Theory of Coherent Transients

Eiichi Hanamura

V. V. Kozlov

A. Pietiläinen, M. Kujala, Erkki Ikonen

We investigated coherent transient oscillations in the transmission intensity of a frequency-modulated probe-laser beam through a sample of trapped atoms. The transients occur when the frequency of the probe-laser beam crosses a resonance of the atoms in a time of the order of the lifetime of the excited state. A theoretical description used previously to explain transient effects observed in Mössbauer spectroscopy has been developed further to adapt for the specific frequency- and amplitude-modulation characteristics of current-modulated laser diodes. The transients were recorded at various experimental parameters, and the results of the experiments were compared with results obtained from slow frequency sweeps and independent measurements of the modulation characteristics of the laser. The results show that the theory accurately explains the coherent transient phenomena.

Joseph H. Eberly, Carlos R. Stroud

Alexander L. Dobryakov, Sergey A. Kovalenko, Nikolaus P. Ernsting

The theory of transient absorption with chirped supercontinuum probing is developed for electronic excitation of a vibronic four-level scheme. Dephasing is modeled as homogeneous in the Bloch approximation together with inhomogeneous broadening. The time correction routine for transient spectra is shown to be identical to that of the nonresonant case which was treated previously. Contributions from sequential and coherent terms are calculated and compared to each other. The simulated data reveal how electronic and vibrational dephasing, detuning, and inhomogeneous broadening manifest themselves in the coherent component of femtosecond transient absorption spectra.

Pierre Meystre, Murray Sargent