Third harmonic scattering in liquids

Abstract

Third harmonic scattering (THS) from liquids has been observed and analyzed in several recent papers. It is considered to be analogous to second harmonic scattering (hyper-Rayleigh scattering) and to provide a means for measuring the second hyperpolarizability tensor of molecules in a liquid. However, the observed signal for a pure solvent is in fact mainly due to coherent third harmonic generation followed by Rayleigh scattering and direct incoherent THS (direct THS) makes only a small contribution (<2% for parallel polarized THS). This invalidates the internal reference method and the polarization analysis that has been applied for pure liquids. Theoretical comparison for the two processes, extensive experimental measurements for CCl 4 liquid, SiO 2 glass, and CCl 2 F 2 gas and survey measurements for D 2 O, CDCl 3 , CD 3 CN, and (CD 3) 2 SO liquid, are presented.

Optical Activity in Third‐Harmonic Rayleigh Scattering: A New Route for Measuring Chirality

“…Next, we address a possible alternative explanation: Our result could be produced by coherent, forward‐propagating THG from the glass interfaces, followed by linear optical regime Rayleigh scattering. [ 54 ] To rule out this possibility, we rebuild the detection arm of our experiment and examine the forward emission signal, at the third‐harmonic wavelength.…”

Third-harmonic Mie scattering from semiconductor nanohelices

“…Both effects are coherent and would produce strong forward emission. Moreover, THG followed by a linear optical scattering process by the nanohelices would direct a small amount of light at the right angle 48 , which could explain the large difference in intensity between Figs. 2 and 3; however, THG is forbidden in an isotropic medium with circularly polarized light 49 .…”

Irreducible Cartesian Tensor Analysis of Harmonic Scattering from Chiral Fluids

“…With striking chiroptical effects having recently been demonstrated in optical second harmonic scattering [16], the focus here, too, is on circularly polarised pump input, for which case important new symmetry rules are established for the specific case of chiral media. Notably, for liquid or randomly oriented media, for the reasons identified above, having a circularly polarised input obviates any possible competition from a process of coherent third harmonic generation followed by conventional scattering, a scenario recently explored by Shelton [17]. Pursuing the analysis in a formulation cast in terms of irreducible Cartesian tensors facilitates the elucidation of the detailed electrodynamical origin, also eliciting the character of the salient material properties.…”