Spectral lineshape analysis of four‐wave mixing spectra and its application to quasi‐zero‐dimensional II–VI semiconductor crystallites

Theoretical and experimental investigations are presented in order to analyze the lineshape of four-wave mixing spectra recorded by means of electronically resonant folded BOXCARS spectroscopy (special technique of CARS, coherent anti-Stokes Raman scattering). The theoretical framework presented is based on the quantum-mechanical expression of the non-linear third-order susceptibility. In order to obtain model equations those contributions of the third-order susceptibility which give rise to strong electronic resonance enhancement were exclusively used. The participation of two-photon resonances and the inhomogeneous broadening of the electronic transitions is taken into account. The theoretical background presented was applied to a semi -conductor model system consisting of quasi-zero-dimensional CdSxSe1−x nanocrystallites. The inhomogeneous broadening of this low-dimensional system is mainly caused by the size distribution of the nanocrystallites. The lineshapes of the experimentally obtained four-wave mixing spectra are well described within the theoretical framework and the homogeneous linewidth of the resonantly excited electronic state can be deduced. Copyright © 1999 John Wiley & Sons, Ltd.