An optical design space that can highly benefit from the recent developments in metasurfaces is the folded optics architecture where light is confined between reflective surfaces, and the wavefront is controlled at the reflective interfaces. In this manuscript, we introduce the concept of folded metasurface optics by demonstrating a compact spectrometer made from a 1-mm-thick glass slab with a volume of 7 cubic millimeters. The spectrometer has a resolution of ~1.2 nm, resolving more than 80 spectral points from 760 to 860 nm. The device is composed of three reflective dielectric metasurfaces, all fabricated in a single lithographic step on one side of a substrate, which simultaneously acts as the propagation space for light. The folded metasystem design can be applied to many optical systems, such as optical signal processors, interferometers, hyperspectral imagers, and computational optical systems, significantly reducing their sizes and increasing their mechanical robustness and potential for integration.
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http://dx.doi.org/10.1038/s41467-018-06495-5 | DOI Listing |
In this work, a specially designed multilayer indium tin oxide (ITO) mesh structure metasurface was proposed as a microwave absorber, achieving both excellent angle-insensitive broadband absorption and high shielding effectiveness (SE). It features gradually changing surface resistance ( ), to expand the absorption bandwidth while maintaining high SE. Also, a folded square ring metasurface was designed to effectively suppress surface wave grating lobes, as well as to reduce the unit size of the metasurface and thus the absorber.
View Article and Find Full Text PDFMaterials (Basel)
December 2024
Xi'an Key Laboratory of Extreme Environment and Protection Technology, School of Aerospace Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
Tunable perfect acoustic absorption at subwavelength thickness has been a prominent topic in scientific research and engineering applications. Although metamaterials such as labyrinthine metasurfaces and coiling-up-space metamaterials can achieve subwavelength low-frequency acoustic absorption, efficiently realizing tunable absorption under uniform and limited size conditions remains challenging. In this paper, we introduce a folded slit to enhance the micro-slit acoustic absorber, effectively improving its low-frequency acoustic absorption performance and successfully achieving a perfect acoustic absorption coefficient of 0.
View Article and Find Full Text PDFNanophotonics
April 2024
National Laboratory of Solid-State Microstructures, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
High-Q resonances in metasurfaces, stemming from symmetry-protected bound states in the continuum (BICs), have proven to be effective for achieving high-performance optical devices. However, the properties associated with symmetry-protected BICs are inherently limited, as even a slight variation in the asymmetry parameter leads to a noticeable shift in the resonance location. Herein, we introduce the concept of relative shift-induced quasi-BICs (QBICs) within dimerized silicon (Si) meta-lattices (DSMs), which can be excited when a nonzero relative shift occurs, a result of in-plane inversion symmetry breaking and Brillouin zone folding within the structure.
View Article and Find Full Text PDFNat Commun
November 2024
Department of Biomedical Engineering, University of Wisconsin-Madison Madison, Madison, WI, 53706, USA.
Polarization, temporal coherence, and spatial coherence are crucial for far-field thermal emission. However, achieving chiral thermal emission with both ultra-narrow bandwidth and ultrahigh directionality remains a challenge. In this study, we address this problem by combining the principles of band folding and chiral quasi bound states in the continuum.
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