One-photon Dick-narrowing absorption spectroscopy from a thin atomic vapor film can be extended to the two-photon case, in which the sub-Doppler absorption structures are obtained in a cascade three-level system. The periodic line shapes of two photon spectroscopy are similar to one-photon case. It is found that Dicke-narrowing is apparent when L/λ=(2n+1)/2 (n an integer, L the film thickness, and λ the wavelength of the probe field)in the case of one-photon process, and this feature is maintained in the case of two-photon process but not in the one-photon process when L/λ=2n/2. Due to the contribution of atom-wall collision in the cell and the pump-probe scheme, a very narrow structure can be obtained when the pump and the probe fields are in counter-propagation regime.
下载:
