Second-harmonic generation in centrosymmetric molecular films: Analysis under anisotropic conditions

Resonant enhancement of second-harmonic generation of electric quadrupole origin in phthalocyanine films

“…9,10 The experimental results were reproduced with the MDC, EQC, or EQ mechanism under D ϱh symmetry, though it was assumed that the SHG is nonresonant. 10 Thus, further studies are required to clarify the origin of the SHG.…”

“…The notations in this paper are the same as those in our previous paper. 10 We describe the resonant terms of microscopic expressions for four mechanisms. 2,7 The MDC mechanism or the EQC mechanism is due to a MD transition or an EQ transition at one input field, respectively, and an ED transition at the other input field, as illustrated in Figs.…”

“…Among them, the MD mechanism can be ruled out from a symmetrical consideration as shown in our previous paper. 10 The SH resonance spectra and the absorption spectra for a CuPc film and a H 2 Pc film are displayed in Figs. 2͑a͒ and 2͑b͒, respectively, where I(s,p) stands for p-polarized SH intensity under the incidence of s-polarized fundamental light, as illustrated in Fig.…”

“…20,21 In D 4h symmetry, I(s,p) is expressed as a sum of -independent and -dependent terms in the EQ mechanism, where is a rotation angle about the film surface normal. In the experiment using 1064 nm fundamental wavelength, we observed large -dependent SHG with 90°p eriodicity.…”

“…In the experiment using 1064 nm fundamental wavelength, we observed large -dependent SHG with 90°p eriodicity. 20 According to the detailed analysis, in-plane components of ⌳ in the crystal coordinate system play an important role in the SHG. The planelike CuPc molecules tend to lie parallel to the KCl͑100͒ plane, 21 so that in-plane components in the crystal coordinate system are related to in-plane components of the molecular coordinate system.…”