Use of laser properties to improve the sensitivity of laser magnetic resonance spectrometers

The rate equations for a laser are used in the single-mode approximation to analyze theoretically the absorption signal in laser magnetic resonance spectrometers. Single-pass and intracavity absorption is considered. It is shown that in those cases when the spectrometer noise increases with the incident power, the sensitivity of a spectrometer with intracavity absorption improves on approach to the stimulated emission threshold. A method is suggested for resonance accumulation of the intracavity absorption signal, based on the selection of the magnetic modulation frequency identical with the frequency of relaxational fluctuations of the laser intensity. This method may increase the sensitivity by 3–4 orders of magnitude compared with the single-pass absorption case. The sensitivities of laser magnetic resonance spectrometers are calculated for different types of noise. The maximum theoretical sensitivity in the method of resonance accumulation of the absorption signal can reach 10⁴ particles/cm³.