Comparison of operation modes for spin-exchange optically-pumped spin oscillators.

The nuclear spin precesses continually when a positive feedback nuclear magnetic resonance field is applied. The characteristics of this behaviour depend not only on the parameters of the spin ensemble but also on the type and parameters of the feedback loop. We theoretically analysed two types of feedback loops which use direct feedback and phase-lock feedback, respectively. We also compared the oscillating frequency of the spin oscillators using rotating and linear magnetic fields, respectively. Some interesting results on the frequency and start-time of the oscillator were found. These findings will be useful to improve the accuracy of fundamental physical theory tests, such as the Lorentz-violation and electron dipole moment (EDM) test, using spin oscillators. And moreover, they are also very useful for achieving a high performance NMR gyroscope.