Flat Lenses Based on 2D Perovskite Nanosheets

Abstract

Ultrathin flat lenses based on metasurfaces or metamaterials have shown great promise as essential components in nano optical system with capability of abrupt changes of light wavefronts in recent years. However, such structural designs require complex nanopatterns and time-consuming nanofabrication process. In this regard, we developed flat lenses based on 2D perovskite nanosheets using a cost-effective mask-free femtosecond direct laser writing system. The optical properties of 2D perovskite are rationally adjusted through facile composition engineering as well as thicknessdependent quantum-size confinement. Diffraction theory model is derived to understand the focusing mechanism of the 2D perovskite nanosheets flat lenses. The as-fabricated lenses exploit the tunable material property variations to effectively manipulate not only amplitude but also phase of the incident light to focus into a 3D focal spot with a sub-wavelength resolution in the range of 0.5-0.9 λ. The results pave the way towards low-cost and large-scale high-resolution imaging application in the future.

Directional Lasing from Nanopatterned Halide Perovskite Nanowire

“…Such processing conditions avoided the uneven coupling of the incident laser radiation in the CsPbBr 3 NW, which could result in preferential ablation near its corners, as illustrated by corresponding full-wave calculations (see Figure c). The fabrication method used demonstrated an accuracy that was high enough to imprint a subwavelength grating with a period Λ down to 200 nm, thus outperforming the previously reported approach based on scanning laser ablation. − A remarkable reproducibility of the fabrication approach used is revealed in Figure d where a 30 μm long CsPbBr 3 NW patterned with a 260 nm period nanograting on its top face is shown.…”

Fabrication Technologies for the On‐Chip Integration of 2D Materials

“…[223] Recently, gate-tunable frequency comb generation was also demonstrated based on a graphene/silicon nitride hybrid microring resonator (MRR). [126] The patterning of ultrathin graphene, [195] GO, [207] TMDCs, [217,224] and perovskite [258] films has formed the basis of flat optical lenses. Chip-scale sensors incorporating 2D materials have also demonstrated the detection for a wide range of targets, from gases, [30,239,285] humidity, [235,281] and metal ions, [31,218] to pressure, [32,270] and biomolecules.…”

“…[394] In situ patterning of γ-CsPbI 3 quantum dot-based films (Figure 5l) was also achieved, [395] which exhibited bright red PL with a high quantum yield of up to 92%. Finally, ultrathin flat lenses in 2D perovskite (Figure 5m) were fabricated by using a femtosecond laser, [258] where the feature size of the lens rings was ≈400 nm.…”

Fabrication Methods for Integrating 2D Materials

“…[214] Recently, gate-tunable frequency comb generation was also demonstrated based on a graphene/silicon nitride hybrid microring resonator (MRR). [121] The patterning of ultrathin graphene, [186] GO, [198] TMDCs, [208,216] and perovskite [250] films has formed the basis of flat optical lenses. Chip-scale sensors incorporating 2D materials have also demonstrated the detection for a wide range of targets, from gases, [30,231] humidity, [227,272] and metal ions, [31,209] to pressure, [32,262] and biomolecules.…”