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Register a new userOptical cages made of graphitic frameworks
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In pursuit of infrared (IR) radiation absorbers, we examine quasicrystal structures made of graphite wires. An array of graphitic cages and cage-within-cage, and whose overall dimensions is smaller than the radiation wavelength exhibit a flat absorption spectrum, A~0.83 between 10-30 microns and a quality loss factor of L~0.83 (L=A/Q, with Q, the quality factor). Simulations at microwave frequencies show multiple absorption lines. In the case of a cage within cage, energy is funneled towards the inner cage which result in a rather hot structure. Applications are envisioned as anti-fogging surfaces, EM shields and energy harvesting.
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We examine array of metal-mesh frameworks for their wide-band absorption. These take the form of quasi-crystal optical cages. An array of cages tends to focus the incoming radiation within each framework. An array of cage-within-cage funnels the radiation from the outer cage to its inner core even further.
Recently, we developed a new family of 3D photonic hollow resonators which theoretically allow tight confinement of light in a fluid (gaz or liquid): the photon cages. These new resonators could be ideal for sensing applications since they not only localize the electromagnetic energy in a small mode volume but also enforce maximal overlap between this localized field and the environment (i.e. a potential volume of nano-particles). In this work, we will present numerical and experimental studies of the interaction of a photon cage optical mode with nano-emitters. For this, PbS quantum dot emitters in a PDMS host matrix have been introduced in photon cages designed to have optimal confinement properties when containing a PDMS-based active medium. Photoluminescence measurements have been performed and the presence of quantum dot emitters in the photon cages has been demonstrated.
Optical bottle beams can be used to trap atoms and small low-index particles. We introduce a figure of merit for optical bottle beams, specifically in the context of optical traps, and use it to compare optical bottle-beam traps obtained by three different methods. Using this figure of merit and an optimization algorithm, we identified optical bottle-beam traps based on a Gaussian beam illuminating a metasurface that are superior in terms of power efficiency than existing approaches. We numerically demonstrate a silicon metasurface for creating an optical bottle-beam trap.
Optical nanoantennas, i.e., elements transforming localized light or waveguide modes into freely propagating fields and vice versa, are vital components for modern nanophotonics. Optical antennas have been demonstrated to cause the Dicke superradiance effect, i.e., collective spontaneous emission of quantum sources. However, the impact of coherent excitation on the antenna performance, such as directivity, efficiency, and Purcell effect, remains mostly unexplored. Herein, using full-wave numerical simulations backed by a quantum model, we unveil that coherent excitation allows controlling antenna multipoles, on-demand excitation of nonradiative states, enhanced directivity and improves antenna radiation efficiency. This collective excitation corresponds to the states with nonzero dipole moment in the quantum picture, where the quantum phase is well defined. The results of this work bring another degree of freedom - the collective phase of an ensemble of quantum emitters - to control optical nanoantennas and, as such, pave the way to the use of collective excitations for nanophotonic devices with superb performance. To make the discussion independent of the frequency range, we consider the all-dielectric design and use dimensionless units.
Whispering gallery modes (WGMs), circulating modes near the surface of a spheroidal material, have been known to exhibit high quality factors for both acoustic and electromagnetic waves. Here, we report an electro-optomechanical system, where the overlapping WGMs of acoustic and optical waves along the equator of a dielectric sphere strongly couple to each other. The triple-resonance phase-matching condition provides a large enhancement of the Brillouin scattering only in a single sideband, and conversion from the input radio-frequency signal exciting the acoustic mode to the output optical signal is observed.
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