Coherence and Two-Photon Absorption

Abstract

A kinetic theory of the two-photon absorption from a single mode of the radiation field is presented. It is found that, in general, the rate of two-photon absorption depends on certain correlation functions ; and hence on the coherence properties, of the field. The results are applied to the case of a pure coherent state and the case of a chaotic field.

Enhanced two-photon absorption in a hollow-core photonic-band-gap fiber

“…When the pump beam (at 778.1 nm) is far detuned from the intermediate level, or when ∆ ≫ Γ, where Γ is the linewidth of the intermediate level, then the process is termed off-resonant two-photon excitation. We characterize the nonlinearity of the Rb-PBGF system for this process by calculating the imaginary part of the third-order susceptibility χ (3) Im [17] corresponding to the relevant two-photon transition using,…”

“…It also represents one of the simplest nonlinear processes that allows one to characterize the strength of the light-matter interaction and to generate novel non-classical effects. As a result, TPA processes have also been widely studied for various nonlinear and quantum optical phenomena with applications in precision spectroscopy [1], the generation of single photons [2], the measurement of coherence and photon statistics [3], and all-optical switching [4,5].…”

Quantum correlations in the two-photon decay of few-electron ions

“…(1)], the two-photon state's coherences are jeopardized as well and hence a loss of quantum correlations is induced. The density (statistical) operators of the initial and the final states of the overall system are connected by the standard relation [26][27][28]…”

“…(4)]. Most naturally such an amplitude can be evaluated within the framework of secondorder perturbation theory [6,26,27]:…”

“…Calculations are performed for two relative energies η = 1/10 and 1/4, both within the dipole approximation [Eq. (26)], and by using the exact theory, which accounts for the higher-multipole channels. As seen from the figure, both theoretical approximations predict maximal entanglement C = 1 for the parallel and back-to-back photon emission at any energy sharing η, a feature that could be expected from the conservation laws.…”