Optically pumped magnetometer based on a laser light source

Abstract

The application provides a laser light source-based optically pumped magnetometer, realizes frequency stabilization and miniaturization design, and improves the sensitivity of magnetic field measurement.The laser in the application emits a laser beam, which is split into two by a light splitting unit, and the two laser beams realize frequency stabilization and magnetic field measurement respectively.In the process of realizing frequency stabilization, the laser enters a frequency stabilization gas chamber again through a reflecting mirror after pumping atoms in the frequency stabilization gas chamber, and is totally reflected at a second polarization light splitting prism under the action of a first lambda / 4 wave plate, enters a first photoelectric detector, the first photoelectric detector measures the saturated absorption spectrum of the laser, and a frequency stabilization circuit realizes the frequency locking of the laser;in the process of realizing magnetic field measurement, the other laser acts on a magnetic probe unit and outputs the measured magnetic field strength through a magnetic measurement signal processing unit.

Description

Technical Field

[0001] This invention relates to the field of atomic magnetometer technology, and more specifically to an optically pumped magnetometer based on a laser light source. Background Technology

[0002] The light source, as the core component of an atomic magnetometer, significantly impacts system performance. Traditional optically pumped magnetometers use atomic spectral lamps as their light source. With the development of semiconductor technology, lasers, due to their monochromaticity and strong spectral selectivity, can precisely manipulate atomic energy levels, providing a new means for optical pump magnetic resonance (EPR) technology. Optically pumped magnetometers that use semiconductor lasers instead of high-frequency excited atomic spectral lamps offer an increase in sensitivity of more than an order of magnitude. However, laser light sources have complex structures, are inconvenient to install, and require frequency stabilization designs, including additional optical and circuit design. Therefore, they are generally used on optical platforms.

[0003] Therefore, there is an urgent need for an optically pumped magnetometer that can adapt to laser light sources and is easy to set up. Summary of the Invention

[0004] In view of this, the present invention provides an optically pumped magnetometer based on a laser light source, which can improve the sensitivity of magnetic field measurement.

[0005] To achieve the above-mentioned objectives, the technical solution of this invention is as follows:

[0006] A laser-based optically pumped magnetometer includes a laser source, a magnetic probe unit, and a magnetic signal processing unit.

[0007] The laser source includes a laser, a beam splitting unit, a second λ / 2 waveplate, a second polarizing beam splitter, a first λ / 4 waveplate, a frequency stabilizing gas chamber, an attenuator, a reflector, a first photodetector, and a frequency stabilizing circuit.

[0008] The laser emits a laser beam; the beam splitter divides the laser beam into two laser beams with perpendicular polarization directions.

[0009] The first laser beam passes through the second λ / 2 waveplate and is completely transmitted through the second polarizing beam splitter to form a pump beam; the pump beam enters the frequency-stabilizing gas chamber through the first λ / 4 waveplate to excite the atomic gas.

[0010] The emitted beam from the frequency-stabilized gas chamber is converted into a probe beam by an attenuator and a reflector. The probe beam enters the frequency-stabilized gas chamber through the attenuator and is partially absorbed by the excited atomic gas. The remaining probe beam is reflected to the first photodetector by the first λ / 4 waveplate and the second polarizing beam splitter.

[0011] The photodetector acquires the differential curve of the saturated absorption spectrum of the first laser beam, and the laser is frequency-locked by the frequency stabilization circuit to achieve frequency stabilization.

[0012] The second laser beam enters the magnetic probe unit via an optical fiber, is converted into current, and transmitted to the magnetic measurement signal processing unit.

[0013] The magnetic signal processing unit converts the current into a magnetic field value.

[0014] Furthermore, the laser source also includes a shaping unit located behind the laser, which includes an aspherical lens and a shaping prism.

[0015] Furthermore, the laser source also includes an isolation unit located after the shaping unit. The isolation unit includes a Faraday isolator to prevent light path reflection after the isolation unit.

[0016] Furthermore, the beam splitting unit includes a first λ / 2 waveplate and a first polarizing beam splitter prism.

[0017] Furthermore, it also includes a shielding shell located outside the laser source and the magnetic signal processing unit.

[0018] Beneficial effects:

[0019] This invention proposes a laser-based optically pumped magnetometer, achieving frequency stabilization and miniaturization, and improving the sensitivity of magnetic field measurement. In this invention, the laser emits a laser beam, which is split into two by a beam splitting unit. The two beams are used for frequency stabilization and magnetic field measurement, respectively. For frequency stabilization, the laser beam pumps atoms in a frequency-stabilizing gas chamber, then re-enters the chamber via a mirror for detection. Under the action of a first λ / 4 waveplate, the beam is completely reflected at a second polarizing beam splitter and enters a first photodetector. The photodetector measures the saturated absorption spectrum of the laser, and the frequency is locked by a frequency stabilization circuit. For magnetic field measurement, the other laser beam outputs the measured magnetic field strength via a magnetic probe unit and a magnetic signal processing unit. This optical path design uses the same light source for both laser frequency stabilization and magnetic field detection, and utilizes a λ / 4 waveplate, a mirror, and a polarizing beam splitter to achieve both atom pumping and detection with the same beam. This invention integrates the optical system and electronic units into a single chassis, overcoming the complexity and difficulty of building traditional laser-based optically pumped magnetometer systems, and achieving an instrument-grade, high-sensitivity laser-based optically pumped magnetometer design.

[0020] 2. The present invention employs a shaping unit to shape the laser beam into a uniform circular beam.

[0021] 3. The present invention employs an isolation unit to prevent optical path reflection behind the isolation unit and protect the laser.

[0022] 4. The present invention also includes a shielding shell, in which the laser light source and the magnetic signal processing unit are placed to avoid interference from the external environment. Attached Figure Description

[0023] Figure 1This is a simplified structural diagram of the present invention.

[0024] Figure 2 This is a structural diagram of an optically pumped magnetometer. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] like Figure 1 As shown, the optically pumped magnetometer includes a light source unit 100, a magnetic probe unit 200, a magnetic signal processing unit 300, and a shielding shell 400 surrounding the light source unit 100 and the magnetic signal processing unit 300. The light source unit 100 outputs a laser with stable frequency and power, which is guided into the magnetic probe unit 200 via an optical fiber coupler 107 and an optical fiber 118. The magnetic probe unit 200 introduces the laser into the atomic gas cell, where it undergoes magnetic resonance under the influence of an external magnetic field. The magnetic resonance signal (current) is processed by the magnetic signal processing unit 300. The magnetic signal processing unit 300 converts the magnetic resonance signal into the measured magnetic field strength and provides an radio frequency excitation signal to the magnetic probe 200, while also heating the atomic gas cell of the magnetic probe 200.

[0027] like Figure 2 As shown, the laser source 100 includes a laser 101, a shaping unit, an isolation unit, a beam splitting unit, a first fiber coupler 107, a second λ / 2 waveplate 108, a second polarizing beam splitter prism 109, a first λ / 4 waveplate 110, a frequency stabilizing gas chamber 111, an attenuator 112, a reflector 113, a first photodetector 114, a frequency stabilizing circuit 115, a laser temperature control circuit 116, a frequency stabilizing gas chamber temperature control circuit 117, and an optical fiber 118.

[0028] The shaping unit shapes the laser beam into a uniform circular beam and includes an aspherical lens 102 and a shaping prism 103. An isolation unit, located after the shaping unit, prevents optical path reflection after the isolation unit and includes a Faraday isolator 104. A beam splitting unit, located after the isolation unit, includes a first λ / 2 waveplate 105 and a first polarizing beam splitter prism 106. The beam splitting unit splits the shaped laser beam into two beams with mutually perpendicular polarization directions, namely a first laser beam and a second laser beam. The first laser beam stabilizes the frequency of the laser 101, and the second laser beam measures the magnetic field to be measured.

[0029] The first laser beam, under the action of the second λ / 2 waveplate 108, is completely transmitted through the second polarizing beam splitter 109. The first laser beam is relatively strong and can pump cesium atoms in the frequency-stabilizing gas chamber 111, exciting them to undergo energy level transitions. Simultaneously, the first laser beam is absorbed by the cesium atoms. After absorption, the first laser beam passes through the attenuator 112 and the reflector 113 to form a weaker probe beam, with a propagation path essentially the same as the pump beam but in the opposite direction. When the frequencies of the pump beam and the probe beam are the same as the resonant transition frequency from the ground state to the excited state of the cesium atoms, due to the Doppler effect, atoms with zero velocity along the propagation path resonate, accompanied by a significant reduction in the number of ground-state atoms due to the strong pumping effect. Therefore, the cesium atoms absorb less probe light, obtaining a corresponding saturated absorption spectrum. Most of the remaining reflected light, under the action of the first λ / 4 waveplate 110, is reflected onto the first photodetector 114 at the incident surface of the second polarizing beam splitter 109. The first photodetector 114 obtains the differential curve of the saturated absorption spectrum. After modulation and demodulation by the frequency stabilization circuit 115, the current of the laser 101 is adjusted in real time to achieve laser frequency locking. After locking by the saturated absorption spectrum, the laser frequency jitter is suppressed within MHz, resulting in good laser frequency stability.

[0030] Laser temperature control circuit 116 adjusts the temperature of laser 101 to maintain it at a set threshold. Frequency stabilizing gas chamber temperature control circuit 117 adjusts the temperature of frequency stabilizing gas chamber 104 to maintain it at a set threshold. (Example:) Figure 2 As shown, the magnetic probe unit 200 includes a second fiber optic coupler 201, a first lens 202, a polarizer 203, a second λ / 4 waveplate 204, an atomic gas cell 205, a coil 206, a second lens 207, and a second photodetector 208. The magnetic signal processing unit 300 includes an atomic gas cell temperature control circuit 301, a signal processing circuit 302, and a frequency measurement circuit 303. The second laser beam enters the optical fiber 118 through the first fiber optic coupler 107, and then enters the second fiber optic coupler 201. The beam output from the second fiber optic coupler 201 is expanded and collimated by the first lens 202, its polarization state is adjusted by the polarizer 203, and it forms circularly polarized light by the second λ / 4 waveplate 204. The circularly polarized light reacts with cesium atoms inside the atomic gas cell 205, and under the combined action of the radio frequency field generated by the coil 206 and the external magnetic field, the magnetic field changes the light intensity. The second lens 207 focuses the light beam, and the second photodetector 208 converts the optical signal into an electrical signal, which is then output as the magnetic field strength to be measured via the signal processing circuit 302 and the frequency measurement circuit 303. The atomic gas chamber temperature control circuit 301 adjusts the temperature of the atomic gas chamber 205 to maintain it at a set threshold.

[0031] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A laser-based optically pumped magnetometer, characterized in that, Includes a laser source, a magnetic probe unit, and a magnetic measurement signal processing unit; The laser source includes a laser, a beam splitting unit, a second λ / 2 waveplate, a second polarizing beam splitter, a first λ / 4 waveplate, a frequency stabilizing gas cell, an attenuator, a reflector, a first photodetector, and a frequency stabilizing circuit. The laser emits a laser beam; The beam splitter unit splits the laser beam into two laser beams with perpendicular polarization directions. The first laser beam passes through the second λ / 2 waveplate and is completely transmitted through the second polarization beam splitter to form a pump beam; the pump beam enters the frequency-stabilized gas chamber through the first λ / 4 waveplate to excite the atomic gas. The emitted beam from the frequency-stabilized gas chamber is converted into a probe beam by an attenuator and a reflector. The probe beam enters the frequency-stabilized gas chamber through the attenuator and is partially absorbed by the excited atomic gas. The remaining probe beam is completely reflected to the first photodetector by the first λ / 4 waveplate and the second polarizing beam splitter. The frequency-stabilizing gas chamber is a cesium atom gas chamber; The photodetector acquires the differential curve of the saturated absorption spectrum of the first laser beam, and the laser is frequency-locked by the frequency stabilization circuit to achieve frequency stabilization. The second laser beam enters the magnetic probe unit through an optical fiber, is converted into current, and is transmitted to the magnetic measurement signal processing unit. The magnetic probe unit includes a second fiber optic coupler, a first lens, a polarizer, a second λ / 4 waveplate, an atomic gas cell, a coil, a second lens, and a second photodetector; the atomic gas cell is a rubidium atomic gas cell. The magnetic signal processing unit converts the current into a magnetic field value.

2. The optically pumped magnetometer as described in claim 1, characterized in that, The laser source also includes a shaping unit located behind the laser, the shaping unit comprising an aspherical lens and a shaping prism.

3. The optically pumped magnetometer as described in claim 2, characterized in that, The laser source also includes an isolation unit located after the shaping unit. The isolation unit includes a Faraday isolator to prevent light path reflection after the isolation unit.

4. The optically pumped magnetometer as described in claim 3, characterized in that, The beam splitting unit includes a first λ / 2 waveplate and a first polarizing beam splitter prism.

5. The optically pumped magnetometer as described in claim 1 or 2, characterized in that, It also includes a shielding housing located outside the laser source and the magnetic signal processing unit.

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