Radiation transfer in high density atomic vapours with various detunings of probe laser from resonance transition

In this work, we studied the process of resonance radiation transfer in dense rubidium vapour with various detuning of the probe laser from $5S_{1/2} - 5P_{3/2}$ atomic transition. At the working atomic concentration of $8 \times 10^{16}$ cm$^{-3}$, the spectral half-width of the transition was 4 GHz. The cw probe laser had a spectrum width of 1 MHz. Test pulses of 1 ms duration and the repetition rate of 1 kHz were formed by an acousto-optic modulator. Due to the radiation trapping, the lifetime of excited atoms $\tau$ was much longer than the spontaneous decay time of 26 ns. In the range of detuning from 16 GHz to 220 GHz, the time $\tau$ linearly increased from $3\times 10^3$ ns to $15 \times 10^3$ ns. The long lifetime of the excitation can significantly increase the efficiency of the optical saturation of atomic gas media.