Wei Xu

Hunan University

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Co-Authors

Changyuan Yu

Hong Kong Polytechnic University

H. Mandel

Heidelberg University

W. Seifert

Heidelberg University

A. Quirrenbach

Heidelberg University

A. Reiners

University of Göttingen

MÁ

M. Á. Sánchez Carrasco

Instituto de Astrofísica de Andalucía

J. A. Caballero

Centro de Astrobiología

I. Ribas

Institut d'Estudis Espacials de Catalunya

P. J. Amado

Instituto de Astrofísica de Andalucía

A. Ramón

Universitat de València

Cooperative Institutions

Max Planck Institute for Astronomy

164

Max Planck Society

150

Leibniz Institute for Astrophysics Potsdam

102

Consejo Superior de Investigaciones Científicas

Instituto de Astrofísica de Andalucía

Centre National de la Recherche Scientifique

University of Göttingen

Heidelberg University

Instituto de Astrofísica de Canarias

Calar Alto Observatory

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Photonic Weyl waveguide and saddle-chips-like modes

Hanyu Wang Wei Xu Zhu Hong Biao Yang

Topological Weyl semimetals are characterized by open Fermi arcs on their terminal surfaces, which not only renewed our well-accepted concepts of the Fermi loop but also enabled many exotic phenomena, such as one-way propagation. The key prerequisite is that the two terminal surfaces have to be well-separated far away, i.e. the Fermi arcs are not allowed to couple with each other. Thus, their interaction was overlooked before. Here, we consider the coupled Fermi arcs and propose a Weyl planar waveguide, where we found a saddle-chips-like guiding mode. Compared with the conventional waveguiding mode, the new guiding mode propagates along different directions depending on the vertical excitation position. Experimentally, we drill periodic holes in metal plates to sandwich an ideal Weyl meta-crystal and characterize the topological guiding mode. Our study shows the intriguing behaviors of topological photonic waveguides, which could lead to beam manipulation, position sensing, and even 3D information processing on photonic chips.

Saddle

Waveguide

10.1364/opticaopen.25059545.v1

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Citations (0)

Plasmonic Structure Assisted All-Optical Tunable Fiber Laser

Zhen Li Wei Xu Enqing Chen Ying Qiu Tiancai Jiang

In this paper, we proposed and demonstrated a tunable fiber laser using all-optical plasmonic modulation, where the localized surface plasmon resonance effect of gold nanobipyramids (GNBPs) and polarization maintaining thin-cladding photonic crystal fiber were utilized to realize tunable output wavelength controlled by the 980 nm pump light. The laser achieves a tunability of 2.21 nm in C-band, with a side mode suppression ratio of 27dB and the peak intensity can also be tuned continuously. The proposed tunable laser shows an average power fluctuation of less than 1 dB and the output wavelength and the power intensity both exhibit high stability. Therefore, the proposed plasmonic structure assisted all-optical tunable laser has advantages such as compact structure, good reproducibility, continuous tuning, and simple operation, which indicates great potential in future all-optical applications.

10.2139/ssrn.4516635

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All-optical tunable fiber filter based on a few-mode optical fiber mode interferometer coated with graphene epoxy resin composite material

Optics Communications (2021)

Enqing Chen Bo Dong Li Yang Ziwan Li Xiaoli Wang

10.1016/j.optcom.2021.127140

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Citations (7)

Tunableness of single-band and dual-band absorption and filtering using vanadium-dioxide-based metamaterial

Applied Physics A (2022)

Yangkuan Wu Wei Xu Haiquan Zhou Xiaoyong Qiu Yifeng He

Split-ring resonator

Figure of Merit

Absorption band

10.1007/s00339-022-06065-z

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Citations (8)

From weak to strong coupling with enhanced dualband magnetoplasmonic Kerr sensing in the dimer-grating metamaterial

Applied Physics Express (2022)

Ruxian Zhu Xiaoming Zhang Wei Xu Leyi Chen Shaolong Tang

Abstract We investigate the evolution of plasmonic spectral features from weak to strong coupling regime, with a large Rabi splitting of 210 meV, in the designed dimer-grating metamaterial. The two-driven coupled oscillator model has been proposed to quantitatively analyze the evolution, where the two oscillators are directly excited by the external driving light wave, demonstrating that the evolution is caused by not only aligning the resonance wavelength of related SP modes, but also low-loss. The proposed metamaterial is of high magnetoplasmonic refractive index sensitivity of 280.05 nm RIU −1 and figure of merit of 3*10 4 RIU −1 , suggesting promising applications in biochemical sensing.

Figure of Merit

10.35848/1882-0786/aca9bb

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Citations (1)

Non-Invasive Measurement for Cardiac Variations Using a Fiber Optic Sensor

IEEE Photonics Technology Letters (2021)

Weimin Lyu Wei Xu Fangang Yang Shuyang Chen Fengze Tan

Cardiovascular diseases (CVDs) are very common in modern society, such as atherosclerosis, hypertension, etc., which have a great impact on heart function. Therefore, hospitalization monitoring alone is far from enough. Long-term monitoring of the heart is needed in daily life. The technology of non-invasive monitoring of the cardiovascular system can meet the needs of long-term monitoring of the heart condition, helping to promote the improvement of lifestyle and daily care, reducing the overall risk of developing CVDs. The purpose of this study is to investigate the cardiac response after different exercises using a

$3\times 3$

demodulation scheme-based ballistocardiography (BCG) monitoring system. A fiber optic sensor (FOS)-based smart cushion is used to replace the traditional inconvenient electrocardiogram (ECG) for heart rate variability (HRV). The correlation between BCG inter-beat interval (IBI) and ECG IBI is 0.9862, and the RMSE is 0.0139. The BCG signal can assess cardiac contractility by analyzing RJ interval with ECG, which is a practical alternative to the pre-ejection period (PEP).

Ballistocardiography

Cardiac monitoring

10.1109/lpt.2021.3078757

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Citations (25)

Fiber-optic in-line Mach-Zehnder modal interferometer for breathing monitoring application

Ketian Wang Wei Xu Na Zhang Kunpu Li Cheungchuem Yu

A simple fiber-optic in-line Mach-Zehnder modal interferometer is fabricated and studied for monitoring human being's breathing rate, which is one of the most important vital signs. The sensing structure is simply fabricated by a couple of up-tapers manufactured in the common telecommunication single mode fiber (SMF) by a commercial splicer. Sensing performances with different distances between the dual up-tapers are addressed. The whole setup only contains one laser source, one photo-detector and one section of SMF with dual up-tapers. It can real-timely monitor people's respiration rhythm without complex signal processing and the scheme is simple and low-cost.

SIGNAL (programming language)

10.1109/cleopr.2017.8118841

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Citations (6)

Research and Design of a LC-VCO for 3.125Gbps Serial Communication Applications

Advanced materials research (2013)

Ji Hai Duan Sheng Huang Zheng Chen Wei Xu

A LC voltage-control oscillator（LC-VCO） with two stage LC cross coupling structure is designed for serial communication applications. The design constraints and tradeoffs among power dissipation and startup condition, tank amplitude, tuning range are executed using graphical optimization method. This design strategy leads to a good phase noise performance which is demonstrated through design example. This LC-VCO is implemented using 0.18-m RF CMOS process. The post-simulation results show that the circuit has an output frequency from 3.23G to 3GHz, and phase noise is -125.2dBc/1MHz. The VCO only occupies a chip area of 600m*800m, and it consumes 16 mW. A Comparison to prior arts further supports this design example and its optimization technique. The most important thing of this work is that a method of separating variables to analyze design problems is suggested.

10.4028/www.scientific.net/amr.662.902

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LINC-NIRVANA: the single arm MCAO experiment

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2004)

Sebastian Egner Wolfgang Gäessler Tom Herbst Roberto Ragazzoni R. Stuik

LINC-NIRVANA is an imaging interferometer for the Large Binocular Telescope (LBT) and will make use of multi-conjugated adaptive optics (MCAO) with two 349 actuators deformable mirrors (DM), two 672 actuator deformable secondary mirrors and a total of 4 wavefront sensors (WFS) by using 8 or 12 natural guide stars each. The goal of the MCAO is to increase sky coverage and achieve a medium Strehl-ratio over the 2 arcmin field of view. To test the concepts and prototypes, a laboratory setup of one MCAO arm is being built. We present the layout of the MCAO prototype, planned and accomplished tests, especially for the used Xinetics DMs, and a possible setup for a test on sky with an existing 8m class telescope.

Strehl ratio

Deformable Mirror

Large Binocular Telescope

Field of view

10.1117/12.550046

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Citations (10)

The CARMENES search for exoplanets around M dwarfs

Astronomy and Astrophysics (2019)

M. Zechmeister S. Dreizler I. Ribas A. Reiners J. A. Caballero

Context. Teegarden's Star is the brightest and one of the nearest ultra-cool dwarfs in the solar neighbourhood. For its late spectral type (M7.0V), the star shows relatively little activity and is a prime target for near-infrared radial velocity surveys such as CARMENES. Aims. As part of the CARMENES search for exoplanets around M dwarfs, we obtained more than 200 radial-velocity measurements of Teegarden's Star and analysed them for planetary signals. Methods. We find periodic variability in the radial velocities of Teegarden's Star. We also studied photometric measurements to rule out stellar brightness variations mimicking planetary signals. Results. We find evidence for two planet candidates, each with $1.1M_\oplus$ minimum mass, orbiting at periods of 4.91 and 11.4 d, respectively. No evidence for planetary transits could be found in archival and follow-up photometry. Small photometric variability is suggestive of slow rotation and old age. Conclusions. The two planets are among the lowest-mass planets discovered so far, and they are the first Earth-mass planets around an ultra-cool dwarf for which the masses have been determined using radial velocities.

Radial velocity

Starspot

Stellar rotation

Minimum mass

10.1051/0004-6361/201935460

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Citations (128)