Features of faraday rotation in Cs atomic vapor in a cell thinner than the wavelength of light

Features of the effect of Faraday rotation (the rotation of the radiation polarization plane) in a magnetic field of the $D_1$ line in Cs atomic vapor in a nanocell with the thickness $L$ varying in the range of $80$–$900$ nm have been analyzed. The key parameter is the ratio $L/\lambda$, where $\lambda=895$ nm is the wavelength of laser radiation resonant with the $D_1$ line. The comparison of the parameters for two selected thicknesses $L=\lambda$ and $\lambda/2$ has revealed an unusual behavior of the Faraday rotation signal: the spectrum of the Faraday rotation signal at $L=\lambda/2=448$ nm is several times narrower than the spectrum of the signal at $L=\lambda$, whereas its amplitude is larger by a factor of about $3$. These differences become more dramatic with an increase in the power of the laser: the amplitude of the Faraday rotation signal at $L=\lambda/2$ increases, whereas the amplitude of the signal at $L=\lambda$ almost vanishes. Such dependences on $L$ are absent in centimeter-length cells. They are inherent only in nanocells. In spite of a small thickness, $L=448$ nm, the Faraday rotation signal is certainly detected at magnetic fields $\ge 0.4$ G, which ensures its application. At thicknesses $L< 150$ nm, the Faraday rotation signal exhibits “redshift”, which is manifestation of the van der Waals effect. The developed theoretical model describes the experiment well.