Generation of multiple sub-diffraction-limit spots in 3D space with propagating light

This paper reports on diffractive fan-out elements generating multiple sub-diffraction-limit spots in three-dimensional (3D) space. To arrange the sub-diffraction-limit spots, we introduce particular constraints and transfer functions corresponding to the Fresnel diffraction into an iterative Fourier transform algorithm. Experimental results demonstrate that the size of spots generated in 3D space is reduced to 77% of the diffraction limit on average.