Search

To accelerate the design of metamaterial microwave absorbers (MMAs), in this work, we developed a deep neural network model to predict the spectrum based on the known structural parameters at the beginning. Then, a tandem network was constructed, which can predict the geometries of an unknown MMA based on a desired absorption characteristics with a small mean square errors of validation set (8.3 × 10−4). With the help of the tandem network, a dual band absorber that achieves an absorption rate greater than 85% in the range of 5.1–14 GHz was obtained. By comparing with traditional methods, the demonstrated methodology can greatly accelerate the whole process and realize an inverse design. [ABSTRACT FROM AUTHOR]

Cavity polaritons, originating from the strong coupling effect between cavity modes and excitons, have been tremendously investigated because of their high potential in new or quantum optoelectronic devices. Among them, realization of their dynamic controllability is highly desirable for real applications. In this work, we present a dynamic modulation of cavity polaritons via strain-engineering in the ZnO whispering gallery microcavity. By using a home-made strain apparatus, a nearly uniaxial stress is precisely applied to ZnO microwires, thus inducing an internal strain along its c-axis. Dynamic tuning of cavity polariton modes is clearly characterized by angle-resolved microphotoluminescence spectroscopy. The coupled oscillator's model with fitting parameters of strain-dependent excitons' energies can well describe the modes' redshift. Moreover, we show that the modes' redshift can also be understood by the strain-induced refractive index increase, described by the Lorentz model, of which the underlying mechanism is also related to light-exciton strong coupling. Finally, the strain-engineered dynamic tuning of polariton lasing modes is demonstrated as well, and this actually provides convincing evidence for the polariton states surviving above the threshold. This work indicates that strain-engineered cavity polaritons would pave an alternative way for developing polariton-based integrated or flexible optoelectronic devices. [ABSTRACT FROM AUTHOR]

A robust exciton-polariton effect in a ZnO whispering gallery microcavity well above room temperature is presented. The lower polariton branches are tuned by current induced thermal effect. The red shift can be as large as ∼40 meV. It is found that the strong coupling can be preserved and the polariton-phonon interaction quenching effect remains up to ∼550 K, while the Rabi splitting is about 330 meV. The tuning speed is in the order of millisecond, showing its potential in polariton-based optoelectronic device application. [ABSTRACT FROM AUTHOR]

High-quality In2O3 polyhedrons with different morphologies were fabricated and studied as vertical Fabry-Pérot (FP) microcavities. By using the microphotoluminescence technique, we identified a series of FP resonant modes in such systems, whose energies lie in the visible spectral range and are scalable with the cavity size. Experimental results are in good agreement with full-wave numerical simulations and can be well fitted with a plane wave interference model. Compared with the conventional one dimensional nanowire/nanobelt FP cavities, such vertical FP microcavities have much less optical loss and provide efficient optical modulations, which may find many applications in developing optical devices. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) to NIR upconversion emission is investigated in Tm3+/Yb3+/Li+ triply doped Y2O3 nanocrystals. Li+ ions doped in Y2O3:Tm3+/Yb3+ nanocrystals can greatly enhance the NIR upconversion emission intensity of Tm3+ ions. The abnormal shift of the (222) diffraction peak position determined from x-ray diffraction measurements is discussed, by introducing Li+ ions in the Y2O3:Tm3+/Yb3+ nanocrystals. The cause of the enhancement is the modification of the local symmetry induced by the Li+ ions, which increases the intra-4f transitions of Tm3+ ion. Li+ ions doped in Y2O3:Tm3+/Yb3+ nanocrystals also can reduce the OH groups, dissociate the Yb3+ and Tm3+ ion clusters, and create the oxygen vacancies, which are the other reasons for enhancing the upconversion emission intensities. This material may be promising for in vitro and in vivo bioimaging probes. [ABSTRACT FROM AUTHOR]

Nearly perfect In2O3 octahedra were fabricated and studied as optical resonators. Electron microscopy images revealed that the octahedra have single-crystal structures, very smooth surfaces, and regular geometric morphologies. Bow-tielike modes in the visible spectral range were clearly observed at room temperature by using the spatially resolved spectroscopic technique. The experimental observations are described and fitted well with the plane wave interference model and Cauchy dispersion formula for refractive indices. [ABSTRACT FROM AUTHOR]

We report on the use of In2O3 nanowires with hexagonal cross section as optical whispering gallery resonators. The single-crystal In2O3 nanowires were fabricated by an in situ thermal oxidation method. Whispering gallery modes (WGMs) in the visible spectral range were directly observed at room temperature. Due to the slight tapering of the nanowires, the energies and orders of the WGMs were modulated when excitations were scanned along the c-axis (length) of the nanowires. The experimental results were explained and fitted well with a plane wave interference model and Cauchy dispersion formula for refractive indices. [ABSTRACT FROM AUTHOR]