Theory of three-photon absorption

Bing Gu, Wei Ji

We report a theoretical investigation of effective four-photon absorption (4PA) process and propose a two-step 4PA model of three-photon- induced excited-state absorption (ESA). Based on three-level rate-equation theory, we find an analytical result for the effective 4PA coefficient that depends on the three-photon absorption (3PA) cross-section, excited-state photophysical properties, and laser pulse duration. We present the analytical theory of the z-dependent nonlinear transmission for straightforwardly yet unambiguously evaluating the 3PA and effective 4PA coefficients simultaneously.

清 西川, 昭 佐道, Hiroshi Sekiya +3 more

Hiroshi Sekiya, Seikyo Tsunekawa, Kiyoshi Nishikawa +1 more

M. Elk, P. Lambropoulos, Xian Tang

We investigate the theory of cancellation by interference between the absorption of three fundamental laser photons and one third-harmonic photon. The theory is formulated in terms of the density matrix so as to take detunings, dephasing, and and laser bandwidth into account. The result is a theory of cancellation for finite detuning that explains how four-photon resonances can be canceled by a three-photon mechanism, if there is an atomic level at near three-photon resonance. We obtain explicit conditions for this to happen, and perform calculations pertaining to a recent experiment [D. Charalambdis et al., Phys. Rev. A (to be published)] where cancellation of 4+1 resonantly enhanced multiphoton ionization has been observed.

NILOY KUMAR DUTTA

Chad A. Husko, Sylvain Combrié, Quynh Vy Tran +3 more

We demonstrate experimental results and analytical formulation of slow-light-enhanced self-phase modulation limited only by three-photon absorption. We present nonlinear figure-of-merits on three-photon-limited ultrafast switching, and critical intensities for free-carrier effects in photonic crystals.