Highly Efficient Broadband Achromatic Microlens Design Based on Low-Dispersion Materials

Abstract

Metalenses with achromatic performance offer a new opportunity for high-quality imaging with an ultra-compact configuration; however, they suffer from complex fabrication processes and low focusing efficiency. In this study, we propose an efficient design method for achromatic microlenses on a wavelength scale using materials with low dispersion, an adequately designed convex surface, and a thickness profile distribution. By taking into account the absolute chromatic aberration, relative focal length shift (FLS), and numerical aperture (NA), microlens with a certain focal length can be realized through our realized map of geometric features. Accordingly, the designed achromatic microlenses with low-dispersion fused silica were fabricated using a focused ion beam, and precise surface profiles were obtained. The fabricated microlenses exhibited a high average focusing efficiency of 65% at visible wavelengths of 410–680 nm and excellent achromatic capability via white light imaging. Moreover, the design exhibited the advantages of being polarization-insensitive and near-diffraction-limited. These results demonstrate the effectiveness of our proposed achromatic microlens design approach, which expands the prospects of miniaturized optics such as virtual and augmented reality, ultracompact microscopes, and biological endoscopy.