Recently, transient phase response associated with surface mode molecular relaxation from highly deformed nematic liquid crystal (LC) directors has been employed to achieve high speed liquid crystal modulators.1-3 This transient nematic effect was analyzed experimentally and numerically. The transient decay time was found to be fast, insensitive to cell thickness, but cell proportional to (X/An0)2; being the optical wavelength and Ano the corresponding birefringence of LC. Based on both computer simulations and experimental results, decay time of the fast LC amplitude modulator was derived. Together with multiple pass technique and optimal temperature effect, the response speed of transient nematic effect can be further improved. Nematic liquid crystal modulators with frame time <40 pis have been achieved in the visible spectral region.