A dual closed-loop drive and control system of photoelastic modulator for atomic magnetometer

Abstract

Resonance frequency shift and vibration amplitude instability can occur during the operation processes of photoelastic modulators in atomic magnetometers, resulting in low driving efficiency and unstable modulation amplitudes. To solve these problems, a dual closed-loop drive and control system for photoelastic modulators based on a field-programmable gate array has been developed, which includes a resonance tracking loop and a phase modulation amplitude stabilization loop. According to the relationship between the photoelastic modulator's resonance frequency and the phase difference of its voltage and current, a resonance tracking strategy based on a direct digital synthesizer can automatically track the photoelastic modulator's resonance frequency. A proportional integral derivative controller is used to stabilize the modulation amplitude. The experimental results demonstrate that the designed system is effective, since it is able to lock the phase difference at 1.0209° with a maximum deviation of 0.0036° and has a 7.7% higher modulation amplitude stability performance than that of a commercial controller over 60 min. This can improve the performance of photoelastic modulation detection systems in atomic magnetometers. In particular, the designed system is flexible, efficient and adaptable because of the softwarebased control algorithm.

Analysis on the Magnetic Field Response for Nuclear Spin Co-Magnetometer Operated in Spin-Exchange Relaxation-Free Regime

“…x and the output voltage of the co-magnetometer is directly defined as K probe here. The readers can refer to [26] and [27] for more detailed measurement principles.…”

Theoretical study of the close-loop atomic magnetometer with a transverse pumping feedback

“…Furthermore, the inductance of the compensation coil also limits the bandwidth of the feedback system. The second one (method 2 in figure 2) adjusts the polarization of laser to compensate the polarization rotation caused by the atoms in the vapor cell, such as the Faraday rotator [12,13], liquid crystal variable retarder [14], photo elastic modulator [15], et al However, the feedback cannot increase the measurement range limited by the SERF linewidth and the variation of k 2 cannot be eliminated. Comparatively, the feedback scheme (show in figure 2) proposed in this work can eliminate both the variation of k 2 and k 3 , and no three-dimensional coils are needed.…”

On-Chip Mach-Zehnder-Like Interferometer for Atomic Spin Precession Detection

“…With the addition of the modulation module, the PMD methods can achieve highly accurate detection of atomic spin precession signals under laboratory conditions. However, the modulation module itself suffers from drift issues and is susceptible to fluctuations in ambient temperature, light source power, wavelength, and magnetic field, necessitating the introduction of sophisticated means of control [16,17]. Another atomic spin precession detection method is to detect the phase difference of circularly polarized light (CPL), such as Liu et al used a Sagnac-like interferometer to detect the phase difference of CPL, and also used a phase modulator to modulate the phase difference signal, so as to achieve the effect of filtering out low frequency noise [18].…”