Partially coherent beam generation with metasurfaces

An optical system for the generation of partially coherent beams with genuine cross-spectral density functions from spatially modulated globally incoherent sources is presented.The spatial intensity modulation of the incoherent source is achieved by quasi-planar metasurfaces based on spatial-frequency modulation of binary Bragg surface-relief diffraction gratings.Two types of beams are demonstrated experimentally:(i)azimuthally periodic,radially quasi-periodic beams and(ii)rotationally symmetric Bessel-correlated beams with annular far-zone radiation patterns.