In the recent years, metasurfaces, being flat and lightweight, have been designed to replace bulky optical components with various functions. We demonstrate a monolithic Micro-Electro-Mechanical System (MEMS) integrated with a metasurface-based flat lens that focuses light in the mid-infrared spectrum. A two-dimensional scanning MEMS platform controls the angle of the lens along the two orthogonal axes (tip-tilt) by ±9 degrees, thus enabling dynamic beam steering. The device can compensate for off-axis incident light and thus correct for aberrations such as coma. We show that for low angular displacements, the integrated lens-on-MEMS system does not affect the mechanical performance of the MEMS actuators and preserves the focused beam profile as well as the measured full width at half maximum. We envision a new class of flat optical devices with active control provided by the combination of metasurfaces and MEMS for a wide range of applications, such as miniaturized MEMS-based microscope systems, LIDAR scanners, and projection systems.
The possibility of chaos control in biological systems has been stimulated by recent advances in the study of heart and brain tissue dynamics. More recently, some authors have conjectured that such a method might be applied to population dynamics and even play a nontrivial evolutionary role in ecology. In this paper we explore this idea by means of both mathematical and individual-based simulation models. Because of the intrinsic noise linked to individual behavior, controlling a noisy system becomes more difficult but, as shown here, it is a feasible task allowed to be experimentally tested.
Optical metasurfacesplanar
nanostructured devices that
can arbitrarily tailor the wavefront of lightmay be reconfigured
by changing their dielectric environment. The application of external
stimuli to liquid crystals is a particularly promising means of tuning
the optical properties of embedded metasurfaces because of liquid
crystals’ large and broadband optical anisotropy. However,
the detailed behavior of liquid crystals immediately adjacent to the
nanostructured meta-atoms elements is often overlooked, despite the
optics of the device depending sensitively on this behavior (e.g.,
the spectral position of the meta-atom resonances). This is of increasing
concern as the wavelength of operation further approaches the short-wavelength
end of the visible spectrum and, therefore, the length scale of the
inhomogeneities in the liquid crystal director field. In this manuscript,
we undertake a fully comprehensive study, across the metasurface geometrical
parameter space, of broadband (450–700 nm) all-dielectric
liquid crystal tunable metasurfaces operating in the visible. Through
combined experimental characterization, liquid crystal modeling, and
optical simulations, we reveal and quantify the improved accuracy
with which the optical properties of the liquid crystal tunable metasurfaces
may be described, and identify the underlying physical mechanism:
the three-dimensional spatial overlap of the liquid crystal director
field and metasurface optical near fields in the vicinity of the meta-atoms.
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