Ultrafast nonlinear spectroscopy of nematic liquid crystals via transient frequency-shear detection

We report a novel time-resolved ultrafast transient spectroscopy setup to investigate third-order nonlinear dynamics on the femtosecond time-scale. Through measurement of the transient Kerr-induced carrier-frequency shift, the method enables to detect weak nonlinear phase-shift (below 50 mrad) without heterodyne detection. It provides temporal resolution to investigate both instantaneous and delayed nonlinear processes and polarization resolution to probe various terms of the third-order nonlinear susceptibility.