Effect of Light-Induced Drift in Confined Semiconductors Heterostructures,
STATE UNIV OF NEW YORK AT BUFFALO AMHERST
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The effect of light-induced drift LID in gases, predicted by Gelmukhanov and Shalagin and observed later, is manifested in mechanical drift of the absorbing atoms molecules in response to optical excitation. The effect of LID takes place if the atom interaction with light is velocity-dependent due to the Doppler effect, the spectrum of the exciting radiation is asymmetric with respect to the the absorption line, and the absorbing molecules experience collisions with a buffer gas, with the collision rate dependent upon their internal state. The idea of LID is the following. Suppose for the sake of definiteness that the collision frequency of the absorbing molecules with the buffer is greater in the excited state and that the exciting light is red-shifted with respect to the absorption contour. Then due to the Doppler shift, the radiation interacts mainly with the counter-moving molecules, which undergo transitions into an excited state, in which their friction upon the buffer component is increased. Due to this increase, the counter-flying molecules are slowed down, while the molecules moving in the direction of light are not affected. The net effect is a drift of the absorbing component in the direction of light. The drift alternates its direction with the change of signs of either the detaining or the difference in the collision frequencies.
- Electrooptical and Optoelectronic Devices