Linear and Non-Linear Optical Responses of a Strongly Coupled Electron-Lattice System

抄録

The spectrum of resonant second-harmonic generation (SHG) isfar sharper than that of linear photo-absorption (LA), as observed for Cr₂O₃ crystal. We show theoretically this comes from the difference that strong coupling between the localized electronic excitation and latticevibration works as intermediate state interaction in SHG while it does as final state interaction in LA.