The Equivalence of Microlens and Metalens for THz High Spatial‐Spectral Resolution Hyperspectral Imaging with a Large Field of View

Abstract Terahertz (THz) hyperspectral imaging (HSI) is a promising non‐invasive analytical technique that enables the simultaneous capture of spatial and spectral information. However, traditional lenses used in THz HSI systems are bulky and suffer from severe chromatic and spherical aberrations, which result in large dispersion and a limited field of view (FOV). Furthermore, the diffraction limit also restricts the corresponding spatial‐spectral resolution. Therefore, lenses are urgently needed to achieve high spatial‐spectral resolution THz HSI with a wide field of view. In this study, an equivalence is established between the precise refractive index distribution required for a metalens with a wide FOV and its thickness profile, greatly simplifying the fabrication process. The associated THz microlenses enable high spatial‐spectral resolution HSI from 0.2 to 0.7 THz. The finest spatial and spectral resolutions are ≈0.6λ and 0.1 THz, respectively, with a numerical aperture (NA) of 0.555 and a large FOV of 60°. The associated sample is fabricated using 3D printing technology and low‐dispersion materials. The approach provides practical and cost‐effective means to achieve achromatic super‐resolution HSI, underscoring the significant importance of THz HSI in various domains, including bioimaging, biosensing, and non‐destructive testing.