New features of the speckle phase singularity produced in large angle scattering

Based on the interference patterns of the speckle field and the reference beam recorded by the charge-coupled device, and the digital Fourier transform technique, the complex amplitudes and phases of speckle field produced at different scattering angles are extracted. The phase distribution and the statistical properties at the singular point, such as the angle between two zero-contour lines of real part and imaginary part of the complex amplitude, the eccentricity of the intensity contours, etc. are studied. We find that there are some special properties of phase singularity when the scattering angle is large enough. With the increase of the scattering angle, great changes have taken place in the spatial distributions of the amplitude and the phase, and the probability of the angle between two zero-contour lines of real part and imaginary part is close to a smaller value, and the average eccentricity of the intensity contours around the phase singularity gradually increase. Moreover, the most interesting thing is that the eccentricity is probably greater than 1 in large anger scattering. The phase singular line as a new kind of phase singularity is found at a large scattering angle; the phase mutation rules and the vortex distribution characteristics of the phase on both sides of the phase singular line are investigated, and the hyperbolic or parabolic shape intensity contour around the phase singular line is found.