Constructing a Frequency-Dependent Phase Profile of Linear Dispersion for Achromatic Superresolution Focusing

Achromatic lenses are crucial to light focusing and imaging. However, conventional achromatic lenses are restricted by the Abbe diffraction limit. Although superresolution optical lenses have been demonstrated to overcome the limit, the correction of chromatic aberration in continuous broadband for superresolution lenses still remains challenging. To address this issue, we propose a generalized strategy of constructing a frequency-dependent phase profile of linear dispersion for achromatic superresolution focusing in a continuous broad bandwidth. Specifically, based on an arbitrary wavelength-independent discrete phase profile of a monochromatic superresolution lens optimized at a given single optical frequency, a frequency-dependent phase profile of an achromatic superresolution lens can be constructed as the sum of the given discrete phase profile and a linear dispersion phase term. Based on the proposed approach, broadband achromatic superresolution metalenses are designed and demonstrated in the terahertz regime. The proposed method can be applied to visible and infrared optical spectra, which could have promising potential in various superresolution-related applications.