How defects of the end surfaces of a lightguide affect the mode-interference parameters when optical vortices are present

摘要

The mode interference that accompanies spatial filtering of the radiation coming out of a multimode fiber lightguide with scattering and nonscattering end surfaces has been experimentally studied for propagation both of optical vortices and of ordinary waveguide modes. It is established that the mode interference created by the output radiation of optical vortices with identical directions of rotation of the wave front is greater than that created by waveguide modes with a planar wave front, because of the difference of the size of the speckle spots. It is shown that, when optical vortices are present in a lightguide, the SNR can be increased by artificially creating diffuse scattering at the input or output end surface.