Rapid passage effects have been demonstrated in a Lamb dip experiment for the first time, by researchers from Oxford, UK.
Grant Ritchie’s team conducted Lamb dip spectroscopy on a low pressure sample of NO using a narrow-linewidth, high-power, single-mode quantum cascade laser. They were able to determine the laser linewidth, and that the power was sufficient to induce significant population transfer of up to 35%, from the widths of the Lamb dips. The population transfer efficiencies could be controlled by the laser chirp rate.
The lamb dip signals became increasingly asymmetric as the chirp rate was increased. At sufficiently high chirp rates rapid passage oscillations on the Lamb dips were observed due to the narrow laser linewidth, and were seen to be affected by the hyperfine splitting in the transition.
Furthermore, the team showed that it was possible to separate the asymmetry effect from the rapid passage oscillations by pumping a single velocity group using a second laser at a fixed frequency.
Read this HOT article today:
Coherent transient spectroscopy with continuous wave quantum cascade lasers
James M. R. Kirkbride, Sarah K. Causier, Elin A. McCormack, Damien Weidmann and Grant A. D. Ritchie
DOI: 10.1039/C2CP44116K
