Single-frequency ultranarrow linewidth on-chip microlasers with a fast wavelength tunability play a game-changing role in a broad spectrum of applications ranging from coherent communication,light detection and rangin...Single-frequency ultranarrow linewidth on-chip microlasers with a fast wavelength tunability play a game-changing role in a broad spectrum of applications ranging from coherent communication,light detection and ranging,to metrology and sensing.Design and fabrication of such light sources remain a challenge due to the difficulties in making a laser cavity that has an ultrahigh optical quality(Q)factor and supports only a single lasing frequency simultaneously.Here,we demonstrate a unique single-frequency ultranarrow linewidth lasing mechanism on an erbium ion-doped lithium niobate(LN)microdisk through simultaneous excitation of high-Q polygon modes at both pump and laser wavelengths.As the polygon modes are sparse within the optical gain bandwidth compared with the whispering gallery mode counterpart,while their Q factors(above 10 million)are even higher due to the significantly reduced scattering on their propagation paths,single-frequency lasing with a linewidth as narrow as 322 Hz is observed.The measured linewidth is three orders of magnitude narrower than the previous record in on-chip LN microlasers.Finally,enabled by the strong linear electro-optic effect of LN,real-time electro-optical tuning of the microlaser with a high tuning efficiency of∼50 pm∕100 V is demonstrated.展开更多
As miniature fibre-optic platforms,micro/nanofibres(MNFs)taper-drawn from silica fibres have been widely studied for applications from optical sensing,nonlinear optics to optomechanics and atom optics.While continuous...As miniature fibre-optic platforms,micro/nanofibres(MNFs)taper-drawn from silica fibres have been widely studied for applications from optical sensing,nonlinear optics to optomechanics and atom optics.While continuous-wave(CW)optical waveguiding is frequently adopted,so far almost all MNFs are operated in low-power region(e.g.,<0.1 W).Here,we demonstrate high-power low-loss CW optical waveguiding in MNFs around 1550-nm wavelength.We show that a pristine MNF,even with a diameter down to 410 nm,can waveguide an optical power higher than 10 W,which is about 30 times higher than demonstrated previously.Also,we predict an optical damage threshold of 70 W.In highpower CW waveguiding MNFs,we demonstrate high-speed optomechanical driving of microparticles in air,and second harmonic generation efficiency higher than those pumped by short pulses.Our results may pave a way towards high-power MNF optics,for both scientific research and technological applications.展开更多
In animal experiments,ischemic stroke is usually induced through middle cerebral artery occlusion(MCAO),and quality assessment of this procedure is crucial.However,an accurate assessment method based on 18F-fluorodeox...In animal experiments,ischemic stroke is usually induced through middle cerebral artery occlusion(MCAO),and quality assessment of this procedure is crucial.However,an accurate assessment method based on 18F-fluorodeoxyglucose(FDG)positron emission tomography(PET)is still lacking.The difficulty lies in the inconsistent preprocessing pipeline,biased intensity normalization,or unclear spatiotemporal uptake of FDG.Here,we propose an image feature-based protocol to assess the quality of the procedure using a 3D scale-invariant feature transform and support vector machine.This feature-based protocol provides a convenient,accurate,and reliable tool to assess the quality of the MCAO procedure in FDG PET studies.Compared with existing approaches,the proposed protocol is fully quantitative,objective,automatic,and bypasses the intensity normalization step.An online interface was constructed to check images and obtain assessment results.展开更多
Many applications requiring both spectral and spatial information at high resolution benefit from spectral imaging.Although different technical methods have been developed and commercially available,computational spec...Many applications requiring both spectral and spatial information at high resolution benefit from spectral imaging.Although different technical methods have been developed and commercially available,computational spectral cameras represent a compact,lightweight,and inexpensive solution.However,the tradeoff between spatial and spectral resolutions,dominated by the limited data volume and environmental noise,limits the potential of these cameras.In this study,we developed a deeply learned broadband encoding stochastic hyperspectral camera.In particular,using advanced artificial intelligenee in filter design and spectrum reconstruction,we achieved 7000-11,000 times faster signal processing and〜10 times improvement regarding noise toleranee.These improvements enabled us to precisely and dynamically reconstruct the spectra of the entire field of view,previously unreachable with compact computational spectral cameras.展开更多
We propose to generate a sub-nanometer-confined optical field in a nanoslit waveguiding mode in a coupled nanowire pair(CNP).We show that,when a conventional waveguide mode with a proper polarization is evanescently c...We propose to generate a sub-nanometer-confined optical field in a nanoslit waveguiding mode in a coupled nanowire pair(CNP).We show that,when a conventional waveguide mode with a proper polarization is evanescently coupled into a properly designed CNP with a central nanoslit,it can be efficiently channeled into a high-purity nanoslit mode within a waveguiding length<10μm.The CNP can be either freestanding or on-chip by using a tapered fiber or planar waveguide for input-coupling,with a coupling efficiency up to 95%.Within the slit region,the output diffraction-limited nanoslit mode offers an extremely confined optical field(∼0.3 nm×3.3 nm)with a peak-to-background ratio higher than 25 dB and can be operated within a 200-nm bandwidth.The group velocity dispersion of the nanoslit mode for ultrafast pulsed operation is also briefly investigated.Compared with the previous lasing configuration,the waveguiding scheme demonstrated here is not only simple and straightforward in structural design but is also much flexible and versatile in operation.Therefore,the waveguiding scheme we show here may offer an efficient and flexible platform for exploring light–matter interactions beyond the nanometer scale,and developing optical technologies ranging from superresolution nanoscopy and atom/molecule manipulation to ultra-sensitivity detection.展开更多
Industrial development is an essential foundation of the national economy,but the industry is also the largest source of air pollution,of which power plants,iron and steel,building materials,and other industries emit ...Industrial development is an essential foundation of the national economy,but the industry is also the largest source of air pollution,of which power plants,iron and steel,building materials,and other industries emit large amounts of pollutants.Therefore,the Chinese government has promulgated a series of stringent emission regulations,and it is against this backdrop that research into air pollution control technologies for key industrial sectors is in full swing.In particular,during the 13th Five-Year Plan,breakthroughs have been made in pollution control technology for key industrial sectors.A multi-pollutant treatment technology system of desulfurization,denitrification,and dust collection,which applies to key industries such as power plants,steel,and building materials,has been developed.High-performance materials for the treatment of different pollutants,such as denitrification catalysts and desulfurization absorbers,were developed.At the same time,multi-pollutant synergistic removal technologies for flue gas in various industries have also become a hot research topic,with important breakthroughs in the synergistic removal of NO_(x),SO_(x),and Hg.Due to the increasingly stringent emission standards and regulations in China,there is still a need to work on the development of multi-pollutant synergistic technologies and further research and development of synergistic abatement technologies for CO_(2) to meet the requirements of ultra-low emissions in industrial sectors.展开更多
In vivo fluorescence imaging in the second near-infrared window(NIR-II)has been considered as a promising technique for visualizing mammals.However,the definition of the NIR-II region and the mechanism accounting for ...In vivo fluorescence imaging in the second near-infrared window(NIR-II)has been considered as a promising technique for visualizing mammals.However,the definition of the NIR-II region and the mechanism accounting for the excellent performance still need to be perfected.Herein,we simulate the photon propagation in the NIR region(to 2340 nm),confirm the positive contribution of moderate light absorption by water in intravital imaging and perfect the NIR-II window as 900–1880 nm,where 1400–1500 and 1700–1880 nm are defined as NIR-IIx and NIR-IIc regions,respectively.Moreover,2080–2340 nm is newly proposed as the third near-infrared(NIR-III)window,which is believed to provide the best imaging quality.The wide-field fluorescence microscopy in the brain is performed around the NIRIIx region,with excellent optical sectioning strength and the largest imaging depth of intravital NIR-II fluorescence microscopy to date.We also propose 1400 nm long-pass detection in off-peak NIR-II imaging whose performance exceeds that of NIR-IIb imaging,using bright fluorophores with short emission wavelength.展开更多
基金the National Key R&D Program of China(2019YFA0705000)the National Natural Science Foundation of China(12192251,62122079,11734009,62035013,61635009,62075192,11874375,and 11874154)+4 种基金Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)Science and Technology Commission of Shanghai Municipality(21DZ1101500)the Quantum Joint Funds of the Natural Foundation of Shandong Province(ZR2020LLZ007)the Fundamental Research Funds for the Central University,Nature Science and Engineering Research Council of Canada(NSERC)Discovery(RGPIN-2020-05938)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2020249).
文摘Single-frequency ultranarrow linewidth on-chip microlasers with a fast wavelength tunability play a game-changing role in a broad spectrum of applications ranging from coherent communication,light detection and ranging,to metrology and sensing.Design and fabrication of such light sources remain a challenge due to the difficulties in making a laser cavity that has an ultrahigh optical quality(Q)factor and supports only a single lasing frequency simultaneously.Here,we demonstrate a unique single-frequency ultranarrow linewidth lasing mechanism on an erbium ion-doped lithium niobate(LN)microdisk through simultaneous excitation of high-Q polygon modes at both pump and laser wavelengths.As the polygon modes are sparse within the optical gain bandwidth compared with the whispering gallery mode counterpart,while their Q factors(above 10 million)are even higher due to the significantly reduced scattering on their propagation paths,single-frequency lasing with a linewidth as narrow as 322 Hz is observed.The measured linewidth is three orders of magnitude narrower than the previous record in on-chip LN microlasers.Finally,enabled by the strong linear electro-optic effect of LN,real-time electro-optical tuning of the microlaser with a high tuning efficiency of∼50 pm∕100 V is demonstrated.
基金supported by the National Key Research and Development Project of China(2018YFB2200404)the National Natural Science Foundation of China(62175213,62175122,and 92150302)+1 种基金the Zhejiang Provincial Natural Science Foundation of China(LR21F050002)the Fundamental Research Funds for the Central Universities.
文摘As miniature fibre-optic platforms,micro/nanofibres(MNFs)taper-drawn from silica fibres have been widely studied for applications from optical sensing,nonlinear optics to optomechanics and atom optics.While continuous-wave(CW)optical waveguiding is frequently adopted,so far almost all MNFs are operated in low-power region(e.g.,<0.1 W).Here,we demonstrate high-power low-loss CW optical waveguiding in MNFs around 1550-nm wavelength.We show that a pristine MNF,even with a diameter down to 410 nm,can waveguide an optical power higher than 10 W,which is about 30 times higher than demonstrated previously.Also,we predict an optical damage threshold of 70 W.In highpower CW waveguiding MNFs,we demonstrate high-speed optomechanical driving of microparticles in air,and second harmonic generation efficiency higher than those pumped by short pulses.Our results may pave a way towards high-power MNF optics,for both scientific research and technological applications.
基金supported by R4012-18,C6021-19EF and GRF 16306919 from the Research Grant Council(RGC)ITS/480/18FP and MHP/033/20+2 种基金from the Innovation and Technology Commission(ITC)of the Hong Kong S.A.R.,Hetao Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone Projec(HZQB-KCZYB-2020083)the National Natural Science Foundation of China(U1809204)the Talent Program of Zhejiang Province(2021R51004)。
文摘In animal experiments,ischemic stroke is usually induced through middle cerebral artery occlusion(MCAO),and quality assessment of this procedure is crucial.However,an accurate assessment method based on 18F-fluorodeoxyglucose(FDG)positron emission tomography(PET)is still lacking.The difficulty lies in the inconsistent preprocessing pipeline,biased intensity normalization,or unclear spatiotemporal uptake of FDG.Here,we propose an image feature-based protocol to assess the quality of the procedure using a 3D scale-invariant feature transform and support vector machine.This feature-based protocol provides a convenient,accurate,and reliable tool to assess the quality of the MCAO procedure in FDG PET studies.Compared with existing approaches,the proposed protocol is fully quantitative,objective,automatic,and bypasses the intensity normalization step.An online interface was constructed to check images and obtain assessment results.
基金the Major Research Plan of the National Natural Science Foundation of China(92050115)Zhejiang Provincial Natural Science Foundation of China(LZ21F050003)ZJU-Sunny Innovation Center(2019-01).
文摘Many applications requiring both spectral and spatial information at high resolution benefit from spectral imaging.Although different technical methods have been developed and commercially available,computational spectral cameras represent a compact,lightweight,and inexpensive solution.However,the tradeoff between spatial and spectral resolutions,dominated by the limited data volume and environmental noise,limits the potential of these cameras.In this study,we developed a deeply learned broadband encoding stochastic hyperspectral camera.In particular,using advanced artificial intelligenee in filter design and spectrum reconstruction,we achieved 7000-11,000 times faster signal processing and〜10 times improvement regarding noise toleranee.These improvements enabled us to precisely and dynamically reconstruct the spectra of the entire field of view,previously unreachable with compact computational spectral cameras.
基金This work was sup-ported by the National Key Research and Development Program of China(2018YFB2200404)the New Cornerstone Science Foundation,the National Natural Science Foundation of China(92150302 and 62175213)+1 种基金the Natural Science Foundation of Zhejiang Province(LR21F050002)the Fundamental Research Funds for the Central Universities.
文摘We propose to generate a sub-nanometer-confined optical field in a nanoslit waveguiding mode in a coupled nanowire pair(CNP).We show that,when a conventional waveguide mode with a proper polarization is evanescently coupled into a properly designed CNP with a central nanoslit,it can be efficiently channeled into a high-purity nanoslit mode within a waveguiding length<10μm.The CNP can be either freestanding or on-chip by using a tapered fiber or planar waveguide for input-coupling,with a coupling efficiency up to 95%.Within the slit region,the output diffraction-limited nanoslit mode offers an extremely confined optical field(∼0.3 nm×3.3 nm)with a peak-to-background ratio higher than 25 dB and can be operated within a 200-nm bandwidth.The group velocity dispersion of the nanoslit mode for ultrafast pulsed operation is also briefly investigated.Compared with the previous lasing configuration,the waveguiding scheme demonstrated here is not only simple and straightforward in structural design but is also much flexible and versatile in operation.Therefore,the waveguiding scheme we show here may offer an efficient and flexible platform for exploring light–matter interactions beyond the nanometer scale,and developing optical technologies ranging from superresolution nanoscopy and atom/molecule manipulation to ultra-sensitivity detection.
基金supported by the National Key Research and Development Program of China(No.2019YFC0214803)。
文摘Industrial development is an essential foundation of the national economy,but the industry is also the largest source of air pollution,of which power plants,iron and steel,building materials,and other industries emit large amounts of pollutants.Therefore,the Chinese government has promulgated a series of stringent emission regulations,and it is against this backdrop that research into air pollution control technologies for key industrial sectors is in full swing.In particular,during the 13th Five-Year Plan,breakthroughs have been made in pollution control technology for key industrial sectors.A multi-pollutant treatment technology system of desulfurization,denitrification,and dust collection,which applies to key industries such as power plants,steel,and building materials,has been developed.High-performance materials for the treatment of different pollutants,such as denitrification catalysts and desulfurization absorbers,were developed.At the same time,multi-pollutant synergistic removal technologies for flue gas in various industries have also become a hot research topic,with important breakthroughs in the synergistic removal of NO_(x),SO_(x),and Hg.Due to the increasingly stringent emission standards and regulations in China,there is still a need to work on the development of multi-pollutant synergistic technologies and further research and development of synergistic abatement technologies for CO_(2) to meet the requirements of ultra-low emissions in industrial sectors.
基金This work was supported by the National Natural Science Foundation of China(61975172,82001874,and 21974104)Fundamental Research Funds for the Central Universities(2020-KYY-511108-0007)Natural Science Foundation of Zhejiang Province(LR17F050001).
文摘In vivo fluorescence imaging in the second near-infrared window(NIR-II)has been considered as a promising technique for visualizing mammals.However,the definition of the NIR-II region and the mechanism accounting for the excellent performance still need to be perfected.Herein,we simulate the photon propagation in the NIR region(to 2340 nm),confirm the positive contribution of moderate light absorption by water in intravital imaging and perfect the NIR-II window as 900–1880 nm,where 1400–1500 and 1700–1880 nm are defined as NIR-IIx and NIR-IIc regions,respectively.Moreover,2080–2340 nm is newly proposed as the third near-infrared(NIR-III)window,which is believed to provide the best imaging quality.The wide-field fluorescence microscopy in the brain is performed around the NIRIIx region,with excellent optical sectioning strength and the largest imaging depth of intravital NIR-II fluorescence microscopy to date.We also propose 1400 nm long-pass detection in off-peak NIR-II imaging whose performance exceeds that of NIR-IIb imaging,using bright fluorophores with short emission wavelength.
