Large aperture phase-coded diffractive lens for achromatic and 16° field-of-view imaging with high efficiency

Abstract

Diffractive lenses (DLs) can realize high-resolution imaging with lightweight and compact size. Conventional DLs suffer from large chromatic and off-axis aberration, which significantly limits their practical application. Although many achromatic methods have been proposed, most of them are for small aperture DL and the diffraction efficiency is low. In the design of diffractive achromatic lenses, increasing the aperture and improving the diffraction efficiency have become two of the most important design issues. Here, a novel phase-coded diffractive lens (PCDL) for achromatic imaging with a large aperture and high efficiency is proposed and demonstrated experimentally, which has wide field-of-view (FOV) imaging at the same time. The phase distribution of the conventional phase-type DL is coded with a cubic function to both expand the working bandwidth and FOV of conventional DL. Fabrication of the proposed phase-type DL was performed using the laser direct writing of grey-scale patterns for a PCDL of a diameter of 10 mm, a focal length of 100 mm, and a cubic phase coding parameter of 30π. Experimental results show that the working bandwidth and the FOV of the PCDL reach 50 nm and 16° with over 80% focusing efficiency, which are in significant contrast to the conventional DL and good agreement with the theoretical predictions. This work provides a novel way for achromatic, wide FOV, and high-efficiency imaging with large aperture DL.