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Indefinite metacavities coupled to a mirror:bound states in the continuum with anomalous resonance scaling

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Photonics Research 2024年第3期12卷 598-607页

作者： QIANG ZHANG PEIXIANG LI ZHIYUAN GU SHAODING LIU ZEJUN DUAN College of Electronic Information and Optical Engineering Taiyuan University of TechnologyTaiyuan 030024China Key Laboratory of Advanced Transducers and Intelligent Control System Ministry of EducationTaiyuan University of TechnologyTaiyuan 030024China

Indefinite metacavities(IMCs)made of hyperbolic metamaterials show great advantages in terms of extremely small mode volume due to large wave vectors endowed by the unique hyperbolic dispersion.However,quality(Q)factors of IMCs are limited by Ohmic loss of metals and radiative loss of leaked waves.Despite the fact that Ohmic loss of metals is inevitable in IMCs,the radiative loss can be further suppressed by leakage engineering.Here we propose a mirror coupled IMC structure which is able to operate at Fabry–Pérot bound states in the continuum(BICs)while the hyperbolic nature of IMCs is retained.At the BIC point,the radiative loss of magnetic dipolar cavity modes in IMCs is completely absent,resulting in a considerably increased Q factor(>90).Deviating from the BIC point,perfect absorption bands(>0.99)along with a strong near-field intensity enhancement(>1.8×10^(4))appear when the condition of critical coupling is almost fulfilled.The proposed BICs are robust to the geometry and material composition of IMCs and anomalous scaling law of resonance is verified during the tuning of optical responses.We also demonstrate that the Purcell effect of the structure can be significantly improved under BIC and quasi-BIC regimes due to the further enhanced Q factor to mode volume ratio.Our results provide a new train of thought to design ultra-small optical nanocavities that may find many applications benefitting from strong light–matter interactions.

关键词： hyperbolic mirror definite

Is a mirror necessary for mirror therapy?

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Neural Regeneration Research 2023年第12期18卷 2703-2704页

作者： Richard G.Carson Alannah Morley Trinity College Institute of Neuroscience and School of Psychology Trinity College DublinDublinIreland Dublin Ireland(Carson RG)School of PsychologyQueen’s University BelfastBelfastNorthern IrelandUK(Carson RG)School of MedicineTrinity College DublinDublinIreland

Since it was first described as a method to treat phantom limb pain, mirror therapy(MT) has been applied in many areas of rehabilitation. Its seminal application with the aim of restoring motor function following stro... 详细信息

关键词： mirror al. therapy

Towards automatic freeform optics design: coarse and fine search of the three-mirror solution space

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Light(Science & Applications) 2021年第4期10卷 660-670页

作者： Benqi Zhang Guofan Jin Jun Zhu State Key Laboratory of Precision Measurement Technology and Instruments Departm ent of Precision InstrumentTsinghua UniversityBeijing 100084China

Design of an optical system,whether classic or novel,in the past or the present,requires significant effort from the designer.In addition to design methods and theories,the designer’s skills and experience in optical system design are particularly important,which may require years of practice to learn.The diversity and variety of results are limited because of the difficulty,time,and labor costs required.In this article,we propose an automatic design method for freeform optics that can achieve a diverse range of three-mirror designs.The optical specifications and the design constraints are the only inputs required,and a variety of results can be obtained automatically.The output results have various structures and various optical power distributions with high imaging qualities.By implementing the design method,designers can not only realize an overview of the solution space of the three-mirror freeform system,but can also focus on specific designs.

关键词： mirror optics system

Spin-preserving chiral photonic crystal mirror

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Light(Science & Applications) 2020年第1期9卷 1787-1798页

作者： Behrooz Semnani Jeremy Flannery Rubayet Al Maruf Michal Bajcsy Institute for Quantum Computing(IQC) University of WaterlooWaterloo N2L3G1 ONCanada Department of Electrical&Computer Engineering University of WaterlooWaterloo N2L3G1 ONCanada Department of Physics and Astronomy University of WaterlooWaterloo N2L3G1 ONCanada

Chirality refers to a geometric phenomenon in which objects are not superimposable on their mirror image.Structures made of nanoscale chiral elements can exhibit chiroptical effects,such as dichroism for left-and right-handed circularly polarized light,which makes these structures highly suitable for applications ranging from quantum information processing and quantum optics to circular dichroism spectroscopy and molecular recognition.At the same time,strong chiroptical effects have been challenging to achieve even in synthetic optical media,and chiroptical effects for light with normal incidence have been speculated to be prohibited in thin,lossless quasi-two-dimensional structures.Here,we report an experimental realization of a giant chiroptical effect in a thin monolithic photonic crystal mirror.Unlike conventional mirrors,our mirror selectively reflects only one spin state of light while preserving its handedness,with a near-unity level of circular dichroism.The operational principle of the photonic crystal mirror relies on guided-mode resonance(GMR)with a simultaneous excitation of leaky transverse electric(TE-like)and transverse magnetic(TM-like)Bloch modes in the photonic crystal slab.Such modes are not reliant on the suppression of radiative losses through long-range destructive interference,and even small areas of the photonic crystal exhibit robust circular dichroism.Despite its simplicity,the mirror strongly outperforms earlier reported structures and,contrary to a prevailing notion,demonstrates that near-unity reflectivity contrast for opposite helicities is achievable in a quasi-two-dimensional structure.

关键词： mirror crystal circular

Aphasia rehabilitation based on mirror neuron theory: a randomized-block-design study of neuropsychology and functional magnetic resonance imaging

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Neural Regeneration Research 2019年第6期14卷 1004-1012页

作者： Wen-Li Chen Qian Ye Si-Cong Zhang Yang Xia Xi Yang Ti-Fei Yuan Chun-Lei Shan Jian-An Li Department of Rehabilitation Medicine The First Affiliated Hospital of Nanjing Medical University Department of Rehabilitation Medicine Zhangjiagang Hospital Affiliated to Nanjing University of Chinese Medicine School of Rehabilitation Sciences Nanjing Normal University of Special Education Yueyang Hospital of Integrated Chinese and Western Medicine Shanghai University of Traditional Chinese Medicine Department of Rehabilitation Medicine Zhongda HospitalSoutheast University Shanghai Key Laboratory of Psychotic Disorders Shanghai Mental Health CenterShanghai Jiao Tong University School of Medicine School of Rehabilitation Science Shanghai University of Traditional Chinese Medicine Institute of Rehabilitation Medicine Shanghai Academy of Traditional Chinese Medicine

When watching someone performs an action, mirror neurons are activated in a way that is very similar to the activation that occurs when actually performing that action. Previous single-sample case studies indicate that hand-action observation training may lead to activation and remodeling of mirror neuron systems, which include important language centers, and may improve language function in aphasia patients. In this randomized-block-design experiment, we recruited 24 aphasia patients from, Zhongda Hospital, Southeast University, China. The patients were divided into three groups where they underwent hand-action observation and repetition, dynamic-object observation and repetition, or conventional speech therapy. Training took place 5 days per week, 35 minutes per day, for 2 weeks. We assessed language function via picture naming tests for objects and actions and the Western Aphasia Battery. Among the participants, one patient, his wife and four healthy student volunteers underwent functional magnetic resonance imaging to analyze changes in brain activation during hand-action observation and dynamic-object observation. Results demonstrated that, compared with dynamic-object observation, hand-action observation led to greater performance with respect to the aphasia quotient and affiliated naming sub-tests and a greater Western Aphasia Battery test score. The overall effect was similar to that of conventional aphasia training, yet hand-action observation had advantages compared with conventional training in terms of vocabulary extraction and spontaneous speech. Thus, hand-action observation appears to more strongly activate the mirror neuron system compared with dynamic-object observation. The activated areas included Broca's area, Wernicke's area, and the supramarginal gyrus. These results suggest that hand-action observation combined with repetition might better improve language function in aphasia patients compared with dynamic-object observation combined with repetition. The therapeutic mechanism of this interv

关键词： nerve regeneration mirror neuron hand-action observation aphasia rehabilitation stroke functional magnetic resonance imaging neuropsychology neural regeneration

mirror,mirror on the wall,who is the best of them all?Artificial intelligence versus gastroenterologists in solving clinical problems

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Gastroenterology Report 2023年第1期11卷 579-581页

作者： Felice Benedicenti Tommaso Pessarelli Mattia Corradi Marco Michelon Nicoletta Nandi Pietro Lampertico Maurizio Vecchi Lucia Scaramella Luca Elli Department of Pathophysiology and Transplantation University of MilanMilanItaly Gastroenterology and Endoscopy Unit Foundation IRCCS Ca’Granda Ospedale Maggiore PoliclinicoMilanItaly Division of Gastroenterology and Hepatology CRC“A.M.and A.Migliavacca”Center for the Study of Liver DiseaseFoundation IRCCS Ca’Granda Ospedale Maggiore PoliclinicoMilanItaly

Introduction Artificial intelligence(AI)is a concept that commonly refers to machines mimicking human cognitive behavior during learning and problem-solving[1].Chatbots are a typical example of an AI system,capable of interacting with humans[2].ChatGPT(OpenAI,San Francisco,CA,USA)[3]is a new-generation chatbot that captures the context and relationship between words in input sequences through multiple layers of self-attention and feedforward neural networks.Then,it predicts the most likely“token”to succeed the previous one based on patterns in its training data.Therefore,it is a self-contained system that does not copy existing information[4].

关键词： token neural mirror

Nanolaminate-based design for UV laser mirror coatings

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Light(Science & Applications) 2020年第1期9卷 1820-1825页

作者： Meiping Zhu Nuo Xu Behshad Roshanzadeh STPBoyd Wolfgang Rudolph Yingjie Chai Jianda Shao Laboratory of Thin Film Optics Shanghai Institute of Optics and Fine MechanicsChinese Academy of SciencesShanghai 201800China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Hangzhou Institute for Advanced Study University of Chinese Academy of SciencesHangzhou 310024China Key Laboratory of Materials for High Power Laser Shanghai Institute of Optics and Fine MechanicsChinese Academy of SciencesShanghai 201800China Department of Physics and Astronomy University of New MexicoAlbuquerqueNM 87131USA CREOL The College of Optics and PhotonicsUniversity of Central FloridaOrlandoFL 32816USA

With ever-increasing laser power,the requirements for ultraviolet(UV)coatings increase continuously.The fundamental challenge for UV laser-resistant mirror coatings is to simultaneously exhibit a high reflectivity with a large bandwidth and high laser resistance.These characteristics are traditionally achieved by the deposition of laser-resistant layers on highly reflective layers.We propose a“reflectivity and laser resistance in one”design by using tunable nanolaminate layers that serve as an effective layer with a high refractive index and a large optical bandgap.An Al_(2)O_(3)-HfO_(2) nanolaminate-based mirror coating for UV laser applications is experimentally demonstrated using ebeam deposition.The bandwidth,over which the reflectance is >99.5%,is more than twice that of a traditional mirror with a comparable overall thickness.The laser-induced damage threshold is increased by a factor of ~1.3 for 7.6 ns pulses at a wavelength of 355 nm.This tunable,nanolaminate-based new design strategy paves the way toward a new generation of UV coatings for high-power laser applications.

关键词： tunable mirror reflectivity

High-precision fabrication of 4m SiC aspheric mirror

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Light(Science & Applications) 2023年第1期12卷 3-4页

作者： Xiangang Luo State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering Institute of Optics and ElectronicsChinese Academy of Sciences610209 ChengduChina School of Optoelectronics University of Chinese Academy of Sciences100049 BeijingChina

The 4 m diameter SiC aspheric mirror emerges due to a series of technological breakthroughs in blank mirror preparation,asphere fabrication,and testing,as well as cladding and coating,laying the groundwork for future ... 详细信息

关键词： mirror breakthrough coating

Study on plasma cleaning of the large-scale first mirror of the charge exchange recombination spectroscopy diagnostic on EAST

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Plasma Science and Technology 2020年第3期22卷 24-33页

作者：彭姣鄢容陈俊凌丁锐李颖颖种法力 Institute of Plasma Physics Chinese Academy of SciencesHefei 230031People’s Republic of China Xuzhou University of Technology Xuzhou 221000People’s Republic of China

In the Experimental Advanced Superconducting Tokamak(EAST),the reflectivity of the charge exchange recombination spectroscopy(CXRS)first mirror(FM)was dramatically dropped down to 20%of the original value after the operation of two EAST experimental campaigns from 2014-2015,leading to degradation of the signal intensity of the CXRS diagnostic to an unacceptably low level.The radio frequency(RF)plasma cleaning of the CXRS FM with a dimension of 303×81×76 mm3 and a small curvature of 0.008 mm-1 was performed to remove deposits to recover the reflectivity.After 168 h cleaning by RF plasma,the maximum specular reflectivity of the FM could reach 92%of the original value at 532 nm,making the cleaned CXRS FM eligible to be reused for the CXRS diagnostic in the 2016 EAST campaign.Dedicated tests of sputtering polished mirror samples were performed to explore the cleaning uniformity and possible damage to the mirror surface.The specular reflectivity did not show obvious dependence on locations along the surface with the same cleaning time.The measured surface roughness gradually increased with sputtering time.The reflectivity remained almost unchanged regardless of different sputtering times and locations,indicating negligible damage to the FM surface even after 100 h sputtering.The recontaminated CXRS FM in the 2016 EAST campaign was firstly cleaned for 81 h,and the least reflectivity recovery for areas with relatively thick deposits was only 40%.After continuing cleaning to 147 h,redeposition of the sputtered residual deposits on the FM surface was observed.In the future for in situ cleaning of the FMs in EAST and ITER,deposits should be removed timely when they are very thin taking into account a very long cleaning time and presumable redeposition of thick and nonuniform deposits.

关键词： first mirror CXRS EAST plasma cleaning cleaning uniformity