Coherent coupling and transient optical Kerr effect in liquids

Pump-probe optical Kerr effect (OKE) detected in the time domain with a resolution a few tens of femtosecond has proved useful for the study of the coherent transients in liquids at room temperature. Experimental procedure is more or less standardized. However, results are not always consistent because of experimental complexities that, as shown in the report, mainly arise from coherent coupling. Coherent coupling persists for the full pulse-duration, and can overwhelm the Kerr signal. Fine-tuning the optical alignment is thus needed to discriminate against it. This, along with the ensuing results for CS₂, is given. As expected the strength of coherent coupling relative to that of the Kerr effect is found to be very sensitive to a change in the angle (β) subtended by the pump and probe beams, which is set at -9° to begin with