Selective reflection from Rb vapor in half- and quarter-wave cells: Features and possible applications

The features of the effect of selective reflection from rubidium vapor in a nanocell with the thickness $L\approx\lambda/2$ and $L\approx\lambda/4$, where $\lambda = 795$ nm is the wavelength of laser radiation resonant with the Rb $D_1$ line, are studied. It is shown that, because of the behavior of the nanocell as a low-$Q$-factor Fabry–Pérot etalon, the sign of the derivative of the selective reflection spectra changes near $L\approx\lambda/2$ from negative at $L>\lambda/2$ to positive at $L<\lambda/2$. The simplicity of the experimental implementation, large amplitude, and sub-Doppler width ($40$MHz) of a detected signal at an atomic transition frequency are appropriate for applications in metrology and magnetometry. In particular, selective reflection from the nanocell is a convenient frequency marker of atomic transitions; in this case, the amplitudes of peaks are proportional to the transition probabilities. The remote optical monitoring of a magnetic field with a spatial resolution $L=\lambda/4\approx199$ of nm is possible on the basis of the splitting of selective reflection peaks in a strong magnetic field (up to $3$ kG). A theoretical model describes well the experimental results.