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IMAGE: a, sketch of a system with an array of main resonance modes a m connected via a series of connecting modes c m^((n)), with the decay rate κ m^((n)); b, sketch of a. view more
Credit: by Xinyao Huang, Cuicui Lu, Chao Liang, Honggeng Tao, and Yong-Chun Liu
Optical nonreciprocity, which prohibits the light field returning along the original path after passing through the optical system in one direction, is not only of vast interest to fundamental science, which brings us a deeper understanding of Lorentz reciprocity, time-reversal symmetry, and topological effects, but is also of great importance for realizing nonreciprocal optical and electromagnetics devices such as isolators, circulator and directional amplifiers, which are indispensable for applications ranging from optical communication to optical information processing.
Bloch oscillations (BOs) were initially predicted for electrons in a solid lattice as a static electric field is applied. Scientists in China created a synthetic frequency lattice in a fibre loop under detuned phase modulation and directly observed the frequency BOs in real time. The frequency spectrum in telecommunication band can be shifted as large as hundreds of GHz. The study may find applications in frequency manipulations in optical fiber communication systems.
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IMAGE: a, Modulation on the Coulomb interaction. (left) Illustration of increased screening of Coulomb interactions in 2D semiconductors. (right) Schematic illustration showing the impact of increased screening of Coulomb interactions on. view more
Credit: by Yuhan Wang, Zhonghui Nie, Fengqiu Wang
Two-dimensional (2D) semiconductors can host a rich set of excitonic species because of the greatly enhanced Coulomb interactions. The excitonic states can exhibit large oscillator strengths and strong light-matter interactions, and dominate the optical properties of 2D semiconductors. In addition, because of the low dimensionality, excitonic dynamics of 2D semiconductors can be more susceptible to various external stimuli, enriching the possible tailoring methods that can be exploited. Understanding the factors that can influence the dynamics of the optically-generated excited states represents an important aspect of excitonic physics in 2D semiconductors, and is als
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IMAGE: A new $7.5 million Department of Defense grant is seeking to build a super camera that combines multiple metasurfaces that together can extract almost every bit of information that light. view more
Credit: Mark Brongersma, Stanford
DURHAM, N.C. - Engineers at Duke University are leading a nationwide effort to develop a camera that takes pictures worth not just a thousand words, but an entire encyclopedia.
Funded by a five-year, $7.5 million grant through the Department of Defense s Multidisciplinary University Research Initiative (MURI) competition, the team will develop a super camera that captures just about every type of information that light can carry, such as polarization, depth, phase, coherence and incidence angle. The new camera will also use edge computing and hardware acceleration technologies to process the vast amount of information it captures within the device in real-time.
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IMAGE: a, A 3D Dirac sonic crystal and its transition to a Weyl sonic crystal. a Photograph of the 3D Dirac sonic crystal. b,c Geometry of the unit cells for b. view more
Credit: by Boyang Xie, Hui Liu, Hua Cheng, Zhengyou Liu, Jianguo Tian, and Shuqi Chen
Recently, the three-dimensional (3D) Dirac points and 3D Dirac semimetals have attracted tremendous attention in the field of topological physics. The 3D Dirac point is a fourfold band crossing in 3D momentum space, which can be view as the degeneracy of two opposite Weyl points. However, the 3D Dirac points can be described by the Z2 topological invariant other than the Chern number. The topological property of 3D Dirac point is not totally the same as Weyl point. Besides, the transition from Dirac points to Weyl points has not been experimentally studied in both photonic and acoustic systems so far. Therefore, the theoretical or experimental breakthrough of 3D Dirac points and the study on their transition