Linearized approximations of reflection and transmission coefficients set a foundation for amplitude versus offset（AVO） analysis and inversion in exploration geophysics.However,the weak properties contrast hypothesi...Linearized approximations of reflection and transmission coefficients set a foundation for amplitude versus offset（AVO） analysis and inversion in exploration geophysics.However,the weak properties contrast hypothesis of those linearized approximate equations leads to big errors when the two media across the interface vary dramatically.To extend the application of AVO analysis and inversion to high contrast between the properties of the two layers,we derive a novel nonlinearized high-contrast approximation of the PP-wave reflection coefficient,which establishes the direct relationship between PPwave reflection coefficient and P-wave velocities,S-wave velocities and densities across the interface.（A PP wave is a reflected compressional wave from an incident compressional wave（P-wave）.） This novel approximation is derived from the exact reflection coefficient equation with Taylor expansion for the incident angle.Model tests demonstrate that,compared with the reflection coefficients of the linearized approximations,the reflection coefficients of the novel nonlinearized approximate equation agree with those of the exact PP equation better for a high contrast interface with a moderate incident angle.Furthermore,we introduce a nonlinear direct inversion method utilizing the novel reflection coefficient equation as forward solver,to implement the direct inversion for the six parameters including P-wave velocities,S-wave velocities,and densities in the upper and lower layers across the interface.This nonlinear inversion algorithm is able to estimate the inverse of the nonlinear function in terms of model parameters directly rather than in a conventional optimization way.Three examples verified the feasibility and suitability of this novel approximation for a high contrast interface,and we still could estimate the six parameters across the interface reasonably when the parameters in both media across the interface vary about 50%.展开更多
To achieve the enhancement and manipulation of light absorption in graphene within the visible and near infrared regions, a design consists of high-contrast gratings and two evanescently coupled slabs with graphene mo...To achieve the enhancement and manipulation of light absorption in graphene within the visible and near infrared regions, a design consists of high-contrast gratings and two evanescently coupled slabs with graphene monolayer is demonstrated. The operation principle and design process of the proposed structure are analyzed using the coupled mode theory, which is confirmed by the rigorous coupled wave analysis. It is proved that the absorptance of graphene monolayer can be greatly enhanced to unity. The thickness of grating and slab layers can significantly change the line width and resonant mode position in the absorption spectra. Furthermore, high tunability in amplitude and bandwidth of the absorption spectra can be achieved by controlling the structural parameters of the hybrid structure. The proposed devices could be efficiently exploited as tunable and selective absorbers, and could be allowed to realize other two-dimensional materials-based selective photo-detectors.展开更多
Photoacoustic(PA) imaging has drawn tremendous research interest for various applications in biomedicine and experienced exponential growth over the past decade. Since the scattering effect of biological tissue on ult...Photoacoustic(PA) imaging has drawn tremendous research interest for various applications in biomedicine and experienced exponential growth over the past decade. Since the scattering effect of biological tissue on ultrasound is two-to three-orders magnitude weaker than that of light, photoacoustic imaging can effectively improve the imaging depth.However, as the depth of imaging further increases, the incident light is seriously affected by scattering that the generated photoacoustic signal is very weak and the signal-to-noise ratio(SNR) is quite low. Low SNR signals can reduce imaging quality and even cause imaging failure. In this paper, we proposed a new wavefront shaping and imaging method of low SNR photoacoustic signal using digital micromirror device(DMD) based superpixel method. We combined the superpixel method with DMD to modulate the phase and amplitude of the incident light, and the genetic algorithm(GA) was used as the wavefront shaping algorithm. The enhancement of the photoacoustic signal reached 10.46. Then we performed scanning imaging by moving the absorber with the translation stage. A clear image with contrast of 8.57 was obtained while imaging with original photoacoustic signals could not be achieved. The proposed method opens new perspectives for imaging with weak photoacoustic signals.展开更多
Starlight is generally unpolarized,but the light reflected from the planet is linearly polarized as the result of the Rayleigh scattering.For ground-based exoplanet imaging,atmospheres turbulence is changing from time...Starlight is generally unpolarized,but the light reflected from the planet is linearly polarized as the result of the Rayleigh scattering.For ground-based exoplanet imaging,atmospheres turbulence is changing from time to time,which induces speckle noise and hampers the high-contrast imaging of the faint exoplanets.In this paper,we propose a differential-imaging polarimeter dedicated for exoplanet high-contrast imaging.The system contains a zero-order half-wave plate(HWP)located on the optical pupil plane,which can rotate to modulate the incoming light,and a Wollaston prism(WP)is used to generate two polarized images,which is used for simultaneously polarization differential imaging and thus our system is fundamentally immune to the atmospheric turbulence induced temporally-variable wavefront aberration.Our polarimeter can be inserted near the telescope image focal plane,and provide an extra contrast for the exoplanet high-contrast imaging.To achieve best differential-imaging performance,dedicated algorithm is developed,which can effectively correct the distortion and the intensity unbalance between the two differential images.The system successfully achieves an extra contrast of^30~50 times,which can be used with current adaptive optics and coronagraph system for directly imaging of giant Jupiter-like exoplanets.展开更多
The plasma mirror system was installed on the 1 PW laser beamline of Shanghai Superintense Ultrafast Laser Facility[SULF]for enhancing the temporal contrast of the laser pulse.About 2 orders of magnitude improvement o...The plasma mirror system was installed on the 1 PW laser beamline of Shanghai Superintense Ultrafast Laser Facility[SULF]for enhancing the temporal contrast of the laser pulse.About 2 orders of magnitude improvement on pulse contrast was measured on picosecond and nanosecond time scales.The experiments show that high-contrast laser pulses can significantly improve the cutoff energy and quantity of proton beams.Then different target distributions are assumed in particles in cell simulations,which can qualitatively assume the expansion of nanometer-scale foil.The high-contrast laser enables the SULF-1PW beamline to generally be of benefit for many potential applications.展开更多
High-contrast imaging provided by a coronagraph is critical for the direction imaging of the Earth-like planet orbiting its bright parent star.A major limitation for such direct imaging is the speckle noise that is in...High-contrast imaging provided by a coronagraph is critical for the direction imaging of the Earth-like planet orbiting its bright parent star.A major limitation for such direct imaging is the speckle noise that is induced from the wave-front error of an optical system.We derive an algorithm for the wave-front measurement directly from 3 focal plane images.The 3 images are achieved through a deformable mirror to provide specific phases for the optics system.We introduce an extra amplitude modulation on one deformable mirror configuration to create an uncorrelated wave-front,which is a critical procedure for wave-front sensing.The simulation shows that the reconstructed wave-front is consistent with the original wave-front theoretically,which indicates that such an algorithm is a promising technique for the wave-front measurement for the high-contrast imaging.展开更多
Novel construction of a resonant-cavity-enhanced photodetector(RCE-PD) with monolithic high-contrast grating(HCG)is proposed to overcome the difficulty of fabricating a high reflective mirror of RCE-PD at 1 550 nm. In...Novel construction of a resonant-cavity-enhanced photodetector(RCE-PD) with monolithic high-contrast grating(HCG)is proposed to overcome the difficulty of fabricating a high reflective mirror of RCE-PD at 1 550 nm. In this structure,HCG serves as the top mirror of the RCE-PD, whereas InGaAs serves as a sacrificial layer to achieve monolithic integration.During the bandwidth optimization, the ratio of the thickness of the total intrinsic region and the absorption layer is introduced to realize the simultaneous optimization of the thickness of spacing layers and absorption layer. After structural optimization, the quantum efficiency of the device with diameter of 20 μm is 82% at 1 550 nm, and the 3-dB bandwidth is 34 GHz at a bias of 3 V.展开更多
Developing dual-state luminophores(DSLs)with strong fluorescence in both the monomer and aggregate states is urgently needed but remains a huge challenge because most current luminophores are either aggregation-induce...Developing dual-state luminophores(DSLs)with strong fluorescence in both the monomer and aggregate states is urgently needed but remains a huge challenge because most current luminophores are either aggregation-induced emission or aggregation-caused quenching molecules.Moreover,limited by the structural conservation of the few existing DSLs,there are not enough response sites that can be used to customize various activatable fluorescent probes for specific molecular imaging.Herein,we engineered a general integration strategy for the fabrication of such DSLs with excellent photophysical properties.The DSLs,with their tunable spectra,a large Stokes shift(>170 nm),and achievable near-infrared(NIR)emission,show great potential for high-contrast imaging.Importantly,DSLs can be used as a universal platform for probe customization due to their activatable fluorescence through protection-deprotection of the phenolic hydroxyl group.Based on this,an NIR fluorescent probe DSL-Gal was developed for sensing of β-galactosidase in solutions,senescent cells,and liver metastases with high contrast,further confirming the superiority and universal feasibility of DSLs in probe design.The integration strategy may provide a novel approach for the generation of other DSLs and have great potential applications in bioimaging.展开更多
High-contrast mechanochromic(MC)materials are prominent candidates for sensor,security,and memory applications;however,the development of materials with a large luminescence change(Δλem>100 nm)under external stim...High-contrast mechanochromic(MC)materials are prominent candidates for sensor,security,and memory applications;however,the development of materials with a large luminescence change(Δλem>100 nm)under external stimuli is challenging.Considering that polymorphic molecules usually exhibit reversible mechanochromism,polymorph prediction is adopted for thefirst time to guide the design of high-contrastMC materials in this study.We designed and synthesized a series of donor–π–acceptor pyran derivatives bearing different electron donors and acceptors as model systems.The polymorph prediction indicated that 4-dicyanomethylene-2,6-distyryl-4H-pyran and 4H-pyran-4-one derivatives had the potential to crystallize in both monomer andπ-dimer aggregates,while barbituric acid-based compound tended to pack tightly in all aggregated states.The experimental results agreed well with the prediction that the derivatives potentially possessing both monomer andπ-dimer aggregate structures exhibit excellent MC behavior,whereas the fluorescence difference for the barbituric acid-based compounds is minimal.Moreover,a compound with an excellent fluorescence difference of three colors during reversible mechanochromism was chosen as the candidate for an optical recording material and security ink.This work proposes an effective method to guide the design of stimuli-responsive materials,which may open promising avenues for the development of high-contrast MC molecules.展开更多
基金the sponsorship of the National 973 Program of China (2013CB228604)the National Grand Project for Science and Technology (2011ZX05030-004-002, 2011ZX05019-003 and 2011ZX05006-002) for funding this research+2 种基金the support of the Australian and Western Australian Governments and the North West Shelf Joint Venture Partnersthe Western Australian Energy Research Alliance (WA:ERA)Foundation from Geophysical Key Lab of SINOPEC (WTYJYWX2013-04-01)
文摘Linearized approximations of reflection and transmission coefficients set a foundation for amplitude versus offset（AVO） analysis and inversion in exploration geophysics.However,the weak properties contrast hypothesis of those linearized approximate equations leads to big errors when the two media across the interface vary dramatically.To extend the application of AVO analysis and inversion to high contrast between the properties of the two layers,we derive a novel nonlinearized high-contrast approximation of the PP-wave reflection coefficient,which establishes the direct relationship between PPwave reflection coefficient and P-wave velocities,S-wave velocities and densities across the interface.（A PP wave is a reflected compressional wave from an incident compressional wave（P-wave）.） This novel approximation is derived from the exact reflection coefficient equation with Taylor expansion for the incident angle.Model tests demonstrate that,compared with the reflection coefficients of the linearized approximations,the reflection coefficients of the novel nonlinearized approximate equation agree with those of the exact PP equation better for a high contrast interface with a moderate incident angle.Furthermore,we introduce a nonlinear direct inversion method utilizing the novel reflection coefficient equation as forward solver,to implement the direct inversion for the six parameters including P-wave velocities,S-wave velocities,and densities in the upper and lower layers across the interface.This nonlinear inversion algorithm is able to estimate the inverse of the nonlinear function in terms of model parameters directly rather than in a conventional optimization way.Three examples verified the feasibility and suitability of this novel approximation for a high contrast interface,and we still could estimate the six parameters across the interface reasonably when the parameters in both media across the interface vary about 50%.
基金Supported by the National Natural Science Foundation of China under Grant No 41675154the Six Major Talent Peak Expert of Jiangsu Province under Grant No 2015-XXRJ-014the Jiangsu 333 High-Level Talent Cultivation Program under Grant No BRA2016425
文摘To achieve the enhancement and manipulation of light absorption in graphene within the visible and near infrared regions, a design consists of high-contrast gratings and two evanescently coupled slabs with graphene monolayer is demonstrated. The operation principle and design process of the proposed structure are analyzed using the coupled mode theory, which is confirmed by the rigorous coupled wave analysis. It is proved that the absorptance of graphene monolayer can be greatly enhanced to unity. The thickness of grating and slab layers can significantly change the line width and resonant mode position in the absorption spectra. Furthermore, high tunability in amplitude and bandwidth of the absorption spectra can be achieved by controlling the structural parameters of the hybrid structure. The proposed devices could be efficiently exploited as tunable and selective absorbers, and could be allowed to realize other two-dimensional materials-based selective photo-detectors.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB1104500)the Beijing Natural Science Foundation,China(Grant No.7182091)+1 种基金the National Natural Science Foundation of China(Grant No.21627813)the Research Projects on Biomedical Transformation of China–Japan Friendship Hospital(Grant No.PYBZ1801)。
文摘Photoacoustic(PA) imaging has drawn tremendous research interest for various applications in biomedicine and experienced exponential growth over the past decade. Since the scattering effect of biological tissue on ultrasound is two-to three-orders magnitude weaker than that of light, photoacoustic imaging can effectively improve the imaging depth.However, as the depth of imaging further increases, the incident light is seriously affected by scattering that the generated photoacoustic signal is very weak and the signal-to-noise ratio(SNR) is quite low. Low SNR signals can reduce imaging quality and even cause imaging failure. In this paper, we proposed a new wavefront shaping and imaging method of low SNR photoacoustic signal using digital micromirror device(DMD) based superpixel method. We combined the superpixel method with DMD to modulate the phase and amplitude of the incident light, and the genetic algorithm(GA) was used as the wavefront shaping algorithm. The enhancement of the photoacoustic signal reached 10.46. Then we performed scanning imaging by moving the absorber with the translation stage. A clear image with contrast of 8.57 was obtained while imaging with original photoacoustic signals could not be achieved. The proposed method opens new perspectives for imaging with weak photoacoustic signals.
基金the National Natural Science Foundation of China (NSFC, 11703058, 11703056, 11661161011, 11433007, 11220101001, 11328302, 11373005 and 11303064)the Opening Project of Key Laboratory of Astronomical Optics & Technology, Nanjing Institute of Astronomical Optics & Technology, Chinese Academy of Sciences (CASKLAOT-KF201606)+5 种基金the “Strategic Priority Research Program” of the ChineseAcademy of Sciences (XDA04075200)the Special Fund for astronomy of CAS (2015–2016)the Special Fund for Young Researcher of Nanjing Institute of Astronomical Optics & Technologythe International Partnership Program of the Chinese Academy of Sciences (114A32KYSB20160018)carried out at California State University Northridge with the support from NSF AST-1607921the Mt. Cuba Astronomical Foundation
文摘Starlight is generally unpolarized,but the light reflected from the planet is linearly polarized as the result of the Rayleigh scattering.For ground-based exoplanet imaging,atmospheres turbulence is changing from time to time,which induces speckle noise and hampers the high-contrast imaging of the faint exoplanets.In this paper,we propose a differential-imaging polarimeter dedicated for exoplanet high-contrast imaging.The system contains a zero-order half-wave plate(HWP)located on the optical pupil plane,which can rotate to modulate the incoming light,and a Wollaston prism(WP)is used to generate two polarized images,which is used for simultaneously polarization differential imaging and thus our system is fundamentally immune to the atmospheric turbulence induced temporally-variable wavefront aberration.Our polarimeter can be inserted near the telescope image focal plane,and provide an extra contrast for the exoplanet high-contrast imaging.To achieve best differential-imaging performance,dedicated algorithm is developed,which can effectively correct the distortion and the intensity unbalance between the two differential images.The system successfully achieves an extra contrast of^30~50 times,which can be used with current adaptive optics and coronagraph system for directly imaging of giant Jupiter-like exoplanets.
基金supported by the National Natural Science Foundation of China(No.12075306)the Natural Science Foundation of Shanghai(No.22ZR1470900)+1 种基金the Key Research Programs in Frontier Science(No.ZDBSLY-SLH006)the China Postdoctoral Science Foundation(No.2021M703328)。
文摘The plasma mirror system was installed on the 1 PW laser beamline of Shanghai Superintense Ultrafast Laser Facility[SULF]for enhancing the temporal contrast of the laser pulse.About 2 orders of magnitude improvement on pulse contrast was measured on picosecond and nanosecond time scales.The experiments show that high-contrast laser pulses can significantly improve the cutoff energy and quantity of proton beams.Then different target distributions are assumed in particles in cell simulations,which can qualitatively assume the expansion of nanometer-scale foil.The high-contrast laser enables the SULF-1PW beamline to generally be of benefit for many potential applications.
基金Supported by the National Natural Science Foundation of China (Grant No. 10873024)
文摘High-contrast imaging provided by a coronagraph is critical for the direction imaging of the Earth-like planet orbiting its bright parent star.A major limitation for such direct imaging is the speckle noise that is induced from the wave-front error of an optical system.We derive an algorithm for the wave-front measurement directly from 3 focal plane images.The 3 images are achieved through a deformable mirror to provide specific phases for the optics system.We introduce an extra amplitude modulation on one deformable mirror configuration to create an uncorrelated wave-front,which is a critical procedure for wave-front sensing.The simulation shows that the reconstructed wave-front is consistent with the original wave-front theoretically,which indicates that such an algorithm is a promising technique for the wave-front measurement for the high-contrast imaging.
基金supported by the National Natural Science Foundation of China(Nos.61674018,61574019 and 61674020)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20130005130001)the Beijing Municipality Natural Science Foundation(No.4132069)
文摘Novel construction of a resonant-cavity-enhanced photodetector(RCE-PD) with monolithic high-contrast grating(HCG)is proposed to overcome the difficulty of fabricating a high reflective mirror of RCE-PD at 1 550 nm. In this structure,HCG serves as the top mirror of the RCE-PD, whereas InGaAs serves as a sacrificial layer to achieve monolithic integration.During the bandwidth optimization, the ratio of the thickness of the total intrinsic region and the absorption layer is introduced to realize the simultaneous optimization of the thickness of spacing layers and absorption layer. After structural optimization, the quantum efficiency of the device with diameter of 20 μm is 82% at 1 550 nm, and the 3-dB bandwidth is 34 GHz at a bias of 3 V.
基金the generous financial support of the National Key R&D Program of China(grant no.2019YFA0210100)the National Natural Science Foundation of China(grant nos.21890744 and 21877029)+1 种基金the Hunan Postgraduate Research and Innovation Project(grant no.CX2018B187)the China Postdoctoral Science Foundation(grant nos.2019TQ0085 and 2020M682538).
文摘Developing dual-state luminophores(DSLs)with strong fluorescence in both the monomer and aggregate states is urgently needed but remains a huge challenge because most current luminophores are either aggregation-induced emission or aggregation-caused quenching molecules.Moreover,limited by the structural conservation of the few existing DSLs,there are not enough response sites that can be used to customize various activatable fluorescent probes for specific molecular imaging.Herein,we engineered a general integration strategy for the fabrication of such DSLs with excellent photophysical properties.The DSLs,with their tunable spectra,a large Stokes shift(>170 nm),and achievable near-infrared(NIR)emission,show great potential for high-contrast imaging.Importantly,DSLs can be used as a universal platform for probe customization due to their activatable fluorescence through protection-deprotection of the phenolic hydroxyl group.Based on this,an NIR fluorescent probe DSL-Gal was developed for sensing of β-galactosidase in solutions,senescent cells,and liver metastases with high contrast,further confirming the superiority and universal feasibility of DSLs in probe design.The integration strategy may provide a novel approach for the generation of other DSLs and have great potential applications in bioimaging.
基金This research was made possible as a result of a generous grant from National Natural Science Foundation of China(nos.21472111 and 21877013)the 111 Project(no.D20015).
文摘High-contrast mechanochromic(MC)materials are prominent candidates for sensor,security,and memory applications;however,the development of materials with a large luminescence change(Δλem>100 nm)under external stimuli is challenging.Considering that polymorphic molecules usually exhibit reversible mechanochromism,polymorph prediction is adopted for thefirst time to guide the design of high-contrastMC materials in this study.We designed and synthesized a series of donor–π–acceptor pyran derivatives bearing different electron donors and acceptors as model systems.The polymorph prediction indicated that 4-dicyanomethylene-2,6-distyryl-4H-pyran and 4H-pyran-4-one derivatives had the potential to crystallize in both monomer andπ-dimer aggregates,while barbituric acid-based compound tended to pack tightly in all aggregated states.The experimental results agreed well with the prediction that the derivatives potentially possessing both monomer andπ-dimer aggregate structures exhibit excellent MC behavior,whereas the fluorescence difference for the barbituric acid-based compounds is minimal.Moreover,a compound with an excellent fluorescence difference of three colors during reversible mechanochromism was chosen as the candidate for an optical recording material and security ink.This work proposes an effective method to guide the design of stimuli-responsive materials,which may open promising avenues for the development of high-contrast MC molecules.
