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2006 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 74, no 3, article id 033814Article in journal (Refereed) Published
Abstract [en]
A dynamical theory is developed with the purpose of explaining recent experimental results on multiphoton-excited amplified stimulated emission (ASE). Several conspicuous features of this experiment are analyzed, like the threshold dependence of the spectral profile on the pump intensity, and spectral shifts of the ASE pulses co- and counterpropagating relative to the pump pulse. Two models are proposed and evaluated, one based on the isolated molecule and another which involves solvent interaction. The spectral shift between the forward and backward ASE pulses arises in the first model through the competition between the ASE transitions from the pumped vibrational levels and from the bottom of the excited-state well, while in the solvent-related model the dynamical solute-solvent interaction leads to a relaxed excited state, producing an additional ASE channel. In the latter model the additional redshifted ASE channel makes the dynamics of ASE essentially different from that in the molecular model because the formation of the relaxed state takes a longer time. The variation of the pump intensity influences strongly the relative intensities of the different ASE channels and, hence, the spectral shape of ASE in both models. The regime of ASE changes character when the pump intensity crosses a threshold value. Such a phase transition occurs when the ASE rate approaches the rate of vibrational relaxation or the rate of solute-solvent relaxation in the first excited state.
Keywords
Cavitation; Electric excitation; Laser applications; Mathematical models; Optical pumping; Photons; Solvents; Stimulated emission; Vibration control; Amplified stimulated emission (ASE); Multiphoton excitation; Solute-solvent relaxation; Vibrational relaxation; Ultrafast phenomena
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-6994 (URN)10.1103/PhysRevA.74.033814 (DOI)000241067100139 ()2-s2.0-33748950997 (Scopus ID)
Note
QC 20100813. Tidigare titel: Dynamics of cavityless lasing generated by ultra-fast multi-photon excitation. Titel ändrad 20100813.
2007-04-202007-04-202017-12-14Bibliographically approved