The Microscopic Origin of Second Harmonic Generation Response: The Spatial Structure of Instantaneous Dipole Moments in Electron Excitation

Abstract

A deep understanding on the crucial factors of the enhanced macroscopic second harmonic generation (SHG) in some deep-ultraviolet nonlinear optical (NLO) materials is needed to design new NLO materials. Since an optical process relates to the electron excitation and polarization simultaneously, the instantaneous dipole moments and their structures in excitation should be seriously taken account to seek the principal factor in SHG response. In this work, we study the Ba 4 B 11 O 20 F (BBOF), a NLO material, by using the orbital projection technique. From the projected SHG of our theoretic calculation, we recognize the principal dipole moment of the dominant influence on SHG and the relevant atom groups between which the dipole moment is accommodated. With the conclusion that the dipole moment with the most significant influence on SHG is the one between the oxygen-boron polyhedral anion group and barium cation, we predict that Ba 4 Al 11 O 20 F (BAOF) has a comparable SHG response.

Two pairs of chiral YbIII enantiomers presenting distinct NIR luminescence and circularly polarized luminescence performances with giant differences in second-harmonic generation responses

“…We believe that D-1/L-1 show such outstanding SHG performances and exhibit much larger SHG responses than D-2/L-2 mainly thanks to the btfa − ligand containing a –CF 3 group with large polarity, 109 resulting in a large dipole moment in D-1/L-1 which is beneficial for the observation of larger SHG responses in D-1/L-1 . 71,72…”

“…In particular, it is well recognized that the SHG response is a polarity-dependent process and using organic ligands with different polarities to assemble the NLO-active complexes should give them different molecular dipole moments, which can realize the modulation of their SHG performances. 71,72…”

From Centrosymmetry to Noncentrosymmetry: Precise Structural Regulation and Characterization on ZnHPO3·2H2O Polymorphs

“…Among these, the rational combination of different NLO-active groups has been widely recognized as an efficient strategy to enhance the NLO properties. Asymmetric units with high polarizability, such as π-conjugated groups, d 0 cations with second-order Jahn-Teller distortion, cations with stereochemically active lone pairs, and asymmetric tetrahedral groups, have attracted continuous research attention, and a bunch of new NLO materials with enhanced properties have been developed recently. − …”