Consideration About Optimal Conditions for Backward Scattering Signals in Four-Wave-Mixing Techniques

Abstract

The investigation of opaque samples is very important for many fields of research in physics (semiconductors), biology, chemistry and medicine in finding correlations between structures and other optical and electrical qualities. For these samples the use of backscattering arrangements are possible only. In vibrational spectroscopy such schemes for IR and Raman techniques are well known. But the introduction of coherent vibrational methods are still very difficult and limited to only a few special cases. But the supplementary informations which are inherent in coherent methods demand for their corresponding application. Some results are already obtained by the method of Sum Frequency Generation [1], but with restrictions to special frequency regions, due to the lack of proper IR sources. Experiments obtained by Degenerate Four Wave Mixing Techniques show also very interesting results, but they are limited to investigations of electronic states [2]. For Nondegenerated Four Wave Mixing techniques up to now only one result is published concerning ps-CARS at silicon [3].