Abstract A two‐step spectral hole burning (SHB) is considered, where the selective excitation of the first step is fixed by a photochemical transformation through the second excitation step. It is shown that in a three‐level system excited by two consecutive pulses, the kinetics of the forming spectral hole differs essentially from the one on stationary irradiation. In the case of a short second pulse the shape of the hole in the inhomogeneous distribution function (IDF) of the purely electronic line frequency Ω01 is dependent on the time interval T between the first and second excitation steps and under certain conditions a hole can be obtained which is narrower than in the one‐step SHB with monochromatic light. It is considered how the hole in IDF is manifested in the absorption and two‐step pulse excitation spectra. It is shown that the hole in the absorption spectrum may be narrower than 2γ1 and in the two‐step pulse excitation, −γ1 (γ1 is the energy relaxation constant of the first excited level).
Fluorescence has been detected from Rb atoms following narrow-line excitation by a short coherent optical pulse. The fluorescence oscillates as a function of the pulse area
A with maxima for $A=\ensuremath{\pi},3\ensuremath{\pi},5\ensuremath{\pi},\dots{}$ and minima for $A=0,2\ensuremath{\pi},4\ensuremath{\pi},\dots{}$. In addition to demonstrating one of the simplest coherent optical effects, this experiment dramatizes the potential of the technique for determining dipole moments, pulse areas, relaxation times, and lifetimes. The details of the experimental apparatus are described. Results of a computer simulation of the experiment including the actuai excitation pulse shape, absorption frequency width, finite absorption (5-10% of pulse), and loss to a third level are given.
We theoretically investigate two-photon excitation by spectrally shaped entangled photons with energy anticorrelation in terms of how the real excitation of an intermediate state affects two-photon absorption by entangled photons. Spectral holes are introduced in the entangled photons around the energy levels of an intermediate state so that two-step excitation via the real excitation of the intermediated state can be suppressed. Using a three-level atomic system as an example, we show that the spectral holes well suppress the real excitation of the intermediate state and recover two-photon absorption via a virtual state. Furthermore, for a short pulse close to a monocycle, we show that the excitation efficiency by the spectrally shaped entangled photons can be enhanced a thousand times as large as that by uncorrelated photons.