An All‐Silicon Hybrid Refractive–Metalens Bifocal Imaging System With Dual Image Planes and Broadband Achromatic Performance

ABSTRACT In this study, we experimentally demonstrate a bifocal meta‐optical module for dual field‐of‐view (FoV) imaging in the long‐wave infrared regime. The system comprises a refractive lens integrated with a metalens that shunts the incident wavefront into modulated and unmodulated components. The unmodulated component preserves the original focusing behavior of the refractive lens, resulting in an effective focal length of 26.7 mm, whereas the modulated component acquires additional positive optical power, leading to a shortened effective focal length of 10 mm. The measured modulation transfer function reaches 0.3 at spatial frequencies of 33 and 12 cycles/mm for the short‐ and long‐focal‐length modes, respectively. Notably, both the refractive lens and the metalens remain fixed, utilizing simultaneous dual focal planes to switch the FoV. This compact dual‐FoV meta‐optical system provides an efficient and robust solution for applications such as thermal target detection and tracking.