Near-field scanning optical microscopy is used to investigate the waveguiding properties of optical micro/nanofibres （MNFs） by means of detecting optical power carried by evanescent waves. Taper drawn silica and tel...Near-field scanning optical microscopy is used to investigate the waveguiding properties of optical micro/nanofibres （MNFs） by means of detecting optical power carried by evanescent waves. Taper drawn silica and tellurite MNFs, supported on low-index substrates, are used to guide a 532-nm-wavelength light beam for the test. Modification of the single-mode condition of the MNF in the presence of a substrate is observed. Spatial modulation of the longitudinal field intensity （with a 195-nm period） near the output end of a 760-nm-diameter silica MNF is well resolved. Energy exchange through evanescent coupling between two parallel MNFs is also investigated.展开更多
The multimode evolution, optical losses and wavelength response of non-adiabatic micro/nano-fiber （MNF） tapers are numerically simulated using a three-dimensional finite-difference beam propagation method. For a non...The multimode evolution, optical losses and wavelength response of non-adiabatic micro/nano-fiber （MNF） tapers are numerically simulated using a three-dimensional finite-difference beam propagation method. For a non-adiabatic MNF taper, it is illustrated that optical losses vary with the transition region length and the optical wavelength. We explain how the complicated multimode evolutions result in the complicated optical loss and wavelength response properties, especially when the waist diameters are large enough to allow much higher-order modes. These results may offer valuable references for trapping and guiding cold atoms in atom optics and practical application of micro/nano-devices.展开更多
Dedicated experiments are designed to collect the infrared spectra of dissolved gas-in-oil of power transformers. Spectra of diagnostic gases are collected by 3 different laboratorial FTIR spectrometers using 3 differ...Dedicated experiments are designed to collect the infrared spectra of dissolved gas-in-oil of power transformers. Spectra of diagnostic gases are collected by 3 different laboratorial FTIR spectrometers using 3 different gas cells with various sets of equipment parameters. A formula is deduced to calculate the shortest optical length to detect a specific concentration according to measurements on gases with known concentrations near to the minimum detection limit. Collected spectra and calculated results suggested that the optimum optical length of the gas cell should be 150 mm to realize on-line monitoring of diagnostic gases within the required concentration range. At the end, an economic novel design of the gas cell is proposed based on the optimum length.展开更多
The fundamental measurement of space gravitational wave detection is to monitor the relative motion between pairs of freely falling test masses using heterodyne laser interferometry to a precision of 10 pm. The masses...The fundamental measurement of space gravitational wave detection is to monitor the relative motion between pairs of freely falling test masses using heterodyne laser interferometry to a precision of 10 pm. The masses under test are millions of kilometers apart. The inter-spacecraft laser interferometry telescope deliver laser efficiently from one spacecraft to another. It is an important component of the gravitational wave detection observatory. It needs to meet the requirements of large compression ratio, high image quality and extraordinary stray light suppression ability. Based on the primary aberration theory, the method of the large compression ratio off-axis four-mirror optical system design is explored. After optimization, the system has an entrance pupil of 200 mm, compression ratio of 40 times, scientific field of view (FOV) of ±8 μrad. To facilitate suppressing the stray light and delivering the laser beam to the back-end scientific interferometers, the intermediate images and the real exit pupils are spatially available. Over the full FOV, the maximum root mean square (RMS) wavefront error is less than 0.007λ, PV value is less than 0.03λ (λ = 1064 nm). The image quality is approached to the diffraction-limit. The TTL noise caused by the wavefront error of the telescope is analyzed. The TTL noise in the image space of 300 μrad range is less than 1 × 10-10 m whose slope is lower than 0.6 μm/rad, which is under the noise budget of the laser interferometer space antenna (LISA), satisfying the requirements of space gravitational wave detection.展开更多
We numerically demonstrate that ＇mode-entangled states＇ based on the transverse modes of classical optical fields in multimode waveguides violate Bell＇s inequality. Numerically simulating the correlation measuremen...We numerically demonstrate that ＇mode-entangled states＇ based on the transverse modes of classical optical fields in multimode waveguides violate Bell＇s inequality. Numerically simulating the correlation measurement scheme of Bell＇s inequality, we obtain the normalized correlation functions of the intensity fluctuations for the two entangled classical fields. By using the correlation functions, the maximum violations of Bell＇s inequality are obtained. This implies that the two classical fields in the mode-entangled states, although spatially separated, present a nonlocal correlation.展开更多
The two types of nonlinear optical cryptosystems(NOCs)that are respectively based on amplitude-phase retrieval algorithm(APRA)and phase retrieval algorithm(PRA)have attracted a lot of attention due to their unique mec...The two types of nonlinear optical cryptosystems(NOCs)that are respectively based on amplitude-phase retrieval algorithm(APRA)and phase retrieval algorithm(PRA)have attracted a lot of attention due to their unique mechanism of encryption process and remarkable ability to resist common attacks.In this paper,the securities of the two types of NOCs are evaluated by using a deep-learning(DL)method,where an end-to-end densely connected convolutional network(DenseNet)model for cryptanalysis is developed.The proposed DL-based method is able to retrieve unknown plaintexts from the given ciphertexts by using the trained DenseNet model without prior knowledge of any public or private key.The results of numerical experiments with the DenseNet model clearly demonstrate the validity and good performance of the proposed the DL-based attack on NOCs.展开更多
The properties of controllable soliton switching in Kerr-type optical lattices with different modulation are investigated theoretically and simulated numerically.The results show that the optical lattices can be avail...The properties of controllable soliton switching in Kerr-type optical lattices with different modulation are investigated theoretically and simulated numerically.The results show that the optical lattices can be available for all- optical soliton switching through utilization for length-scale competition effects.And through longitudinal exponential- asymptotic modulation for the linear refractive index,the properties of soliton switching in the optical lattices can be improved.The number of output channels of soliton switching can be controlled by the parameters such as incident angle,asymptotic rate of longitudinal modulation,guiding parameter and form factor.展开更多
A novel design is proposed for highly sensitive surface-plasmon-resonance sensors. The sensor is based on a microstructured optical fiber with two layers of annular-shaped holes. A gold layer is deposited on the inner...A novel design is proposed for highly sensitive surface-plasmon-resonance sensors. The sensor is based on a microstructured optical fiber with two layers of annular-shaped holes. A gold layer is deposited on the inner surface of the second hole-layer, in which the holes have several micrometers thickness in size, facilitating analyte infiltration and metal layer deposition. In the first layer of holes, the sector-ring^shaped arms, used as supporting strips, are utilized to tune the resonance depth of the sensor. Numerical results indicate that the sensor operation wavelength can be tuned across the C＋L-band. The spectral sensitivity of 1.0.104 nm. RIU-1 order of magnitude and a detection limit of 1.0.10-4 RIU order are demonstrated over a wide range of analyte refractive index from 1.320 to 1.335.展开更多
Ultrathin iron films with different thicknesses from 7.1 to 51.7 nm are deposited by magnetron sputtering and covered by tantalum layers protecting them from being oxidized.These ultrathin iron films are studied by sp...Ultrathin iron films with different thicknesses from 7.1 to 51.7 nm are deposited by magnetron sputtering and covered by tantalum layers protecting them from being oxidized.These ultrathin iron films are studied by spectroscopic ellipsometry and transmittance measurement.An extra tantalum film is deposited under the same sputtering conditions and its optical constants and film thickness are obtained by a combination of ellipsometry and transmission measurement.After introducing these obtained optical constants and film thickness into the tantalum-iron film,the optical constants and film thicknesses of ultrathin iron films with different thicknesses are obtained.The results show that combining ellipsometry and transmission measurement improves the uniqueness of the obtained film thickness.The optical constants of ultrathin iron films depend strongly on film thicknesses.There is a broad absorption peak at about 370 nm and it shifts to 410 nm with film thickness decreasing.展开更多
The longitudinal generalized magneto-optical ellipsometry （GME） method is extended to the measurement of three- layer ultrathin magnetic films. In this work, the theory of the reflection matrix is introduced into th...The longitudinal generalized magneto-optical ellipsometry （GME） method is extended to the measurement of three- layer ultrathin magnetic films. In this work, the theory of the reflection matrix is introduced into the GME measurement to obtain the reflective matrix parameters of ultrathin multilayer magnetic films with different thicknesses. After that, a spectroscopic ellipsometry is used to determine the optical parameter and the thickness of every layer of these samples, then the magneto-optical coupling constant of the multilayer magnetic ultrathin film can be obtained. After measurements of a series of ultrathin Fe films, the results show that the magneto-optical coupling constant Q is independent of the thickness of the magnetic film. The magneto-optical Kerr rotations and ellipticity are measured to confirm the validity of this experiment. Combined with the optical constants and the Q constant, the Kerr rotations and ellipticity are calculated in theory. The results show that the theoretical curve fits very well with the experimental data.展开更多
Non-line-of-sight(NLOS)imaging has emerged as a prominent technique for reconstructing obscured objects from images that undergo multiple diffuse reflections.This imaging method has garnered significant attention in d...Non-line-of-sight(NLOS)imaging has emerged as a prominent technique for reconstructing obscured objects from images that undergo multiple diffuse reflections.This imaging method has garnered significant attention in diverse domains,including remote sensing,rescue operations,and intelligent driving,due to its wide-ranging potential applications.Nevertheless,accurately modeling the incident light direction,which carries energy and is captured by the detector amidst random diffuse reflection directions,poses a considerable challenge.This challenge hinders the acquisition of precise forward and inverse physical models for NLOS imaging,which are crucial for achieving high-quality reconstructions.In this study,we propose a point spread function(PSF)model for the NLOS imaging system utilizing ray tracing with random angles.Furthermore,we introduce a reconstruction method,termed the physics-constrained inverse network(PCIN),which establishes an accurate PSF model and inverse physical model by leveraging the interplay between PSF constraints and the optimization of a convolutional neural network.The PCIN approach initializes the parameters randomly,guided by the constraints of the forward PSF model,thereby obviating the need for extensive training data sets,as required by traditional deep-learning methods.Through alternating iteration and gradient descent algorithms,we iteratively optimize the diffuse reflection angles in the PSF model and the neural network parameters.The results demonstrate that PCIN achieves efficient data utilization by not necessitating a large number of actual ground data groups.Moreover,the experimental findings confirm that the proposed method effectively restores the hidden object features with high accuracy.展开更多
Lidar （Light detection and ranging） has special capabilities for remote sensing of many different behaviours of the atmosphere. One of the techniques which show a great deal of promise for several applications is Ra...Lidar （Light detection and ranging） has special capabilities for remote sensing of many different behaviours of the atmosphere. One of the techniques which show a great deal of promise for several applications is Raman scattering. The detecting capability, including maximum operation range and minimum detectable gas concentration is one of the most significant parameters for lidar remote sensing of pollutants. In this paper, based on the new method for evaluating the capabilities of a Raman lidar system, we present an evaluation of detecting capability of Raman lidar for monitoring atmospheric CO2 in Hefei. Numerical simulations about the influence of atmospheric conditions on lidar detecting capability were carried out, and a conclusion can be drawn that the maximum difference of the operation ranges caused by the weather conditions alone can reach about 0.4 to 0.5km with a measuring precision within 30ppmv. The range of minimum detectable concentration caused by the weather conditions alone can reach about 20 to 35 ppmv in vertical direction for 20000 shots at a distance of 1 km on the assumption that other parameters are kept constant. The other corresponding parameters under different conditions are also given. The capability of Raman lidar operated in vertical direction was found to be superior to that operated in horizontal direction. During practical measurement with the Raman lidar whose hardware components were fixed, aerosol scattering extinction effect would be a significant factor that influenced the capability of Raman lidar. This work may be a valuable reference for lidar system designing, measurement accuracy improving and data processing.展开更多
The accurate determination of surface-layer turbulent fluxes over urban areas is critical to understanding urban boundary layer （UBL） evolution. In this study, a remote-sensing technique using a large aperture scint...The accurate determination of surface-layer turbulent fluxes over urban areas is critical to understanding urban boundary layer （UBL） evolution. In this study, a remote-sensing technique using a large aperture scintillometer （LAS） was investigated to estimate surface-layer turbulent fluxes over a highly heterogeneous urban area. The LAS system, with an optical path length of 2.1 km, was deployed in an urban area characterized by a complicated land-use mix （residential houses, water body, bare ground, etc.）. The turbulent sensible heat （QH） and momentum fluxes （z） were estimated from the scintillation measurements obtained from the LAS system during the cold season. Three-dimensional LAS footprint modeling was introduced to identify the source areas （＂footprint＂） of the estimated turbulent fluxes. The analysis results showed that the LAS-derived turbulent fluxes for the highly heterogeneous urban area revealed reasonable temporal variation during daytime on clear days, in comparison to the land-surface process-resolving numerical modeling. A series of sensitivity tests indicated that the overall uncertainty in the LAS-derived daytime QH was within 20%-30% in terms of the influence of input parameters and the non- dimensional similarity function for the temperature structure function parameter, while the estimation errors in z were less sensitive to the factors of influence, except aerodynamic roughness length. The 3D LAS footprint modeling characterized the source areas of the LAS-derived turbulent fluxes in the heterogeneous urban area, revealing that the representative spatial scales of the LAS system deployed with the 2.1 km optical path distance ranged from 0.2 to 2 km2 （a ＂micro-a scale＂）, depending on local meteorological conditions.展开更多
Laser-induced breakdown spectroscopy （LIBS） has attracted many academic and industrial interests world-wide due to its unique advantages, such as little or no sample preparation requirement, in-situ/online and multi...Laser-induced breakdown spectroscopy （LIBS） has attracted many academic and industrial interests world-wide due to its unique advantages, such as little or no sample preparation requirement, in-situ/online and multi-elemental analysis, and remote sensing etc., and it has been regarded as a ＂future super star＂ for chemical analysis for many years . In China,展开更多
A theory of the far spatial coherent-suppressed single-peak field distribution of a rectangular wave-guide CO2 laser is presented. The theoretical analysis shows that a rectangular wave-guide laser can have an output ...A theory of the far spatial coherent-suppressed single-peak field distribution of a rectangular wave-guide CO2 laser is presented. The theoretical analysis shows that a rectangular wave-guide laser can have an output intensity distribution in far field similar to that produced from a wave-guide array laser, which is in agreement with the experimental result. A single-peak mode output is obtained within 5 metres. The experimental far-field spread angle in the bigger-Fresnel number direction is 0.63 mrad, compared to the calculated one, 0.6 mrad, and when the length of the laser resonator is changed, a double-peak or multi-peak in far-field distribution of the laser is obtained.展开更多
In this paper, a low-cost measurement approach with bi-beam was presented, which can be used for real-time detection and online analysis of solution refractive index, based on systematical analysis and experiments of ...In this paper, a low-cost measurement approach with bi-beam was presented, which can be used for real-time detection and online analysis of solution refractive index, based on systematical analysis and experiments of conventional detection methods on surface plasmon resonance sensor. This novel method was analyzed theoretically and based on it a sensor system set was established. The factors that affect the sensor's sensitivity and working range were discussed. The angular adjustment setup was simplified, errors produced by movable components were avoided and the maneuverability was enhanced with this new method. The noiseproof feature and stability of the sensor system were greatly improved as well.展开更多
We demonstrate that the etalon effects of alkali cells can be used as the output coupler of an alkali laser.Based on a rubidium cell with highly parallelized windows,a 2.7 W rubidium laser with optical efficiency of 2...We demonstrate that the etalon effects of alkali cells can be used as the output coupler of an alkali laser.Based on a rubidium cell with highly parallelized windows,a 2.7 W rubidium laser with optical efficiency of 20.9%and slope efficiency of 31.8%is obtained by adopting unconventional output couplers.Since it has compact configuration and the inner surface of the rubidium cell is uncoated,this may be used in high power laser systems with long lifetimes.展开更多
The temporal characteristics of GaAs NEA and alkali metal photocathodes are studied using Monte Carlo simulation method. The electron transit time and its distribution functions in the photocathodes are calculated. Ba...The temporal characteristics of GaAs NEA and alkali metal photocathodes are studied using Monte Carlo simulation method. The electron transit time and its distribution functions in the photocathodes are calculated. Based on the results, the time modulation transfer functions and temporal resolutions of the photocathodes are obtained. The results show that the response time and temporal resolution of alkali metal photocathode is in femitosecond order and those of GaAs NEA photocathode are in picosecond order.展开更多
Optical micro-scanning technology can be used to increase spatial resolution of many optical imaging systems,especially thermal imaging system. One of its key issues is relevant image processing algorithm. A fast reco...Optical micro-scanning technology can be used to increase spatial resolution of many optical imaging systems,especially thermal imaging system. One of its key issues is relevant image processing algorithm. A fast reconstruction algorithm is proposed for two dimensional 2×2 micro-scanning based on the sub-pixel imaging and reconstruction principle of two-dimensional staring focal plane arrays (FPA). Specifically,three initialization methods are presented and implemented with the simulated data,their performances are compared according to image quality index.Experiment results show that,by the first initialization approach,timely over-sampled image can be accurately recovered,although special field diaphragm is needed. In the second initialization,the extrapolation approximation in obtaining reconstruction results is better than either bilinear interpolation or over-sampling reconstruction,without requiring any special process on system. The proposed algorithm has simple structure,low computational cost and can be realized in real-time. A high-resolution image can be obtained by low-resolution detectors. So,the algorithm has potential applications in visible light and infrared imaging area.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 60425517 and 60378036.
文摘Near-field scanning optical microscopy is used to investigate the waveguiding properties of optical micro/nanofibres （MNFs） by means of detecting optical power carried by evanescent waves. Taper drawn silica and tellurite MNFs, supported on low-index substrates, are used to guide a 532-nm-wavelength light beam for the test. Modification of the single-mode condition of the MNF in the presence of a substrate is observed. Spatial modulation of the longitudinal field intensity （with a 195-nm period） near the output end of a 760-nm-diameter silica MNF is well resolved. Energy exchange through evanescent coupling between two parallel MNFs is also investigated.
基金Supported by the National Natural Science Foundation of China under Crant No 60407003, and the National Basic Research Program of China under Grant No 2007CB307003.
文摘The multimode evolution, optical losses and wavelength response of non-adiabatic micro/nano-fiber （MNF） tapers are numerically simulated using a three-dimensional finite-difference beam propagation method. For a non-adiabatic MNF taper, it is illustrated that optical losses vary with the transition region length and the optical wavelength. We explain how the complicated multimode evolutions result in the complicated optical loss and wavelength response properties, especially when the waist diameters are large enough to allow much higher-order modes. These results may offer valuable references for trapping and guiding cold atoms in atom optics and practical application of micro/nano-devices.
文摘Dedicated experiments are designed to collect the infrared spectra of dissolved gas-in-oil of power transformers. Spectra of diagnostic gases are collected by 3 different laboratorial FTIR spectrometers using 3 different gas cells with various sets of equipment parameters. A formula is deduced to calculate the shortest optical length to detect a specific concentration according to measurements on gases with known concentrations near to the minimum detection limit. Collected spectra and calculated results suggested that the optimum optical length of the gas cell should be 150 mm to realize on-line monitoring of diagnostic gases within the required concentration range. At the end, an economic novel design of the gas cell is proposed based on the optimum length.
文摘The fundamental measurement of space gravitational wave detection is to monitor the relative motion between pairs of freely falling test masses using heterodyne laser interferometry to a precision of 10 pm. The masses under test are millions of kilometers apart. The inter-spacecraft laser interferometry telescope deliver laser efficiently from one spacecraft to another. It is an important component of the gravitational wave detection observatory. It needs to meet the requirements of large compression ratio, high image quality and extraordinary stray light suppression ability. Based on the primary aberration theory, the method of the large compression ratio off-axis four-mirror optical system design is explored. After optimization, the system has an entrance pupil of 200 mm, compression ratio of 40 times, scientific field of view (FOV) of ±8 μrad. To facilitate suppressing the stray light and delivering the laser beam to the back-end scientific interferometers, the intermediate images and the real exit pupils are spatially available. Over the full FOV, the maximum root mean square (RMS) wavefront error is less than 0.007λ, PV value is less than 0.03λ (λ = 1064 nm). The image quality is approached to the diffraction-limit. The TTL noise caused by the wavefront error of the telescope is analyzed. The TTL noise in the image space of 300 μrad range is less than 1 × 10-10 m whose slope is lower than 0.6 μm/rad, which is under the noise budget of the laser interferometer space antenna (LISA), satisfying the requirements of space gravitational wave detection.
基金Supported by the National Natural Science Foundation of China under Grant No 60407003, and the National Basic Research Programme of China under Grant No 2007CB307003.
文摘We numerically demonstrate that ＇mode-entangled states＇ based on the transverse modes of classical optical fields in multimode waveguides violate Bell＇s inequality. Numerically simulating the correlation measurement scheme of Bell＇s inequality, we obtain the normalized correlation functions of the intensity fluctuations for the two entangled classical fields. By using the correlation functions, the maximum violations of Bell＇s inequality are obtained. This implies that the two classical fields in the mode-entangled states, although spatially separated, present a nonlocal correlation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61975185 and 61575178)the Natural Science Foundation of Zhejiang Province,China(Grant No.LY19F030004)the Scientific Research and Development Fund of Zhejiang University of Science and Technology,China(Grant No.F701108L03).
文摘The two types of nonlinear optical cryptosystems(NOCs)that are respectively based on amplitude-phase retrieval algorithm(APRA)and phase retrieval algorithm(PRA)have attracted a lot of attention due to their unique mechanism of encryption process and remarkable ability to resist common attacks.In this paper,the securities of the two types of NOCs are evaluated by using a deep-learning(DL)method,where an end-to-end densely connected convolutional network(DenseNet)model for cryptanalysis is developed.The proposed DL-based method is able to retrieve unknown plaintexts from the given ciphertexts by using the trained DenseNet model without prior knowledge of any public or private key.The results of numerical experiments with the DenseNet model clearly demonstrate the validity and good performance of the proposed the DL-based attack on NOCs.
基金supported by National Natural Science Foundation of China under Grant No.10574058the Scientific Research Foundation of Ningbo under Grant No.2008A610001sponsored by K.C.Wong Magna Fund in Ningbo University
文摘The properties of controllable soliton switching in Kerr-type optical lattices with different modulation are investigated theoretically and simulated numerically.The results show that the optical lattices can be available for all- optical soliton switching through utilization for length-scale competition effects.And through longitudinal exponential- asymptotic modulation for the linear refractive index,the properties of soliton switching in the optical lattices can be improved.The number of output channels of soliton switching can be controlled by the parameters such as incident angle,asymptotic rate of longitudinal modulation,guiding parameter and form factor.
基金supported by the Program Sponsored for Scientific Innovation Research of College Graduates in Jangsu Province,China(No.CXZZ12 0656)the Qing Lan Project of Jiangsu Province,Open Fund Supported by Jiangsu Provincial Key Laboratory for Science and Technology of Photon Manufacturing(Jiangsu University)of China(No.GZ201201)
文摘A novel design is proposed for highly sensitive surface-plasmon-resonance sensors. The sensor is based on a microstructured optical fiber with two layers of annular-shaped holes. A gold layer is deposited on the inner surface of the second hole-layer, in which the holes have several micrometers thickness in size, facilitating analyte infiltration and metal layer deposition. In the first layer of holes, the sector-ring^shaped arms, used as supporting strips, are utilized to tune the resonance depth of the sensor. Numerical results indicate that the sensor operation wavelength can be tuned across the C＋L-band. The spectral sensitivity of 1.0.104 nm. RIU-1 order of magnitude and a detection limit of 1.0.10-4 RIU order are demonstrated over a wide range of analyte refractive index from 1.320 to 1.335.
基金Supported by the National Basic Research Program of China under Grant No 2009CB929401the Natural Science Foundation of Shandong Province under Grant No ZR2009GM023.
文摘Ultrathin iron films with different thicknesses from 7.1 to 51.7 nm are deposited by magnetron sputtering and covered by tantalum layers protecting them from being oxidized.These ultrathin iron films are studied by spectroscopic ellipsometry and transmittance measurement.An extra tantalum film is deposited under the same sputtering conditions and its optical constants and film thickness are obtained by a combination of ellipsometry and transmission measurement.After introducing these obtained optical constants and film thickness into the tantalum-iron film,the optical constants and film thicknesses of ultrathin iron films with different thicknesses are obtained.The results show that combining ellipsometry and transmission measurement improves the uniqueness of the obtained film thickness.The optical constants of ultrathin iron films depend strongly on film thicknesses.There is a broad absorption peak at about 370 nm and it shifts to 410 nm with film thickness decreasing.
基金Project supported by the National Basic Research Program of China(Grant No.2009CB929400)the Independent Innovation Foundation of Shandong University,China(Grant No.2012ZB040)
文摘The longitudinal generalized magneto-optical ellipsometry （GME） method is extended to the measurement of three- layer ultrathin magnetic films. In this work, the theory of the reflection matrix is introduced into the GME measurement to obtain the reflective matrix parameters of ultrathin multilayer magnetic films with different thicknesses. After that, a spectroscopic ellipsometry is used to determine the optical parameter and the thickness of every layer of these samples, then the magneto-optical coupling constant of the multilayer magnetic ultrathin film can be obtained. After measurements of a series of ultrathin Fe films, the results show that the magneto-optical coupling constant Q is independent of the thickness of the magnetic film. The magneto-optical Kerr rotations and ellipticity are measured to confirm the validity of this experiment. Combined with the optical constants and the Q constant, the Kerr rotations and ellipticity are calculated in theory. The results show that the theoretical curve fits very well with the experimental data.
基金supported by the Instrument Developing Project of the Chinese Academy of Sciences (Grant No.YJKYYQ20190044)the National Key Research and Development Program of China (Grant No.2022YFB3903100)+1 种基金the High-level introduction of talent research start-up fund of Hefei Normal University in 2020 (Grant No.2020rcjj34)the HFIPS Director’s Fund (Grant No.YZJJ2022QN12).
文摘Non-line-of-sight(NLOS)imaging has emerged as a prominent technique for reconstructing obscured objects from images that undergo multiple diffuse reflections.This imaging method has garnered significant attention in diverse domains,including remote sensing,rescue operations,and intelligent driving,due to its wide-ranging potential applications.Nevertheless,accurately modeling the incident light direction,which carries energy and is captured by the detector amidst random diffuse reflection directions,poses a considerable challenge.This challenge hinders the acquisition of precise forward and inverse physical models for NLOS imaging,which are crucial for achieving high-quality reconstructions.In this study,we propose a point spread function(PSF)model for the NLOS imaging system utilizing ray tracing with random angles.Furthermore,we introduce a reconstruction method,termed the physics-constrained inverse network(PCIN),which establishes an accurate PSF model and inverse physical model by leveraging the interplay between PSF constraints and the optimization of a convolutional neural network.The PCIN approach initializes the parameters randomly,guided by the constraints of the forward PSF model,thereby obviating the need for extensive training data sets,as required by traditional deep-learning methods.Through alternating iteration and gradient descent algorithms,we iteratively optimize the diffuse reflection angles in the PSF model and the neural network parameters.The results demonstrate that PCIN achieves efficient data utilization by not necessitating a large number of actual ground data groups.Moreover,the experimental findings confirm that the proposed method effectively restores the hidden object features with high accuracy.
基金Project supported by National High Technology Development Program of China (Grant No 2002AA135030)
文摘Lidar （Light detection and ranging） has special capabilities for remote sensing of many different behaviours of the atmosphere. One of the techniques which show a great deal of promise for several applications is Raman scattering. The detecting capability, including maximum operation range and minimum detectable gas concentration is one of the most significant parameters for lidar remote sensing of pollutants. In this paper, based on the new method for evaluating the capabilities of a Raman lidar system, we present an evaluation of detecting capability of Raman lidar for monitoring atmospheric CO2 in Hefei. Numerical simulations about the influence of atmospheric conditions on lidar detecting capability were carried out, and a conclusion can be drawn that the maximum difference of the operation ranges caused by the weather conditions alone can reach about 0.4 to 0.5km with a measuring precision within 30ppmv. The range of minimum detectable concentration caused by the weather conditions alone can reach about 20 to 35 ppmv in vertical direction for 20000 shots at a distance of 1 km on the assumption that other parameters are kept constant. The other corresponding parameters under different conditions are also given. The capability of Raman lidar operated in vertical direction was found to be superior to that operated in horizontal direction. During practical measurement with the Raman lidar whose hardware components were fixed, aerosol scattering extinction effect would be a significant factor that influenced the capability of Raman lidar. This work may be a valuable reference for lidar system designing, measurement accuracy improving and data processing.
基金supported by the Korea Meteorological Administration Research and Development Program (Grant No. CATER 2012-3081)
文摘The accurate determination of surface-layer turbulent fluxes over urban areas is critical to understanding urban boundary layer （UBL） evolution. In this study, a remote-sensing technique using a large aperture scintillometer （LAS） was investigated to estimate surface-layer turbulent fluxes over a highly heterogeneous urban area. The LAS system, with an optical path length of 2.1 km, was deployed in an urban area characterized by a complicated land-use mix （residential houses, water body, bare ground, etc.）. The turbulent sensible heat （QH） and momentum fluxes （z） were estimated from the scintillation measurements obtained from the LAS system during the cold season. Three-dimensional LAS footprint modeling was introduced to identify the source areas （＂footprint＂） of the estimated turbulent fluxes. The analysis results showed that the LAS-derived turbulent fluxes for the highly heterogeneous urban area revealed reasonable temporal variation during daytime on clear days, in comparison to the land-surface process-resolving numerical modeling. A series of sensitivity tests indicated that the overall uncertainty in the LAS-derived daytime QH was within 20%-30% in terms of the influence of input parameters and the non- dimensional similarity function for the temperature structure function parameter, while the estimation errors in z were less sensitive to the factors of influence, except aerodynamic roughness length. The 3D LAS footprint modeling characterized the source areas of the LAS-derived turbulent fluxes in the heterogeneous urban area, revealing that the representative spatial scales of the LAS system deployed with the 2.1 km optical path distance ranged from 0.2 to 2 km2 （a ＂micro-a scale＂）, depending on local meteorological conditions.
文摘Laser-induced breakdown spectroscopy （LIBS） has attracted many academic and industrial interests world-wide due to its unique advantages, such as little or no sample preparation requirement, in-situ/online and multi-elemental analysis, and remote sensing etc., and it has been regarded as a ＂future super star＂ for chemical analysis for many years . In China,
文摘A theory of the far spatial coherent-suppressed single-peak field distribution of a rectangular wave-guide CO2 laser is presented. The theoretical analysis shows that a rectangular wave-guide laser can have an output intensity distribution in far field similar to that produced from a wave-guide array laser, which is in agreement with the experimental result. A single-peak mode output is obtained within 5 metres. The experimental far-field spread angle in the bigger-Fresnel number direction is 0.63 mrad, compared to the calculated one, 0.6 mrad, and when the length of the laser resonator is changed, a double-peak or multi-peak in far-field distribution of the laser is obtained.
基金the Hi-Tech Research and Development Pro-gram (863) of China (No. 2006AA06Z406)the Natural ScienceFoundation of Zhejiang Province (No. Z504009), China
文摘In this paper, a low-cost measurement approach with bi-beam was presented, which can be used for real-time detection and online analysis of solution refractive index, based on systematical analysis and experiments of conventional detection methods on surface plasmon resonance sensor. This novel method was analyzed theoretically and based on it a sensor system set was established. The factors that affect the sensor's sensitivity and working range were discussed. The angular adjustment setup was simplified, errors produced by movable components were avoided and the maneuverability was enhanced with this new method. The noiseproof feature and stability of the sensor system were greatly improved as well.
基金Supported by the National Natural Science Foundation of China under Grant Nos.61875198 and 61775215the Foundation of Military Commission of Science and Technology of China under Grant No.61404140107。
文摘We demonstrate that the etalon effects of alkali cells can be used as the output coupler of an alkali laser.Based on a rubidium cell with highly parallelized windows,a 2.7 W rubidium laser with optical efficiency of 20.9%and slope efficiency of 31.8%is obtained by adopting unconventional output couplers.Since it has compact configuration and the inner surface of the rubidium cell is uncoated,this may be used in high power laser systems with long lifetimes.
文摘The temporal characteristics of GaAs NEA and alkali metal photocathodes are studied using Monte Carlo simulation method. The electron transit time and its distribution functions in the photocathodes are calculated. Based on the results, the time modulation transfer functions and temporal resolutions of the photocathodes are obtained. The results show that the response time and temporal resolution of alkali metal photocathode is in femitosecond order and those of GaAs NEA photocathode are in picosecond order.
文摘Optical micro-scanning technology can be used to increase spatial resolution of many optical imaging systems,especially thermal imaging system. One of its key issues is relevant image processing algorithm. A fast reconstruction algorithm is proposed for two dimensional 2×2 micro-scanning based on the sub-pixel imaging and reconstruction principle of two-dimensional staring focal plane arrays (FPA). Specifically,three initialization methods are presented and implemented with the simulated data,their performances are compared according to image quality index.Experiment results show that,by the first initialization approach,timely over-sampled image can be accurately recovered,although special field diaphragm is needed. In the second initialization,the extrapolation approximation in obtaining reconstruction results is better than either bilinear interpolation or over-sampling reconstruction,without requiring any special process on system. The proposed algorithm has simple structure,low computational cost and can be realized in real-time. A high-resolution image can be obtained by low-resolution detectors. So,the algorithm has potential applications in visible light and infrared imaging area.
