Browsing by Subject "Plasmonic metasurfaces"

Now showing 1 - 2 of 2

Open Access
Broad-band polarization-insensitive all-dielectric metalens enabled by intentional off-resonance waveguiding at mid-wave infrared
(American Institute of Physics, 2019) Tanrıöver, İbrahim; Demir, Hilmi Volkan
Metasurfaces are promising candidates to take the place of conventional optical components as they enable wavefront engineering at sub- and near-wavelength distances along both lateral and vertical directions. Plasmonic metasurfaces containing sub-wavelength metallic structures constitute initial examples of this concept. However, plasmonic metasurfaces cannot achieve satisfactory efficiencies in the transmission mode due to their intrinsic losses. The low efficiencies of transmissive plasmonic metasurfaces motivated solutions using dielectric ones. Such high-efficiency all dielectric metasurfaces depend on either resonance tuning or Pancharatnam–Berry (geometrical) phase approaches. However, these approaches are limited to either narrow operation bands or suffer polarization dependency. Here, we propose and show high-index dielectric nanopillars operated as cylindrical waveguides deliberately in the off-resonance regime to achieve polarization independent wavefront control over wide spectral bands. As a proof-of-concept structure, we demonstrated a focusing metalens operating at wavelengths from 4.0 to 4.6 μm under both s- and p-polarized illuminations. The designed lens maintains the focusing operation with a maximum of 4% focal distance shift having a relative efficiency of >94% and an absolute efficiency of >67% all over the defined spectral band of 600 nm, which outperforms the previously reported metalenses in terms of wide-band operation with high performance.
Embargo
Micrometasense: coupling plasmonic metasurfaces with fluorescence for enhanced detection of microplastics in real samples
(American Chemical Society, 2024-12-27) Ece, Emre; Aslan, Yusuf; Hacıosmanoglu, Nedim; İnci, Fatih
Diverse analytical techniques are employed to scrutinize microplastics (MPs)-pervasive at hazardous concentrations across diverse sources ranging from water reservoirs to consumable substances. The limitations inherent in existing methods, such as their diminished detection capacities, render them inadequate for analyzing MPs of diminutive dimensions (microplastics: 1-5 mu m; nanoplastics: < 1 mu m). Consequently, there is an imperative need to devise methodologies that afford improved sensitivity and lower detection limits for analyzing these pollutants. In this study, we introduce a holistic strategy, i.e., MicroMetaSense, reliant on a metal-enhanced fluorescence (MEF) phenomenon in detecting a myriad size and types of MPs (i.e., poly(methyl methacrylate) (PMMA) and poly(ethylene terephthalate) (PET)) down to 183-205 fg, as well as validated the system with real samples (tap and lake) and artificial ocean samples as a real-world scenario. To obtain precise size distribution in nanometer scale, MPs are initially processed with an ultrafiltration on-a-chip method, and subsequently, the MPs stained with Nile Red dye are subjected to meticulous analysis under a fluorescence microscope, utilizing both a conventional method (glass substrate) and the MicroMetaSense platform. Our approach employs a metasurface to augment fluorescence signals, leveraging the MEF phenomenon, and it demonstrates an enhancement rate of 36.56-fold in detecting MPs compared to the standardized protocols. This low-cost ($2), time-saving (under 30 min), and highly sensitive (183-205 femtogram) strategy presents a promising method for precise size distribution and notable improvements in detection efficacy not only for laboratory samples but also in real environmental samples; hence, signifying a pivotal advancement in conventional methodologies in MP detection.