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Abstract Femtosecond laser‐induced damage threshold (LIDT) testing is carried out at 515 nm on 4‐mm‐sized metalens arrays that are manufactured by direct nanoimprinting of a TiO2nanoparticle (NP)‐based ink containing either polymeric or inorganic binders. The all‐inorganic TiO2metalenses exhibit ≈80% absolute focusing efficiency and demonstrate an LIDT of ≈90 mJ cm−2based on a single‐shot determination using Liu's method, while the metalenses with the polymeric binder achieve ≈137 mJ cm−2and an efficiency of ≈76%. Despite the higher LIDT of the TiO2‐polymer composite metalenses in the single‐shot experiment, these lenses exhibit significant damage at fluences as low as ≈8 mJ cm−2when subjected to ≈6 × 10⁸ pulses at 60 kHz. On the other hand, the all‐inorganic metalenses remain intact under identical conditions at ≈64 mJ cm−2. That is, the inorganic binder provides superior long‐term stability relative to the polymeric binder and is a more viable solution for high‐energy applications. Structural damages observed in nanostructures result in a reduced deflection efficiency and increase light scattering at the focal plane of the metalens. The LIDT testing is also performed in the nanosecond regime at 532 and 1064 nm with the all‐inorganic metalenses, yielding thresholds of ≈0.5 and ≈5 J cm−2, respectively.
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Full Wafer Scale Manufacturing of Directly Printed TiO 2 Metalenses at Visible Wavelengths with Outstanding Focusing Efficiencies
Abstract Highly efficient metalens arrays designed for 550 nm are directly printed using UV‐assisted nanoimprint lithography (UV‐NIL) and a TiO2nanoparticle (NP)‐based ink on 8″ optical wafers with imprint times less than 5 min. Approximately one‐thousand 4‐mm metalenses are fabricated per wafer with uniform optical performance using a reusable PDMS‐based elastomeric stamp. The absolute and relative focusing efficiencies are as high as 81.2% and 90.4%, respectively, matching closely with the simulated maximum efficiencies of 83% and 91% achievable with the given master design, indicating that future improvements are possible, and efficiencies are not limited by materials or process. The imprinted metalenses are free from organics due to a post‐imprint calcination step and exhibit outstanding dimensional and optical stabilities. The highest efficiencies are attained using imprint formulations comprised of mixtures of 10 and 20 nm TiO2NPs, whose denser packing not only increases the refractive index (RI) of the calcined lenses up to 2.0 but also reduces the feature shrinkage relative to the master. 25 cycles of atomic layer deposition of TiO2following imprinting increase the RI up to 2.3 without changing dimensions by uniform gap filling between NPs. This work opens a path for true, full‐scale additive manufacturing of metaoptics.
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- PAR ID:
- 10593725
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 37
- Issue:
- 30
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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