An official website of the United States government
Elastodynamic metasurfaces composed of surface-mounted resonators show great promise for guided wave control in diverse applications, e.g., seismic and vibration isolation, nondestructive evaluation, or surface acoustic wave devices. In this work, we revisit the well-studied problem of “rod-shaped” resonators coupled to a plate to reveal the relationship between the resonator's resonances and antiresonances obtained under unidirectional harmonic excitation, and the resultant frequency bandgap for S0 Lamb mode propagation once a metasurface is arranged. This relationship is shown to hold true even for non-prismatic resonators, such as those presented in our recent studies, in which we established a systematic resonator design methodology using topology optimization by matching a single resonator's antiresonance with a predefined target frequency. Our present study suggests that considering the waveguide (plate) during the resonator design is not essential and encourages a feasible resonator design approach to achieve wide bandgaps just by customizing a single resonator's resonances and antiresonances. We present a topology optimization design methodology for resonators that drive resonances away from antiresonances, i.e., a resonance gap enhancement, yielding a broadband S0 mode bandgap while ensuring the desired bandgap formation by matching antiresonances with a target frequency. The transmission loss of metasurfaces composed with topology-optimized resonators is numerically verified, confirming the generation of wider bandgaps compared to resonators designed without resonance gap enhancement and broadening the applicability of locally resonant metasurfaces.
more »
« less
Ellipticity‐Controlled Exceptional Points and Cross‐Polarized Phase Singularities in Multi‐Layer Silicon Guided Mode Resonant Metasurfaces
Abstract Precise control over light polarization is critical for advancing technologies in telecommunications, quantum computing, and image sensing. However, existing methods for manipulating polarization around exceptional points (EPs) in non‐Hermitian systems have exclusively focused on circular polarization and work with reflected light. To address this limitation, a novel metasurface platform with high‐Q resonators is developed that enables tunable control of polarization exceptional points across arbitrary ellipticity for transmitted light. This design employs orthogonally polarized guided mode resonators in a two‐layer silicon metasurface, where careful tuning of the dipolar guided mode resonances (DGMRs) and layer spacing allows us to control the ellipticity of EPs. By leveraging high‐quality factor resonances, strong orthogonal mode coupling over distances up to a quarter wavelength is achieved. This platform exhibits omnipolarizer behavior and the corresponding phase singularity can imprint phase shifts from 0 to 2π with small perturbations in the geometry. This approach opens new possibilities for polarization control and programmable wavefront shaping, offering significant potential for next‐generation optical devices.
more »
« less
- PAR ID:
- 10615019
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Optical Materials
- Volume:
- 13
- Issue:
- 26
- ISSN:
- 2195-1071
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
We propose, design, and experimentally demonstrate a nonlocal metasurface with frequency-selective, wavefront shaping capabilities and at the same time polarization-selective chiral response. This operation requires the implementation of bilayer metasurfaces with engineered nonlocal response, wherein each layer controls locally a specific linear polarization, while the coupled system supports arbitrary polarization states. We demonstrate that this platform enables unprecedented control over wavefront manipulation, including frequency-selective, spin-selective reflection with arbitrary geometric phase. We observe a highly chiral response with record-high reflectance efficiency over a narrow frequency window, both for a uniform metasurface and for one with tailored phase gradient for anomalous reflection. Both devices provide an efficiency well above the theoretical limit of 25% for conventional single-layer devices. Our work opens exciting opportunities for augmented reality and enhanced secure wireless communications.more » « less
-
Metasurfaces, composed of engineered nanoantennas, enable unprecedented control over electromagnetic waves by leveraging multipolar resonances to tailor light–matter interactions. This review explores key physical mechanisms that govern their optical properties, including the role of multipolar resonances in shaping metasurface responses, the emergence of bound states in the continuum (BICs) that support high-quality factor modes, and the Purcell effect, which enhances spontaneous emission rates at the nanoscale. These effects collectively underpin the design of advanced photonic devices with tailored spectral, angular, and polarization-dependent properties. This review discusses recent advances in metasurfaces and applications based on them, highlighting research that employs full-wave numerical simulations, analytical and semi-analytic techniques, multipolar decomposition, nanofabrication, and experimental characterization to explore the interplay of multipolar resonances, bound and quasi-bound states, and enhanced light–matter interactions. A particular focus is given to metasurface-enhanced photodetectors, where structured nanoantennas improve light absorption, spectral selectivity, and quantum efficiency. By integrating metasurfaces with conventional photodetector architectures, it is possible to enhance responsivity, engineer photocarrier generation rates, and even enable functionalities such as polarization-sensitive detection. The interplay between multipolar resonances, BICs, and emission control mechanisms provides a unified framework for designing next-generation optoelectronic devices. This review consolidates recent progress in these areas, emphasizing the potential of metasurface-based approaches for high-performance sensing, imaging, and energy-harvesting applications.more » « less
-
ABSTRACT When arranged in a metasurface, the collective enhancement of field interactions within scattering elements enables precise control over the incident light phase and amplitude. In this work, we analyze collective multipolar resonances in metasurfaces that arise from the spatially extended nature of electromagnetic interactions within these structures, with particular emphasis on MXene metasurfaces. This collective scattering leads to unique and tunable resonance behaviors that reach beyond the simple dipolar approximations, thus enabling advanced manipulation of light at subwavelength scales. We also explore resonances in the scatterers and metasurfaces made of different materials, categorizing them into lossy materials, including transition metal dichalcogenides and conventional metals, and high‐refractive‐index materials, such as silicon. We observe the excitation of MXene multipolar resonances across the visible‐ and infrared‐wavelength spectra and demonstrate their control through the design of scattering elements of the metasurface. We show that periodic lattice arrays support strong localized resonances through the collective response of individual nanoresonators and that one can control multipolar resonances by engineering metasurface nanoresonators and their distribution.more » « less
-
Abstract Metasurface has emerged as a powerful platform for controlling light at subwavelength thickness, enabling new functionalities for imaging, polarization manipulation, and angular momentum conversion within a flat surface. An integrated asymmetric metasurface simultaneously achieving broadband, low loss forward power transmission, and significant back reflection suppression in multi‐mode waveguides is explored. The tapering along the direction of light propagation leads to low loss and space‐efficient mode conversion. Enhanced by a double‐flipped structure, a thin (2.5 µm) metasurface can simultaneously achieve high conversion efficiency (>80%), and back‐reflection efficiency of 90% over a 200 nm wavelength range. Such single‐side reflectors can be one of the enabling components for gain‐integrated adaptive optics on a chip.more » « less
