Coherent population trapping on $^{87}$Rb atoms in small-size absorption cells with buffer gas

Coherent population trapping (CPT) on $^{87}$Rb atoms in neon atmosphere has been studied in small-size glass absorption cells under conditions of pumping with narrow-band laser radiation at the $D_2$ line of the main doublet. Parameters of the absorption signal have been measured in 3-mm-diameter cells at buffer gas (Ne) pressures varied within 200–400 Torr, cell temperatures within 65–120$^\circ$C, and pumping radiation power densities within 30–400 $\mu$W/cm$^2$. Optimum values of the buffer gas pressures, cell temperature, and pumping power are determined at which the short-term instability of the resonance line is at minimum. Orientational shifts of the CPT resonance signal in gas-filled cells and small-size cells with antirelaxation coating have been compared.