Highly tunable refractive index visible-light metasurface from block copolymer self-assembly

Abstract

The refractive index of natural transparent materials is limited to 2–3 throughout the visible wavelength range. Wider controllability of the refractive index is desired for novel optical applications such as nanoimaging and integrated photonics. We report that metamaterials consisting of period and symmetry-tunable self-assembled nanopatterns can provide a controllable refractive index medium for a broad wavelength range, including the visible region. Our approach exploits the independent control of permeability and permittivity with nanoscale objects smaller than the skin depth. The precise manipulation of the interobject distance in block copolymer nanopatterns via pattern shrinkage increased the effective refractive index up to 5.10. The effective refractive index remains above 3.0 over more than 1,000 nm wavelength bandwidth. Spatially graded and anisotropic refractive indices are also obtained with the design of transitional and rotational symmetry modification.

Viable stretchable plasmonics based on unidirectional nanoprisms

“…[13][14][15][16] Recently, increasing attention has been paid to explore unique plasmonic properties on stretchable substrates. [17][18][19][20][21][22][23] Representatively, researchers have investigated sensory behaviors using plasmonic nanostructures on flexible substrates.…”

“…The precise inter-distance manipulation of the patterns by inhomogeneous thermal shrinkage was monitored following the refractive index of the resulting metamaterials, essential for an effective enhancement of refractive index. 21 Aksu et al reported the development of high-quality bow tie antennas based on high-resolution nanostencil lithography on a PDMS substrate. The optical responses of the antenna arrays were shown to be tuned by the mechanical stretching of the stretchable substrate.…”

A wide-angle shift-free metamaterial filter design for anti-laser striking application

“…The fabrication process can be enabled with material systems that include PS-b-PMMA, which can exhibit a high-order natural spacing length of 10 nm to 200 nm depending on the annealing process [51]. Two-dimensional periodic and symmetric metasurfaces has previously been demonstrated and reported by Ju Young Kim et al in 2016, where it was successfully demonstrated that a large area assembly of structured plasmonic materials using block copolymer self-assembly method was possible [52]. Moving towards a three-dimensional array can be achieved with multi-layer thin film BCP's [53,54], and would empower the next generation of complex optical metamaterials for various applications.…”

Electrospun Carbon Nanofibers with Embedded Co-Ceria Nanoparticles for Efficient Hydrogen Evolution and Overall Water Splitting

“…Electro-chemical water splitting has been considered as a promising eco-friendly process that avoids the emission of greenhouse gases or harmful components (i.e., CO 2 or NO x ) [2,3]. In recent decades, several studies have been performed to replace noble-metal-based electrocatalysts with earth-abundant nonnoble metals and highly active materials such as transition-metal alloys, oxides, carbides, nitrides, and phosphides [4][5][6][7][8][9][10][11][12][13][14][15]. However, various issues need to be addressed to achieve high-efficiency overall water electrolysis.…”