A broadband metamaterial absorber (MA) composed of hexagonal-arranged single-sized titanium nitride (TiN) nano-disk array and monolayer molybdenum disulfide (MoS2) is studied using finite-difference time-domain (FDTD) simulations. The structure of TiN nano-disk array/dielectric silica (SiO2)/aluminum (Al) is adopted in our design. By optimizing the dimension parameters of the structure, an average absorption of 96.1% is achieved from 400 to 850 nm. In addition, by inserting a monolayer MoS2 which has high absorption at the short wavelength side underneath the TiN nano-disk array, an average absorption of 98.1% over the entire visible regime from 400 to 850 nm was achieved, with a peak absorption near 100% and absorption over 99% from 475 to 772 nm. Moreover, the absorber presented in this paper is polarization insensitive. This compact and unique design with TiN nano-disk/monolayer MoS2/ SiO2/Al structure may have great potential for applications in photovoltaics and light trapping.
Based on an integrated array of refractory titanium nitride (TiN), a metasurface perfect absorber (MPA) in the visible-to-near infrared (NIR) band is reported. The systematic and detailed simulation study of the absorption of the MPA is performed with the finite-different time-domain (FDTD) method. Tailoring the structure, the MPA realizes as high an average as 99.6% broadband absorption, ranging from 400 nm to 1500 nm. The broadband perfect absorption can be attributed to localized surface plasmonic resonance (LSPR), excited by the continuous diameter evolution from the apex to the base of the nanocone, and the gap plasmons excited among the nanocones, as well as in the spacer layer at longer wavelengths. Particularly, the coupling of the resonances is essentially behind the broadening of the absorption spectrum. We also evaluated the electric field intensity and polarization-dependence of the nanocone MPA to offer further physical insight into light trapping capability. The MPA shows about 90% average absorption even at an oblique incidence up to 50°, which improves the acceptance capability of light-harvesting system applications. This unique design with the TiN nanocone array/aluminium oxide (Al2O3)/TiN structure shows potential in imminent applications in light trapping and thermophotovoltaics.
Phase
retrieval is a noninterferometric quantitative phase imaging
technique that has become an essential tool in optical metrology and
label-free microscopy. Phase retrieval techniques require multiple
intensity measurements traditionally recorded by camera or sample
translation, which limits their applicability mostly to static objects.
In this work, we propose the use of a single polarization-dependent
all-dielectric metasurface to facilitate the simultaneous recording
of two images, which are utilized in phase calculation based on the
transport-of-intensity equation. The metasurface acts as a multifunctional
device that splits two orthogonal polarization components and adds
a propagation phase shift onto one of them. As a proof-of-principle,
we demonstrate the technique in the wavefront sensing of technical
samples using a standard imaging setup. Our metasurface-based approach
fosters a fast and compact configuration that can be integrated into
commercial imaging systems.
In this paper, a thin metasurface perfect absorber based on refractory titanium nitride (TiN) is proposed. The size parameter of the metasurface is investigated based on the finite difference time domain method and transfer matrix method. With only a 15-nm-thick TiN layer inside the silica/TiN/silica stacks standing on the TiN substrate, the near-perfect absorption throughout the visible regime is realized. The cross-talk between the upper and lower dielectric layers enables the broadening of the absorption peak. After patterning the thin film into a nanodisk array, the resonances from the nanodisk array emerge to broaden the high absorption bandwidth. As a result, the proposed metasurface achieves perfect absorption in the waveband from 400 to 2000 nm with an average absorption of 95% and polarization-insensitivity under the normal incidence. The proposed metasurface maintains average absorbance of 90% up to 50-degree oblique incidence for unpolarized light. Our work shows promising potential in the application of solar energy harvesting and other applications requiring refractory metasurfaces.
In this paper, we report a polarization-independent broadband metasurface perfect absorber based on tunable gap magnetic resonance and Fabry–Perot (FP) resonance in a structure with consecutive size variation. By using the finite-difference time-domain method, the effects of size parameters are investigated. Due to the coexistence of the FP-like resonance and gap magnetic resonance, the near-unit absorption reaches as high as 99.46% with nanocone morphology throughout the visible-to-near infrared regime where most solar radiation is located. The structure raised in this paper is less complex and more thermally stable due to abandoning the spacer layer in traditional tri-layer structures. This method can be developed for other refractory materials and has great potential in solar energy related optoelectronics applications.
Long-ranged surface plasmon polaritons (SPPs) and their coupling with upconversion emissions (UCEs) were studied in indium tin oxide (ITO)-coated erbium and iron codoped
L
i
N
b
O
3
(Er,Fe:LN). In this work, ITO is coated on Er,Fe:LN grains to form a noble-metal-like modified ITO layer, namely, a two-dimensional electron gas layer. By meeting phase-matching conditions, SPPs with a definite wave vector can be excited most efficiently. By calculating the attenuated total reflection spectra of the sandwich structure of unmodified ITO/modified ITO layer/LN, the propagation length of SPP can reach as long as 2.0 cm due to the subnanometer ITO modified layer. Experimentally, the location of missing spectral lines in the diffraction pattern and a valley in the transmission spectra are consistent well with the calculations of the phase-matching condition, both serving as valid proofs for SPP excitation. In the ITO-coated Er,Fe:LN grains, a sharp dropping-down process was observed in the UCE’s dynamics, indicating high coupling efficiency from UCEs to SPPs. This work advances the fundamental understanding in electrostatic modification of transparent oxides into visible nonmetal plasmonic materials by simply neighboring to ferroelectric oxides and leads a way toward designing and implementing shortwave plasmonic devices, apart from conventionally used lossy metal constituents.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.