Giant intrinsic chiro-optical activity in planar dielectric nanostructures
| Autor: | Cheng-Wei Qiu, Yao-Wei Huang, Alexander Y. Zhu, Mohammadreza Khorasaninejad, Wei Ting Chen, Aun Zaidi, Vyshakh Sanjeev, Federico Capasso |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
optical activity
Physics::Optics 02 engineering and technology Dielectric 01 natural sciences Article Photonic metamaterial 010309 optics Planar 0103 physical sciences dielectric Physics Birefringence business.industry Metamaterial Fano resonance 021001 nanoscience & nanotechnology Polarization (waves) Atomic and Molecular Physics and Optics Electronic Optical and Magnetic Materials chiral metasurface Optoelectronics 0210 nano-technology Chirality (chemistry) business extrinsic chirality |
| Zdroj: | Light, Science & Applications |
| ISSN: | 2047-7538 2095-5545 |
| Popis: | The strong optical chirality arising from certain synthetic metamaterials has important and widespread applications in polarization optics, stereochemistry and spintronics. However, these intrinsically chiral metamaterials are restricted to a complicated three-dimensional (3D) geometry, which leads to significant fabrication challenges, particularly at visible wavelengths. Their planar two-dimensional (2D) counterparts are limited by symmetry considerations to operation at oblique angles (extrinsic chirality) and possess significantly weaker chiro-optical responses close to normal incidence. Here, we address the challenge of realizing strong intrinsic chirality from thin, planar dielectric nanostructures. Most notably, we experimentally achieve near-unity circular dichroism with ~90% of the light with the chosen helicity being transmitted at a wavelength of 540 nm. This is the highest value demonstrated to date for any geometry in the visible spectrum. We interpret this result within the charge-current multipole expansion framework and show that the excitation of higher-order multipoles is responsible for the giant circular dichroism. These experimental results enable the realization of high-performance miniaturized chiro-optical components in a scalable manner at optical frequencies. Giant optical chirality has been realized at visible wavelengths in planar engineered surfaces. Strong optical chirality is desired for various applications. Metamaterials are promising for realizing this, but three-dimensional ones are difficult to make, while planar ones impart low chirality. Now, Alexander Zhu of Harvard University and co-workers have made metasurfaces consisting of an array of miniature gammadion-cross-shaped dielectric structures that gave a circular dichroism in transmission of 80% for green light, while numerical simulations suggested that 95% should be possible. Furthermore, 600-namometer-thick surfaces can provide a circular birefringence as large 60 degrees of polarization rotation, equivalent to 100,000 degrees per millimeter thickness — much larger than that measured in other media, whether natural or engineered. The metasurfaces could lead to high-performance flat devices for controlling the polarization of light beams in applications such as telecommunications. |
| Databáze: | OpenAIRE |
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