Feedback spectroscopy of atomic resonances. Physical Review A - Atomic, Molecular, and Optical Physics Volume 87, Issue 6, 4 June 2013, Article number 063806

We propose a general alternative spectroscopic approach that uses a feedback control of the input probe field parameters to stabilize the mediums response at a fixed constant level while taking the spectra. In this case the extractable spectroscopic information is contained in the variable input parameters. Along this line, we have found a universal and simple way, using the spontaneous emission for feedback control, to dramatically increase the amplitude, contrast, and quality factor of different atomic resonances. Our method, unlike the conventional spectroscopy, does not require an optically dense medium. Theoretical analysis has been experimentally confirmed with spectroscopy of the dark resonance in atomic rubidium vapor. The considerable increase (2 orders) of the resonance amplitude and a threefold decrease of the width have been observed in optically thin medium. As a result, the quality factor of the dark resonance is increased by 2 orders of magnitude and its contrast reaches a record level of 260%. Different schemes, including magneto-optical Hanle spectroscopy and Doppler-free spectroscopy, have also shown an enhanced performance by using the proposed technique.
Indexed keywords
Atomic resonances; Conventional spectroscopy; Doppler-free spectroscopy; Magneto-optical; Optically dense mediums; Orders of magnitude; Resonance amplitudes; Spectroscopic information