The nanofluid-based direct absorption solar collector(NDASC)ensures that solar radiation passing through the tube wall is directly absorbed by the nanofluid,reducing thermal resistance in the energy transfer process.H...The nanofluid-based direct absorption solar collector(NDASC)ensures that solar radiation passing through the tube wall is directly absorbed by the nanofluid,reducing thermal resistance in the energy transfer process.However,further exploration is required to suppress the outward thermal losses from the nanofluid at high temperatures.Herein,this paper proposes a novel NDASC in which the outer surface of the collector tube is covered with functional coatings and a three-dimensional computational fluid dynamics model is established to study the energy flow distributions on the collector within the temperature range of 400-600 K.When the nanofluid’s absorption coefficient reaches 80 m^(-1),the NDASC shows the optimal thermal performance,and the NDASC with local Sn-In_(2)O_(3) coating achieves a 7.8% improvement in thermal efficiency at 400 K compared to the original NDASC.Furthermore,hybrid coatings with Sn In_(2)O_(3)/WTi-Al_(2)O_(3) are explored,and the optimal coverage angles are determined.The NDASC with such coatings shows a 10.22%-17.9% increase in thermal efficiency compared to the original NDASC and a 7.6%-19.5% increase compared to the traditional surface-type solar collectors,demonstrating the effectiveness of the proposed energy flow control strategy for DASCs.展开更多
AIM: To describe the characteristics of modulation transfer function (MTF) of anterior corneal surface, and obtain the the normal reference range of MTF at different spatial frequencies and optical zones of the anteri...AIM: To describe the characteristics of modulation transfer function (MTF) of anterior corneal surface, and obtain the the normal reference range of MTF at different spatial frequencies and optical zones of the anterior corneal surface in myopes. METHODS: Four hundred eyes from 200 patients were examined under SIRIUS corneal topography system. Phoenis analysis software was applied to simulate the MTF curves of anterior corneal surface at vertical and horizontal meridians at the 3, 4, 5, 6, 7mm optical zones of cornea. The MTF values at spatial frequencies of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 and 60 cycles/degree (c/d) were selected. RESULTS: The MTF curve of anterior corneal surface decreased rapidly from low to intermediate frequency (0-15cpd) at various optical zones of cornea, the value decreased to 0 slowly at higher frequency (>15cpd). With the increase of the optical zones of cornea, MTF curve decreased gradually. 3) In the range of 3 mm- 6 mm optical zones of the cornea, the MTF values measured at horizontal meridian were greater than the corresponding values at horizontal meridian of each spatial frequency, the difference was statistically significant (P<0.05). At 7 mm optical zones of cornea, the MTF values measured at horizontal meridian were less than the corresponding values at vertical meridian at 10-60 spatial frequencies (cpd), and the difference was statistically significant in 25, 30, 35, 40, 45, 50 cpd(P<0.05). CONCLUSION: MTF can be used to describe the imaging quality of optical systems at anterior corneal surface objectively in detail.展开更多
AIM:To investigate the size of functional optical zone(FOZ)after small incision lenticule extraction(SMILE)versus femtosecond laser assisted excimer laser keratomileusis(FS-LASIK)for myopia correction and potential as...AIM:To investigate the size of functional optical zone(FOZ)after small incision lenticule extraction(SMILE)versus femtosecond laser assisted excimer laser keratomileusis(FS-LASIK)for myopia correction and potential associated factors for FOZ.METHODS:A total of 133 patients who received corneal refractive surgery in our hospital between November 2018 and July 2021 were retrospectively enrolled.There were 63 patients(123 eyes)in SMILE group and 70patients(139 eyes)in FS-LASIK group.The size of FOZ was measured using Pentacam 3-dementional anterior segment analyzer before and 3mo after surgery,so as to analyze postoperative achieved functional optical zone(AFOZ)and its contributing parameters.RESULTS:When planned functional optical zone(PFOZ)was 6.5 mm for both groups,AFOZ was 1.45±0.27 and 1.67±0.25 mm smaller than preoperative FOZ in SMILE group and FS-LASIK group 3mo after surgery.AFOZ in SMILE group was significantly larger than that in FS-LASIK group(P<0.001).Variation of FOZ was negatively correlated with preoperative spherical equivalent(SE)and positively correlated with variation of mean keratometry value(△Km),variation of spherical aberration(△SA),and variation of Q-value(△Q,all P<0.001)in both groups.Multiple variable linear regression equations were△FOZ=1.354-0.1×pre-SE+0.336×△Q+1.462×△SA in SMILE group and△FOZ=1.512+0.137×△Q+0.468×△SA in FS-LASIK group.CONCLUSION:AFOZ is significantly smaller than preoperative FOZ in both SMILE and FS-LASIK groups.With the same PFOZ,larger AFOZ is achieved in SMILE group than in FS-LASIK group.展开更多
An optical transfer function （OTF） reconstruction model is first embedded into incoherent Fourier ptychography （IFP）. The leading result is a proposed algorithm that can recover both the super-resolution image and...An optical transfer function （OTF） reconstruction model is first embedded into incoherent Fourier ptychography （IFP）. The leading result is a proposed algorithm that can recover both the super-resolution image and the OTF of an imaging system with unknown aberrations simultaneously. This model overcomes the difficult problem of OTF estimation that the previous IFP faces. The effectiveness of this algorithm is demonstrated by numerical simulations, and the superior reconstruction is presented. We believe that the reported algorithm can extend the original IFP for more complex conditions and may provide a solution by using structured light for characterization of optical systems＇ aberrations.展开更多
The density distribution of a supersonic turbulent boundary layer is measured with the nanoparticle-based planar laser scattering technique, and the temporal evolution of its optical path difference （OPD） in a short...The density distribution of a supersonic turbulent boundary layer is measured with the nanoparticle-based planar laser scattering technique, and the temporal evolution of its optical path difference （OPD） in a short time interval is characterized by proper orthogonal decomposition （POD）. Based on the advantage of POD in capturing the energy of a signal, a temporal evolution model is suggested for the POD coefficients of the OPD. In this model, the first few coefficients vary linearly with time, and the others are modeled by Gaussian statistics. As an application, this method is used to compute the shortexposure optical transfer function.展开更多
The atmospheric scattering optical transfer function （OTF） is solved by applying the multi-coupled single scattering （MCSS） method to the three-dimensional radiative transfer equation （RTE） under the periodic gr...The atmospheric scattering optical transfer function （OTF） is solved by applying the multi-coupled single scattering （MCSS） method to the three-dimensional radiative transfer equation （RTE） under the periodic ground condition. This approach is a direct hit to the atmospheric scattering OTF using the same original context of modulation transfer function （MTF） measurement, i.e., images of sinusoidal grating at different spatial frequencies. Both the amplitude and phase shift of the OTF at various zenith and azimuth angles can be obtained at an arbitrary spatial frequency.展开更多
Structural, electronic, and optical properties of alloys BexMgl-xX （X = S, Se, Te） in the assortment 0 〈 x 〈 1 were theoretically reported for the first time in zinc-blende （ZB） phase. The calculations were carr...Structural, electronic, and optical properties of alloys BexMgl-xX （X = S, Se, Te） in the assortment 0 〈 x 〈 1 were theoretically reported for the first time in zinc-blende （ZB） phase. The calculations were carried out by using full-potential linearized augmented plane wave plus local orbitals （FP-LAPW＋lo） formalism contained by the framework of density functional theory （DFT）. Wu--Cohen （WC） generalized gradient approximation （GGA）, based on optimization energy, has been applied to calculate these theoretical results. In addition, we used Becke and Johnson （mBJ-GGA） potential, modified form of GGA functional, to calculate electronic structural properties up to a high precision degree. The alloys were composed with the concentrations x = 0.25, 0.5, and 0.75 in pursuance of ＇special quasi-random structures＇ （SQS） approach of Zunger for the restoration of disorder around the observed site of alloys in the first few shells. The structural parameters have been predicted by minimizing the total energy in correspondence of unit cell volume. Our alloys established direct band gap at different concentrations that make their importance in optically active materials. Furthermore, density of states was discussed in terms of the contribution of Be and Mg s and chalcogen （S, Se, and Te） s and p states and observed charge density helped us to investigate the bonding nature. By taking into consideration of immense importance in optoelectronics of these materials, the complex dielectric function was calculated for incident photon energy in the range 0--15 eV.展开更多
The first-principles calculations have been performed to determine the effects of Te doping to the structural, electronic, and optical properties of Ga As NWs. The calculated formation energies show that the single Te...The first-principles calculations have been performed to determine the effects of Te doping to the structural, electronic, and optical properties of Ga As NWs. The calculated formation energies show that the single Te energetically prefers to substitute the core Ga（Ef = 0.4111 eV） under As-rich conditions of Ga As nanowires, while on surface, the single Te tends to substitute the surface As site. With increasing the Te concentration, the favorable substitution sites are 2Te–Ga–A and 3Te–Ga–D. Thus, the stability of the structure of the electronic structure and optical properties are discussed.展开更多
We present structural,magnetic and optical characteristics of Zn_（1-x）TM_xTe（TM = Mn,Fe,Co,Ni and x = 6.25%）,calculated through Wien2 k code,by using full potential linearized augmented plane wave（FP-LAPW） techn...We present structural,magnetic and optical characteristics of Zn_（1-x）TM_xTe（TM = Mn,Fe,Co,Ni and x = 6.25%）,calculated through Wien2 k code,by using full potential linearized augmented plane wave（FP-LAPW） technique.The optimization of the crystal structures have been done to compare the ferromagnetic（FM） and antiferromagnetic（AFM） ground state energies,to elucidate the ferromagnetic phase stability,which further has been verified through the formation and cohesive energies.Moreover,the estimated Curie temperatures T_c have demonstrated above room temperature ferromagnetism（RTFM） in Zn_（1-x）TM_xTe（TM =Mn,Fe,Co,Ni and x= 6.25%）.The calculated electronic properties have depicted that Mn- and Co-doped ZnTe behave as ferromagnetic semiconductors,while half-metallic ferromagnetic behaviors are observed in Fe- and Ni-doped ZnTe.The presence of ferromagnetism is also demonstrated to be due to both the p-d and s-d hybridizations between the host lattice cations and TM impurities.The calculated band gaps and static real dielectric constants have been observed to vary according to Penn＇s model.The evaluated band gaps lie in near visible and ultraviolet regions,which make these materials suitable for various important device applications in optoelectronic and spintronic.展开更多
We have seen a lot of unique features off vertical cavity surface emitting lasers （VCSELs）, such as low power consumption, wafer-level testing, small packaging capability, and so on. The market of VCSELs has been gr...We have seen a lot of unique features off vertical cavity surface emitting lasers （VCSELs）, such as low power consumption, wafer-level testing, small packaging capability, and so on. The market of VCSELs has been growing up rapidly in recent years and they are now the key devices in local area networks using multi-mode optical fibers. In addition, new functions on VCSELs have been demonstrated. In this paper, the recent advances of VCSEL photonics will be reviewed which include the wavelength engineering and the athermal operation based on microelectro mechanical system （MEMS） technologies. Also, this paper explores the potential and challenges for new functions of VCSELs, including high-speed control of optical phase, slow light devices, plasmonic VCSELs, and so on.展开更多
We study the photon statistics of pulse-pumped four-wave mixing in fibers with weak coherent signal injection by measuring the intensity correlation functions of individual signal and idler fields. The experimental re...We study the photon statistics of pulse-pumped four-wave mixing in fibers with weak coherent signal injection by measuring the intensity correlation functions of individual signal and idler fields. The experimental results show that the intensity correlation function of individual signal（idler） field g_（s（i））^（2） decreases with the intensity of signal injection. After applying narrow band filter in signal（idler） band, the value of g_（s（i））^（2） decreases from 1.9 ± 0.02（1.9 ± 0.02） to 1.03 ± 0.02（1.05 ± 0.02） when the intensity of signal injection varies from 0 to 120 photons/pulse. The results indicate that the photon statistics changes from Bose–Einstein distribution to Poisson distribution. We calculate the intensity correlation functions by using the multi-mode theory of four-wave mixing in fibers. The theoretical curves well fit the experimental results.Our investigation will be useful for mitigating the crosstalk between quantum and classical channels in a dense wavelength division multiplexing network.展开更多
Unmanned aerial vehicle(UAV) remote imaging is affected by the bad weather, and the obtained images have the disadvantages of low contrast, complex texture and blurring. In this paper, we propose a blind deconvolution...Unmanned aerial vehicle(UAV) remote imaging is affected by the bad weather, and the obtained images have the disadvantages of low contrast, complex texture and blurring. In this paper, we propose a blind deconvolution model based on multiple scattering atmosphere point spread function(APSF) estimation to recovery the remote sensing image. According to Narasimhan analytical theory, a new multiple scattering restoration model is established based on the improved dichromatic model. Then using the L0 norm sparse priors of gradient and dark channel to estimate APSF blur kernel, the fast Fourier transform is used to recover the original clear image by Wiener filtering. By comparing with other state-of-the-art methods, the proposed method can correctly estimate blur kernel, effectively remove the atmospheric degradation phenomena, preserve image detail information and increase the quality evaluation indexes.展开更多
A new phase-correction method in a realistic loss superlens imaging system is theoretically predicted. The image resolution is enhanced using the near-field active phase-correction method. Resolvable separation betwee...A new phase-correction method in a realistic loss superlens imaging system is theoretically predicted. The image resolution is enhanced using the near-field active phase-correction method. Resolvable separation between two slits has been significantly improved to λ/20 for the symmetrical superlens system and λ/12 for unsymmetrical system.展开更多
In photonic crystal slab(PCS)structures,the bound states in the continuum(BICs)and circularly polarised states(dubbed C-points)are critical topological polarisation singularities in momentum space that have garnered s...In photonic crystal slab(PCS)structures,the bound states in the continuum(BICs)and circularly polarised states(dubbed C-points)are critical topological polarisation singularities in momentum space that have garnered significant attention owing to their novel topological and optical properties.In this study,we engineered a novel PCS imager featuring two C-points with opposite chirality through symmetry breaking,resulting in maximal asymmetric transmission responses characterised by near-unity circular dichroism(CD)values.By harnessing the chiral selectivity of the C-points,a high-CD PCS imager can provide two sets of optical transfer functions(OTFs)to facilitate both edge detection and bright-field imaging.Notably,one set of OTFs was finely tuned to a Lorentzian line shape to achieve perfect edge detection.We developed a multifunctional imaging system by integrating a PCS imager into a traditional optical system.Both theoretical and experimental demonstrations confirmed that this system provides bright-field and edge-enhanced images with micrometer-scale resolution.Furthermore,these two independent functions can be easily switched by altering the circular polarisation state of the light source.展开更多
Dielectric metasurfaces-based planar optical spatial differentiator and edge detection have recently been proposed to play an important role in the parallel and fast image processing technology.With the development of...Dielectric metasurfaces-based planar optical spatial differentiator and edge detection have recently been proposed to play an important role in the parallel and fast image processing technology.With the development of dielectric metasurfaces of different geometries and resonance mechanisms,diverse on-chip spatial differentiators have been proposed by tailoring the dispersion characteristics of subwavelength structures.This review focuses on the basic principles and characteristic parameters of dielectric metasurfaces as first-and second-order spatial differentiators realized via the Green's function approach.The spatial bandwidth and polarization dependence are emphasized as key properties by comparing the optical transfer flinctions of metasurfaces for different incident wavevectors and polarizations.To present the operational capabilities of a two-dimensional spatial differentiator in image information acquisition,edge detection is described to illustrate the practicability of the device.As an application example,experimental demonstrations of edge detection for different biological cells and a flower mold are discussed,in which a spatial differentiator and objective lens or camera are integrated in three optical pathway configurations.The realization of spatial differentiators and edge detection with dielectric metasurfaces provides new opportunities for ultrafast information identification in biological imaging and machine vision.展开更多
A 5-bit photonic analog-to-digital conversion under a sampling rate of 10 Gs/s is experimentally demon- strated. In the experiment, the birefringence walk-off in the scheme is compensated, and 16 high-extinction ratio...A 5-bit photonic analog-to-digital conversion under a sampling rate of 10 Gs/s is experimentally demon- strated. In the experiment, the birefringence walk-off in the scheme is compensated, and 16 high-extinction ratio optical transfer functions with different phase shifts are obtained. A I-GHz sinusoidal analog signal is sampled and Quantized by optical processing, and the effective number of bits obtained is 4.17.展开更多
We demonstrated long-period grating(LPG) inscription on polymer functionalized optical microfibers and its applications in optical sensing. Optical microfibers were functionalized with ultraviolet-sensitive polymethyl...We demonstrated long-period grating(LPG) inscription on polymer functionalized optical microfibers and its applications in optical sensing. Optical microfibers were functionalized with ultraviolet-sensitive polymethyl methacrylate jackets and, thus, LPGs could be inscribed on optical microfibers via point-by-point ultraviolet laser exposure. For a 2 mm long microfiber LPG(MLPG) inscribed on optical microfibers with a diameter of 5.4 μm, a resonant dip of 15 d B at 1377 nm was observed. This MLPG showed a high sensitivity of strain and axial force, i.e.,-1.93 pm∕με and-1.15 pm∕μN, respectively. Although the intrinsic temperature sensitivity of the LPGs is relatively low, i.e.,-12.75 pm∕°C, it can be increased to be-385.11 pm∕°C by appropriate sealing. Benefiting from the small footprint and high sensitivity, MLPGs could have potential applications in optical sensing of strain,axial force, and temperature.展开更多
Tight-binding models for ultracold atoms in optical lattices can be properly defined by using the concept of maximally localized Wannier functions for composite bands. The basic principles of this approach are reviewe...Tight-binding models for ultracold atoms in optical lattices can be properly defined by using the concept of maximally localized Wannier functions for composite bands. The basic principles of this approach are reviewed here, along with different applications to lattice potentials with two minima per unit cell, in one and two spatial dimensions. Two independent methods for computing the tight-binding coefficients—one ab initio, based on the maximally localized Wannier functions, the other through analytic expressions in terms of the energy spectrum—are considered. In the one dimensional case, where the tight-binding coefficients can be obtained by designing a specific gauge transformation, we consider both the case of quasi resonance between the two lowest bands, and that between s and p orbitals. In the latter case, the role of the Wannier functions in the derivation of an effective Dirac equation is also reviewed. Then, we consider the case of a two dimensional honeycomb potential, with particular emphasis on the Haldane model, its phase diagram, and the breakdown of the Peierls substitution. Tunable honeycomb lattices, characterized by movable Dirac points, are also considered. Finally, general considerations for dealing with the interaction terms are presented.展开更多
In optical scanning holography, one pupil produces a spherical wave and another produces a plane wave. They interfere with each other and result in a fringe pattern for scanning a three-dimensional object. The resolut...In optical scanning holography, one pupil produces a spherical wave and another produces a plane wave. They interfere with each other and result in a fringe pattern for scanning a three-dimensional object. The resolution of the hologram reconstruction is affected by the point spread function(PSF) of the optical system. In this paper, we modulate the PSF by a spiral phase plate, which significantly enhances the lateral and depth resolution. We explain the theory for such resolution enhancement and show simulation results to verify the efficacy of the approach.展开更多
Wavefront coding （WFC） is used to extend the field depth of an incoherent optical system by employing a phase mask on the pupil. We uses a Fisher information （FI） metric based optimization method to design a phase...Wavefront coding （WFC） is used to extend the field depth of an incoherent optical system by employing a phase mask on the pupil. We uses a Fisher information （FI） metric based optimization method to design a phase mask by taking the modulation transfer function （MTF） of the practical optical system into consid- eration. This method can modulate the wavefront so that the point spread function and optical transfer function are insensitive to the object distance. The simulation results show that the optimized phase mask based on the proposed method can further improve the defocusing image quality while maintaining the focusing image quality.展开更多
基金Project(52476095)supported by the National Natural Science Foundation of ChinaProject(kq2506013)supported by Changsha Outstanding Innovative Youth Training Program,China。
文摘The nanofluid-based direct absorption solar collector(NDASC)ensures that solar radiation passing through the tube wall is directly absorbed by the nanofluid,reducing thermal resistance in the energy transfer process.However,further exploration is required to suppress the outward thermal losses from the nanofluid at high temperatures.Herein,this paper proposes a novel NDASC in which the outer surface of the collector tube is covered with functional coatings and a three-dimensional computational fluid dynamics model is established to study the energy flow distributions on the collector within the temperature range of 400-600 K.When the nanofluid’s absorption coefficient reaches 80 m^(-1),the NDASC shows the optimal thermal performance,and the NDASC with local Sn-In_(2)O_(3) coating achieves a 7.8% improvement in thermal efficiency at 400 K compared to the original NDASC.Furthermore,hybrid coatings with Sn In_(2)O_(3)/WTi-Al_(2)O_(3) are explored,and the optimal coverage angles are determined.The NDASC with such coatings shows a 10.22%-17.9% increase in thermal efficiency compared to the original NDASC and a 7.6%-19.5% increase compared to the traditional surface-type solar collectors,demonstrating the effectiveness of the proposed energy flow control strategy for DASCs.
文摘AIM: To describe the characteristics of modulation transfer function (MTF) of anterior corneal surface, and obtain the the normal reference range of MTF at different spatial frequencies and optical zones of the anterior corneal surface in myopes. METHODS: Four hundred eyes from 200 patients were examined under SIRIUS corneal topography system. Phoenis analysis software was applied to simulate the MTF curves of anterior corneal surface at vertical and horizontal meridians at the 3, 4, 5, 6, 7mm optical zones of cornea. The MTF values at spatial frequencies of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 and 60 cycles/degree (c/d) were selected. RESULTS: The MTF curve of anterior corneal surface decreased rapidly from low to intermediate frequency (0-15cpd) at various optical zones of cornea, the value decreased to 0 slowly at higher frequency (>15cpd). With the increase of the optical zones of cornea, MTF curve decreased gradually. 3) In the range of 3 mm- 6 mm optical zones of the cornea, the MTF values measured at horizontal meridian were greater than the corresponding values at horizontal meridian of each spatial frequency, the difference was statistically significant (P<0.05). At 7 mm optical zones of cornea, the MTF values measured at horizontal meridian were less than the corresponding values at vertical meridian at 10-60 spatial frequencies (cpd), and the difference was statistically significant in 25, 30, 35, 40, 45, 50 cpd(P<0.05). CONCLUSION: MTF can be used to describe the imaging quality of optical systems at anterior corneal surface objectively in detail.
基金Supported by Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(No.2022L201)。
文摘AIM:To investigate the size of functional optical zone(FOZ)after small incision lenticule extraction(SMILE)versus femtosecond laser assisted excimer laser keratomileusis(FS-LASIK)for myopia correction and potential associated factors for FOZ.METHODS:A total of 133 patients who received corneal refractive surgery in our hospital between November 2018 and July 2021 were retrospectively enrolled.There were 63 patients(123 eyes)in SMILE group and 70patients(139 eyes)in FS-LASIK group.The size of FOZ was measured using Pentacam 3-dementional anterior segment analyzer before and 3mo after surgery,so as to analyze postoperative achieved functional optical zone(AFOZ)and its contributing parameters.RESULTS:When planned functional optical zone(PFOZ)was 6.5 mm for both groups,AFOZ was 1.45±0.27 and 1.67±0.25 mm smaller than preoperative FOZ in SMILE group and FS-LASIK group 3mo after surgery.AFOZ in SMILE group was significantly larger than that in FS-LASIK group(P<0.001).Variation of FOZ was negatively correlated with preoperative spherical equivalent(SE)and positively correlated with variation of mean keratometry value(△Km),variation of spherical aberration(△SA),and variation of Q-value(△Q,all P<0.001)in both groups.Multiple variable linear regression equations were△FOZ=1.354-0.1×pre-SE+0.336×△Q+1.462×△SA in SMILE group and△FOZ=1.512+0.137×△Q+0.468×△SA in FS-LASIK group.CONCLUSION:AFOZ is significantly smaller than preoperative FOZ in both SMILE and FS-LASIK groups.With the same PFOZ,larger AFOZ is achieved in SMILE group than in FS-LASIK group.
基金Supported by the National Natural Science Foundation of China under Grant No 61205144the Research Project of National University of Defense Technology under Grant No JC13-07-01the Key Laboratory of High Power Laser and Physics of Chinese Academy of Sciences
文摘An optical transfer function （OTF） reconstruction model is first embedded into incoherent Fourier ptychography （IFP）. The leading result is a proposed algorithm that can recover both the super-resolution image and the OTF of an imaging system with unknown aberrations simultaneously. This model overcomes the difficult problem of OTF estimation that the previous IFP faces. The effectiveness of this algorithm is demonstrated by numerical simulations, and the superior reconstruction is presented. We believe that the reported algorithm can extend the original IFP for more complex conditions and may provide a solution by using structured light for characterization of optical systems＇ aberrations.
基金Project supported by the Innovation Research Foundations for Postgraduates of National University of Defense Technology and Hunan Province, Chinathe National Natural Science Foundation of China (Grant No. 61008037)
文摘The density distribution of a supersonic turbulent boundary layer is measured with the nanoparticle-based planar laser scattering technique, and the temporal evolution of its optical path difference （OPD） in a short time interval is characterized by proper orthogonal decomposition （POD）. Based on the advantage of POD in capturing the energy of a signal, a temporal evolution model is suggested for the POD coefficients of the OPD. In this model, the first few coefficients vary linearly with time, and the others are modeled by Gaussian statistics. As an application, this method is used to compute the shortexposure optical transfer function.
基金supported by the Main Direction Program of Knowledge Innovation of Chinese Academy of Sciences(Grant No.KGFZD-125-13-006)
文摘The atmospheric scattering optical transfer function （OTF） is solved by applying the multi-coupled single scattering （MCSS） method to the three-dimensional radiative transfer equation （RTE） under the periodic ground condition. This approach is a direct hit to the atmospheric scattering OTF using the same original context of modulation transfer function （MTF） measurement, i.e., images of sinusoidal grating at different spatial frequencies. Both the amplitude and phase shift of the OTF at various zenith and azimuth angles can be obtained at an arbitrary spatial frequency.
基金the Deanship of Scientific Research at King Saud University for funding this Research group No.RG 1435-004
文摘Structural, electronic, and optical properties of alloys BexMgl-xX （X = S, Se, Te） in the assortment 0 〈 x 〈 1 were theoretically reported for the first time in zinc-blende （ZB） phase. The calculations were carried out by using full-potential linearized augmented plane wave plus local orbitals （FP-LAPW＋lo） formalism contained by the framework of density functional theory （DFT）. Wu--Cohen （WC） generalized gradient approximation （GGA）, based on optimization energy, has been applied to calculate these theoretical results. In addition, we used Becke and Johnson （mBJ-GGA） potential, modified form of GGA functional, to calculate electronic structural properties up to a high precision degree. The alloys were composed with the concentrations x = 0.25, 0.5, and 0.75 in pursuance of ＇special quasi-random structures＇ （SQS） approach of Zunger for the restoration of disorder around the observed site of alloys in the first few shells. The structural parameters have been predicted by minimizing the total energy in correspondence of unit cell volume. Our alloys established direct band gap at different concentrations that make their importance in optically active materials. Furthermore, density of states was discussed in terms of the contribution of Be and Mg s and chalcogen （S, Se, and Te） s and p states and observed charge density helped us to investigate the bonding nature. By taking into consideration of immense importance in optoelectronics of these materials, the complex dielectric function was calculated for incident photon energy in the range 0--15 eV.
基金supported by the Open Fund of State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications,China,No.2012LF1003)the Research Foundation of Education Bureau of Sichuan Province(No.16ZA0316)
文摘The first-principles calculations have been performed to determine the effects of Te doping to the structural, electronic, and optical properties of Ga As NWs. The calculated formation energies show that the single Te energetically prefers to substitute the core Ga（Ef = 0.4111 eV） under As-rich conditions of Ga As nanowires, while on surface, the single Te tends to substitute the surface As site. With increasing the Te concentration, the favorable substitution sites are 2Te–Ga–A and 3Te–Ga–D. Thus, the stability of the structure of the electronic structure and optical properties are discussed.
基金the University of the Punjab, Lahore for financial support through faculty research grant program
文摘We present structural,magnetic and optical characteristics of Zn_（1-x）TM_xTe（TM = Mn,Fe,Co,Ni and x = 6.25%）,calculated through Wien2 k code,by using full potential linearized augmented plane wave（FP-LAPW） technique.The optimization of the crystal structures have been done to compare the ferromagnetic（FM） and antiferromagnetic（AFM） ground state energies,to elucidate the ferromagnetic phase stability,which further has been verified through the formation and cohesive energies.Moreover,the estimated Curie temperatures T_c have demonstrated above room temperature ferromagnetism（RTFM） in Zn_（1-x）TM_xTe（TM =Mn,Fe,Co,Ni and x= 6.25%）.The calculated electronic properties have depicted that Mn- and Co-doped ZnTe behave as ferromagnetic semiconductors,while half-metallic ferromagnetic behaviors are observed in Fe- and Ni-doped ZnTe.The presence of ferromagnetism is also demonstrated to be due to both the p-d and s-d hybridizations between the host lattice cations and TM impurities.The calculated band gaps and static real dielectric constants have been observed to vary according to Penn＇s model.The evaluated band gaps lie in near visible and ultraviolet regions,which make these materials suitable for various important device applications in optoelectronic and spintronic.
基金Grant-in-Aid for Creative Scientific Research from the Ministry of Education,Science,Sport and Culture(#14GS0212")and was partly by NICT
文摘We have seen a lot of unique features off vertical cavity surface emitting lasers （VCSELs）, such as low power consumption, wafer-level testing, small packaging capability, and so on. The market of VCSELs has been growing up rapidly in recent years and they are now the key devices in local area networks using multi-mode optical fibers. In addition, new functions on VCSELs have been demonstrated. In this paper, the recent advances of VCSEL photonics will be reviewed which include the wavelength engineering and the athermal operation based on microelectro mechanical system （MEMS） technologies. Also, this paper explores the potential and challenges for new functions of VCSELs, including high-speed control of optical phase, slow light devices, plasmonic VCSELs, and so on.
基金Project supported by the National Natural Science Foundation of China(Grant No.11527808)the State Key Development Program for Basic Research of China(Grant No.2014CB340103)+3 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120032110055)the Natural Science Foundation of Tianjin,China(Grant No.14JCQNJC02300)the Program for Changjiang Scholars and Innovative Research Team in University,Chinathe Program of Introducing Talents of Discipline to Universities,China(Grant No.B07014)
文摘We study the photon statistics of pulse-pumped four-wave mixing in fibers with weak coherent signal injection by measuring the intensity correlation functions of individual signal and idler fields. The experimental results show that the intensity correlation function of individual signal（idler） field g_（s（i））^（2） decreases with the intensity of signal injection. After applying narrow band filter in signal（idler） band, the value of g_（s（i））^（2） decreases from 1.9 ± 0.02（1.9 ± 0.02） to 1.03 ± 0.02（1.05 ± 0.02） when the intensity of signal injection varies from 0 to 120 photons/pulse. The results indicate that the photon statistics changes from Bose–Einstein distribution to Poisson distribution. We calculate the intensity correlation functions by using the multi-mode theory of four-wave mixing in fibers. The theoretical curves well fit the experimental results.Our investigation will be useful for mitigating the crosstalk between quantum and classical channels in a dense wavelength division multiplexing network.
基金supported by the National Natural Science Foundation of China(No.61405191)
文摘Unmanned aerial vehicle(UAV) remote imaging is affected by the bad weather, and the obtained images have the disadvantages of low contrast, complex texture and blurring. In this paper, we propose a blind deconvolution model based on multiple scattering atmosphere point spread function(APSF) estimation to recovery the remote sensing image. According to Narasimhan analytical theory, a new multiple scattering restoration model is established based on the improved dichromatic model. Then using the L0 norm sparse priors of gradient and dark channel to estimate APSF blur kernel, the fast Fourier transform is used to recover the original clear image by Wiener filtering. By comparing with other state-of-the-art methods, the proposed method can correctly estimate blur kernel, effectively remove the atmospheric degradation phenomena, preserve image detail information and increase the quality evaluation indexes.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB301801)the National Natural Science Foundation of China(Grant Nos.10904099 and 11174211)
文摘A new phase-correction method in a realistic loss superlens imaging system is theoretically predicted. The image resolution is enhanced using the near-field active phase-correction method. Resolvable separation between two slits has been significantly improved to λ/20 for the symmetrical superlens system and λ/12 for unsymmetrical system.
基金supported in part by the National Key Research and Development Program of China under Grant 2022YFA1405000in part by the Natural Science Foundation of Jiangsu Province through Major Project under Grant BK20243067+3 种基金in part by the Leading-Edge Technology Program of Jiangsu Natural Science Foundation under Grant BK20232001in part by the National Natural Science Fund for Excellent Young Scholars(Overseas)in part by Fundamental Research Funds for the Central Universitiesin part by Nanjing University Integrated Research Platform of the Ministry of Education-Top Talents Program.
文摘In photonic crystal slab(PCS)structures,the bound states in the continuum(BICs)and circularly polarised states(dubbed C-points)are critical topological polarisation singularities in momentum space that have garnered significant attention owing to their novel topological and optical properties.In this study,we engineered a novel PCS imager featuring two C-points with opposite chirality through symmetry breaking,resulting in maximal asymmetric transmission responses characterised by near-unity circular dichroism(CD)values.By harnessing the chiral selectivity of the C-points,a high-CD PCS imager can provide two sets of optical transfer functions(OTFs)to facilitate both edge detection and bright-field imaging.Notably,one set of OTFs was finely tuned to a Lorentzian line shape to achieve perfect edge detection.We developed a multifunctional imaging system by integrating a PCS imager into a traditional optical system.Both theoretical and experimental demonstrations confirmed that this system provides bright-field and edge-enhanced images with micrometer-scale resolution.Furthermore,these two independent functions can be easily switched by altering the circular polarisation state of the light source.
基金the National Key R&D Program of China(No.2019YFB1803904)in part by the National Natural Science Foundation of China(Grant Nos.61805104,11704156,61935013,61875076,and 61865014)in part by the Open Project of Wuhan National Laboratory for Optoelectronics,China(No.2018WNLOKF015).
文摘Dielectric metasurfaces-based planar optical spatial differentiator and edge detection have recently been proposed to play an important role in the parallel and fast image processing technology.With the development of dielectric metasurfaces of different geometries and resonance mechanisms,diverse on-chip spatial differentiators have been proposed by tailoring the dispersion characteristics of subwavelength structures.This review focuses on the basic principles and characteristic parameters of dielectric metasurfaces as first-and second-order spatial differentiators realized via the Green's function approach.The spatial bandwidth and polarization dependence are emphasized as key properties by comparing the optical transfer flinctions of metasurfaces for different incident wavevectors and polarizations.To present the operational capabilities of a two-dimensional spatial differentiator in image information acquisition,edge detection is described to illustrate the practicability of the device.As an application example,experimental demonstrations of edge detection for different biological cells and a flower mold are discussed,in which a spatial differentiator and objective lens or camera are integrated in three optical pathway configurations.The realization of spatial differentiators and edge detection with dielectric metasurfaces provides new opportunities for ultrafast information identification in biological imaging and machine vision.
基金Foundation of China under Grant Nos.60977003 and 61032005
文摘A 5-bit photonic analog-to-digital conversion under a sampling rate of 10 Gs/s is experimentally demon- strated. In the experiment, the birefringence walk-off in the scheme is compensated, and 16 high-extinction ratio optical transfer functions with different phase shifts are obtained. A I-GHz sinusoidal analog signal is sampled and Quantized by optical processing, and the effective number of bits obtained is 4.17.
基金supported by National Natural Science Foundation of China(Grant No.61505096)
文摘We demonstrated long-period grating(LPG) inscription on polymer functionalized optical microfibers and its applications in optical sensing. Optical microfibers were functionalized with ultraviolet-sensitive polymethyl methacrylate jackets and, thus, LPGs could be inscribed on optical microfibers via point-by-point ultraviolet laser exposure. For a 2 mm long microfiber LPG(MLPG) inscribed on optical microfibers with a diameter of 5.4 μm, a resonant dip of 15 d B at 1377 nm was observed. This MLPG showed a high sensitivity of strain and axial force, i.e.,-1.93 pm∕με and-1.15 pm∕μN, respectively. Although the intrinsic temperature sensitivity of the LPGs is relatively low, i.e.,-12.75 pm∕°C, it can be increased to be-385.11 pm∕°C by appropriate sealing. Benefiting from the small footprint and high sensitivity, MLPGs could have potential applications in optical sensing of strain,axial force, and temperature.
基金supported by the Universidad del Pais Vasco/Euskal Herriko Unibertsitatea (Grant No. UFI 11/55)the Ministerio de Economia y Competitividad (Grant No. FIS2012-36673-C03-03)+2 种基金the Basque Government (Grant No. IT472-10)the Helmholtz Gemeinschaft Deutscher-Young Investigators Group (Grant No. VH-NG-717, Functional Nanoscale Structure and Probe Simulation Laboratory)the Impuls und Vernetzungsfonds der HelmholtzGemeinschaft Postdoc Programme
文摘Tight-binding models for ultracold atoms in optical lattices can be properly defined by using the concept of maximally localized Wannier functions for composite bands. The basic principles of this approach are reviewed here, along with different applications to lattice potentials with two minima per unit cell, in one and two spatial dimensions. Two independent methods for computing the tight-binding coefficients—one ab initio, based on the maximally localized Wannier functions, the other through analytic expressions in terms of the energy spectrum—are considered. In the one dimensional case, where the tight-binding coefficients can be obtained by designing a specific gauge transformation, we consider both the case of quasi resonance between the two lowest bands, and that between s and p orbitals. In the latter case, the role of the Wannier functions in the derivation of an effective Dirac equation is also reviewed. Then, we consider the case of a two dimensional honeycomb potential, with particular emphasis on the Haldane model, its phase diagram, and the breakdown of the Peierls substitution. Tunable honeycomb lattices, characterized by movable Dirac points, are also considered. Finally, general considerations for dealing with the interaction terms are presented.
基金supported in part by the Research Grants Council of the Hong Kong Special Administrative Region,China, under project 7131–12Ethe NSFC RGC grant under project N–HKU714–13
文摘In optical scanning holography, one pupil produces a spherical wave and another produces a plane wave. They interfere with each other and result in a fringe pattern for scanning a three-dimensional object. The resolution of the hologram reconstruction is affected by the point spread function(PSF) of the optical system. In this paper, we modulate the PSF by a spiral phase plate, which significantly enhances the lateral and depth resolution. We explain the theory for such resolution enhancement and show simulation results to verify the efficacy of the approach.
基金supported by the National Natural Science Foundation of China(No.60777002)Ningbo Science and Technology Bureau(No.2008A610035).
文摘Wavefront coding （WFC） is used to extend the field depth of an incoherent optical system by employing a phase mask on the pupil. We uses a Fisher information （FI） metric based optimization method to design a phase mask by taking the modulation transfer function （MTF） of the practical optical system into consid- eration. This method can modulate the wavefront so that the point spread function and optical transfer function are insensitive to the object distance. The simulation results show that the optimized phase mask based on the proposed method can further improve the defocusing image quality while maintaining the focusing image quality.
