789 research outputs found
Optomechanical guitar: reconfiguring metamaterials with sub-wavelength spatial resolution
Optomechanical metamaterials, where optical signals actuate unique elements of the nanostructure at their eigenfrequency, can be used to modulate metamaterials with sub-wavelength spatial resolution. We demonstrate the first all-optically addressable metadevice operating in the near infrared
Intrinsic optical bistability in nanomechanical metamaterials at milliwatt power levels
We report the first demonstration of optical bistability in nanomechanical metamaterials - arrays of plasmonic or dielectric resonators on flexible nano-membranes. Bistability results from the nonlinearity of the near-field forces induced by light
Photonic Metamaterial Analogue of a Continuous Time Crystal
Time crystals are an eagerly sought phase of matter with broken
time-translation symmetry. Quantum time crystals with discretely broken
time-translation symmetry have been demonstrated in trapped ions, atoms and
spins while continuously broken time-translation symmetry has been observed in
an atomic condensate inside an optical cavity. Here we report that a classical
metamaterial nanostructure, a two-dimensional array of plasmonic metamolecules
supported on flexible nanowires, can be driven to a state possessing all of the
key features of a continuous time crystal: continuous coherent illumination by
light resonant with the metamolecules' plasmonic mode triggers a spontaneous
phase transition to a superradiant-like state of transmissivity oscillations,
resulting from many-body interactions among the metamolecules, characterized by
long-range order in space and time. The phenomenon is of interest to the study
of dynamic classical many-body states in the strongly correlated regime and
applications in all-optical modulation, frequency conversion and timing.Comment: 10 pages, 6 figure
Ultrafast all-optical switching via coherent modulation of metamaterial absorption
We report on the demonstration of a femtosecond all-optical modulator
providing, without nonlinearity and therefore at arbitrarily low intensity,
ultrafast light-by-light control. The device engages the coherent interaction
of optical waves on a metamaterial nanostructure only 30 nm thick to
efficiently control absorption of near-infrared (750-1040 nm) femtosecond
pulses, providing switching contrast ratios approaching 3:1 with a modulation
bandwidth in excess of 2 THz. The functional paradigm illustrated here opens
the path to a family of novel meta-devices for ultra-fast optical data
processing in coherent networks.Comment: 5 pages, 4 figure
Random access actuation of nanowire grid metamaterial
While metamaterials offer engineered static optical properties, future artificial media with dynamic random-access control over shape and position of meta-molecules will provide arbitrary control of light propagation. The simplest example of such a reconfigurable metamaterial is a nanowire grid metasurface with subwavelength wire spacing. Recently we demonstrated computationally that such a metadevice with individually controlled wire positions could be used as dynamic diffraction grating, beam steering module and tunable focusing element. Here we report on the nanomembrane realization of such a nanowire grid metasurface constructed from individually addressable plasmonic chevron nanowires with a 230 nm × 100 nm cross-section, which consist of gold and silicon nitride. The active structure of the metadevice consists of 15 nanowires each 18 μm long and is fabricated by a combination of electron beam lithography and ion beam milling. It is packaged as a microchip device where the nanowires can be individually actuated by control currents via differential thermal expansion
Robust Identification of Developmentally Active Endothelial Enhancers in Zebrafish Using FANS-Assisted ATAC-Seq
Identification of tissue-specific and developmentally active enhancers provides insights into mechanisms that control gene expression during embryogenesis. However, robust detection of these regulatory elements remains challenging, especially in vertebrate genomes. Here, we apply fluorescent-activated nuclei sorting (FANS) followed by Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq) to identify developmentally active endothelial enhancers in the zebrafish genome. ATAC-seq of nuclei from Tg(fli1a:egfp)(y1) transgenic embryos revealed expected patterns of nucleosomal positioning at transcriptional start sites throughout the genome and association with active histone modifications. Comparison of ATAC-seq from GFP-positive and -negative nuclei identified more than 5,000 open elements specific to endothelial cells. These elements flanked genes functionally important for vascular development and that displayed endothelial-specific gene expression. Importantly, a majority of tested elements drove endothelial gene expression in zebrafish embryos. Thus, FANS-assisted ATAC-seq using transgenic zebrafish embryos provides a robust approach for genome-wide identification of active tissue-specific enhancer elements
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