Monolithic CMOS-compatible zero-index metamaterials

Zero-index materials exhibit exotic optical properties that can be utilized for integrated-optics applications. However, practical implementation requires compatibility with complementary metallic-oxide-semiconductor (CMOS) technologies. We demonstrate a CMOS-compatible zero-index metamaterial consisting of a square array of air holes in a 220-nm-thick silicon-on-insulator (SOI) wafer. This design is achieved through a Dirac-cone dispersion. The metamaterial is entirely composed of silicon and offers compatibility through low-aspect-ratio structures that can be simply fabricated in a standard device layer. This platform enables mass adoption and exploration of zero-index-based photonic devices at low cost and high fidelity.Comment: 18 pages, 4 figure

Reduced Nogo-P3 in adults with developmental coordination disorder (DCD)

Nogo-N2 is associated with the premotor cognitive process that precedes motor response (e.g., conflict monitoring), whereas Nogo-P3 is related to the inhibition of the actual motor response. We examined the influence of motor clumsiness of developmental coordination disorder (DCD) on components of the event-related potential in a Go/Nogo task. Participants were healthy adults (N = 81) that were classified into control and DCD groups based on the Movement Assessment Battery for Children Second Edition. We manipulated the difficulty in stopping a response by varying the frequency of Nogo stimuli in a response task into rare (20%) and frequent (80%) conditions, and Nogo-N2 and Nogo-P3 were calculated from electroencephalograms (EEGs) during the Go/Nogo tasks. The commission error rate in the rare condition was significantly higher in the DCD group than in the control group, indicating that motor clumsiness decreases task performance. There were no differences in Nogo-N2 between DCD and control groups. However, Nogo-P3 in the rare condition was reduced in the DCD group compared to the control group. These results suggest that the influence of motor clumsiness is limited to the cognitive process after the initiation of the actual motor response.Peer reviewe

Coherent control of high efficiency metasurface beam deflectors with a back partial reflector

Recently, coherent control of absorption in metallic metasurfaces has been demonstrated, and this phenomenon was applied to intriguing light-by-light switching operation. Here we experimentally demonstrate coherent control of beam deflection by high-efficiency metasurfaces for the first time. Although the beam deflection efficiency by a metasurface is generally small, high-efficiency metasurfaces, which consist of a single layer metasurface with a back reflector, are known to exhibit significantly high deflection efficiency. A key point of our study is to replace the back reflector with a partial reflector instead, which enables light-by-light control of a high-efficiency metasurface with a pair of counter-propagating coherent beam inputs. By adjusting the partial reflector thickness appropriately, the proposed device outperforms ones without a reflector, especially for the deflection efficiency. We finally experimentally demonstrate the expected operation of the fabricated device at a visible wavelength, which reveals that the deflection efficiency of 45% (49% in theory). This result demonstrates highly efficient light-by-light control of the beam deflection by a metasurface, which opens up possible applications to ultrathin photonic devices for linear all-optical switching and logic functions