Chirality‐Reversed Bidirectional High‐Efficiency Dichroic Metalens based on Hybrid Helical Surfaces. Issue 12 (17th September 2022)

• Record Type: Journal Article
• Authors: Wang, Chenqian; Wang, Chinhua
• Is Part Of: Laser & photonics reviews. Volume 16:Issue 12(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-09-17
• Subjects: bidirectional -- chiral metalenses -- chirality reversed -- high efficiency -- hybrid helical surfaces; Lasers -- Periodicals; Photonics -- Periodicals; Lasers -- Périodiques; Photonique -- Périodiques; 621.36
• DOI: 10.1002/lpor.202200346
• Languages: English
• ISSNs: 1863-8880

Abstract

Abstract: A conventional chiral metalens based on helical structures have the disadvantages of fixed chirality and low conversion efficiency of cross‐circular polarization. In this study, a chirality‐reversed bidirectional high‐efficiency dichroic metalens based on hybrid helical surfaces (HHSs) is proposed and experimentally demonstrated, which is composed of a pair of half‐pitch helical surfaces with left‐ and right‐handedness. It is found that the cross‐polarization conversion efficiency of the hybrid structure reaches 78.5%, which is ≈20 times higher than that (≈4%) of a conventional normal helical structure. The chirality of the hybrid structure can be flexibly switched between left‐ and right‐handedness by simply flipping the metalens by 180°, rendering a chirality‐reversed bidirectional operation. A comprehensive analysis of the physical mechanism and experimental verification are conducted. Two‐photon laser direct writing and electron beam evaporation are employed to fabricate the dichroic metalens with a scale of a 101 × 101 HHS array, and dichroism focusing and imaging are successfully realized by lock‐in thermography in the IR wavelength range from 3 to 5 μm. The demonstrated high‐efficiency bidirectional dichroic metalens promises important applications in polarimetric imaging and biomedical chirality detection. Abstract : A chirality‐reversed bidirectional high‐efficiency dichroic metalens based on hybrid helical surfaces (HHSs) is proposed and experimentally demonstrated. The cross‐polarization conversion efficiency of the HHS reaches 78.5%, which is ≈20 times higher than that of a conventional normal helical structure. The chirality of the HHS can be flexibly switched between left‐ and right‐handedness by simply flipping the metalens by 180°.