The development of flat, compact beam‐steering devices with no bulky moving parts is opening up a new route to a variety of exciting applications, such as LIDAR scanning systems for autonomous ...vehicles, robotics and sensing, free‐space, and even surface wave optical signal coupling. In this paper, the design, fabrication and characterization of innovative, nonvolatile, and reconfigurable beam‐steering metadevices enabled by a combination of optical metasurfaces and chalcogenide phase‐change materials is reported. The metadevices reflect an incident optical beam in a mirror‐like fashion when the phase‐change layer is in the crystalline state, but reflect anomalously at predesigned angles when the phase‐change layer is switched into its amorphous state. Experimental angle‐resolved spectrometry measurements verify that fabricated devices perform as designed, with high efficiencies, up to 40%, when operating at 1550 nm. Laser‐induced crystallization and reamorphization experiments confirm reversible switching of the device. It is believed that reconfigurable phase‐change‐based beam‐steering and beam‐shaping metadevices, such as those reported here, can offer real applications advantages, such as high efficiency, compactness, fast switching times and, due to the nonvolatile nature of chalcogenide phase‐change materials, low power consumption.
Beam‐steering devices with no moving parts are likely to find widespread applications in areas such as LIDAR scanning systems for autonomous vehicles, robotics and sensing, telecommunications, and optical signal coupling. Here, the design, fabrication and characterization of innovative, fast, nonvolatile, and reconfigurable beam‐steering devices enabled by a combination of optical metasurfaces and chalcogenide phase‐change materials is reported.
Atomically thin layers of two-dimensional materials can be assembled in vertical stacks that are held together by relatively weak van der Waals forces, enabling coupling between monolayer crystals ...with incommensurate lattices and arbitrary mutual rotation
. Consequently, an overarching periodicity emerges in the local atomic registry of the constituent crystal structures, which is known as a moiré superlattice
. In graphene/hexagonal boron nitride structures
, the presence of a moiré superlattice can lead to the observation of electronic minibands
, whereas in twisted graphene bilayers its effects are enhanced by interlayer resonant conditions, resulting in a superconductor-insulator transition at magic twist angles
. Here, using semiconducting heterostructures assembled from incommensurate molybdenum diselenide (MoSe
) and tungsten disulfide (WS
) monolayers, we demonstrate that excitonic bands can hybridize, resulting in a resonant enhancement of moiré superlattice effects. MoSe
and WS
were chosen for the near-degeneracy of their conduction-band edges, in order to promote the hybridization of intra- and interlayer excitons. Hybridization manifests through a pronounced exciton energy shift as a periodic function of the interlayer rotation angle, which occurs as hybridized excitons are formed by holes that reside in MoSe
binding to a twist-dependent superposition of electron states in the adjacent monolayers. For heterostructures in which the monolayer pairs are nearly aligned, resonant mixing of the electron states leads to pronounced effects of the geometrical moiré pattern of the heterostructure on the dispersion and optical spectra of the hybridized excitons. Our findings underpin strategies for band-structure engineering in semiconductor devices based on van der Waals heterostructures
.
Abstract
Strong coupling of monolayer metal dichalcogenide semiconductors with light offers encouraging prospects for realistic exciton devices at room temperature. However, the nature of this ...coupling depends extremely sensitively on the optical confinement and the orientation of electronic dipoles and fields. Here, we show how plasmon strong coupling can be achieved in compact, robust, and easily assembled gold nano-gap resonators at room temperature. We prove that strong-coupling is impossible with monolayers due to the large exciton coherence size, but resolve clear anti-crossings for greater than 7 layer devices with Rabi splittings exceeding 135 meV. We show that such structures improve on prospects for nonlinear exciton functionalities by at least 10
4
, while retaining quantum efficiencies above 50%, and demonstrate evidence for superlinear light emission.
Abstract
Energy relaxation of photo-excited charge carriers is of significant fundamental interest and crucial for the performance of monolayer transition metal dichalcogenides in optoelectronics. ...The primary stages of carrier relaxation affect a plethora of subsequent physical mechanisms. Here we measure light scattering and emission in tungsten diselenide monolayers close to the laser excitation energy (down to ~0.6 meV). We reveal a series of periodic maxima in the hot photoluminescence intensity, stemming from energy states higher than the A-exciton state. We find a period ~15 meV for 7 peaks below (Stokes) and 5 peaks above (anti-Stokes) the laser excitation energy, with a strong temperature dependence. These are assigned to phonon cascades, whereby carriers undergo phonon-induced transitions between real states above the free-carrier gap with a probability of radiative recombination at each step. We infer that intermediate states in the conduction band at the Λ-valley of the Brillouin zone participate in the cascade process of tungsten diselenide monolayers. This provides a fundamental understanding of the first stages of carrier–phonon interaction, useful for optoelectronic applications of layered semiconductors.
We present the development and testing of a Micromegas detector prototype and its front end intended to be a candidate for the substitutions of some of the Multiwire Proportional Chambers in the ...future AMBER (NA66) experiment at CERN. Results of the test of the first small size prototype are discussed.
•The Apparatus for Mesons and Baryon Experimental Research at CERN is requiring new detectors.•Micro-Pattern Gaseous Detector technology is a good candidate for the future upgrades.•MICRO-MEsh GAS detector read-out by the Torino Integrated Gem Electronics for Read-out ASIC.
For many of the envisioned optoelectronic applications of graphene, it is crucial to understand the subpicosecond carrier dynamics immediately following photoexcitation and the effect of ...photoexcitation on the electrical conductivity-the photoconductivity. Whereas these topics have been studied using various ultrafast experiments and theoretical approaches, controversial and incomplete explanations concerning the sign of the photoconductivity, the occurrence and significance of the creation of additional electron-hole pairs, and, in particular, how the relevant processes depend on Fermi energy have been put forward. We present a unified and intuitive physical picture of the ultrafast carrier dynamics and the photoconductivity, combining optical pump-terahertz probe measurements on a gate-tunable graphene device, with numerical calculations using the Boltzmann equation. We distinguish two types of ultrafast photo-induced carrier heating processes: At low (equilibrium) Fermi energy (
≲ 0.1 eV for our experiments), broadening of the carrier distribution involves interband transitions (interband heating). At higher Fermi energy (
≳ 0.15 eV), broadening of the carrier distribution involves intraband transitions (intraband heating). Under certain conditions, additional electron-hole pairs can be created carrier multiplication (CM) for low
, and hot carriers (hot-CM) for higher
. The resultant photoconductivity is positive (negative) for low (high)
, which in our physical picture, is explained using solely electronic effects: It follows from the effect of the heated carrier distributions on the screening of impurities, consistent with the DC conductivity being mostly due to impurity scattering. The importance of these insights is highlighted by a discussion of the implications for graphene photodetector applications.
Experimental results on laminar propane flames propagating in a narrow gap between parallel glass plates are presented. Development and evolution of cellular flame structure is demonstrated by video ...and long-exposure photo recordings for stoichiometric and fuel-rich mixtures with equivalence ratio of 1.0:1.25. It is shown that in narrow gaps the lateral cell sizes by far exceed the gap width. Average flame propagation speed obtained for gap widths between 2.5 and 4.4 mm is shown to depend significantly on the gap width due to the effect of heat losses on the normal flame speed, as well as due to cooling of products behind the flame. Effect of gap width on the cellular structure is demonstrated, and statistical characteristics of the cells are obtained for two gap widths. Flame propagation patterns are also obtained for non-central ignition performed at one or simultaneously at two points.
Abstract
Interlayer excitons in layered materials constitute a novel platform to study many-body phenomena arising from long-range interactions between quantum particles. Long-lived excitons are ...required to achieve high particle densities, to mediate thermalisation, and to allow for spatially and temporally correlated phases. Additionally, the ability to confine them in periodic arrays is key to building a solid-state analogue to atoms in optical lattices. Here, we demonstrate interlayer excitons with lifetime approaching 0.2 ms in a layered-material heterostructure made from WS
2
and WSe
2
monolayers. We show that interlayer excitons can be localised in an array using a nano-patterned substrate. These confined excitons exhibit microsecond-lifetime, enhanced emission rate, and optical selection rules inherited from the host material. The combination of a permanent dipole, deterministic spatial confinement and long lifetime places interlayer excitons in a regime that satisfies one of the requirements for simulating quantum Ising models in optically resolvable lattices.
All-dielectric metasurfaces comprising arrays of nanostructured high-refractive-index materials are re-imagining what is achievable in terms of the manipulation of light. However, the functionality ...of conventional dielectric-based metasurfaces is fixed by design; thus, their optical response is locked in at the fabrication stage. A far wider range of applications could be addressed if dynamic and reconfigurable control were possible. We demonstrate this here via the novel concept of hybrid metasurfaces, in which reconfigurability is achieved by embedding sub-wavelength inclusions of chalcogenide phase-change materials within the body of silicon nanoresonators. By strategic placement of an ultra-thin
G
e
2
S
b
2
T
e
5
layer and reversible switching of its phase-state, we show individual, multilevel, and dynamic control of metasurface resonances. We showcase our concept via the design, fabrication, and characterization of metadevices capable of dynamically filtering and modulating light in the near infrared (O and C telecom bands), with modulation depths as high as 70% and multilevel tunability. Finally, we show numerically how the same approach can be re-scaled to shorter wavelengths via appropriate material selection, paving the way to additional applications, such as high-efficiency vivid structural color generators in the visible spectrum. We believe that the concept of hybrid all-dielectric/phase-change metasurfaces presented in this work could pave the way for a wide range of design possibilities in terms of multilevel, reconfigurable, and high-efficiency light manipulation.
BCD-022 is a trastuzumab biosimilar which was shown to be equivalent to reference trastuzumab in a wide panel of physicochemical studies as well as preclinical studies in vitro and in vivo. ...International multicenter phase III clinical trial was conducted to comparatively assess efficacy and safety of BCD-022 and reference trastuzumab in combination with paclitaxel used as the therapy of metastatic HER2(+) breast cancer. Pharmacokinetics and immunogenicity were also studied.
Patients with no previous treatment for metastatic HER2(+) breast cancer were randomly assigned 1:1 to BCD-022 or reference trastuzumab and were treated with trastuzumab + paclitaxel. Therapy continued for 6 cycles of therapy (every 3 weeks), until progression of the disease or unbearable toxicity. Primary study endpoint was overall response rate. Study goal was to prove equivalent efficacy of BCD-022 and reference trastuzumab. Equivalence margins for 95% CI for difference in overall response rates were set at - 20%; 20%.
In total 225 patients were enrolled into the study, 115 in BCD-022 arm and 110 in reference trastuzumab arm. Overall response rate was 49.6% in BCD-022 arm and 43.6% in reference trastuzumab arm. Limits of 95% CI for difference of overall response rates between arms were (- 8.05)-19.89%, thus, they lied within predetermined equivalence margins - 20%; 20%. Profile of adverse events was similar between groups (any AEs were reported in 93.81% of patients in BCD-022 arm and 94.55% of patients in reference arm). No unexpected adverse reactions were reported throughout the study. No statistically significant differences regarding antibody occurrence rate (either BAb or NAb) was found between BCD-022 (n = 3; 2.65%) and comparator (n = 4; 3.64%). Both drug products are characterized with low occurrence rate and short life of anti-trastuzumab antibodies. Pharmacokinetics assessment after 1st and 6th study drug injection also demonstrated equivalent PK parameters by all outcome measures: AUC
, С
, Т
, T
. Analysis of C
did not reveal any significant inter-group differences as well.
Thus, results of this study have demonstrated therapeutic equivalence of trastuzumab biosimilar BCD-022 and referent trastuzumab drug.
The trial was registered with ClinicalTrials.gov (Study Number NCT01764022 ). The date of registration was January 9, 2013.
PDF
