Single-focus phase singularity generated by spiral zone plate with quasi-random distributed quantum dots

Abstract

We report on a new vortex lens for producing a single-focus phase singularity which is termed as a quasi-random-dot-array binary spiral zone plates (QBSZPs). Differing from the abrupt transitions of the conventional spiral zone plates (SZPs), the key idea of the QBSZPs is to realize a sinusoidal transmittance by properly arranging lots of quantum dot arrays which take on the values of 0 and 1 in two dimensions. In this typical design, the number density of the selected primitives obey sinusoidal distribution along the radial direction and quasi-random in the azimuthal direction. Theoretical analysis indicates that the higher-order foci which inevitably exist in the SZPs have been indeed effectively suppressed with the QBSZPs. Moreover, the focusing performance of the QBSZPs is influenced by the ratio of circumcircle diameter of the primitives to the outermost zone width. These findings, which have been demonstrated by the performed experiment, may offer a new direction towards improving the performance of biomedical imaging, quantum computation and optical manipulation.