Silicon-based spectrally selective emitters with good high-temperature stability on stepped metasurfaces

An elliptical nanoantenna array plasmonic metasurface for efficient solar energy harvesting

Plasmonic metasurfaces with subwavelength nanoantenna arrays have attracted much attention for their ability to control and manage optical properties. Solar absorbers are potential candidates for effectively converting photons into heat and electricity. This study introduces a novel ultrathin metasurface solar absorber employing elliptical-shaped nanoantenna arrays. We theoretically and numerically demonstrate a near-perfect broadband absorber with over 90% absorption efficiency in a wide range of wavelengths of 300-2500 nm, using finite element (FEM) and finite-difference time-domain (FDTD) methods. The proposed nanostructure configuration enhances light absorption by exciting localized surface plasmon resonances (LSPRs) between elliptical-shaped nanoantenna gaps at many wavelengths, maintaining stability at wide incident angles and insensitivity to light polarization. Compared to other state-of-the-art absorbers with a thickness of less than 300 nm, the designed nanostructure with 260 nm thickness achieves over 90% optical absorption across a broad range of wavelengths of 300-1116 nm in air (or vacuum) environments and performs effectively under water conditions for solar energy harvesting in a range of wavelengths of 300-1436 nm, and therefore can serve as a solar evaporator. Combining refractory plasmonic titanium nitride (TiN) and semiconductor gallium nitride (GaN) nanostructures holds great potential for efficient optoelectronic and photocatalytic applications, especially in harsh and high-temperature environments like thermophotovoltaic systems. The TiN-based metasurface absorber, with its ultrathin nanostructure and suitable spectral absorption in ultraviolet-visible-infrared spectra, offers scalability and cost-effectiveness. The findings in this work will deepen our understanding of LSPRs and pave a novel path for efficient solar energy conversion.

Thermal tuning nanoprinting based on liquid crystal tunable dual-layered metasurfaces for optical information encryption

Dynamic tuning metasurfaces represent a significant advancement in optical encryption techniques, enabling highly secure multichannel responses. This paper proposes a liquid crystal (LC) tunable dual-layered metasurface to establish a thermal-encrypted optical platform for information storage. Through the screening of unit cells and coupling of characteristics, a dynamic polarization-dependent beam-steering metasurface is vertically cascaded with an angular multiplexing nanoprinting metasurface, separated by a dielectric layer. By integrating high-birefringence LCs into dual-layered metasurfaces, the cascaded meta-system can achieve dynamic thermal-switching for pre-encoded nanoprinting images. This work provides a promising solution for developing compact dynamic meta-systems for customized optical storage and information encryption.