Absorption line shape of homogeneously broadened degenerate transition

Robert W. Boyd, Lloyd W. Hillman, Mark Kramer +3 more

A. E. Korolev, Vladimir N. Nazarov, Dmitry I. Staselko

Anatoly A. Afanas'ev, B. A. Samson

The absorption line shape at frequency-degenerate two-wave mixing in an ensemble of three- level quantum systems with the doublet structure of the upper state has been calculated. The effect has been predicted of weak signal amplification at the saturating pump frequency in the regime of stationary interaction at homogeneous broadening of resonance absorption lines.

V. V. Batygin, M. B. Gornyi, Boris G. Matisov

Albert T. Rosenberger

One characteristic normally used to distinguish inhomogeneous broadening from homogeneous broadening is the saturation behavior occurring when irradiation takes place at line center. The usual behavior found is that the absorption coefficient decreases as a negative power of 1 + I/Isat; a power of −1 indicates homogeneous broadening and a power of −½ denotes inhomogeneous broadening. It is shown here that, in the rate equation limit, this behavior is followed in most cases even though the homogeneous and inhomogeneous absorption profiles can have any line shape. The homogeneous line shape, in particular, need not be Lorentzian; its line center saturation behavior will be the same as that of a Lorentzian, however. If the inhomogeneous broadening is due to a distribution of atomic center frequencies, in the inhomogeneous limit the usual line center saturation behavior will be found no matter what the combination of homogeneous and inhomogeneous line shapes. However, if the broadening is inhomogeneous because of a distribution, among the individual atoms, in any property of the absorption profile other than center frequency (for example, the homogeneous linewidth), the saturation properties are not as simple, and in fact the inhomogeneous limit may not even exist.

Aleksander K. Rebane, Mikhail A. Drobizhev, Nikolay S. Makarov

We study narrowing of nonlinear two photon absorption line shape in system with non-zero permanent dipole moment difference between the ground- and excited state. The temperature-induced broadening of one photon absorption (1PA) and two photon absorption (2PA) line shapes is modeled by subjecting the resonance transition frequency to random fluctuations of varying amplitude and by solving numerically the corresponding two-level density matrix equation of motion. We show that under conditions, when 1PA and 2PA transitions are both far from saturation, the 2PA homogeneous line width may be as much as 25% narrower than the corresponding 1PA line width. This offers novel possibilities for reducing the temperature-induced dephasing in quantum computing, quantum memory and other applications based on coherent multi-photon interactions.