The optical properties of atomic vapors near resonance

G. Grynberg

We present a brief review of optical phase conjugation by four-wave mixing in atomic vapors. We emphasize the particular properties of vapors for this process. We discuss the case of nearly resonant excitation for two-level atoms, the case of multilevel atoms where the nonlinearity arises from optical pumping and the nearly resonant two-photon excitation. We finally describe the modification of phase-conjugate signals when one goes from the Bragg regime to the Raman-Nath regime and we show how one can achieve a phase-contrast mirror rather than a phase-conjugate mirror in this last case.

James J. Wynne, P. P. Sorokin

Stephan Wielandy

Alexander L. Gaeta, Robert W. Boyd, G. S. Agarwal

We investigate theoretically the noise properties of the amplification of a weak probe beam in an atomic vapor pumped by an intense nearly resonant pump field. For the case of gain via the three-photon effect, we find that only in the limit in which collisional broadening is absent can the system operate as an ideal quantum-noise limited optical amplifier for the probe wave. For the case of gain via stimulated Rayleight scattering, we find that the minimum noise figure is four times that of an ideal optical amplifier, and that it occurs when the atomic system is predominantly collisionally broadened.

Tadeusz Skalinski, K. Rosiński

T. A. Vartanyan, D. L. Lin

Understanding the processes underlying the optical excitation of atomic vapor in the vicinity of solid surfaces is of interest both from physical and technical points of view. Selective reflection spectra of laser light from an interface of a transparent dielectric material and resonant vapor are known to be Doppler-free and to provide important spectroscopic information about the atom-wall interaction. On the other hand, atomic vapors have such a large and fast nonlinear response on or near resonances that they are capable of processing signals and images with milliwatt lasers at a time scale of submicroseconds. In the present paper we investigate linear and nonlinear optical properties of a thin film of atomic vapor confined between two solid surfaces. Assuming two-level atoms, we solve the Maxwell- Bloch equations for light reflection from resonant atoms. The interaction between the resonant atoms and the wall is accounted for through the boundary conditions for all elements of density matrix. The transient polarization is shown to make an important contribution not only to the field structure in the vicinity of the wall but also to the interference pattern of the reflected field. It is found that the spectrum of reflection depends remarkably on the film thickness. Strong enhancement of signal is also found from this study and possible devices for the detection are discussed.