Selective reflection of laser radiation from submicron layers of Rb and Cs atomic vapors: Applications in atomic spectroscopy

We studied selective reflection (SR) of laser radiation from a window of a nanocell with thickness L similar to lambda (1,2)/2 filled with Rb and Cs atoms, where lambda (1) = 780 nm and lambda (2) = 852 nm are the wavelengths resonant with the D (2) laser lines for Rb and Cs, respectively. It is demonstrated that the negative derivative of the SR signal profile for L > lambda/2 changes to the positive one for L < lambda/2. It is shown that the real-time formation of the SR signal profile derivative (SRD) with the spectral width 30-40 MHz and located at the atomic transition is, in particular, a convenient frequency marker of D (2) transitions in Rb and Cs. The amplitudes of SRD signals are proportional to the atomic transition probabilities. A comparison with the known saturated absorption (SA) method demonstrated a number of advantages, such as the absence of cross-over resonances in the SRD spectrum, the simplicity of realization, a low required power, etc. An SRD frequency marker also operates in the presence of the Ne buffer gas at a pressure of 6 Torr, which allowed us to determine the Ne-Rb collisional broadening, whereas the SA method is already inapplicable at buffer gas pressures above 0.1 Torr. The realization simplicity makes the SRD method a convenient tool for atomic spectroscopy. Our theoretical model well describes the SRD signal.