Full-visible achromatic imaging with a single dual-pinhole-coded diffractive photon sieve.

Abstract

Conventional diffractive optical elements suffer from large chromatic aberration due to its nature of severe dispersion so that they can only work at a single wavelength with near zero bandwidth. Here, we propose and experimentally demonstrate an achromatic imaging in the full-visible wavelength range with a single dual-pinhole-coded diffractive photon sieve (PS). The pinhole pattern (i.e., distribution of the position and size of each pinhole) is generated with dual wavelength-multiplexing coding (WMC) and wavefront coding (WFC), in which WMC makes multiple wavelengths that are optimally selected within the full visible range focus coherently on a common designed focal length while WFC expands the bandwidth of the diffracted imaging at each of the selected wavelengths. Numerical simulations show that when seven wavelengths (i.e., 484.8, 515.3, 547.8, 582.4, 619.1, 658.1 and 699.5 nm) within the visible range between 470 nm to 720 nm and a cubic wavefront coding parameter α = 30π are selected, a broadband achromatic imaging can be obtained within the full range of visible wavelength. Experimental fabrication of the proposed dual-pinhole-coded PS with a focal length of 500 mm and a diameter of 50 mm are performed using the mask-free UV-lithography. The experimental imaging results agree with the numerical results. The demonstrated work provides a novel and practical way for achieving achromatic imaging in the full visible range with features of thin, light and planar.