Four equal-intensity foci generated by a Cantor–Thue–Morse zone plate

Abstract

A Cantor–Thue–Morse zone plate (CTMZP) is proposed to generate four foci with equal intensities along the optic axis. Moreover, the intensity non-uniformity of four foci is low for the CTMZP with the large number of duplicate cells. In addition, the CTMZPs with the different sizes and numbers of duplicate cells can generate four equal-intensity foci with high intensities and unchanged intensity non-uniformity. Furthermore, four foci for the CTMZP located at the required axial positions, and the energy efficiency in the focus increases with the focal length. We will illustrate the construction method of the CTMZP in the details. It will be proved in the simulations and experiments that the proposed zone plate can generate four equal-intensity foci. The proposed zone plate can be applied to trap particles with an equal trapping force at four planes, and generate the same clear images of four planes in a single output plane of an image forming system simultaneously.