Enhancing the sensitivity of spin-exchange relaxation-free magnetometers using phase-modulated pump light with external Gaussian noise.

An optical pumping scheme is proposed for reducing the gradient of electron spin polarization and suppressing light source noise in a spin-exchange relaxation-free magnetometer. This is achieved by modulating only the phase of a narrow-linewidth pump light field with external Gaussian noise. Compared to the absence of phase modulation, the uniformity of electron spin polarization was improved by over 40%, and the light-frequency noise suppression ratio of the magnetometer was enhanced by 4.

Demonstration of a high-density alkali-metal atomic magnetometer based on the frequency-symmetrical detuning effect of two pumping lights.

The existence of an approximately uniform and unsaturated electron spin polarization distribution within a high-density alkali-metal vapor is considered of great importance for significantly improving the response amplitude and sensitivity properties of an atomic magnetometer. However, when a high-density alkali-metal vapor is formed, the optical depth is much larger than the value of one, resulting in the electron spin polarization gradient. In this work, it was demonstrated from both numerical simulations and experimental points of view, that by replacing the resonant pumping light with two off-resonant pumping light sources, the signal amplitude of the magnetometer can be doubled.

Analysis and Measurement of Differential-Mode Magnetic Noise in Mn-Zn Soft Ferrite Shield for Ultra-Sensitive Sensors.

The magnetic noise generated by the ferrite magnetic shield affects the performance of ultra-sensitive atomic sensors. Differential measurement can effectively suppress the influence of common-mode (CM) magnetic noise, but the limit of suppression capability is not clear at present. In this paper, a finite element analysis model using power loss to calculate differential-mode (DM) magnetic noise under a ferrite magnetic shield is proposed.

Triaxial precise magnetic field compensation of a zero-field optically pumped magnetometer based on a single-beam configuration.

Triaxial magnetic field compensation is crucial for a zero-field optically pumped magnetometer (OPM) in pursuit of a zero-field environment. In this work, we demonstrate a triaxial magnetic field compensation method for zero-field OPM based on single-beam configuration. It consists of two procedures: (1) pre-compensation to preliminarily cancel out ambient residual magnetic field by low-frequency magnetic field modulation; and (2) precise compensation to further compensate the residual magnetic field by high-frequency magnetic field modulation.

Three-axis closed-loop optically pumped magnetometer operated in the SERF regime.

We propose a three-axis closed-loop optically pumped magnetometer with high sensitivity. The closed-loop magnetometer has a three-axis sensitivity of approximately 30 fT/Hz using two orthogonal laser beams for pumping and probing the alkali metal atoms. In the closed-loop mode, the dynamic range is improved from ±5 nT to ±150 nT.

Fast extraction of the electron spin-relaxation rate in the SERF magnetometer from a transient response.

The magnitude of the electron spin-relaxation rate R of the atomic ensemble directly affects the sensitivity of the spin-exchange relaxation-free (SERF) atomic magnetometer (AM). The rapid and in-situ characterization of R is of great importance. In this work, a fast extraction method of R is proposed with a measurement period shorten to 0.

Scanning multi-channel spin-exchange relaxation-free atomic magnetometer with high spatial and time resolution: publisher's note.

This publisher's note contains a correction to Opt. Lett.47, 3908 (2022)10.

Scanning a multi-channel spin-exchange relaxation-free atomic magnetometer with high spatial and time resolution.

The emerging multi-channel spin-exchange relaxation-free (SERF) atomic magnetometer is a promising candidate for non-intrusive biomagnetism imaging. In this study, we propose a scanning 9-channel SERF magnetometer based on an acousto-optic modulator (AOM). Using the diffraction light of the AOM as the probe laser (with a low laser power of 1.

Suppression of the magnetic noise response caused by elliptically polarized light in an optical rotation detection system.

We analyze and suppress the magnetic noise response in optical rotation detection system (ORDS) in atomic magnetometers in this study. Because of the imperfections of the optical elements, the probe light is actually elliptically polarized in ORDS, which can polarize the atom ensemble and cause the responses to the three-axis magnetic noise. We theoretically analyze the frequency responses to the magnetic noise, and prove that the responses are closely associated with the DC magnetic field.

Probe noise characteristics of the spin-exchange relaxation-free (SERF) magnetometer.

In the spin-exchange relaxation-free (SERF) magnetometer, the probe noise is a consequential factor affecting the gradiometric measurement sensitivities. In this paper, we proposed a new characteristics model of the probe noise based on noise separation. Different from noise analysis on single noise source, we considered most of the noise sources influencing the probe system and realized noise sources level measurement experimentally.

In-Situ Measurement of Electrical-Heating-Induced Magnetic Field for an Atomic Magnetometer.

Electrical heating elements, which are widely used to heat the vapor cell of ultrasensitive atomic magnetometers, inevitably produce a magnetic field interference. In this paper, we propose a novel measurement method of the amplitude of electrical-heating-induced magnetic field for an atomic magnetometer. In contrast to conventional methods, this method can be implemented in the atomic magnetometer itself without the need for extra magnetometers.

Suppression of vapor cell temperature error for spin-exchange-relaxation-free magnetometer.

This paper presents a method to reduce the vapor cell temperature error of the spin-exchange-relaxation-free (SERF) magnetometer. The fluctuation of cell temperature can induce variations of the optical rotation angle, resulting in a scale factor error of the SERF magnetometer. In order to suppress this error, we employ the variation of the probe beam absorption to offset the variation of the optical rotation angle.

[Measurement of atomic number of alkali vapor and pressure of buffer gas based on atomic absorption].

High sensitivitymagnetic measurementscanbe achieved by utilizing atomic spinmanipulation in the spin-exchange-relaxation-free (SERF) regime, which uses an alkali cell as a sensing element. The atomic number density of the alkali vapor and the pressure of the buffer gasare among the most important parameters of the cell andrequire accurate measurement. A method has been proposed and developedto measure the atomic number density and the pressure based on absorption spectroscopy, by sweeping the absorption line and fittingthe experiment data with a Lorentzian profile to obtainboth parameters.

A fast determination method for transverse relaxation of spin-exchange-relaxation-free magnetometer.

We propose a fast and accurate determination method for transverse relaxation of the spin-exchange-relaxation-free (SERF) magnetometer. This method is based on the measurement of magnetic resonance linewidth via a chirped magnetic field excitation and the amplitude spectrum analysis. Compared with the frequency sweeping via separate sinusoidal excitation, our method can realize linewidth determination within only few seconds and meanwhile obtain good frequency resolution.