On a new class of absorption phenomena

Sergey G. Rautian, Э. Г. Сапрыкин, А. А. Черненко

The absorption spectrum of a probe field upon self-saturation on the transition between levels with angular momenta equal to 1/2 is considered. A new class of nonlinear spectroscopic phenomena caused by the nonlinearity (with respect to the density matrix) of the radiative relaxation matrix is predicted. The relative role of the own spontaneous radiation in the broadening of the combining levels and the line, as well as the dependence of the absorption on the polarization of the probe field, is elucidated.

Sergey G. Rautian, Igor I Sobel'man

Bryan J. Dalton

Luigi Accardi, Kentaro Imafuku, Sergei Vladimirovich Kozyrev

The stochastic limit of quantum theory suggests a new, constructive, approach to nonequilibrium phenomena. We illustrate this approach when considering the interaction of 3-level system with a quantum field in a nonequilibrium state. We describe a class of states of the quantum field for which a stationary state drives the system to an inversely populated state. We find that the quotient of the population of the energy levels in the simplest case is described by the double Einstein formula which involves products of two Einstein emission/absorption factors. Emission and absorption of radiation by 3-level atom in nonequilibrium stationary state is described.

Jane E. Zucker, A. VonLehmen, D. S. Chemla +1 more

We have identified several physical processes by which below-gap photons can modify excitonic absorption in GaAs quantum wells.1-3 These different phenomena can be distinguished by their temporal response times, which range from tens of nanoseconds to less than one picosecond. Our experiments also show that the relative contributions of these mechanisms to below-gap optical modulation of exciton absorption depend strongly on temperature as well as on the wavelength of the below-gap modulating beam. The size of the modulation indicates that a new class of absorptive and dispersive devices for optical signal processing is possible in which signals propagate in the transparent region of the crystal and experience negligible attenuation. In order to successfully interpret and calculate the magnitude of these exciting new effects, we show that it is necessary to take into account the special properties of two-dimensional excitons in semiconductor quantum wells.