We study the colour-locked twin-noisy-field correlation effects in the fifth-order nonlinear susceptibility of ultrafast polarization beats in a cascade four-level system.More importantly,the fifth-order phase-sensitive heterodyne detection of ultrafast polarization beats has been exploited.The fifth-order nonlinear optical response can be controlled and modified through the colour-locked correlation of twin noisy fields.Thus,this method with the phase dispersion information is a good way to measure the real and imaginary parts of the fifth-order nonlinear susceptibility.
We study the co-existing four-wave mixing(FWM)process with two dressing fields and the six-wave mixing (SWM)process with one dressing field in a five-level system with carefully arranged laser beams.We also show two kinds of doubly dressing mechanisms in the FWM process.FWM and SWM signals propagating along the same direction compete with each other.With the properly controlled dressing fields,the FWM signals can be suppressed,while the SWM signals have been enhanced.
