Showing 1–38 of 38 results for author: Xin, Y

Ambiguity-Free Inertial Measurement with Multi-Wavelength Atom Interferometry

Authors: Wei-Chen Jia, Yue Xin, Ke Shen, Yan-Ying Feng

Abstract: White-light interferometry enables ambiguity-free localization by synthesizing interference envelopes from multiple optical wavelengths, but no analogous capability has been realized for coherent matter waves. Here we report the first experimental demonstration of multi-wavelength atom interferometry, establishing the matter-wave counterpart of white-light interferometry. By exploiting counter-pro… ▽ More White-light interferometry enables ambiguity-free localization by synthesizing interference envelopes from multiple optical wavelengths, but no analogous capability has been realized for coherent matter waves. Here we report the first experimental demonstration of multi-wavelength atom interferometry, establishing the matter-wave counterpart of white-light interferometry. By exploiting counter-propagating atomic beams as multi-wavelength matter wave sources and synthesizing interference envelopes from their spectral components, we realize inertial measurements based on envelope localization rather than conventional fringe-phase estimation. The resulting multi-scale interferometric response provides ambiguity-free operation, a well-defined rotational scale factor, and reduced sensitivity to initial phase bias. As a proof of principle, we demonstrate simultaneous dual-axis rotation and acceleration sensing and directly resolve the phase ambiguity that fundamentally limits conventional open-loop atom interferometers. We further measure the Earth's rotation with a relative error of 4.3% and a long-term stability of 93 ppm at an averaging time of 15,000 s. Our results establish multi-wavelength atom interferometry as a new paradigm for coherent matter-wave sensing, extending the principles of white-light interferometry to atom optics and opening new opportunities for inertial sensing, geodesy, precision metrology, and inertial navigation. △ Less

Submitted 10 June, 2026; originally announced June 2026.

Comments: 10 pages,4 figures

Spectral-Domain Coherent Control of Broadband Raman Coupling in Atom Interferometry

Authors: Sheng-Zhe Wang, Wei-Chen Jia, Yue Xin, Qian-Lan Cai, Yingpeng Zhao, Yan-Ying Feng

Abstract: The performance of atom interferometers is commonly limited by the finite spectral acceptance of atomic beam splitters and mirrors, which restricts efficient coupling to atoms with large Doppler shifts and reduces the usable atomic flux. Here, we demonstrate spectral-domain coherent control of Raman coupling by engineering its effective two-photon spectrum. By synthesizing multiple frequency compo… ▽ More The performance of atom interferometers is commonly limited by the finite spectral acceptance of atomic beam splitters and mirrors, which restricts efficient coupling to atoms with large Doppler shifts and reduces the usable atomic flux. Here, we demonstrate spectral-domain coherent control of Raman coupling by engineering its effective two-photon spectrum. By synthesizing multiple frequency components, the Raman interaction simultaneously addresses a broad range of atomic velocities, effectively overcoming the conventional transit-time-limited linewidth. Implemented in a continuous atomic-beam Mach-Zehnder interferometer, where the transverse Doppler broadening is 17 times larger than the intrinsic Raman linewidth, this approach enhances the fringe contrast from 5.9(2)% to 15.1(2)%, indicating a substantial increase in effective atomic participation. Our results establish spectral-domain coherent control as a general strategy for achieving spectrally robust atom interferometry and open new opportunities for quantum sensing in systems with strong inhomogeneous broadening. △ Less

Submitted 4 April, 2026; originally announced April 2026.

Closed-loop dual-channel atomic beam interferometry beyond the half-fringe limit

Authors: Wei-Chen Jia, Yue Xin, Ke Shen, Zhi-Xin Meng, Xiang-Xiang Lu, Yi-Cheng Deng, Yuan-Xing Liu, Yan-Ying Feng

Abstract: Atom interferometric inertial sensors offer exceptional sensitivity but are fundamentally constrained by the periodic phase response of matter-wave interference, which imposes an intrinsic half-fringe dynamic-range limit and prevents continuous inertial tracking. In multi-axis configurations, additional cross coupling between acceleration and rotation further complicates closed-loop operation. Her… ▽ More Atom interferometric inertial sensors offer exceptional sensitivity but are fundamentally constrained by the periodic phase response of matter-wave interference, which imposes an intrinsic half-fringe dynamic-range limit and prevents continuous inertial tracking. In multi-axis configurations, additional cross coupling between acceleration and rotation further complicates closed-loop operation. Here we demonstrate the first dual-channel closed-loop operation of an atomic beam interferometer, realizing decoupled feedback control of acceleration- and rotation-induced phases and overcoming the half-fringe limitation. Using continuous, transversely cooled $^{87}$Rb atomic beams, the interferometric phases associated with rotation and acceleration are independently extracted, tracked across multiple fringes, and actively compensated through Raman frequency modulation. This closed-loop scheme enables unambiguous measurements up to $\pm1\,\mathrm{^{\circ}/s}$ in rotation and $\pm0.17\,\mathrm{g}$ in acceleration while maintaining high fringe contrast, corresponding to nearly two orders-of-magnitude extension beyond the conventional half-fringe limit. The sensor achieves a long-term stability of $4\times10^{-4}\,\mathrm{^{\circ}/h}$ for rotation and $4\,\mathrm{μg}$ for acceleration at an averaging time of $1000\,\mathrm{s}$. By converting the intrinsically periodic interferometric response into stabilized phase-encoded inertial channels, this work establishes a new operating regime for atomic beam interferometry and advances matter-wave sensors toward practical quantum inertial navigation under dynamic conditions. △ Less

Submitted 15 March, 2026; originally announced March 2026.

Comments: 6 pages,4 figures

Towards precision quantitative measurement of radiation reaction within the classical radiation-dominated regime

Authors: Minghao Ma, Ke Liu, Ge Zhou, Zhida Yang, Yulin Xin, Jiadong Yang, Pengfei Zhu, Yipeng Wu, Min Chen, Tongpu Yu, Wenchao Yan, Jie Zhang

Abstract: Radiation reaction (RR) is a fundamental yet incompletely validated process in laser-particle interactions, since it lacks quantitatively definitive experimental verifications, especially the transition from classical to quantum regime. Herein, we propose a novel experimental scenario for investigating radiation RR within the classical radiation-dominated regime (CRDR), via the collision of a high… ▽ More Radiation reaction (RR) is a fundamental yet incompletely validated process in laser-particle interactions, since it lacks quantitatively definitive experimental verifications, especially the transition from classical to quantum regime. Herein, we propose a novel experimental scenario for investigating radiation RR within the classical radiation-dominated regime (CRDR), via the collision of a high-intensity petawatt-class laser with a tens-of-MeV electron beam from a LINAC. This approach enables access to a distinct parameter regime wherein RR dominates electron dynamics while quantum effects remain modest. Numerical simulations demonstrate that three key observables exist for identifying the RR within this CRDR regime: (i) quantitative measurement of energy spectra to validate the quantum correction factor; (ii) control of the collision time delay with charge-counting to map intensity dependence of RR; and (iii) verification of large angle ($90^\circ$) photon emission under the recoil condition $2γ\gtrsim a_0$. These experimental measurements will establish the benchmarks for RR models spanning the classical-to-quantum regime, thereby providing critical insights into fundamental strong-field quantum electrodynamics. △ Less

Submitted 4 January, 2026; originally announced January 2026.

From Disorder to Function: Entropy-Engineered Broadband Photonics with Ion-Transport-Stabilized Spectral Fidelity

Authors: Yuxiang Xin, Chen-Xin Yu, Jianru Wang, Jianbo Jin, Minliang Lai, Yinan Wang, Shuwen Yan, Gu-wen Chen, Liang Fan, Xiachu Xiao, Yutao Yang, Luying Li, Han Wang, Zhi-Pan Liu, Jiang Tang, Li-Ming Yang, Zhuolei Zhang

Abstract: The high-entropy halide-perovskite field has expanded rapidly, yet a key gap remains: configurational entropy is not yet a reliable, designable lever to co-deliver expanded photonic functionality and operational robustness with a composition-transferable mechanistic basis. Here we develop entropy-engineered rare-earth halide double-perovskite single crystals, Cs2Na(Sb, RE)Cl6 (RE3+ = Sc3+, Er3+, Y… ▽ More The high-entropy halide-perovskite field has expanded rapidly, yet a key gap remains: configurational entropy is not yet a reliable, designable lever to co-deliver expanded photonic functionality and operational robustness with a composition-transferable mechanistic basis. Here we develop entropy-engineered rare-earth halide double-perovskite single crystals, Cs2Na(Sb, RE)Cl6 (RE3+ = Sc3+, Er3+, Yb3+, Tm3+), that simultaneously expand near-infrared (NIR) functionality and establish a mechanistic stability rule. Near-equiatomic B(III)-site alloying yields a single-phase high-entropy solid solution (Delta_Sconfig about 1.6R). Sb3+ serves as a sensitizer that unifies excitation and cooperatively activates multiple lanthanide channels, transforming the parent single-mode response into a broadband NIR output (~850-1600 nm) with three spectrally orthogonal fingerprint bands at 996, 1220, and 1540 nm. This tri-peak, self-referenced output enables redundancy-based ratiometric solvent identification and quantitative mixture sensing with reduced susceptibility to intensity drift. Accelerated aging under humidity and oxygen shows improved phase and emission stability versus single-component analogues. DFT and molecular dynamics attribute the robustness to strongly suppressed RE$^{3+}$/Cl$^-$ self-diffusion despite comparable H$_2$O/O$_2$ adsorption, kinetically impeding ion-migration-assisted reconstruction and degradation. Integration into a phosphor-converted LED delivers spectrally stable, broadband NIR illumination, establishing entropy engineering as a practical handle to couple expanded photonic functionality with mechanistically accountable durability in metal-halide photonics. △ Less

Submitted 10 February, 2026; v1 submitted 30 December, 2025; originally announced December 2025.

On-sky Demonstration of Subdiffraction-limited Astronomical Measurement Using a Photonic Lantern

Authors: Yoo Jung Kim, Michael P. Fitzgerald, Sébastien Vievard, Jonathan Lin, Yinzi Xin, Miles Lucas, Olivier Guyon, Julien Lozi, Vincent Deo, Elsa Huby, Sylvestre Lacour, Manon Lallement, Rodrigo Amezcua-Correa, Sergio Leon-Saval, Barnaby Norris, Mathias Nowak, Steph Sallum, Jehanne Sarrazin, Adam Taras, Stephanos Yerolatsitis, Nemanja Jovanovic

Abstract: Resolving fine details of astronomical objects provides critical insights into their underlying physical processes. This drives in part the desire to construct ever-larger telescopes and interferometer arrays and to observe at shorter wavelength to lower the diffraction limit of angular resolution. Alternatively, one can aim to overcome the diffraction limit by extracting more information from a s… ▽ More Resolving fine details of astronomical objects provides critical insights into their underlying physical processes. This drives in part the desire to construct ever-larger telescopes and interferometer arrays and to observe at shorter wavelength to lower the diffraction limit of angular resolution. Alternatively, one can aim to overcome the diffraction limit by extracting more information from a single telescope's aperture. A promising way to do this is spatial mode-based imaging, which projects focal-plane field onto a set of spatial modes before detection, retaining focal-plane phase information crucial at small angular scales but typically lost in intensity imaging. However, the practical implementation of mode-based imaging in astronomy from the ground has been challenged by atmospheric turbulence. Here, we present the first on-sky demonstration of a subdiffraction-limited, mode-based measurement using a photonic lantern (PL)-fed spectrometer installed on the SCExAO instrument at the Subaru Telescope. We introduce a novel calibration strategy that mitigates time-varying wavefront error and misalignment effects, leveraging simultaneously recorded focal-plane images and using a spectral-differential technique that self-calibrates the data. Observing the classical Be star $β$ CMi, we detected spectral-differential spatial signals and reconstructed images of its H$α$-emitting disk. We achieved an unprecedented H$α$ photocenter precision of 50$μ$as in about 10-minute observation with a single telescope, measuring the disk's near-far side asymmetry for the first time. This work demonstrates the high precision, efficiency, and practicality of photonic mode-based imaging techniques to recover subdiffraction-limited information, opening new avenues for high angular resolution spectroscopic studies in astronomy. △ Less

Submitted 22 October, 2025; originally announced October 2025.

Comments: Published in the Astrophysical Journal Letters

Journal ref: The Astrophysical Journal Letters, Volume 993 (2025), Number 1

BigBang-Proton Technical Report: Next-Word-Prediction is Scientific Multitask Learner

Authors: Hengkui Wu, Liujiang Liu, Jihua He, Qihao Wang, Keke Zhao, Shuyang Hu, Renle Fu, Dahao Liang, Lingyu Zeng, Bruce Liu, Yuan Liu, Jin Zhan, Jiaqiang Niu, Xinglong Jia, Yaqin Hu, Wenjun Ji, Panpan Chi, Ken Chen, Hengyuan Wu, Yingsi Xin, Yongfeng Zhu, Yuexin Wang, Manqi Ruan, Ningtao Bian, Xiaohua Wu , et al. (1 additional authors not shown)

Abstract: We introduce BigBang-Proton, a unified sequence-based architecture for auto-regressive language modeling pretrained on cross-scale, cross-structure, cross-discipline real-world scientific tasks to construct a scientific multi-task learner. BigBang-Proton incorporates three fundamental innovations compared to mainstream general-purpose LLMs: Theory-Experiment Learning paradigm aligns large-scale nu… ▽ More We introduce BigBang-Proton, a unified sequence-based architecture for auto-regressive language modeling pretrained on cross-scale, cross-structure, cross-discipline real-world scientific tasks to construct a scientific multi-task learner. BigBang-Proton incorporates three fundamental innovations compared to mainstream general-purpose LLMs: Theory-Experiment Learning paradigm aligns large-scale numerical experimental data with theoretical text corpora; Binary Patch Encoding replaces byte pair encoding(BPE) tokenization; Monte Carlo Attention substitutes traditional transformer architectures. Through next-word-prediction pretraining on cross-discipline scientific datasets of real-world problems mixed with general textual corpus, followed by fine-tuning and inference on downstream tasks, BigBang-Proton demonstrates 100\% accuracy in up to 50-digit arithmetic addition operations, performance on par with leading specialized models in particle physics jet tagging, matching MAE of specialized models in inter-atomic potential simulation, performance comparable to traditional spatiotemporal models in water quality prediction, and benchmark-exceeding performance in genome modeling. These results prove that language-guided scientific computing can match or exceed the performance of task-specific scientific models while maintaining multitask learning capabilities. We further hypothesize to scale the pretraining to the universe scale as a fundamental step toward developing material world foundational model. △ Less

Submitted 30 September, 2025; originally announced October 2025.

Comments: 93 pages, 39 figures

MSC Class: 68T05; 68T50; 00A69; 94A99 ACM Class: I.2.6; I.2.7; J.2; I.6.3; K.4.1

Experimental and on-sky demonstration of spectrally dispersed wavefront sensing using a photonic lantern

Authors: Jonathan Lin, Michael P. Fitzgerald, Yinzi Xin, Yoo Jung Kim, Olivier Guyon, Barnaby Norris, Christopher Betters, Sergio Leon-Saval, Kyohoon Ahn, Vincent Deo, Julien Lozi, Sébastien Vievard, Daniel Levinstein, Steph Sallum, Nemanja Jovanovic

Abstract: Adaptive optics systems are critical in any application where highly resolved imaging or beam control must be performed through a dynamic medium. Such applications include astronomy and free-space optical communications, where light propagates through the atmosphere, as well as medical microscopy and vision science, where light propagates through biological tissue. Recent works have demonstrated c… ▽ More Adaptive optics systems are critical in any application where highly resolved imaging or beam control must be performed through a dynamic medium. Such applications include astronomy and free-space optical communications, where light propagates through the atmosphere, as well as medical microscopy and vision science, where light propagates through biological tissue. Recent works have demonstrated common-path wavefront sensors for adaptive optics using the photonic lantern, a slowly varying waveguide that can efficiently couple multi-moded light into single-mode fibers. We use the SCExAO astrophotonics platform at the 8-m Subaru Telescope to show that spectral dispersion of lantern outputs can improve correction fidelity, culminating with an on-sky demonstration of real-time wavefront control. To our best knowledge, this is the first such result for either a spectrally dispersed or a photonic lantern wavefront sensor. Combined with the benefits offered by lanterns in precision spectroscopy, our results suggest the future possibility of a unified wavefront sensing spectrograph using compact photonic devices. △ Less

Submitted 1 May, 2025; originally announced May 2025.

Journal ref: Opt. Lett. 50, 2780-2783 (2025)

Technical description and performance of the phase II version of the Keck Planet Imager and Characterizer

Authors: Nemanja Jovanovic, Daniel Echeverri, Jacques-Robert Delorme, Luke Finnerty, Tobias Schofield, Jason J. Wang, Yinzi Xin, Jerry Xuan, J. Kent Wallacee, Dimitri Mawet, Aniket Sanghi, Ashley Baker, Randall Bartos, Charlotte Z. Bond, Benjamin Calvin, Sylvain Cetre, Greg Doppmann, Michael P. Fitzgerald, Jason Fucik, Maodong Gao, Jinhao Ge, Charlotte Guthery, Katelyn Horstman, Chih-Chun Hsud, Joshua Liberman , et al. (24 additional authors not shown)

Abstract: The Keck Planet Imager and Characterizer (KPIC) is a series of upgrades for the Keck II Adaptive Optics (AO) system and the NIRSPEC spectrograph to enable diffraction limited, high resolution (R>30000) spectroscopy of exoplanets and low mass companions in the K and L bands. Phase I consisted of single mode fiber injection/extraction units (FIU/FEU) used in conjunction with a H band pyramid wavefro… ▽ More The Keck Planet Imager and Characterizer (KPIC) is a series of upgrades for the Keck II Adaptive Optics (AO) system and the NIRSPEC spectrograph to enable diffraction limited, high resolution (R>30000) spectroscopy of exoplanets and low mass companions in the K and L bands. Phase I consisted of single mode fiber injection/extraction units (FIU/FEU) used in conjunction with a H band pyramid wavefront sensor. The use of single mode fibers provides a gain in stellar rejection, a substantial reduction in sky background, and an extremely stable line spread function in the spectrograph. Phase II, deployed and commissioned in 2022, brought a 1000 actuator deformable mirror, beam shaping optics, a vortex mask, and other upgrades to the FIU/FEU. An additional service mission in 2024 extended operations down to y band, delivered an atmospheric dispersion corrector, and provided access to two laser frequency combs. KPIC phase II brings higher planet throughput, lower stellar leakage and many new observing modes which extend its ability to characterize exoplanets at high spectral resolution, building on the success of phase I. In this paper we present a description of the final phase II version of KPIC, along with results of system level laboratory testing and characterization showing the instrument's phase II throughput, stability, repeatability, and other key performance metrics prior to delivery and during installation at Keck. We outlined the capabilities of the various observing modes enabled by the new modules as well as efforts to compensate for static aberrations and non common path errors at Keck, which were issues that plagued phase I. Finally, we show results from commissioning. △ Less

Submitted 3 February, 2025; originally announced February 2025.

Comments: 36 pages, 16 figures

Report number: 015005

Journal ref: Journal of Astronomical Telescopes, Instruments, and Systems, Vol. 11, Issue 1, 015005 (February 2025)

Scaling Particle Collision Data Analysis

Authors: Hengkui Wu, Panpan Chi, Yongfeng Zhu, Liujiang Liu, Shuyang Hu, Yuexin Wang, Chen Zhou, Qihao Wang, Yingsi Xin, Bruce Liu, Dahao Liang, Xinglong Jia, Manqi Ruan

Abstract: For decades, researchers have developed task-specific models to address scientific challenges across diverse disciplines. Recently, large language models (LLMs) have shown enormous capabilities in handling general tasks; however, these models encounter difficulties in addressing real-world scientific problems, particularly in domains involving large-scale numerical data analysis, such as experimen… ▽ More For decades, researchers have developed task-specific models to address scientific challenges across diverse disciplines. Recently, large language models (LLMs) have shown enormous capabilities in handling general tasks; however, these models encounter difficulties in addressing real-world scientific problems, particularly in domains involving large-scale numerical data analysis, such as experimental high energy physics. This limitation is primarily due to BPE tokenization's inefficacy with numerical data. In this paper, we propose a task-agnostic architecture, BBT-Neutron, which employs a binary tokenization method to facilitate pretraining on a mixture of textual and large-scale numerical experimental data. We demonstrate the application of BBT-Neutron to Jet Origin Identification (JoI), a critical categorization challenge in high-energy physics that distinguishes jets originating from various quarks or gluons. Our results indicate that BBT-Neutron achieves comparable performance to state-of-the-art task-specific JoI models. Furthermore, we examine the scaling behavior of BBT-Neutron's performance with increasing data volume, suggesting the potential for BBT-Neutron to serve as a foundational model for particle physics data analysis, with possible extensions to a broad spectrum of scientific computing applications for Big Science experiments, industrial manufacturing and spacial computing. The project code is available at https://github.com/supersymmetry-technologies/bbt-neutron. △ Less

Submitted 9 December, 2024; v1 submitted 28 November, 2024; originally announced December 2024.

Spectral characterization of a 3-port photonic lantern for application to spectroastrometry

Authors: Yoo Jung Kim, Michael P. Fitzgerald, Jonathan Lin, Julien Lozi, Sébastien Vievard, Yinzi Xin, Daniel Levinstein, Nemanja Jovanovic, Sergio Leon-Saval, Christopher Betters, Olivier Guyon, Barnaby Norris, Steph Sallum

Abstract: Spectroastrometry, which measures wavelength-dependent shifts in the center of light, is well-suited for studying objects whose morphology changes with wavelength at very high angular resolutions. Photonic lantern (PL)-fed spectrometers have potential to enable measurement of spectroastrometric signals because the relative intensities between the PL output SMFs contain spatial information on the i… ▽ More Spectroastrometry, which measures wavelength-dependent shifts in the center of light, is well-suited for studying objects whose morphology changes with wavelength at very high angular resolutions. Photonic lantern (PL)-fed spectrometers have potential to enable measurement of spectroastrometric signals because the relative intensities between the PL output SMFs contain spatial information on the input scene. In order to use PL output spectra for spectroastrometric measurements, it is important to understand the wavelength-dependent behaviors of PL outputs and develop methods to calibrate the effects of time-varying wavefront errors in ground-based observations. We present experimental characterizations of the 3-port PL on the SCExAO testbed at the Subaru Telescope. We develop spectral response models of the PL and verify the behaviors with lab experiments. We find sinusoidal behavior of astrometric sensitivity of the 3-port PL as a function of wavelength, as expected from numerical simulations. Furthermore, we compare experimental and numerically simulated coupling maps and discuss their potential use for offsetting pointing errors. We then present a method of building PL spectral response models (solving for the transfer matrices as a function of wavelength) using coupling maps, which can be used for further calibration strategies. △ Less

Submitted 4 November, 2024; originally announced November 2024.

Comments: Accepted for publication in the Journal of Astronomical Telescopes, Instruments, and Systems (JATIS)

High-Fidelity 3D Lung CT Synthesis in ARDS Swine Models Using Score-Based 3D Residual Diffusion Models

Authors: Siyeop Yoon, Yujin Oh, Xiang Li, Yi Xin, Maurizio Cereda, Quanzheng Li

Abstract: Acute respiratory distress syndrome (ARDS) is a severe condition characterized by lung inflammation and respiratory failure, with a high mortality rate of approximately 40%. Traditional imaging methods, such as chest X-rays, provide only two-dimensional views, limiting their effectiveness in fully assessing lung pathology. Three-dimensional (3D) computed tomography (CT) offers a more comprehensive… ▽ More Acute respiratory distress syndrome (ARDS) is a severe condition characterized by lung inflammation and respiratory failure, with a high mortality rate of approximately 40%. Traditional imaging methods, such as chest X-rays, provide only two-dimensional views, limiting their effectiveness in fully assessing lung pathology. Three-dimensional (3D) computed tomography (CT) offers a more comprehensive visualization, enabling detailed analysis of lung aeration, atelectasis, and the effects of therapeutic interventions. However, the routine use of CT in ARDS management is constrained by practical challenges and risks associated with transporting critically ill patients to remote scanners. In this study, we synthesize high-fidelity 3D lung CT from 2D generated X-ray images with associated physiological parameters using a score-based 3D residual diffusion model. Our preliminary results demonstrate that this approach can produce high-quality 3D CT images that are validated with ground truth, offering a promising solution for enhancing ARDS management. △ Less

Submitted 26 September, 2024; originally announced October 2024.

Comments: 5 page, 3 figures, Submitted to SPIE 2025-Medical Imaging

Super-Bandgap Electroluminescence from Cesium Lead Bromide

Authors: Justin Sculley, Jeremy Kowkabany, Diana K. LaFollette, Carlo Perini, Yan Xin, Juan-Pablo Correa-Baena, Hanwei Gao

Abstract: Halide perovskites is a new class of semiconductors with exceptional optoelectronic properties. Among many advantages offered by halide perovskites, the bandgap energy can be tuned in a much broader range than what was possible in conventional semiconductors. This was commonly achieved in previous research by mixing different species of halides into solid solutions. The tuned bandgap using this me… ▽ More Halide perovskites is a new class of semiconductors with exceptional optoelectronic properties. Among many advantages offered by halide perovskites, the bandgap energy can be tuned in a much broader range than what was possible in conventional semiconductors. This was commonly achieved in previous research by mixing different species of halides into solid solutions. The tuned bandgap using this method, however, often underwent an energy shift under optical or electrical stimuli due to halide segregation. In this work, we discovered an alternative approach to achieve super-bandgap electroluminescence from CsPbBr3. The peak energy of the light emission can be 0.7 eV higher than the reported bandgap energy. Evidence pointed to the radiative recombination at the perovskite-PEDOT:PSS interface being responsible for the unexpected blueshift of electroluminescence. We speculated that perovskite nanocrystals were formed therein and produced higher-energy photons due to quantum confinement. The results suggested an alternative strategy to manipulate and stabilize the color of electroluminescence and achieve particularly blue emission in perovskite-based LEDs. △ Less

Submitted 12 October, 2024; originally announced October 2024.

Strategies to enhance THz harmonic generation combining multilayered, gated, and metamaterial-based architectures

Authors: Ali Maleki, Moritz B. Heindl, Yongbao Xin, Robert W. Boyd, Georg Herink, Jean-Michel Ménard

Abstract: Graphene has unique properties paving the way for groundbreaking future applications. Its large optical nonlinearity and ease of integration in devices notably makes it an ideal candidate to become a key component for all-optical switching and frequency conversion applications. In the terahertz (THz) region, various approaches have been independently demonstrated to optimize the nonlinear effects… ▽ More Graphene has unique properties paving the way for groundbreaking future applications. Its large optical nonlinearity and ease of integration in devices notably makes it an ideal candidate to become a key component for all-optical switching and frequency conversion applications. In the terahertz (THz) region, various approaches have been independently demonstrated to optimize the nonlinear effects in graphene, addressing a critical limitation arising from the atomically thin interaction length. Here, we demonstrate sample architectures that combine strategies to enhance THz nonlinearities in graphene-based structures. We achieve this by increasing the interaction length through a multilayered design, controlling carrier density with an electrical gate, and modulating the THz field spatial distribution with a metallic metasurface substrate. Our study specifically investigates third harmonic generation (THG) using a table-top high-field THz source. We measure THG enhancement factors exceeding thirty and propose architectures capable of achieving a two-order-of-magnitude increase. These findings highlight the potential of engineered graphene-based samples in advancing THz frequency conversion technologies for signal processing and wireless communication applications. △ Less

Submitted 27 May, 2024; originally announced May 2024.

Comments: 13 pages (4 Figures) + 5 pages Supplementary Information (4 Figures)

Data quality control system and long-term performance monitor of the LHAASO-KM2A

Authors: Zhen Cao, F. Aharonian, Axikegu, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, W. Bian, A. V. Bukevich, Q. Cao, W. Y. Cao, Zhe Cao, J. Chang, J. F. Chang, A. M. Chen, E. S. Chen, H. X. Chen, Liang Chen, Lin Chen, Long Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. Chen , et al. (263 additional authors not shown)

Abstract: The KM2A is the largest sub-array of the Large High Altitude Air Shower Observatory (LHAASO). It consists of 5216 electromagnetic particle detectors (EDs) and 1188 muon detectors (MDs). The data recorded by the EDs and MDs are used to reconstruct primary information of cosmic ray and gamma-ray showers. This information is used for physical analysis in gamma-ray astronomy and cosmic ray physics. To… ▽ More The KM2A is the largest sub-array of the Large High Altitude Air Shower Observatory (LHAASO). It consists of 5216 electromagnetic particle detectors (EDs) and 1188 muon detectors (MDs). The data recorded by the EDs and MDs are used to reconstruct primary information of cosmic ray and gamma-ray showers. This information is used for physical analysis in gamma-ray astronomy and cosmic ray physics. To ensure the reliability of the LHAASO-KM2A data, a three-level quality control system has been established. It is used to monitor the status of detector units, stability of reconstructed parameters and the performance of the array based on observations of the Crab Nebula and Moon shadow. This paper will introduce the control system and its application on the LHAASO-KM2A data collected from August 2021 to July 2023. During this period, the pointing and angular resolution of the array were stable. From the observations of the Moon shadow and Crab Nebula, the results achieved using the two methods are consistent with each other. According to the observation of the Crab Nebula at energies from 25 TeV to 100 TeV, the time averaged pointing errors are estimated to be $-0.003^{\circ} \pm 0.005^{\circ}$ and $0.001^{\circ} \pm 0.006^{\circ}$ in the R.A. and Dec directions, respectively. △ Less

Submitted 13 June, 2024; v1 submitted 20 May, 2024; originally announced May 2024.

Comments: 15 pages, 9 figures

Coherent Imaging with Photonic Lanterns

Authors: Yoo Jung Kim, Michael P. Fitzgerald, Jonathan Lin, Steph Sallum, Yinzi Xin, Nemanja Jovanovic, Sergio Leon-Saval

Abstract: Photonic Lanterns (PLs) are tapered waveguides that gradually transition from a multi-mode fiber geometry to a bundle of single-mode fibers (SMFs). They can efficiently couple multi-mode telescope light into a multi-mode fiber entrance at the focal plane and convert it into multiple single-mode beams. Thus, each SMF samples its unique mode (lantern principal mode) of the telescope light in the pup… ▽ More Photonic Lanterns (PLs) are tapered waveguides that gradually transition from a multi-mode fiber geometry to a bundle of single-mode fibers (SMFs). They can efficiently couple multi-mode telescope light into a multi-mode fiber entrance at the focal plane and convert it into multiple single-mode beams. Thus, each SMF samples its unique mode (lantern principal mode) of the telescope light in the pupil, analogous to subapertures in aperture masking interferometry (AMI). Coherent imaging with PLs can be enabled by interfering SMF outputs and applying phase modulation, which can be achieved using a photonic chip beam combiner at the backend (e.g., the ABCD beam combiner). In this study, we investigate the potential of coherent imaging by interfering SMF outputs of a PL with a single telescope. We demonstrate that the visibilities that can be measured from a PL are mutual intensities incident on the pupil weighted by the cross-correlation of a pair of lantern modes. From numerically simulated lantern principal modes of a 6-port PL, we find that interferometric observables using a PL behave similarly to separated-aperture visibilities for simple models on small angular scales ($<λ/D$) but with greater sensitivity to symmetries and capability to break phase angle degeneracies. Furthermore, we present simulated observations with wavefront errors and compare them to AMI. Despite the redundancy caused by extended lantern principal modes, spatial filtering offers stability to wavefront errors. Our simulated observations suggest that PLs may offer significant benefits in the photon noise-limited regime and in resolving small angular scales at low contrast regime. △ Less

Submitted 12 February, 2024; originally announced February 2024.

Comments: Accepted for publication in ApJ

A Continuous Dual-Axis Atomic Interferometric Inertial Sensor

Authors: Pei-Qiang Yan, Wei-Chen Jia, Ke Shen, Yue Xin, Yan-Ying Feng

Abstract: We present an interferometric inertial sensor that utilizes two counter-propagating atomic beams with transverse two-dimensional cooling. By employing three parallel and spatially aligned Raman laser beams for Doppler-sensitive Raman transitions, we successfully generate inertia-sensitive Mach-Zehnder interference fringes with an interrogation length of $2L=54\,\rm{cm}$. The sensor's capability to… ▽ More We present an interferometric inertial sensor that utilizes two counter-propagating atomic beams with transverse two-dimensional cooling. By employing three parallel and spatially aligned Raman laser beams for Doppler-sensitive Raman transitions, we successfully generate inertia-sensitive Mach-Zehnder interference fringes with an interrogation length of $2L=54\,\rm{cm}$. The sensor's capability to measure rotation and acceleration simultaneously in dynamic environments is validated through comparative analysis with classical sensors under force oscillation in different directions. Additionally, we conduct experiments on a turntable to calibrate the gyroscope's scaling factor and address nonlinearity. The angular random walk (ARW) and velocity random walk (VRW) of the senor are $3\times10^{-4}\,^\circ/\rm{\sqrt{h}}$ and $107\,\mathrmμg/\rm{\sqrt{Hz}}$, respectively, with the long-term stability reaching $9\times10^{-4}\,\rm{^\circ/h}$ for rotation and $10\,\rm{μg}$ for acceleration at an integration time of 1000s. △ Less

Submitted 28 July, 2025; v1 submitted 28 November, 2023; originally announced November 2023.

Comments: 11 pages, 6 figures

A causal intervention framework for synthesizing mobility data and evaluating predictive neural networks

Authors: Ye Hong, Yanan Xin, Simon Dirmeier, Fernando Perez-Cruz, Martin Raubal

Abstract: Deep neural networks are increasingly utilized in mobility prediction tasks, yet their intricate internal workings pose challenges for interpretability, especially in comprehending how various aspects of mobility behavior affect predictions. This study introduces a causal intervention framework to assess the impact of mobility-related factors on neural networks designed for next location predictio… ▽ More Deep neural networks are increasingly utilized in mobility prediction tasks, yet their intricate internal workings pose challenges for interpretability, especially in comprehending how various aspects of mobility behavior affect predictions. This study introduces a causal intervention framework to assess the impact of mobility-related factors on neural networks designed for next location prediction -- a task focusing on predicting the immediate next location of an individual. To achieve this, we employ individual mobility models to synthesize location visit sequences and control behavior dynamics by intervening in their data generation process. We evaluate the interventional location sequences using mobility metrics and input them into well-trained networks to analyze performance variations. The results demonstrate the effectiveness in producing location sequences with distinct mobility behaviors, thereby facilitating the simulation of diverse yet realistic spatial and temporal changes. These changes result in performance fluctuations in next location prediction networks, revealing impacts of critical mobility behavior factors, including sequential patterns in location transitions, proclivity for exploring new locations, and preferences in location choices at population and individual levels. The gained insights hold value for the real-world application of mobility prediction networks, and the framework is expected to promote the use of causal inference to enhance the interpretability and robustness of neural networks in mobility applications. △ Less

Submitted 1 August, 2024; v1 submitted 20 November, 2023; originally announced November 2023.

Comments: 34 pages, 8 figures

Focal-plane wavefront sensing with photonic lanterns II: numerical characterization and optimization

Authors: Jonathan Lin, Michael P. Fitzgerald, Yinzi Xin, Yoo Jung Kim, Olivier Guyon, Sergio Leon-Saval, Barnaby Norris, Nemanja Jovanovic

Abstract: We present numerical characterizations of the wavefront sensing performance for few-mode photonic lantern wavefront sensors (PLWFSs). These characterizations include calculations of throughput, control space, sensor linearity, and an estimate of maximum linear reconstruction range for standard and hybrid lanterns with 3 to 19 ports, at a wavelength of 1550 nm. We additionally consider the impact o… ▽ More We present numerical characterizations of the wavefront sensing performance for few-mode photonic lantern wavefront sensors (PLWFSs). These characterizations include calculations of throughput, control space, sensor linearity, and an estimate of maximum linear reconstruction range for standard and hybrid lanterns with 3 to 19 ports, at a wavelength of 1550 nm. We additionally consider the impact of beam-shaping optics and a charge-1 vortex mask, placed in the pupil plane. The former is motivated by the application of PLs to high-resolution spectroscopy, which could enable efficient injection into the spectrometer along with simultaneous focal-plane wavefront sensing; similarly, the latter is motivated by the application of PLs to vortex fiber nulling (VFN), which can simultaneously enable wavefront sensing and the nulling of on-axis starlight. Overall, we find that the PLWFS setups tested in this work exhibit good linearity out to ~0.25-0.5 radians of RMS wavefront error (WFE). Meanwhile, we estimate the maximum amount of WFE that can be handled by these sensors, before the sensor response becomes degenerate, to be around ~1-2 radians RMS. In the future, we expect these limits can be pushed further by increasing the number of degrees of freedom, either by adopting higher-mode-count lanterns, dispersing lantern outputs, or separating polarizations. Lastly, we consider optimization strategies for the design of the PLWFS, which involve both modification of the lantern itself and the use of pre- and post-lantern optics like phase masks and interferometric beam recombiners. △ Less

Submitted 2 November, 2023; originally announced November 2023.

Comments: Accepted to JOSA B

2023 Astrophotonics Roadmap: pathways to realizing multi-functional integrated astrophotonic instruments

Authors: Nemanja Jovanovic, Pradip Gatkine, Narsireddy Anugu, Rodrigo Amezcua-Correa, Ritoban Basu Thakur, Charles Beichman, Chad Bender, Jean-Philippe Berger, Azzurra Bigioli, Joss Bland-Hawthorn, Guillaume Bourdarot, Charles M. Bradford, Ronald Broeke, Julia Bryant, Kevin Bundy, Ross Cheriton, Nick Cvetojevic, Momen Diab, Scott A. Diddams, Aline N. Dinkelaker, Jeroen Duis, Stephen Eikenberry, Simon Ellis, Akira Endo, Donald F. Figer , et al. (55 additional authors not shown)

Abstract: Photonics offer numerous functionalities that can be used to realize astrophotonic instruments. The most spectacular example to date is the ESO Gravity instrument at the Very Large Telescope in Chile. Integrated astrophotonic devices stand to offer critical advantages for instrument development, including extreme miniaturization, as well as integration, superior thermal and mechanical stabilizatio… ▽ More Photonics offer numerous functionalities that can be used to realize astrophotonic instruments. The most spectacular example to date is the ESO Gravity instrument at the Very Large Telescope in Chile. Integrated astrophotonic devices stand to offer critical advantages for instrument development, including extreme miniaturization, as well as integration, superior thermal and mechanical stabilization owing to the small footprint, and high replicability offering cost savings. Numerous astrophotonic technologies have been developed to address shortcomings of conventional instruments to date, including for example the development of photonic lanterns, complex aperiodic fiber Bragg gratings, complex beam combiners to enable long baseline interferometry, and laser frequency combs for high precision spectral calibration of spectrometers. Despite these successes, the facility implementation of photonic solutions in astronomical instrumentation is currently limited because of (1) low throughputs from coupling to fibers, coupling fibers to chips, propagation and bend losses, device losses, etc, (2) difficulties with scaling to large channel count devices needed for large bandwidths and high resolutions, and (3) efficient integration of photonics with detectors, to name a few. In this roadmap, we identify 24 areas that need further development. We outline the challenges and advances needed across those areas covering design tools, simulation capabilities, fabrication processes, the need for entirely new components, integration and hybridization and the characterization of devices. To realize these advances the astrophotonics community will have to work cooperatively with industrial partners who have more advanced manufacturing capabilities. With the advances described herein, multi-functional instruments will be realized leading to novel observing capabilities for both ground and space platforms. △ Less

Submitted 1 November, 2023; originally announced November 2023.

Comments: 191 pages, 47 figures. This is the version of the article before peer review or editing, as submitted by an author to J. Phys. Photonics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://iopscience.iop.org/article/10.1088/2515-7647/ace869/meta

Journal ref: J. Phys. Photonics 5 042501 (2023)

Is A 15-minute City within Reach in the United States? An Investigation of Activity-Based Mobility Flows in the 12 Most Populous US Cities

Authors: Tanhua Jin, Kailai Wang, Yanan Xin, Jian Shi, Ye Hong, Frank Witlox

Abstract: Enhanced efforts in the transportation sector should be implemented to mitigate the adverse effects of CO2 emissions resulting from zoning-based planning paradigms. The innovative concept of the 15-minute city, with a focus on proximity-based planning, holds promise in minimizing unnecessary travel and advancing the progress toward achieving carbon neutrality. However, an important research questi… ▽ More Enhanced efforts in the transportation sector should be implemented to mitigate the adverse effects of CO2 emissions resulting from zoning-based planning paradigms. The innovative concept of the 15-minute city, with a focus on proximity-based planning, holds promise in minimizing unnecessary travel and advancing the progress toward achieving carbon neutrality. However, an important research question that remains insufficiently explored is: to what extent is a 15-minute city concept within reach for US cities? This paper establishes a comprehensive framework to evaluate the 15-minute city concept using SafeGraph Point of Interest (POI) check-in data in the 12 most populous US cities. The results reveal that residents are more likely to rely on cars due to the fact that most of their essential activities are located beyond convenient walking, cycling, and public transit distances. However, there is significant potential for the implementation of the 15-minute city concept, as most residents' current activities can be accommodated within a 15-minute radius by the aforementioned low-emission modes of transportation. Our findings can offer policymakers insight into how far US cities are away from the 15-minute city and the potential CO2 emission reduction they can expect if the concept is successfully implemented. △ Less

Submitted 22 October, 2023; originally announced October 2023.

The path to detecting extraterrestrial life with astrophotonics

Authors: Nemanja Jovanovic, Yinzi Xin, Michael P. Fitzgerald, Olivier Guyon, Peter Tuthill, Barnaby Norris, Pradip Gatkine, Greg Sercel, Svarun Soda, Yoo Jung Kim, Jonathan Lin, Sergio Leon-Saval, Rodrigo Amezcua-Correa, Stephanos Yerolatsitis, Julien Lozi, Sebastien Vievard, Chris Betters, Steph Sallum, Daniel Levinstein, Dimitri Mawet, Jeffrey Jewell, J. Kent Wallace, Nick Cvetojevic

Abstract: Astrophysical research into exoplanets has delivered thousands of confirmed planets orbiting distant stars. These planets span a wide ranges of size and composition, with diversity also being the hallmark of system configurations, the great majority of which do not resemble our own solar system. Unfortunately, only a handful of the known planets have been characterized spectroscopically thus far,… ▽ More Astrophysical research into exoplanets has delivered thousands of confirmed planets orbiting distant stars. These planets span a wide ranges of size and composition, with diversity also being the hallmark of system configurations, the great majority of which do not resemble our own solar system. Unfortunately, only a handful of the known planets have been characterized spectroscopically thus far, leaving a gaping void in our understanding of planetary formation processes and planetary types. To make progress, astronomers studying exoplanets will need new and innovative technical solutions. Astrophotonics -- an emerging field focused on the application of photonic technologies to observational astronomy -- provides one promising avenue forward. In this paper we discuss various astrophotonic technologies that could aid in the detection and subsequent characterization of planets and in particular themes leading towards the detection of extraterrestrial life. △ Less

Submitted 15 September, 2023; originally announced September 2023.

Comments: 9 pages, 2 figures, SPIE Optics and Photonics conference

Report number: 12680-17

Evolution of Maximum Bending Strain on Poisson's Ratio Distribution

Authors: Yang Li, Le Zhang, Dehua Wang, Limei Hou, Shanmei Du, Yang Deng, Yanfeng Du, Yingfei Xin, Chongyang Fu, Yan Gu, Xiaoxiong Wang

Abstract: In recent years, new flexible functional materials have attracted increasing interest, but there is a lack of the designing mechanisms of flexibility design with superstructures. In traditional engineering mechanics, the maximum bending strain (MBS) was considered universal for describing the bendable properties of a given material, leading to the universal designing method of lowering the dimensi… ▽ More In recent years, new flexible functional materials have attracted increasing interest, but there is a lack of the designing mechanisms of flexibility design with superstructures. In traditional engineering mechanics, the maximum bending strain (MBS) was considered universal for describing the bendable properties of a given material, leading to the universal designing method of lowering the dimension such as thin membranes designed flexible functional materials.In this work, the MBS was found only applicable for materials with uniformly distributed Poisson's ratio, while the MBS increases with the thickness of the given material in case there is a variation Poisson's ratio in different areas. This means the MBS can be enhanced by certain Poisson's ratio design in the future to achieve better flexibility of thick materials. Here, the inorganic freestanding nanofiber membranes, which have a nonconstant Poisson's ratio response on stress/strain for creating nonuniformly distributed Poisson's ratio were proven applicable for designing larger MBS and lower Young's modulus for thicker samples. △ Less

Submitted 4 September, 2023; originally announced September 2023.

Hybrid THz architectures for molecular polaritonics

Authors: Ahmed Jaber, Michael Reitz, Avinash Singh, Ali Maleki, Yongbao Xin, Brian Sullivan, Ksenia Dolgaleva, Robert W. Boyd, Claudiu Genes, Jean-Michel Ménard

Abstract: Physical and chemical properties of materials can be modified by a resonant optical mode. Such recent demonstrations have mostly relied on a planar cavity geometry, others have relied on a plasmonic resonator. However, the combination of these two device architectures have remained largely unexplored, especially in the context of maximizing light-matter interactions. Here, we investigate several s… ▽ More Physical and chemical properties of materials can be modified by a resonant optical mode. Such recent demonstrations have mostly relied on a planar cavity geometry, others have relied on a plasmonic resonator. However, the combination of these two device architectures have remained largely unexplored, especially in the context of maximizing light-matter interactions. Here, we investigate several schemes of electromagnetic field confinement aimed at facilitating the collective coupling of a localized photonic mode to molecular vibrations in the terahertz region. The key aspects are the use of metasurface plasmonic structures combined with standard Fabry-Perot configurations and the deposition of a thin layer of glucose, via a spray coating technique, within a tightly focused electromagnetic mode volume. More importantly, we demonstrate enhanced vacuum Rabi splittings reaching up to 200 GHz when combining plasmonic resonances, photonic cavity modes and low-energy molecular resonances. Furthermore, we demonstrate how a cavity mode can be utilized to enhance the zero-point electric field amplitude of a plasmonic resonator. Our study provides key insight into the design of polaritonic platforms with organic molecules to harvest the unique properties of hybrid light-matter states. △ Less

Submitted 25 May, 2024; v1 submitted 7 April, 2023; originally announced April 2023.

Comments: 7 pages (5 Figures) + 7 pages Appendix (5 Figures), updated version

Journal ref: Nature Communications 15, 4427 (2024)

Focal-plane wavefront sensing with photonic lanterns I: theoretical framework

Authors: Jonathan Lin, Michael Fitzgerald, Yinzi Xin, Olivier Guyon, Sergio Leon-Saval, Barnaby Norris, Nemanja Jovanovic

Abstract: The photonic lantern (PL) is a tapered waveguide that can efficiently couple light into multiple single-mode optical fibers. Such devices are currently being considered for a number of tasks, including the coupling of telescopes and high-resolution, fiber-fed spectrometers, coherent detection, nulling interferometry, and vortex-fiber nulling (VFN). In conjunction with these use cases, PLs can simu… ▽ More The photonic lantern (PL) is a tapered waveguide that can efficiently couple light into multiple single-mode optical fibers. Such devices are currently being considered for a number of tasks, including the coupling of telescopes and high-resolution, fiber-fed spectrometers, coherent detection, nulling interferometry, and vortex-fiber nulling (VFN). In conjunction with these use cases, PLs can simultaneously perform low-order focal-plane wavefront sensing. In this work, we provide a mathematical framework for the analysis of the photonic lantern wavefront sensor (PLWFS), deriving linear and higher-order reconstruction models as well as metrics through which sensing performance -- both in the linear and nonlinear regimes -- can be quantified. This framework can be extended to account for additional optics such as beam-shaping optics and vortex masks, and is generalizable to other wavefront sensing architectures. Lastly, we provide initial numerical verification of our mathematical models, by simulating a 6-port PLWFS. In a companion paper, we provide a more comprehensive numerical characterization of few-port PLWFSs, and consider how the sensing properties of these devices can be controlled and optimized. △ Less

Submitted 22 August, 2022; originally announced August 2022.

Comments: Accepted to JOSA B

Metamaterial-based octave-wide terahertz bandpass filters

Authors: Ali Maleki, Avinash Singh, Ahmed Jaber, Wei Cui, Yongbao Xin, Brian T. Sullivan, Robert W. Boyd, Jean-Michel Menard

Abstract: We present octave-wide bandpass filters in the terahertz (THz) region based on bilayer-metamaterial (BLMM) structures. The passband region has a super-Gaussian shape with a maximum transmittance approaching 70% and a typical stopband rejection of 20 dB. The design is based on a metasurface consisting of a metallic square-hole array deposited on a transparent polymer, which is stacked on top of an… ▽ More We present octave-wide bandpass filters in the terahertz (THz) region based on bilayer-metamaterial (BLMM) structures. The passband region has a super-Gaussian shape with a maximum transmittance approaching 70% and a typical stopband rejection of 20 dB. The design is based on a metasurface consisting of a metallic square-hole array deposited on a transparent polymer, which is stacked on top of an identical metasurface with a sub-wavelength separation. The superimposed metasurface structures were designed using finite-difference time-domain (FDTD) simulations and fabricated using a photolithography process. Experimental characterization of these structures between 0.3 to 5.8 THz is performed with a time-domain THz spectroscopy system. Good agreement between experiment and simulation results is observed. We also demonstrate that two superimposed BLMM (2BLMM) devices increase the steepness of the roll-offs to more than 85 dB/octave and enable a superior stopband rejection approaching 40 dB while the maximum transmittance remains above 64%. This work paves the way toward new THz applications, including the detection of THz pulses centered at specific frequencies, and an enhanced time-resolved detection sensitivity towards molecular vibrations that are noise dominated by a strong, off-resonant, driving field. △ Less

Submitted 17 August, 2022; originally announced August 2022.

Comments: 8 pages, 4 figures

Contactless Excitation of Acoustic Resonance in Insulating Wafers

Authors: Gan Zhai, Yizhou Xin, Cameron J. Kopas, Ella Lachman, Mark Field, Josh Y. Mutus, Katarina Cicak, Jose Aumentado, Zuhawn Sung, William P. Halperin

Abstract: Contactless excitation and detection of high harmonic acoustic overtones in a thin insulator single crystal are described using radio frequency spectroscopy techniques. Single crystal [001] silicon wafer samples were investigated, one side covered with a Nb thin film, the common starting point for fabrication of quantum devices. The coupling between electromagnetic signals and mechanical oscillati… ▽ More Contactless excitation and detection of high harmonic acoustic overtones in a thin insulator single crystal are described using radio frequency spectroscopy techniques. Single crystal [001] silicon wafer samples were investigated, one side covered with a Nb thin film, the common starting point for fabrication of quantum devices. The coupling between electromagnetic signals and mechanical oscillation is achieved from the Lorentz force generated by an external magnetic field. This method is suitable for any sample with a metallic surface or covered with a thin metal film. High resolution measurements of the temperature dependence of the sound velocity and elastic constants of silicon are reported and compared with known results. △ Less

Submitted 21 September, 2022; v1 submitted 25 July, 2022; originally announced July 2022.

Comments: 4 pages, 5 figures

Single nanosized graphene/TiOx multi-shells on TiO2 core via rapid-concomitant reaction pathway on metal oxide/polymer interface

Authors: Kunihiko Kato, Yunzi Xin, Sebastien Vaucher, Takashi Shirai

Abstract: A novel design has been proposed for a facile and rapid build-up of highly tailorable nanostructured multishells on metal oxide particles (graphene/TiOx@TiO2) under a dry inert atmosphere to maximize the visible-light photocatalytic performance. We also thoroughly and systematically investigated the as-prepared nanostructured particle surface and the mechanisms of the extraordinary in-situ graphen… ▽ More A novel design has been proposed for a facile and rapid build-up of highly tailorable nanostructured multishells on metal oxide particles (graphene/TiOx@TiO2) under a dry inert atmosphere to maximize the visible-light photocatalytic performance. We also thoroughly and systematically investigated the as-prepared nanostructured particle surface and the mechanisms of the extraordinary in-situ graphene growth on the TiOx@TiO2 nanoparticles achieved by a rapid-concomitant reaction in the metal oxide (TiO2)/polymer (polymethyl methacrylate) interface under microwave irradiation. The as-prepared composite materials are also found to perform a better photocatalytic activity in comparison to the traditional synthesis pathway for degradation of organic pollutants under visible light, associated with the synergetic effects of homo-/hetero-junction on TiO2. △ Less

Submitted 2 February, 2022; originally announced February 2022.

Journal ref: Scripta Materialia, 208 (2022) 114358

TiO2 with Super Narrow Bandgap Achieved in One-Step Single-Mode Magnetic Microwave Induced Plasma Treatment

Authors: Kunihiko Kato, Yunzi Xin, Takashi Shirai

Abstract: TiO2 with super narrow bandgap (1.1 eV~) are successfully synthesized via a facile and novel one-step single-mode magnetic microwave induced plasma treatment. The selectively surface Ti3+-doping on obtained TiO2 as trapping centers which significantly restrain the photo-excited carrier recombination and achieve the enhancement of visible-light photocatalytic performance. In addition, the surface c… ▽ More TiO2 with super narrow bandgap (1.1 eV~) are successfully synthesized via a facile and novel one-step single-mode magnetic microwave induced plasma treatment. The selectively surface Ti3+-doping on obtained TiO2 as trapping centers which significantly restrain the photo-excited carrier recombination and achieve the enhancement of visible-light photocatalytic performance. In addition, the surface chemical composition of TiOx is precisely controlled in a wide region of 1.19 < x < 1.92 during one-step reaction. A detailed XPS analysis reveals that the surface formed Ti3+ shows highly thermal/chemical stability even through high-temperature treatment (~800 oC) in oxidative atmosphere and photocatalytic reaction. △ Less

Submitted 2 February, 2022; originally announced February 2022.

Journal ref: Scripta Materialia 177 (2020) 157-161

Synthesis of Core/Shell Ti/TiOx Photocatalyst via Single-Mode Magnetic Microwave Assisted Direct Oxidation of TiH2

Authors: Kunihiko Kato, Yunzi Xin, Jeongsoo Hong, Ken-ichi Katsumata, Takashi Shirai

Abstract: Submicron core/shell Ti/TiOx photocatalyst is successfully synthesized via single-mode magnetic microwave (SMMW) assisted direct oxidation of planetary ball-milled TiH2. The thickness of TiOx shell including highly concentrated defects such as Ti3+ and/or oxygen vacancies is controllable in the range from 6 to over 18 nm by varying the treatment time in the SMMW assisted reaction. In addition to i… ▽ More Submicron core/shell Ti/TiOx photocatalyst is successfully synthesized via single-mode magnetic microwave (SMMW) assisted direct oxidation of planetary ball-milled TiH2. The thickness of TiOx shell including highly concentrated defects such as Ti3+ and/or oxygen vacancies is controllable in the range from 6 to over 18 nm by varying the treatment time in the SMMW assisted reaction. In addition to its quite narrow optical bandgap (1.34-2.69 eV) and efficient visible-light absorption capacity, the submicron Ti/TiOx particle exhibits superior photocatalytic performance towards H2 production from water under both UV and visible-light irradiation to compare with a commercial TiO2 photocatalyst (P-25). Such excellent performance can be achieved by the synergetic effect of enhancement in visible light absorption capacity and photo-excited carrier separation because of the highly concentrated surface defects and the specific Ti/TiOx core/shell structure, respectively. △ Less

Submitted 2 February, 2022; originally announced February 2022.

Journal ref: Advanced Powder Technology 31 (2020) 1777-1783

A Novel Single-Mode Microwave Assisted Synthesis of Metal Oxide as Visible-light Photocatalyst

Authors: Kunihiko Katoa, Sebastien Vaucher, Patrik Hoffmann, Yunzi Xin, Takashi Shirai

Abstract: Visible-light photocatalyst titanium dioxide (TiO2) was successfully prepared via a novel and facile single-mode microwave assisted synthesis process. In this one-step synthesis, Ti as target material selectively oxides in magnetic field throughout rapid heating, whose process requires less energy consumption and short time. In obtained TiO2, self-doping of Ti3+ was confirmed, which makes TiO2 per… ▽ More Visible-light photocatalyst titanium dioxide (TiO2) was successfully prepared via a novel and facile single-mode microwave assisted synthesis process. In this one-step synthesis, Ti as target material selectively oxides in magnetic field throughout rapid heating, whose process requires less energy consumption and short time. In obtained TiO2, self-doping of Ti3+ was confirmed, which makes TiO2 performed sufficient light absorption in visible region with wavelength above 400 nm. Such Ti3+ self-doped TiO2 exhibits much narrower optical bandgap (2.14 eV) to compare with stoichiometric TiO2 (3.0-3.2 eV). The synthesized TiO2 also shows superior photocatalytic activity to commercially available TiO2 towards the degradation of Rhodamine B under visible light irradiation. △ Less

Submitted 2 February, 2022; originally announced February 2022.

Journal ref: Materials Letters 235 (2019) 125-128

Dynamic Stabilization of Water Bottles

Authors: Yanwen Gu, Yunzhou Bai, Yuxi Xin, Lintao Xiao, Sihui Wang, Hanchao Sun

Abstract: The motion of water filled bottles is studied when it is thrown into the air and falls back to the floor, including the possibilities of an upright landing or rolling down before it finally reaches static state. When dealing with the process after throwing a water bottle, the free falling (bottle falls without initial angular velocity) and flipping (bottle falls with initial angular velocity) are… ▽ More The motion of water filled bottles is studied when it is thrown into the air and falls back to the floor, including the possibilities of an upright landing or rolling down before it finally reaches static state. When dealing with the process after throwing a water bottle, the free falling (bottle falls without initial angular velocity) and flipping (bottle falls with initial angular velocity) are considered. In theory, the physical principles behind the motion are analyzed. In addition, the impacts of initial angle, linear velocity, angular velocity and the water amount on the uprightness of the bottle are discussed. In experiment of throwing bottle, we changed the water amount, angular velocity, and releasing height, and examined the impacts of these factors. The results suggest that a certain amount of water and spinning result in higher possibility of upright landing. When dealing with rolling bottle, theoretically we build the bottle-and-bead model to describe the coupled motion of water and the bottle. Analytical solutions are obtained for small amplitude and the numerical solution can be done in a general situation. In the experiment of rolling bottle, we firstly verified the theoretical model, and then addressed the impact of initial conditions and water amount on the motion patterns of the bottle. △ Less

Submitted 17 December, 2021; originally announced December 2021.

Comments: 48 pages

Comprehensive and Clinically Accurate Head and Neck Organs at Risk Delineation via Stratified Deep Learning: A Large-scale Multi-Institutional Study

Authors: Dazhou Guo, Jia Ge, Xianghua Ye, Senxiang Yan, Yi Xin, Yuchen Song, Bing-shen Huang, Tsung-Min Hung, Zhuotun Zhu, Ling Peng, Yanping Ren, Rui Liu, Gong Zhang, Mengyuan Mao, Xiaohua Chen, Zhongjie Lu, Wenxiang Li, Yuzhen Chen, Lingyun Huang, Jing Xiao, Adam P. Harrison, Le Lu, Chien-Yu Lin, Dakai Jin, Tsung-Ying Ho

Abstract: Accurate organ at risk (OAR) segmentation is critical to reduce the radiotherapy post-treatment complications. Consensus guidelines recommend a set of more than 40 OARs in the head and neck (H&N) region, however, due to the predictable prohibitive labor-cost of this task, most institutions choose a substantially simplified protocol by delineating a smaller subset of OARs and neglecting the dose di… ▽ More Accurate organ at risk (OAR) segmentation is critical to reduce the radiotherapy post-treatment complications. Consensus guidelines recommend a set of more than 40 OARs in the head and neck (H&N) region, however, due to the predictable prohibitive labor-cost of this task, most institutions choose a substantially simplified protocol by delineating a smaller subset of OARs and neglecting the dose distributions associated with other OARs. In this work we propose a novel, automated and highly effective stratified OAR segmentation (SOARS) system using deep learning to precisely delineate a comprehensive set of 42 H&N OARs. SOARS stratifies 42 OARs into anchor, mid-level, and small & hard subcategories, with specifically derived neural network architectures for each category by neural architecture search (NAS) principles. We built SOARS models using 176 training patients in an internal institution and independently evaluated on 1327 external patients across six different institutions. It consistently outperformed other state-of-the-art methods by at least 3-5% in Dice score for each institutional evaluation (up to 36% relative error reduction in other metrics). More importantly, extensive multi-user studies evidently demonstrated that 98% of the SOARS predictions need only very minor or no revisions for direct clinical acceptance (saving 90% radiation oncologists workload), and their segmentation and dosimetric accuracy are within or smaller than the inter-user variation. These findings confirmed the strong clinical applicability of SOARS for the OAR delineation process in H&N cancer radiotherapy workflows, with improved efficiency, comprehensiveness, and quality. △ Less

Submitted 1 November, 2021; originally announced November 2021.

Construction and On-site Performance of the LHAASO WFCTA Camera

Authors: F. Aharonian, Q. An, Axikegu, L. X. Bai, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, H. Cai, J. T. Cai, Z. Cao, Z. Cao, J. Chang, J. F. Chang, X. C. Chang, B. M. Chen, J. Chen, L. Chen, L. Chen, L. Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. H. Chen , et al. (234 additional authors not shown)

Abstract: The focal plane camera is the core component of the Wide Field-of-view Cherenkov/fluorescence Telescope Array (WFCTA) of the Large High-Altitude Air Shower Observatory (LHAASO). Because of the capability of working under moonlight without aging, silicon photomultipliers (SiPM) have been proven to be not only an alternative but also an improvement to conventional photomultiplier tubes (PMT) in this… ▽ More The focal plane camera is the core component of the Wide Field-of-view Cherenkov/fluorescence Telescope Array (WFCTA) of the Large High-Altitude Air Shower Observatory (LHAASO). Because of the capability of working under moonlight without aging, silicon photomultipliers (SiPM) have been proven to be not only an alternative but also an improvement to conventional photomultiplier tubes (PMT) in this application. Eighteen SiPM-based cameras with square light funnels have been built for WFCTA. The telescopes have collected more than 100 million cosmic ray events and preliminary results indicate that these cameras are capable of working under moonlight. The characteristics of the light funnels and SiPMs pose challenges (e.g. dynamic range, dark count rate, assembly techniques). In this paper, we present the design features, manufacturing techniques and performances of these cameras. Finally, the test facilities, the test methods and results of SiPMs in the cameras are reported here. △ Less

Submitted 4 July, 2021; v1 submitted 29 December, 2020; originally announced December 2020.

Comments: 45 pages, 21 figures, article

Journal ref: Eur. Phys. J. C 81, 657 (2021)

Tensile properties of structural I clathrate hydrates:Role of guest-host hydrogen bonding ability

Authors: Yue Xin, Qiao Shi, Ke Xu, Zhi-Sen Zhang, Jian-Yang Wu

Abstract: Clathrate hydrates (CHs) are one of the most promising molecular structures in applications of gas capture and storage, and gas separations. Fundamental knowledge of mechanical characteristics of CHs is of crucial importance for assessing gas storage and separations at cold conditions, as well as understanding their stability and formation mechanisms. Here, the tensile mechanical properties of str… ▽ More Clathrate hydrates (CHs) are one of the most promising molecular structures in applications of gas capture and storage, and gas separations. Fundamental knowledge of mechanical characteristics of CHs is of crucial importance for assessing gas storage and separations at cold conditions, as well as understanding their stability and formation mechanisms. Here, the tensile mechanical properties of structural I CHs encapsulating a variety of guest species (methane, ammonia, sulfureted hydrogen, formaldehyde, methanol, and methyl mercaptan) that have different abilities to form hydrogen (H-) bonds with water molecule are explored by classical molecular dynamics (MD) simulations. All investigated CHs are structurally stable clathrate structures. Basic mechanical properties of CHs including tensile limit and Young's modulus are dominated by the H-bonding ability of host-guest molecules and the guest molecular polarity. CHs containing small methane, formaldehyde and sulfureted hydrogen guest molecules that possess weak H-bonding ability are mechanically robust clathrate structures and mechanically destabilized via brittle failure on the (1 0 1) plane. However, those entrapping methyl mercaptan, methanol, and ammonia that have strong H-bonding ability are mechanically weak molecular structures and mechanically destabilized through ductile failure as a result of gradual global dissociation of clathrate cages. △ Less

Submitted 19 November, 2020; originally announced November 2020.

Contact resistivity due to oxide layers between two REBCO tapes

Authors: Jun Lu, Yan Xin, Eric Lochner, Kyle Radcliff, Jeremy Levitan

Abstract: In a no-insulation (NI) REBCO magnet, the turn-to-turn contact resistivity (Rc) determines its quench self-protection capability, charging delay time and the energy loss during field ramps. Therefore it is critically important to be able to control a range of Rc values suitable for various NI magnet coils. We used a commercial oxidizing agent Ebonol C to treat the copper surface of REBCO tapes. Th… ▽ More In a no-insulation (NI) REBCO magnet, the turn-to-turn contact resistivity (Rc) determines its quench self-protection capability, charging delay time and the energy loss during field ramps. Therefore it is critically important to be able to control a range of Rc values suitable for various NI magnet coils. We used a commercial oxidizing agent Ebonol C to treat the copper surface of REBCO tapes. The copper oxide layer was characterized by cross-sectional transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). The oxide layer formed in Ebonol C at 98 °C for 1 min is Cu2O of about 0.5 um. The Rc between two oxidized REBCO is in the order of 35 mOhm-cm2 at 4.2 K which decreases slowly with contact pressure cycles. The Rc increases but only slightly at 77 K. We also investigated the effect of oxidation of stainless steel co-wind tape on Rc. The native oxides on 316 stainless steel tape as well as those heated in air at 200 - 600 °C were examined by TEM and XPS. The native oxides layer is about 3 nm thick. After heating at 300 °C for 8 min and 600 °C for 1 min, its thickness increases to about 10 and 30 nm respectively. For the stainless steel tapes with about 10 nm surface oxides, pressure cycling for 30,000 cycles decreases Rc by almost 4 orders of magnitude. Whereas at 77 K, it only changes slightly. For a surface with 30 nm oxide, the Rc decreases moderately with load cycles. The results suggest that for an oxidized stainless steel to achieve stable Rc over large number of load cycles a relatively thick oxide film is needed. △ Less

Submitted 3 December, 2019; originally announced December 2019.

Comments: 10 figures

Open-minded imitation can achieve near-optimal vaccination coverage

Authors: Ying Xin, David Gerberry, Winfried Just

Abstract: Studies of voluntary vaccination decisions by rational individuals predict that the population will reach a Nash equilibrium with vaccination coverage below the societal optimum. Human decision-making involves mechanisms in addition to rational calculations of self-interest, such as imitation of successful others. Previous research had shown that imitation alone cannot achieve better results. Unde… ▽ More Studies of voluntary vaccination decisions by rational individuals predict that the population will reach a Nash equilibrium with vaccination coverage below the societal optimum. Human decision-making involves mechanisms in addition to rational calculations of self-interest, such as imitation of successful others. Previous research had shown that imitation alone cannot achieve better results. Under realistic choices of the parameters it may lead to equilibrium vaccination coverage even below the Nash equilibrium. However, these findings rely on the widely accepted use of Fermi functions for modeling the probabilities of switching to another strategy. We consider here a more general functional form of the switching probabilities. It is consistent with functions that give best fits for empirical data in a widely cited psychological experiment and involves one additional parameter $α$. This parameter can be loosely interpreted as a degree of open-mindedness. We found both by means of simulations and analytically that sufficiently high values of $α$ will drive the equilibrium vaccination coverage arbitrarily close to the societal optimum. △ Less

Submitted 23 August, 2018; originally announced August 2018.

Comments: 31 pages, 11 figures

MSC Class: 91A80; 92D30; 91E40

The DArk Matter Particle Explorer mission

Authors: J. Chang, G. Ambrosi, Q. An, R. Asfandiyarov, P. Azzarello, P. Bernardini, B. Bertucci, M. S. Cai, M. Caragiulo, D. Y. Chen, H. F. Chen, J. L. Chen, W. Chen, M. Y. Cui, T. S. Cui, A. D'Amone, A. De Benedittis, I. De Mitri, M. Di Santo, J. N. Dong, T. K. Dong, Y. F. Dong, Z. X. Dong, G. Donvito, D. Droz , et al. (139 additional authors not shown)

Abstract: The DArk Matter Particle Explorer (DAMPE), one of the four scientific space science missions within the framework of the Strategic Pioneer Program on Space Science of the Chinese Academy of Sciences, is a general purpose high energy cosmic-ray and gamma-ray observatory, which was successfully launched on December 17th, 2015 from the Jiuquan Satellite Launch Center. The DAMPE scientific objectives… ▽ More The DArk Matter Particle Explorer (DAMPE), one of the four scientific space science missions within the framework of the Strategic Pioneer Program on Space Science of the Chinese Academy of Sciences, is a general purpose high energy cosmic-ray and gamma-ray observatory, which was successfully launched on December 17th, 2015 from the Jiuquan Satellite Launch Center. The DAMPE scientific objectives include the study of galactic cosmic rays up to $\sim 10$ TeV and hundreds of TeV for electrons/gammas and nuclei respectively, and the search for dark matter signatures in their spectra. In this paper we illustrate the layout of the DAMPE instrument, and discuss the results of beam tests and calibrations performed on ground. Finally we present the expected performance in space and give an overview of the mission key scientific goals. △ Less

Submitted 14 September, 2017; v1 submitted 26 June, 2017; originally announced June 2017.

Comments: 45 pages, including 29 figures and 6 tables. Published in Astropart. Phys

Journal ref: Astropart. Phys. 95 (2017) 6-24