Origin of Second-Harmonic Generation in Vacuum-Evaporated Copper Phthalocyanine Film

In situ observation of second-harmonic generation (SHG) was made as a function of film thickness of centrosymmetric copper phthalocyanine during the evaporation process. In order to clarify the origin of the relatively strong SHG, the experimental results were compared with calculations based on the electric dipole, electric quadrupole and magnetic dipole mechanisms. The comparison clearly ruled out dipolar origin and strongly indicates electric quadrupolar or, more preferably, magnetic dipolar origin.