two beams of driving light generated by the driving optical module in the atomic gas chamber, and respectively extracting precession information of atoms in the atomic gas chamber pumped by the two beams of driving light by the two beams of detection light to realize independent magnetic field measurement;
an excitation coil is arranged outside the atom air chamber to excite atoms in the two atom air chambers which drive light polarization, and an excitation magnetic field generated by the excitation coil is along the detection light direction;
the two beams of detection light are respectively input into a phase-locked amplifier A and a phase-locked amplifier B for signal processing after photoelectric conversion, and the phase-locked amplifier A and the phase-locked amplifier B extract the frequency and phase information of atom precession; after the output signals of the phase-locked amplifier A and the phase-locked amplifier B are subjected to proportion and integration links, the output frequency of the DDS is set according to the output signal of the phase-locked amplifier A, and the DDS drives the exciting coil to lock atoms in the atom air chamber at a resonance point; the DDS output frequency is locked on the precession frequency of atoms in real time to realize the measurement of an external magnetic field; and after the output signal of the phase-locked amplifier B is compared with a set value, the driving optical module is controlled, and the stable control of optical frequency shift is realized.
Further, after the two beams of driving light generated by the driving light module are collimated and shaped, the two beams of driving light enter 1/2 glass slides and a polarization beam splitter prism PBS, 1/2 glass slides are adjusted to enable the two beams of driving light emitted by the PBS to have the same intensity, the two beams of driving light emitted by the PBS respectively enter 2 1/4 glass slides, 2 1/4 glass slides are adjusted to enable the two beams of driving light to be left-handed circular polarization driving light and right-handed circular polarization driving light respectively, and atoms irradiated by the two beams of driving light are subjected to equal and opposite light frequency shift.
Furthermore, the two beams of detection light generated by the detection light module are collimated and shaped, then polarized by a Glan Taylor prism and then incident to the semi-transparent and semi-reflective mirror, and two beams of linear polarization detection light with the same frequency and the same polarization state are obtained to be incident to the atomic gas chamber; the driving light module and the detection light module are adjusted, so that two beams of detection light are respectively crossed with one beam of the two beams of driving light in the atom air chamber, the two beams of detection light respectively extract atom precession information pumped by different driving lights, and independent magnetic field measurement is realized.
Further, when the atom is in a resonance state, the in-phase component output by the phase-locked amplifier is zero; exciting coil output signal BxWhen the frequency difference delta omega occurs with the atom precession, the phase-locked amplifier A outputs the in-phase component XAComprises the following steps:
in the formula: b isxOutputting a signal for the excitation coil; xAOutputting the same-phase component for the phase-locked amplifier A; k is the photoelectric conversion efficiency and is determined by a photoelectric detector; t is1、T2Determining the atom resonance line width by the longitudinal relaxation time and the transverse relaxation time of the atom respectively; gamma is the atom gyromagnetic ratio; b is1Is the excitation signal amplitude; Δ ω is the frequency at which the excitation signal deviates from the resonance signal;
in-phase component X of phase-locked amplifier A outputAAs error input, setting the output frequency of the DDS after proportional and integral links; the DDS drives an exciting coil to lock atoms in the atom air chamber at a resonance point; the output frequency of the DDS is locked on the precession frequency of atoms in real time, and the measurement of an external magnetic field is realized.
Further, when a magnetic field closed loop is realized by using one beam of atoms for driving optical polarization, the other beam of atoms for driving optical polarization senses reverse optical frequency shift and is not in a resonance state, and the in-phase output X of the phase-locked amplifier B is at the momentBComprises the following steps:
in the formula: xBOutputting the same-phase component for the phase-locked amplifier A; k is the photoelectric conversion efficiency and is determined by a photoelectric detector; t is1、T2Determining the atom resonance line width by the longitudinal relaxation time and the transverse relaxation time of the atom respectively; gamma is the atom gyromagnetic ratio; b is1Is the excitation signal amplitude; Δ ω is the frequency at which the excitation signal deviates from the resonance signal; b isLSIs a light frequency shift;
the phase-locked amplifier B outputs X in phaseBAnd after the optical frequency is compared with a set value, the optical module is controlled and driven to realize stable control of optical frequency shift.
The technical scheme provided by the embodiment of the invention has the following beneficial effects:
the invention relates to a stable control system for optical frequency shift of an atomic magnetometer, which is based on a high-sensitivity atomic magnetometer constructed under low buffer gas pressure.
Compared with the prior art, the method improves the authenticity of optical frequency shift measurement and the accuracy of stable control; the high sensitivity of the atomic magnetometer is easy to realize; and an external vacuum air chamber feedback control loop is omitted, and the structure is simple and reliable.
Drawings
FIG. 1 is a schematic diagram of a system for controlling the stabilization of the optical frequency shift of an atomic magnetometer according to the present invention;
FIG. 2 is a schematic diagram of a portion of the optical path in front of the incident gas cell of the present invention;
FIG. 3 is a schematic diagram of the feedback control architecture of the present invention;
FIG. 4 is a diagram illustrating a corresponding relationship between the in-phase output X _ B and the optical frequency shift B _ LS of the lock-in amplifier B according to the present invention.
Detailed Description
The following describes a system for controlling stabilization of optical frequency shift of an atomic magnetometer in detail with reference to the detailed description and the accompanying drawings.
As shown in fig. 1, the system for stably controlling optical frequency shift of an atomic magnetometer of the present invention includes a driving optical module, a detecting optical module, an atomic gas chamber, an exciting coil, a lock-in amplifier, and a frequency synthesizer (DDS);
the driving light module generates two beams of left-handed circular polarization driving light and right-handed circular polarization driving light with the same light intensity to enter the atomic gas chamber;
the detection light module generates two beams of linear polarization detection light with the same frequency and the same polarization state to enter the atomic gas chamber;
adjusting the driving optical module and the detection optical module to enable two beams of detection light generated by the detection optical module to respectively intersect with one beam of two beams of driving light generated by the driving optical module in the atomic gas chamber, and respectively extracting precession information of atoms in the atomic gas chamber pumped by the two beams of driving light by the two beams of detection light to realize independent magnetic field measurement;
an excitation coil is arranged outside the atom air chamber to excite atoms in the two atom air chambers which drive light polarization, and an excitation magnetic field generated by the excitation coil is along the detection light direction;
the two beams of detection light are respectively input into a phase-locked amplifier A and a phase-locked amplifier B for signal processing after photoelectric conversion, and the phase-locked amplifier A and the phase-locked amplifier B extract the frequency and phase information of atom precession;
after the output signals of the phase-locked amplifier A and the phase-locked amplifier B are subjected to proportion and integration links, the output frequency of the DDS is set according to the output signal of the phase-locked amplifier A, and the DDS drives the exciting coil to lock atoms in the atom air chamber at a resonance point; the DDS output frequency is locked on the precession frequency of atoms in real time to realize the measurement of an external magnetic field; and after the output signal of the phase-locked amplifier B is compared with a set value, the driving optical module is controlled, and the stable control of optical frequency shift is realized.
As shown in fig. 2, after two beams of driving light generated by the driving optical module are collimated and shaped, the two beams of driving light are incident into 1/2 glass slides and a Polarization Beam Splitter (PBS), 1/2 glass slides are adjusted to make the two beams of driving light emitted from the PBS have the same intensity, the two beams of driving light emitted from the PBS are respectively incident into 2 1/4 glass slides, and 2 1/4 glass slides are adjusted to make the two beams of driving light respectively be left-handed circularly polarized driving light and right-handed circularly polarized driving light;
as can be seen from the equation (1), when the light intensities of the two driving lights are equal, the two driving lights have the same frequency and light intensity, and only the polarization directions are opposite, because the atoms in the same atom gas chamber have the same parameters, the atoms irradiated by the two driving lights will experience equal and opposite optical frequency shifts, and the difference of the precession frequencies of the atoms reflects the optical frequency shift.
Two beams of detection light generated by the detection light module are collimated and shaped, then polarized by a Glan Taylor (Glan) prism and then incident to a semi-transparent and semi-reflective mirror, and two beams of linear polarization detection light incident atom air chambers with the same frequency and the same polarization state are obtained; the driving light module and the detection light module are adjusted, so that two beams of detection light are respectively crossed with one beam of the two beams of driving light in the atom air chamber, the two beams of detection light respectively extract atom precession information pumped by different driving lights, and independent magnetic field measurement is realized.
As shown in fig. 3, when the atom is in the resonance state, the in-phase component of the output of the lock-in amplifier is zero; exciting coil output signal BxWhen the frequency difference delta omega occurs with the atom precession, the phase-locked amplifier A outputs the in-phase component XAComprises the following steps:
in the formula: b isxOutputting a signal for the excitation coil; xAOutputting the same-phase component for the phase-locked amplifier A; k is the photoelectric conversion efficiency and is determined by a photoelectric detector; t is1、T2Determining the atom resonance line width by the longitudinal relaxation time and the transverse relaxation time of the atom respectively; gamma is the atom gyromagnetic ratio; b is1Is the excitation signal amplitude; Δ ω is the frequency at which the excitation signal deviates from the resonance signal;
with in-phase component X output by phase-locked amplifier AAAs error input, setting the output frequency of the DDS after proportional and integral links; the DDS drives an exciting coil to lock atoms in the atom air chamber at a resonance point; the output frequency of the DDS is locked on the precession frequency of atoms in real time, and the measurement of an external magnetic field is realized.
When a closed loop of magnetic field is realized with one beam of atoms driving the polarization of light, the other beamAtoms driving optical polarization experience an inverse optical frequency shift and will not be in a resonant state; in this case, the in-phase output X of the lock-in amplifier BBComprises the following steps:
in the formula: xBOutputting the same-phase component for the phase-locked amplifier A; k is the photoelectric conversion efficiency and is determined by a photoelectric detector; t is1、T2Determining the atom resonance line width by the longitudinal relaxation time and the transverse relaxation time of the atom respectively; gamma is the atom gyromagnetic ratio; b is1Is the excitation signal amplitude; Δ ω is the frequency at which the excitation signal deviates from the resonance signal; b isLSIs a light frequency shift;
equation (4) establishes an optical frequency shift BLSIn-phase output X with phase-locked amplifier BBA typical diagram of the functional relationship is shown in fig. 4.
As shown in FIG. 4, B is within a certain rangeLSAnd XBApproximately linearly related (as shown by the thick line portion in the figure), the linear portion in the figure is obtained by calibration: b isLS＝K·XBAnd K in the formula is a linear fitting coefficient, so that the measurement of the optical frequency shift is realized.
The phase-locked amplifier B outputs X in phaseBAnd after the optical frequency is compared with a set value, the optical module is controlled and driven to realize stable control of optical frequency shift.
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| CN111337868B (en) * | 2020-03-23 | 2022-07-08 | 北京自动化控制设备研究所 | A method for measuring nuclear spin longitudinal relaxation time |
| CN112540327A (en) * | 2020-12-03 | 2021-03-23 | 中国船舶重工集团有限公司第七一0研究所 | Light path for inhibiting steering difference of laser optical pump magnetometer and design method |
| CN114442009B (en) * | 2021-12-22 | 2024-09-06 | 北京自动化控制设备研究所 | Atomic magnetometer frequency stabilization method and system based on FP cavity frequency stabilization |
| CN114460506B (en) * | 2021-12-22 | 2023-08-15 | 北京自动化控制设备研究所 | Magnetic resonance signal phase closed-loop control method and system based on variable parameter control |
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