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Unformatted text preview: Lecture 14 Quantum-Mechanical Theory of the Nonlinear Optical Susceptibility Using the laws of quantum mechanics b explicit expressions for susceptibility motivation: a) functional dependence on material parameters (dipole transitional moments, atomic energy levels) b) internal symmetries of c) numerical values of In atomic vapors energy levels are sharp (in most solids, allowed energies have the form of broad bands) b large values of through resonant enhancement. .g. THG 1 e.g. THG virtual levels If a real atomic level is nearly coincident with a virtual level, the coupling behavior is particularly strong, and optical susceptibility is large. 3 options: Resonant: 1-photon 2-photon 3-photon All 3 procedures are equally effective at increasing the value of the 3 rd order nonlinear susceptibility. 2-photon enhancement (b) is preferred for THG: a) strong linear absorption of incident field b) attenuation only at low efficiency 2-photon absorption c) strong linear absorption of 3 rd harmonic Schrdinger Equation Calculation of the Nonlinear Optical Susceptibility Q-M perturbation theory in this formalism gives accurate predictions of the...
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- Fall '10