Effect of wave-front field curvature on laser-induced liquid crystal far-feld diffraction ring

To elucidate the effect of field curvature on laser-induced far-field diffraction and its mechanism, the effect of field curvature on the far-field diffraction ring pattern after Gaussian beam propagating through self-defocusing liquid crystal was simulated based on Kirchhoff diffraction integral. Without considering the filed curvature effect, the central spot of the far-field diffraction ring will turn out to be bright and dark alternatively with the incident laser intensity increasing. With divergent beam traversing thin self-defocusing medium, the central spot will turn out to be darkened, while brightened with the convergent case. Finally the phenomena were explained based on the amplitude and phase factors in the integral expression of Kirchhoff diffraction. The phenomena are attributed to the interaction between the wave-curvature and the nonlinear phase factor.