catena-Poly[[tri-n-butyl­tin(IV)]-μ-2-thio­phene­acetato]

The title compound, [Sn(C4H9)3(C6H5O2S)]n, possesses an infinite chain structure. The SnO2C3 centre has a distorted trigonal-bipyramidal geometry (τ = 0.145) with the O atoms in the axial positions. Atoms of the thio­phene group S1 and C4 are disordered over two sites The S atom and one C atom, with attached H atom, of the thiophene ring are disordered over two positions; the site occupancy factors are ca 0.7 and 0.3

2-(Ethoxy­carbon­yl)quinolinium butyl­trichlorido(quinoline-2-carboxyl­ato-κ2 N,O)stannate(IV)

In the title compound, (C12H12NO2)[Sn(C4H9)(C10H6NO2)Cl3], the Sn atom is coordinated by one O and one N atom of a quinolinium-2-carboxyl­ate anion, three Cl atoms and one butyl ligand within a distorted octa­hedron. Three C atoms of the butyl ligand are disordered and were refined using a split model; the site occupancies are 0.57 and 0.43. The NH group of the cation is involved in inter­molecular N—H⋯O hydrogen bonding

VAST: A Vision-Audio-Subtitle-Text Omni-Modality Foundation Model and Dataset

Vision and text have been fully explored in contemporary video-text foundational models, while other modalities such as audio and subtitles in videos have not received sufficient attention. In this paper, we resort to establish connections between multi-modality video tracks, including Vision, Audio, and Subtitle, and Text by exploring an automatically generated large-scale omni-modality video caption dataset called VAST-27M. Specifically, we first collect 27 million open-domain video clips and separately train a vision and an audio captioner to generate vision and audio captions. Then, we employ an off-the-shelf Large Language Model (LLM) to integrate the generated captions, together with subtitles and instructional prompts into omni-modality captions. Based on the proposed VAST-27M dataset, we train an omni-modality video-text foundational model named VAST, which can perceive and process vision, audio, and subtitle modalities from video, and better support various tasks including vision-text, audio-text, and multi-modal video-text tasks (retrieval, captioning and QA). Extensive experiments have been conducted to demonstrate the effectiveness of our proposed VAST-27M corpus and VAST foundation model. VAST achieves 22 new state-of-the-art results on various cross-modality benchmarks. Code, model and dataset will be released at https://github.com/TXH-mercury/VAST.Comment: 23 pages, 5 figure

Controlling photonic spin Hall effect via exceptional points

The photonic spin Hall effect (SHE), featured by a spin-dependent transverse shift of an impinging optical beam driven by its polarization handedness, has many applications including precise metrology and spin-based nanophotonic devices. It is highly desirable to control and enhance the photonic SHE. However, such a goal remains elusive, due to the weak spin-orbit interaction of light, especially for systems with optical loss. Here we reveal a flexible way to modulate the photonic SHE via exceptional points, by exploiting the transverse shift in a parity-time (PT) symmetric system with balanced gain and loss. The underlying physics is associated with the near-zero value and abrupt phase jump of the reflection coefficients at exceptional points. We find that the transverse shift is zero at exceptional points, but it is largely enhanced in their vicinity. In addition, the transverse shift switches its sign across the exceptional point, resulting from spontaneous PT-symmetry breaking. Due to the sensitivity of transverse shift at exceptional points, our work also indicates that the photonic SHE can enable a precise way to probe the location of exceptional point in photonic systems.Comment: 14 pages, 4 figure

Two-photon-induced singlet fission in rubrene single crystal

The two-photon-induced singlet fission was observed in rubrene single crystal and studied by use of femtosecond pump-probe spectroscopy. The location of two-photon excited states was obtained from the nondegenerate two-photon absorption (TPA) spectrum. Time evolution of the two-photon-induced transient absorption spectra reveals the direct singlet fission from the two-photon excited states. The TPA absorption coefficient of rubrene single crystal is 52 cm/GW at 740 nm, as obtained from Z-scan measurements. Quantum chemical calculations based on time-dependent density functional theory support our experimental data

Broadband surface-wave transformation cloak

Guiding surface electromagnetic waves around disorder without disturbing the wave amplitude or phase is in great demand for modern photonic and plasmonic devices, but is fundamentally difficult to realize because light momentum must be conserved in a scattering event. A partial realization has been achieved by exploiting topological electromagnetic surface states, but this approach is limited to narrow-band light transmission and subject to phase disturbances in the presence of disorder. Recent advances in transformation optics apply principles of general relativity to curve the space for light, allowing one to match the momentum and phase of light around any disorder as if that disorder were not there. This feature has been exploited in the development of invisibility cloaks. An ideal invisibility cloak, however, would require the phase velocity of light being guided around the cloaked object to exceed the vacuum speed of light—a feat potentially achievable only over an extremely narrow band. In this work, we theoretically and experimentally show that the bottlenecks encountered in previous studies can be overcome. We introduce a class of cloaks capable of remarkable broadband surface electromagnetic waves guidance around ultrasharp corners and bumps with no perceptible changes in amplitude and phase. These cloaks consist of specifically designed nonmagnetic metamaterials and achieve nearly ideal transmission efficiency over a broadband frequency range from 0+ to 6 GHz. This work provides strong support for the application of transformation optics to plasmonic circuits and could pave the way toward high-performance, large-scale integrated photonic circuits.National Natural Science Foundation (China) (Grant 61322501)National Natural Science Foundation (China) (Grant 61275183)National Top-Notch Young Professionals Program (Grant FANEDDC-200950)Program for New Century Excellent Talents (NCET-12-0489)Fundamental Research Funds for the Central Universities (Grant FRFCU-2014XZZX003-24)Nanyang Assistant Professorship Start-Up GrantSingapore. Ministry of Education (Grant Tier 1 RG27/12)Singapore. Ministry of Education (Grant MOE2011-T3-1-005)Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies (Contract W911NF-13-D-0001)United States. Dept. of Energy (Solid-State Solar-Thermal Energy Conversion Center Grant de-sc0001299

All-Inorganic Colloidal Perovskite Quantum Dots: A New Class of Lasing Materials with Favorable Characteristics

I), which were very recently reported as a high effi ciency luminescent materials. The CsPbX 3 IPQDs adopted here were fabricated following a recipe slightly modifi ed from the literature (see details in Experimental Section). Here, we present a new class of lasing materials with outstanding optical gain signatures of combined advantages of both QDs and halide perovskites: the colloidal all-inorganic cesium lead halide perovskite QDs (IPQDs) (CsPbX 3 , X = Cl, Br, Adv. Mater. 2015