COHERENT TRANSIENT OPTICAL KERR-EFFECT IN LIQUIDS - EXPERIMENTAL CONSIDERATION

The noise tenaciously appearing in the optically heterodyne detected ( OHD) transient optical Kerr effect (OKE) of simple molecular liquids i s investigated. We show that, for liquid samples of interest to us, co herent coupling does exist and appears as noise when not properly reso lved. The strength of coherent coupling relative to the OKE depends cr itically on the sample position, with respect to the beam waist of the probe laser, as well as the angle subtended by the pump and probe bea ms. When the optics alignment is optimized for the OKE against coheren t coupling the OHD-OKE signal is found to increase linearly with the l ocal oscillator strength; the coherent coupling signal also appears to increase though the trend is not clear-cut.