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Title: On the optimization, and the intensity dependence, of the excitation rate for the absorption of two-photons due to the direct permanent dipole moment excitation mechanism

Abstract

A model two-level dipolar molecule, and the rotating wave approximation and perturbation theory, are used to investigate the optimization and the laser intensity dependence of the two-photon excitation rate via the direct permanent dipole mechanism. The rate is proportional to the square of the laser intensity I only for small intensities and times when perturbation theory is applicable. An improvement on perturbation theory is provided by a small time RWA result for the rate which is not proportional to I{sup 2}; rather it is proportional to the square of an effective intensity I{sub eff}. For each laser intensity the optimum RWA excitation rate as a function of time, for low intensities, is proportional to I, not I{sup 2}, and for high intensities it is proportional to I{sub eff}. For a given two-photon transition the laser-molecule coupling optimizes for an intensity I{sub max} which, for example, leads to a maximum possible excitation rate as a function of time. The validity of the RWA results of this paper, and the importance of including the effects of virtual excited states, are also discussed briefly.

Authors:
 [1]
  1. Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7 (Canada)
Publication Date:
OSTI Identifier:
22611488
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Advances; Journal Volume: 6; Journal Issue: 7; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABSORPTION; APPROXIMATIONS; COUPLING; DIPOLE MOMENTS; DIPOLES; DISTURBANCES; EXCITATION; EXCITED STATES; LASER RADIATION; MOLECULES; OPTIMIZATION; PERTURBATION THEORY; PHOTONS; TIME DEPENDENCE

Citation Formats

Meath, William J., E-mail: wmeath@uwo.ca. On the optimization, and the intensity dependence, of the excitation rate for the absorption of two-photons due to the direct permanent dipole moment excitation mechanism. United States: N. p., 2016. Web. doi:10.1063/1.4958306.
Meath, William J., E-mail: wmeath@uwo.ca. On the optimization, and the intensity dependence, of the excitation rate for the absorption of two-photons due to the direct permanent dipole moment excitation mechanism. United States. doi:10.1063/1.4958306.
Meath, William J., E-mail: wmeath@uwo.ca. Fri . "On the optimization, and the intensity dependence, of the excitation rate for the absorption of two-photons due to the direct permanent dipole moment excitation mechanism". United States. doi:10.1063/1.4958306.
@article{osti_22611488,
title = {On the optimization, and the intensity dependence, of the excitation rate for the absorption of two-photons due to the direct permanent dipole moment excitation mechanism},
author = {Meath, William J., E-mail: wmeath@uwo.ca},
abstractNote = {A model two-level dipolar molecule, and the rotating wave approximation and perturbation theory, are used to investigate the optimization and the laser intensity dependence of the two-photon excitation rate via the direct permanent dipole mechanism. The rate is proportional to the square of the laser intensity I only for small intensities and times when perturbation theory is applicable. An improvement on perturbation theory is provided by a small time RWA result for the rate which is not proportional to I{sup 2}; rather it is proportional to the square of an effective intensity I{sub eff}. For each laser intensity the optimum RWA excitation rate as a function of time, for low intensities, is proportional to I, not I{sup 2}, and for high intensities it is proportional to I{sub eff}. For a given two-photon transition the laser-molecule coupling optimizes for an intensity I{sub max} which, for example, leads to a maximum possible excitation rate as a function of time. The validity of the RWA results of this paper, and the importance of including the effects of virtual excited states, are also discussed briefly.},
doi = {10.1063/1.4958306},
journal = {AIP Advances},
number = 7,
volume = 6,
place = {United States},
year = {Fri Jul 15 00:00:00 EDT 2016},
month = {Fri Jul 15 00:00:00 EDT 2016}
}