Physical Review Letters

Observation of Dicke Superradiance in Optically Pumped HF Gas

N. Skribanowitz, Irving P. Herman, J. C. MacGillivray, Michael S. Feld

Published Feb 19, 1973• 765 citations

Abstract

We have found that room-temperature HF gas at millitorr pressures, optically pumped to produce a total inversion at a rotational transition in the $v=1$ vibrational state, emits a superradiant pulse with ringing after a considerable delay (\ensuremath{\sim} microseconds). A semiclassical analysis shows that for a high-gain system the pulse evolution is determined by a single parameter ${\ensuremath{\tau}}_{R}$, and that inhomogeneous broadening is unimportant. Close agreement between theory and experiment is obtained.

DOI: 10.1103/physrevlett.30.309

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Physical Review Letters

Observation of Dicke Superradiance in Optically Pumped HF Gas

N. Skribanowitz, Irving P. Herman, J. C. MacGillivray, Michael S. Feld

Published Feb 19, 1973• 765 citations

Publisher

Abstract

We have found that room-temperature HF gas at millitorr pressures, optically pumped to produce a total inversion at a rotational transition in the

v=1

vibrational state, emits a superradiant pulse with ringing after a considerable delay (\ensuremath{\sim} microseconds). A semiclassical analysis shows that for a high-gain system the pulse evolution is determined by a single parameter

{\ensuremath{\tau}}_{R}

, and that inhomogeneous broadening is unimportant. Close agreement between theory and experiment is obtained.

DOI: 10.1103/physrevlett.30.309

Related papers

Observation of Dicke Superradiance in Far Infrared Emission from CH3F

Albert T. Rosenberger, Samuel J. Petuchowski, Thomas A. DeTemple

International Conference on Submillimeter Waves and Their ApplicationsDec 1, 19760 citations

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M. Groß, Claude Fabre, P. Pillet +1 more

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J. C. MacGillivray, Michael S. Feld

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Ronald E. Jodoin, L. Mandeļ

The problem of superradiant emission from a small atomic system is treated under conditions in which the effects of inhomogeneous broadening are important, as in a solid. The treatment is semiclassical, with the assumption that all atoms see the same electromagnetic field. A set of coupled integrodifferential equations is obtained characterizing the state of each atom of resonant frequency \ensuremath{\omega} at time $t$ . It is found that, in general, atoms of different frequencies evolve differently in time, whether or not they start from the same initial state. The effect of the inhomogeneous broadening is generally to delay the onset and to reduce the amplitude of the superradiant pulse. Some effects of inhomogeneous broadening are manifest even when the inhomogeneous lifetime is much longer than the usual superradiance time. When the atomic system starts in the ground state and is then exposed to a coherent excitation pulse, superradiant effects can appear even when the inhomogeneous lifetime is very short compared with the usual superradiance time.The problem of superradiant emission from a small atomic system is treated under conditions in which the effects of inhomogeneous broadening are important, as in a solid. The treatment is semiclassical, with the assumption that all atoms see the same electromagnetic field. A set of coupled integrodifferential equations is obtained characterizing the state of each atom of resonant frequency \ensuremath{\omega} at time $t$. It is found that, in general, atoms of different frequencies evolve differently in time, whether or not they start from the same initial state. The effect of the inhomogeneous broadening is generally to delay the onset and to reduce the amplitude of the superradiant pulse. Some effects of inhomogeneous broadening are manifest even when the inhomogeneous lifetime is much longer than the usual superradiance time. When the atomic system starts in the ground state and is then exposed to a coherent excitation pulse, superradiant effects can appear even when the inhomogeneous lifetime is very short compared with the usual superradiance time.

Physical Review AFeb 1, 197440 citations

We have found that room-temperature HF gas at millitorr pressures, optically pumped to produce a total inversion at a rotational transition in the

v=1

{\ensuremath{\tau}}_{R}

, and that inhomogeneous broadening is unimportant. Close agreement between theory and experiment is obtained.

We report the observation of near-infrared Dicke superradiant pulses. The active medium (atomic Na vapor) is optically pumped in the

5{S}_{\frac{1}{2}}

state and superradiates on transitions cascading down from this level at 3.41, 2.21, and 9.10 \ensuremath{\mu}m. The superradiant character of the emission is checked by studying variations of pulse heights and delays versus initial population inversion density.

L

of the sample. It is found impossible to obtain even rough agreement. When ${\ensuremath{\tau}}_{c}$ is taken longer than

\frac{L}{c}

, no ringing is predicted; when shorter, the predicted ringing is many times faster than that observed.

{T}_{R}

, the characteristic radiation damping time of the collective system; and ${\ensuremath{\theta}}_{0}$, a function of the conditions which initiate the superradiant process. In this limit one obtains a normalized emission curve and simple analytical expressions for the time delay, pulse width, and peak intensity of the output radiation. These results are in good agreement with experiments. A comparison of our model with previous treatments of superradiance is given.

t

. It is found that, in general, atoms of different frequencies evolve differently in time, whether or not they start from the same initial state. The effect of the inhomogeneous broadening is generally to delay the onset and to reduce the amplitude of the superradiant pulse. Some effects of inhomogeneous broadening are manifest even when the inhomogeneous lifetime is much longer than the usual superradiance time. When the atomic system starts in the ground state and is then exposed to a coherent excitation pulse, superradiant effects can appear even when the inhomogeneous lifetime is very short compared with the usual superradiance time.