Resonant Optical Rectification in Chiral Molecular Systems: Application to a Three-Level Model

Abstract

Α molecular approach to optical rectification via the imaginary part of the second-order susceptibility related to electrie dipole interaction with the radiation freld is presented. Α quantum-mechanical expression for the frequency dependence of the effect is obtained and its magnitude is estimated in absorption bands of a three-level model.PACS numbers: 33.55.Fi, 42.65.ΑrιLinear and nonlinear interactions of an electromagnetic wave with molecules of an isotropic medium induce in them multipole moments which contribute to electric polarization of the system [1]. Out of absorption bands optical rectification (OR) via the second-order susceptibility is forbidden but the fourth-order dipolar electric nonlinearity may cause OR in chiral liquids [2]. However, in absorption bands of optically active molecular system OR is allowed via the imaginary part of the Second-order susceptibility related to electric dipole interaction with the radiation field [3].We consider an isotropic molecular system in which a plane monochromatic light wave with the electric field oscillating with the circular frequency ω, propagates in the z-direction. For a dissipative medium ii is complex with n the refractive index, and κthe absorption coefficient.In this paper we are interested in the calculation of a static polarization P(0) induced in the medium by nonlinear interaction of chiral molecules with the light wave. Restricting our considerations to the second-order susceptibility, we have where N is the number of molecules per unit volume, αijk the nonlinear polarizability related. to electric dipole transitions, whereas the asterisk represents the complex conjugate, the symbol () stands for the isotropic average [4], and