The effect of Doppler averaging for different atoms at two different temperatures, i.e
Figure 5. The effect of Doppler averaging for different atoms at two different temperatures, i.e. 1 and 297 K. The red solid curves are for the six-level system and the blue dashed curves are for the four-level system. The strengths of the control and switching fields are = = 20 MHz for rubidium, = = 14 MHz for sodium and = = 2.5 MHz for lithium. All the graphs are normalized by the same factor. The change in absorption scaling is due to different atomic masses and decay rates of excited states for different atoms. The reduction in the overall scale of absorption at room temperature is due to the spread in absorption over all the velocity classes.
We present a six-level atomic system using a density matrix approach to show variation of the optical properties in an -type Doppler-broadened system for the D2 line of alkali atoms with the nuclear spin I = 3/2, i.e. 87Rb, 23Na and 7Li. The variation in optical properties arises due to the presence of multiple excited states with varying separations. These excited states cause asymmetry in absorption profiles. This asymmetric nature is more prominent for an atom with more closely spaced hyperfine levels in the excited state. In room temperature atomic vapour, the enhanced absorption at the line centre starts to disappear with a decrease in hyperfine separation. We also discuss the transient behaviour of considered atoms, which is in good agreement with an absorption profile in each case. This approach opens a possibility of realizing the optical switching application in a realistic atom.