Nonlinear optical effects in the spectral vicinity of selective-reflection intra-Doppler resonances

A. M. Akulshin, A.A. Celikov, Vladimir A. Sautenkov +2 more

Suneel Pratap Singh, G. S. Agarwal

Pierre Simoneau, S. Le Boiteux, C. De Araujo +2 more

Up to now, Doppler-free nonlinear spectroscopy has been applied to atoms inside a gas medium (volume spectroscopy). We have extended these methods to atoms in the vicinity of a surface. The basic principle consists of monitoring reflectivity changes produced when a laser beam, incident on a glass–vapor interface, is brought into resonance with an atomic transition. For Doppler-free spectroscopy, two counterpropagating beams are used to operate velocity selection. If these two beams are under normal incidence in the glass—velocity selection perpendicular to the surface—one observes saturated dispersion (selective reflection sensitive to the real index). For incidence angles in the glass (prism) larger than the critical angle (total internal reflection), a standing evanescent wave is produced in the gas (velocity selection along the surface), and saturated absorption is detected. Experimental demonstration was performed on the Na resonance line; high sensitivity (10−4 relative reflectivity change) and spectral resolution as good as 20 MHz were obtained. The main limitation to better resolution comes from the short atomic transit time in the evanescent wave (typical extension ~λ). Relevant applications of these techniques should also concern the diagnostics of optically thick media, as analysis of interaction between gas-phase atoms and the surface, notably atom–wall collisions, and modification of the spontaneous emission characteristics.

Vladimir A. Sautenkov, Vladimir L Velichansky, Alexander S. Zibrov +3 more

An investigation was made of selective specular reflection from 133Cs vapor in the range of atomic concentrations between 4×1013 and 2×1015 cm−3 where collisional broadening of the D2 line is less than the Doppler broadening. The radiation source was an injection laser. Intra-Doppler resonances corresponding to the hyperfine structure of the excited state were recorded in the selective reflection profile. Shifts of the reflection resonances relative to the luminescence resonances of the atomic beam did not exceed 50 MHz. The possiblity of using selective reflection for linear spectroscopy of atomic lines without Doppler broadening is discussed.

Vladilen S Letokhov, B. D. Pavlik

A. K. Popov, Vladimir M. Shalaev