Magneto-optical resonances in fluorescence from sodium D2 manifold

We report on magneto-optical resonances observed in sodium fluorescence from D2 manifold with an intensity modulated light illuminating a sodium (Na) cell containing Ne buffer gas. Resonances are measured in fluorescence emitted perpendicular and backward to the light propagation direction in the cell. Properties of these resonances are studied by varying the magnetic field at fixed light modulation frequency, and vice-versa. A dark resonance having maximum amplitude for laser wavelength close to the crossover peak, is observed. The origin of dark resonance observed in Na D2 line is discussed. Pulse modulation with low-duty cycle shows higher-harmonic resonances of the modulation frequency and sub-harmonic resonances of the Larmor frequency. Present study is aimed towards improving the understanding of magneto-optical resonances for remote magnetometry applications with mesospheric sodium.