Accurate modeling of the point spread function(PSF)is essential for scientific measurements derived from observations.This study aims to present the issues related to PSF modeling for the Chinese Space Station Survey ...Accurate modeling of the point spread function(PSF)is essential for scientific measurements derived from observations.This study aims to present the issues related to PSF modeling for the Chinese Space Station Survey Telescope(CSST)and then propose a practical approach for PSF reconstruction specific to CSST.We utilize PSFEx and ePSF to reconstruct the PSFs from simulated images of CSST's PSFs and quantify the impact of image size and setups of the programs on PSF reconstruction by comparing the outputs with the ground truth.We also assessed the effect of the selection of stars on PSF reconstruction,such as unresolved binaries with varying binary fractions and separations in the same manner.Our analysis indicated that both PSFEx and e PSF programs tend to overestimate the radius and introduce biases in the ellipticity measurements of the PSFs,due to the undersampling of the CSST PSF.These biases remain consistent across different program setups and image sizes but can be corrected empirically.In addition,unresolved binaries have a significant influence on PSF modeling.However,our deep learning-based method can effectively identify suitable stars for PSF modeling to avoid this problem,achieving a classification accuracy of 89.1%and an AUC of 0.937.By integrating the source selection with empirical correction modules,the measured parameters of PSFs match the ground truth,as validated by Kolmogorov-Smirnov tests.This combined approach is expected to enhance the measurement of PSFs,leading to more accurate scientific results from CSST data.展开更多
AIM:To compare objective dry retinoscopy and subjective refraction measurements in patients with mild keratoconus(KCN)and quantify any differences.METHODS:This cross-sectional study was done on 68 eyes of 68 patients ...AIM:To compare objective dry retinoscopy and subjective refraction measurements in patients with mild keratoconus(KCN)and quantify any differences.METHODS:This cross-sectional study was done on 68 eyes of 68 patients diagnosed with mild KCN.Objective dry retinoscopy using autorefractometer and subjective refraction measurements were performed.Sphere,cylinder,J0,J45,and spherical equivalent values were compared between the two techniques.RESULTS:The mean age of 68 patients with mild KCN was 21.32±5.03y(12–35y).There were 37(54.4%)males.Objective refraction yielded significantly more myopic sphere(-1.44 D vs-0.57 D),higher cylinder magnitude(-2.24 D vs-1.48 D),and more myopic spherical equivalent(-2.56 D vs-1.31 D)compared to subjective refraction(all P<0.05).The mean differences were-0.87 D for sphere,-0.76 D for cylinder,and-1.25 D for spherical equivalent.No significant differences were found for J0 and J45 values,indicating agreement in astigmatism axis(P>0.05).CONCLUSION:In patients with mild KCN,objective dry retinoscopy overestimates the degree of myopia and astigmatism compared to subjective refraction.The irregular cornea in KCN likely impacts objective measurements.Subjective refraction allows compensation for irregularity,providing a more accurate correction.When determining refractive targets,the tendency of objective methods to overcorrect should be considered.展开更多
AIM:To determine the diagnostic ability of various visual functions in patients with multiple sclerosis(MS)with and without optic neuritis(ON).METHODS:In this cross-sectional study,we assessed and compared refractive ...AIM:To determine the diagnostic ability of various visual functions in patients with multiple sclerosis(MS)with and without optic neuritis(ON).METHODS:In this cross-sectional study,we assessed and compared refractive error,visual acuity(VA),and contrast sensitivity(CS)between patients with MS and a matched control group of healthy individuals.The MS patients were further categorized into those with ON and those without.RESULTS:A total of 133 eyes from 133 participants were assessed,including 66 individuals diagnosed with MS.The mean ages for the MS group and the healthy control group were 37.5±4.27y and 38.45±4.60y,respectively(P=0.346).Among the 66 patients with MS,18 had ON.The presence of MS was associated with a decrease in best-corrected visual acuity(BCVA)and spherical component of refractive error(P<0.05),whereas ON did not lead to any further decline in these parameters(P>0.05).MS was linked to decreased CS at spatial frequencies of 6 and 18 cycles per degree(CPD;P<0.05),while ON in MS patients resulted in an additional decrease in CS at 3 CPD(P=0.03).The most significant sensitivity for distinguishing MS patients from healthy individuals as well as MS patients with ON from those without ON was found with cylindrical component[associated criterion(AC)>-0.75 D;71.21%]and CS at spatial frequency of 6 CPD(AC≤1.56;72.22%),respectively.Conversely,the highest specificity for these diagnostic measures was associated with BCVA(AC>0 logMAR;97.01%)and CS at a spatial frequency of 12 CPD(AC≤0.60;93.75%),respectively.CONCLUSION:MS significantly affects refractive error and CS,with ON further reducing CS.Assessing these visual parameters can improve MS monitoring and management.展开更多
The stabilizing and shifting of laser frequency are very important for the interaction between the laser and atoms. The modulation transfer spectroscopy for the 87Rb atom with D2 line transition F = 2 →F＇ = 3 is use...The stabilizing and shifting of laser frequency are very important for the interaction between the laser and atoms. The modulation transfer spectroscopy for the 87Rb atom with D2 line transition F = 2 →F＇ = 3 is used for stabilizing and shifting the frequency of the external cavity grating feedback diode laser. The resonant phase modulator with electro-optical effect is used to generate frequency sideband to lock the laser frequency. In the locking scheme, circularly polarized pump- and probe-beams are used. By optimizing the temperature of the vapor, the pump- and probe-beam intensity, the laser linewidth of 280 kHz is obtained. Furthermore, the magnetic field generated by a solenoid is added into the system. Therefore the system can achieve the frequency locking at any point in a range of hundreds of megahertz frequency shifting with very low power loss.展开更多
A highly sensitive all-optical atomic magnetometer based on the magnetooptical effect which uses the advanced technique of single laser beam detection is reported and demonstrated experimentally. A sensitivity of 0.5p...A highly sensitive all-optical atomic magnetometer based on the magnetooptical effect which uses the advanced technique of single laser beam detection is reported and demonstrated experimentally. A sensitivity of 0.5pT/Hz^1/2 is obtained by analyzing the magnetic noise spectrum, which exceeds that of most traditional magnetometers. This kind of atomic magnetometer is very compact, has a low power consumption, and has a high theoretical sensitivity limit, which make it suitable for many applications.展开更多
By applying the wavefront coding technique to an optical system, the depth of focus can be greatly increased. Several complicated methods, such as Fisher Information based method, have already been taken to optimize f...By applying the wavefront coding technique to an optical system, the depth of focus can be greatly increased. Several complicated methods, such as Fisher Information based method, have already been taken to optimize for the best pupil phase mask in ideal condition. Here one simple point spread function (PSF) based method with only the standard deviation method used to evaluate the PSF stability over the depth of focus is taken to optimize for the best coefficients of pupil phase mask in practical optical systems. Results of imaging simulations for optical systems with and without pupil phase mask are presented, and the sharpness of image is calculated for comparison. The optimized results showed better and much more stable imaging quality over the original system without changing the position of the image plane.展开更多
A novel setup of saturated absorption spectroscopy (SAS) is presented.It is based on laser reflections at surfaces of a sample vapor cell.It only needs one cell and one photodiode and is more compact than conventional...A novel setup of saturated absorption spectroscopy (SAS) is presented.It is based on laser reflections at surfaces of a sample vapor cell.It only needs one cell and one photodiode and is more compact than conventional setups of SAS.Its spectrum is similar to a conventional SAS.The frequency stabilization performance of an external-cavity diode laser with this setup is investigated.A frequency stability of 1.1 × 10^(-11) is achieved at an averaging time of 60s in the Allen variance measurements.展开更多
We propose a new approach for quantum state transfer（QST） between atomic ensembles separately trapped in two distant cavities connected by an optical fiber via adiabatic passage. The three-level Λ-type atoms in eac...We propose a new approach for quantum state transfer（QST） between atomic ensembles separately trapped in two distant cavities connected by an optical fiber via adiabatic passage. The three-level Λ-type atoms in each ensemble dispersively interact with the nonresonant classical field and cavity mode. By choosing appropriate parameters of the system, the effective Hamiltonian describes two atomic ensembles interacting with ＂the same cavity mode＂ and has a dark state. Consequently, the QST between atomic ensembles can be implemented via adiabatic passage. Numerical calculations show that the scheme is robust against moderate fluctuations of the experimental parameters. In addition, the effect of decoherence can be suppressed effectively. The idea provides a scalable way to an atomic-ensemble-based quantum network, which may be reachable with currently available technology.展开更多
We present an experimental and theoretical investigation of the coherent population trapping （CPT） resonance excited on the D1 line of 87Rb atoms by bichromatic linearly polarized laser light. The experimental resul...We present an experimental and theoretical investigation of the coherent population trapping （CPT） resonance excited on the D1 line of 87Rb atoms by bichromatic linearly polarized laser light. The experimental results show that a lin｜｜lin tran- sition scheme is a promising alternative to the conventional circular-circular transition scheme for an atomic magnetometer. Compared with the circular light transition scheme, linear light accounts for high-contrast transmission resonances, which makes this excitation scheme promising for high-sensitivity magnetometers. We also use linear light and circular light to detect changes of a standard magnetic field, separately.展开更多
AIM： To analytically assess the effect of pupil size upon the refractive power distributions of different designs of multifocal contact lenses.METHODS： Two multifocal contact lenses of center-near design and one mul...AIM： To analytically assess the effect of pupil size upon the refractive power distributions of different designs of multifocal contact lenses.METHODS： Two multifocal contact lenses of center-near design and one multifocal contact lens of center-distance design were used in this study. Their power profiles were measured using the NIMO TR1504 device （LAMBDA-X, Belgium）. Based on their power profiles, the power distribution was assessed as a function of pupil size. For the high addition lenses, the resulting refractive power as a function of viewing distance （far, intermediate, and near） and pupil size was also analyzed.RESULTS： The power distribution of the lenses was affected by pupil size differently. One of the lenses showed a significant spread in refractive power distribution, from about ？3 D to 0 D. Generally, the power distribution of the lenses expanded as the pupil diameter became greater. The surface of the lens dedicated for each distance varied substantially with the design of the lens.CONCLUSION： In an experimental basis, our results show how the lenses power distribution is affected by the pupil size and underlined the necessity of careful evaluation of the patient’s visual needs and the optical properties of a multifocal contact lens for achieving the optimal visual outcome.展开更多
To characterize the degree of similarity inherent to parameters of the optically uniaxial birefringent protein-fibril networks of biological tissues,a new parameter-complex degree of mutual anisotropy-has been offered...To characterize the degree of similarity inherent to parameters of the optically uniaxial birefringent protein-fibril networks of biological tissues,a new parameter-complex degree of mutual anisotropy-has been offered.The technique of polarization measuring the coordinate distributions of the complex degree of mutual anisotropy of biological tissues has been developed.It has been shown that statistical approach to the analysis of complex degree of mutual anisotropy distributions for biological tissues in various morphological and physiological states and for different optical thicknesses appears to be more sensitive and efficient in differentiation of physiological state,as compared to investigations of complex degree of mutual polarization in the corresponding laser images.展开更多
An atomic magnetometer based on optically detected magnetic resonance is investigated and demonstrated experimentally.We build an 894 nm external cavity diode laser which is frequency locked to the F=4→F'=3 trans...An atomic magnetometer based on optically detected magnetic resonance is investigated and demonstrated experimentally.We build an 894 nm external cavity diode laser which is frequency locked to the F=4→F'=3 transition of Cs D_(1) line with DAVLL spectroscopy.With the phase-locked loop,the frequency of the rf coils is actively locked to the Larmor frequency and the magnetometer tracks the magnetic field variations in a phase coherent manner.An ultimate sensitivity of 19 fT/Hz^(1/2) and an intrinsic sensitivity of 8.6 pT/Hz^(1/2) in the magnetic environment which is close to geomagnetic field have been achieved with the spatial resolution smaller than 2 cm.展开更多
Gradient index layers and rugate structures were fabricated on a Leybold Syrus pro deposition system by plasma-assisted coevaporation of the low index material silica and the high index material niobium pentoxide.To o...Gradient index layers and rugate structures were fabricated on a Leybold Syrus pro deposition system by plasma-assisted coevaporation of the low index material silica and the high index material niobium pentoxide.To obtain information about the compositional profiles of the produced layers,cross sectional transmission electron microscopy was used in assistance to deposition rate data recorded by two independent crystal monitors during the film preparation.The depth dependent concentration profiles were transformed to refractive index gradients by means of effective medium approximation.Based on the refractive index gradients the corresponding samples`transmission and reflection spectra could be calculated by utilizing matrix formalism.The relevance of the established refractive index profiles could be verified by comparison of the calculated spectra with the measured ones.展开更多
The cold atom gravimeter offers the prospect of a new generation of inertial sensors for field applications. We ac- complish a mobile atom gravimeter. With the compact and stable system, a sensitivity of 1.4× 10-...The cold atom gravimeter offers the prospect of a new generation of inertial sensors for field applications. We ac- complish a mobile atom gravimeter. With the compact and stable system, a sensitivity of 1.4× 10-7 g.Hz-1/2 is achieved. Moreover, a continuous gravity monitoring of 80 h is carried out. However, the harsh outdoor environment is a big challenge for the atom gravimeter when it is for field applications. In this paper, we present the preliminary investigation of the thermal adaptability for our mobile cold atom gravimeter. Here, we focus on the influence of the air temperature on the performance of the atom gravimeter. The responses to different factors （such as laser power, fiber coupling efficiency, etc.） are evaluated when there is a great temperature shift of 10 ℃. The result is that the performances of all the factors deteriorate to different extent, nevertheless, they can easily recover as the temperature comes back. Finally, we conclude that the variation of air temperature induces the increase of noise and the system error of the atom gravimeter as well, while the process is reversible with the recovery of the temperature.展开更多
We demonstrate experimentally an atomic magnetometer based on optical pumping theory, a magnetic resonance that is induced by a radio frequency field and dependent on the magnetic field strength. Compared with the con...We demonstrate experimentally an atomic magnetometer based on optical pumping theory, a magnetic resonance that is induced by a radio frequency field and dependent on the magnetic field strength. Compared with the conventional method using one radiation field, which is used not only as the probe beam but also as a pump beam, the additional re-pump beam can increase remarkably the amplitude of the signal. It is shown that the amplitude of the magnetic field resonance signal can increase more than 55% by using an additional re-pump beam, which makes the sensitivity of the magnetometer higher. Finally, we investigate the relation between amplitude of the signal and re-pump laser power, and calculate the atomic population in the trapping states with rate equations.展开更多
By using an Ar+ ion laser, a tunable Rh 6G dye laser(Linewidth: 0.5 cm -1) and a Coherent 899-21 dye laser as light sources and using a monochromator and a phase-locking amplifier, the optical properties of Eu 3+∶Y_2...By using an Ar+ ion laser, a tunable Rh 6G dye laser(Linewidth: 0.5 cm -1) and a Coherent 899-21 dye laser as light sources and using a monochromator and a phase-locking amplifier, the optical properties of Eu 3+∶Y_2SiO_5 crystal were detected. Persistent spectral hole burning (PSHB) were also observed in 5D_0-7F_0 transition in the crystal at the temperature of 16 K. For 15 mW dye laser (Wavelength: 579.62 nm) burning the crystal for 0.1 s a spectral hole with about 80 MHz hole width were detected and the hole can been keep for longer than 10 h.展开更多
Ellipse fitting is a useful tool to obtain the differential signal of two atom interference gravimeters. The quality standard of ellipse fitting should be the deviation between the true phase and the fitting phase of ...Ellipse fitting is a useful tool to obtain the differential signal of two atom interference gravimeters. The quality standard of ellipse fitting should be the deviation between the true phase and the fitting phase of the interference fringe. In this paper, we present a new algorithm to fit the ellipse. The algorithm is to minimize the differential noise of two interference gravimeters and obtain a more accurate value of the gravity gradient. We have theoretically derived the expression of the differential-mode noise and implemented the ellipse fitting in the program. This new algorithm is also compared with the classical methods.展开更多
Based on auditory peripheral simulation model,a new Sound Quality Objective Evaluation(SQOE)method is presented,which can be used to model and analyze the impacts of head,shoulder and other parts of human body on soun...Based on auditory peripheral simulation model,a new Sound Quality Objective Evaluation(SQOE)method is presented,which can be used to model and analyze the impacts of head,shoulder and other parts of human body on sound wave trans-mission.This method employs the artificial head technique,in which the head related transfer function was taken into account tothe outer ear simulation phase.First,a bionic artificial head was designed as the outer ear model with considering the outersound field in view of theory and physical explanations.Then the auditory peripheral simulation model was built,which mimicsthe physiological functions of the human hearing,simulating the acoustic signal transfer process and conversion mechanismsfrom the free field to the peripheral auditory system.Finally,performance comparison was made between the proposed SQOEmethod and ArtemiS software,and the verifications of subjective and objective related analysis were made.Results show thatthe proposed method was economical,simple,and with good evaluation quality.展开更多
Two-photon microscopy normally suffers from the scattering of the tissue in biological imaging.Multidither coberent optical adaptive technique(COAT)can correct the scattered wavefront in parallel.However,the determina...Two-photon microscopy normally suffers from the scattering of the tissue in biological imaging.Multidither coberent optical adaptive technique(COAT)can correct the scattered wavefront in parallel.However,the determination of the corrective phases may not be completely accurate using conventional method,which undermines the performance of this technique.In this paper,we theoretically demonstrate a method that can obtain more accurate corrective phases by determining the phase values from the square root of the fuorescence signal.A numnerical simulation model is established to study the performance of adaptive optics in two-photon micros-copy by combining scalar diffraction theory with vector diffraction theory.The results show that the distortion of the wavefront can be corrected more thoroughly with our method in two-photon imaging.In our simulation,with the scattering from a 450-mn-thick mouse brain tissue,excitation focal spots with higher peak-to background ratio(PBR)and images with higher contrast can be obtained.Hence,further enhancement of the multidither COAT correction performance in two-photon imaging can be expected.展开更多
基金supported by the science research grants from the China Manned Space Project(Nos.CMS-CS ST-2021-A01 and CMS-CSST-2025-A19)the National Key R&D Program of China(No.2021YFA1600400/1)+1 种基金the CAS Project for Young Scientists in Basic Research(No.YSBR-062)the Ministry of Science and Technology of China(No.2020SKA0110100)。
文摘Accurate modeling of the point spread function(PSF)is essential for scientific measurements derived from observations.This study aims to present the issues related to PSF modeling for the Chinese Space Station Survey Telescope(CSST)and then propose a practical approach for PSF reconstruction specific to CSST.We utilize PSFEx and ePSF to reconstruct the PSFs from simulated images of CSST's PSFs and quantify the impact of image size and setups of the programs on PSF reconstruction by comparing the outputs with the ground truth.We also assessed the effect of the selection of stars on PSF reconstruction,such as unresolved binaries with varying binary fractions and separations in the same manner.Our analysis indicated that both PSFEx and e PSF programs tend to overestimate the radius and introduce biases in the ellipticity measurements of the PSFs,due to the undersampling of the CSST PSF.These biases remain consistent across different program setups and image sizes but can be corrected empirically.In addition,unresolved binaries have a significant influence on PSF modeling.However,our deep learning-based method can effectively identify suitable stars for PSF modeling to avoid this problem,achieving a classification accuracy of 89.1%and an AUC of 0.937.By integrating the source selection with empirical correction modules,the measured parameters of PSFs match the ground truth,as validated by Kolmogorov-Smirnov tests.This combined approach is expected to enhance the measurement of PSFs,leading to more accurate scientific results from CSST data.
文摘AIM:To compare objective dry retinoscopy and subjective refraction measurements in patients with mild keratoconus(KCN)and quantify any differences.METHODS:This cross-sectional study was done on 68 eyes of 68 patients diagnosed with mild KCN.Objective dry retinoscopy using autorefractometer and subjective refraction measurements were performed.Sphere,cylinder,J0,J45,and spherical equivalent values were compared between the two techniques.RESULTS:The mean age of 68 patients with mild KCN was 21.32±5.03y(12–35y).There were 37(54.4%)males.Objective refraction yielded significantly more myopic sphere(-1.44 D vs-0.57 D),higher cylinder magnitude(-2.24 D vs-1.48 D),and more myopic spherical equivalent(-2.56 D vs-1.31 D)compared to subjective refraction(all P<0.05).The mean differences were-0.87 D for sphere,-0.76 D for cylinder,and-1.25 D for spherical equivalent.No significant differences were found for J0 and J45 values,indicating agreement in astigmatism axis(P>0.05).CONCLUSION:In patients with mild KCN,objective dry retinoscopy overestimates the degree of myopia and astigmatism compared to subjective refraction.The irregular cornea in KCN likely impacts objective measurements.Subjective refraction allows compensation for irregularity,providing a more accurate correction.When determining refractive targets,the tendency of objective methods to overcorrect should be considered.
文摘AIM:To determine the diagnostic ability of various visual functions in patients with multiple sclerosis(MS)with and without optic neuritis(ON).METHODS:In this cross-sectional study,we assessed and compared refractive error,visual acuity(VA),and contrast sensitivity(CS)between patients with MS and a matched control group of healthy individuals.The MS patients were further categorized into those with ON and those without.RESULTS:A total of 133 eyes from 133 participants were assessed,including 66 individuals diagnosed with MS.The mean ages for the MS group and the healthy control group were 37.5±4.27y and 38.45±4.60y,respectively(P=0.346).Among the 66 patients with MS,18 had ON.The presence of MS was associated with a decrease in best-corrected visual acuity(BCVA)and spherical component of refractive error(P<0.05),whereas ON did not lead to any further decline in these parameters(P>0.05).MS was linked to decreased CS at spatial frequencies of 6 and 18 cycles per degree(CPD;P<0.05),while ON in MS patients resulted in an additional decrease in CS at 3 CPD(P=0.03).The most significant sensitivity for distinguishing MS patients from healthy individuals as well as MS patients with ON from those without ON was found with cylindrical component[associated criterion(AC)>-0.75 D;71.21%]and CS at spatial frequency of 6 CPD(AC≤1.56;72.22%),respectively.Conversely,the highest specificity for these diagnostic measures was associated with BCVA(AC>0 logMAR;97.01%)and CS at a spatial frequency of 12 CPD(AC≤0.60;93.75%),respectively.CONCLUSION:MS significantly affects refractive error and CS,with ON further reducing CS.Assessing these visual parameters can improve MS monitoring and management.
基金Project supported by the National Natural Science Foundation of China(Grant No.11174249)the National Key Basic Research Program,China(Grant No.2013CB329501)+1 种基金the National High-Technology Research and Development Program of China(Grant No.2011AA060504)the Fundamental Research Funds for the Central Universities(Grant No.2014FZA3002)
文摘The stabilizing and shifting of laser frequency are very important for the interaction between the laser and atoms. The modulation transfer spectroscopy for the 87Rb atom with D2 line transition F = 2 →F＇ = 3 is used for stabilizing and shifting the frequency of the external cavity grating feedback diode laser. The resonant phase modulator with electro-optical effect is used to generate frequency sideband to lock the laser frequency. In the locking scheme, circularly polarized pump- and probe-beams are used. By optimizing the temperature of the vapor, the pump- and probe-beam intensity, the laser linewidth of 280 kHz is obtained. Furthermore, the magnetic field generated by a solenoid is added into the system. Therefore the system can achieve the frequency locking at any point in a range of hundreds of megahertz frequency shifting with very low power loss.
基金Supported by the National Natural Science Foundation of China under Grant No 10804097）, and the National Basic Research Program of China under Grant No 2006CB921403, and the Zhejiang Provincial Qian-Jiang-Ren-Cai Project of China under Grant No 2006R10025.
文摘A highly sensitive all-optical atomic magnetometer based on the magnetooptical effect which uses the advanced technique of single laser beam detection is reported and demonstrated experimentally. A sensitivity of 0.5pT/Hz^1/2 is obtained by analyzing the magnetic noise spectrum, which exceeds that of most traditional magnetometers. This kind of atomic magnetometer is very compact, has a low power consumption, and has a high theoretical sensitivity limit, which make it suitable for many applications.
文摘By applying the wavefront coding technique to an optical system, the depth of focus can be greatly increased. Several complicated methods, such as Fisher Information based method, have already been taken to optimize for the best pupil phase mask in ideal condition. Here one simple point spread function (PSF) based method with only the standard deviation method used to evaluate the PSF stability over the depth of focus is taken to optimize for the best coefficients of pupil phase mask in practical optical systems. Results of imaging simulations for optical systems with and without pupil phase mask are presented, and the sharpness of image is calculated for comparison. The optimized results showed better and much more stable imaging quality over the original system without changing the position of the image plane.
基金Supported by the National Basic Research Program of China under Grant No 2012CB921602the National Natural Science Foundation of China under Grant Nos 10874012 and 10974177the Program of International Science and Technology Cooperation of China under Grant No 2010DFA04690.
文摘A novel setup of saturated absorption spectroscopy (SAS) is presented.It is based on laser reflections at surfaces of a sample vapor cell.It only needs one cell and one photodiode and is more compact than conventional setups of SAS.Its spectrum is similar to a conventional SAS.The frequency stabilization performance of an external-cavity diode laser with this setup is investigated.A frequency stability of 1.1 × 10^(-11) is achieved at an averaging time of 60s in the Allen variance measurements.
基金Project supported by the Funding(type B)from the Fujian Education Department,China(Grant No.JB13261)
文摘We propose a new approach for quantum state transfer（QST） between atomic ensembles separately trapped in two distant cavities connected by an optical fiber via adiabatic passage. The three-level Λ-type atoms in each ensemble dispersively interact with the nonresonant classical field and cavity mode. By choosing appropriate parameters of the system, the effective Hamiltonian describes two atomic ensembles interacting with ＂the same cavity mode＂ and has a dark state. Consequently, the QST between atomic ensembles can be implemented via adiabatic passage. Numerical calculations show that the scheme is robust against moderate fluctuations of the experimental parameters. In addition, the effect of decoherence can be suppressed effectively. The idea provides a scalable way to an atomic-ensemble-based quantum network, which may be reachable with currently available technology.
基金Project supported by the National Basic Research Program of China (Grant No.2013CB329501)the National Natural Science Foundation of China (Grant Nos.60925022 and 11125863)the Fundamental Research Funds for the Central Universities (Grant No.2012FZA3001)
文摘We present an experimental and theoretical investigation of the coherent population trapping （CPT） resonance excited on the D1 line of 87Rb atoms by bichromatic linearly polarized laser light. The experimental results show that a lin｜｜lin tran- sition scheme is a promising alternative to the conventional circular-circular transition scheme for an atomic magnetometer. Compared with the circular light transition scheme, linear light accounts for high-contrast transmission resonances, which makes this excitation scheme promising for high-sensitivity magnetometers. We also use linear light and circular light to detect changes of a standard magnetic field, separately.
基金Supported by the AGEYE project(No.608049)the Marie Curie Initial Training Network program(No.FP7-PEOPLE-2013-ITN)the European Commission,Brussels,Belgium and by an Atraccióde Talent(University of Valencia)research scholarship granted to Antonio J.Deláguila-Carrasco(No.UV-INV-PREDOC14-179135)
文摘AIM： To analytically assess the effect of pupil size upon the refractive power distributions of different designs of multifocal contact lenses.METHODS： Two multifocal contact lenses of center-near design and one multifocal contact lens of center-distance design were used in this study. Their power profiles were measured using the NIMO TR1504 device （LAMBDA-X, Belgium）. Based on their power profiles, the power distribution was assessed as a function of pupil size. For the high addition lenses, the resulting refractive power as a function of viewing distance （far, intermediate, and near） and pupil size was also analyzed.RESULTS： The power distribution of the lenses was affected by pupil size differently. One of the lenses showed a significant spread in refractive power distribution, from about ？3 D to 0 D. Generally, the power distribution of the lenses expanded as the pupil diameter became greater. The surface of the lens dedicated for each distance varied substantially with the design of the lens.CONCLUSION： In an experimental basis, our results show how the lenses power distribution is affected by the pupil size and underlined the necessity of careful evaluation of the patient’s visual needs and the optical properties of a multifocal contact lens for achieving the optimal visual outcome.
文摘To characterize the degree of similarity inherent to parameters of the optically uniaxial birefringent protein-fibril networks of biological tissues,a new parameter-complex degree of mutual anisotropy-has been offered.The technique of polarization measuring the coordinate distributions of the complex degree of mutual anisotropy of biological tissues has been developed.It has been shown that statistical approach to the analysis of complex degree of mutual anisotropy distributions for biological tissues in various morphological and physiological states and for different optical thicknesses appears to be more sensitive and efficient in differentiation of physiological state,as compared to investigations of complex degree of mutual polarization in the corresponding laser images.
基金Supported in part by the National Basic Research Program of China under Grant No 2012CB921602the National Natural Science Foundation of China under Grant Nos 10874012,10974177the Program of International Science and Technology Cooperation of China under Grant No 2010DFA04690。
文摘An atomic magnetometer based on optically detected magnetic resonance is investigated and demonstrated experimentally.We build an 894 nm external cavity diode laser which is frequency locked to the F=4→F'=3 transition of Cs D_(1) line with DAVLL spectroscopy.With the phase-locked loop,the frequency of the rf coils is actively locked to the Larmor frequency and the magnetometer tracks the magnetic field variations in a phase coherent manner.An ultimate sensitivity of 19 fT/Hz^(1/2) and an intrinsic sensitivity of 8.6 pT/Hz^(1/2) in the magnetic environment which is close to geomagnetic field have been achieved with the spatial resolution smaller than 2 cm.
基金Project supported by the National Natural Science Foundation of China(No.61475139)the National Basic Research Program(973 Program)of China(No.2013CB329501)+1 种基金the National High Technology Research and Development Program(863 Program)of China(No.2013AA063901)the Fundamental Research Funds for the Central Universities,China(No.2017FZA3005)
文摘Gradient index layers and rugate structures were fabricated on a Leybold Syrus pro deposition system by plasma-assisted coevaporation of the low index material silica and the high index material niobium pentoxide.To obtain information about the compositional profiles of the produced layers,cross sectional transmission electron microscopy was used in assistance to deposition rate data recorded by two independent crystal monitors during the film preparation.The depth dependent concentration profiles were transformed to refractive index gradients by means of effective medium approximation.Based on the refractive index gradients the corresponding samples`transmission and reflection spectra could be calculated by utilizing matrix formalism.The relevance of the established refractive index profiles could be verified by comparison of the calculated spectra with the measured ones.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11174249 and 61475139)the National High Technology Research and Development Program of China(Grant No.2011AA060504)+1 种基金the National Basic Research Program of China(Grant No.2013CB329501)the Fundamental Research Funds for the Central Universities,China(Grant No.2016FZA3004)
文摘The cold atom gravimeter offers the prospect of a new generation of inertial sensors for field applications. We ac- complish a mobile atom gravimeter. With the compact and stable system, a sensitivity of 1.4× 10-7 g.Hz-1/2 is achieved. Moreover, a continuous gravity monitoring of 80 h is carried out. However, the harsh outdoor environment is a big challenge for the atom gravimeter when it is for field applications. In this paper, we present the preliminary investigation of the thermal adaptability for our mobile cold atom gravimeter. Here, we focus on the influence of the air temperature on the performance of the atom gravimeter. The responses to different factors （such as laser power, fiber coupling efficiency, etc.） are evaluated when there is a great temperature shift of 10 ℃. The result is that the performances of all the factors deteriorate to different extent, nevertheless, they can easily recover as the temperature comes back. Finally, we conclude that the variation of air temperature induces the increase of noise and the system error of the atom gravimeter as well, while the process is reversible with the recovery of the temperature.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.60925022 and 11104243)the Fundamental Research Funds for the Central Universities,China(Grant No.2012FZA3001)the National Key Basic Research and Development Program of China(Grant No.2013CB329501)
文摘We demonstrate experimentally an atomic magnetometer based on optical pumping theory, a magnetic resonance that is induced by a radio frequency field and dependent on the magnetic field strength. Compared with the conventional method using one radiation field, which is used not only as the probe beam but also as a pump beam, the additional re-pump beam can increase remarkably the amplitude of the signal. It is shown that the amplitude of the magnetic field resonance signal can increase more than 55% by using an additional re-pump beam, which makes the sensitivity of the magnetometer higher. Finally, we investigate the relation between amplitude of the signal and re-pump laser power, and calculate the atomic population in the trapping states with rate equations.
文摘By using an Ar+ ion laser, a tunable Rh 6G dye laser(Linewidth: 0.5 cm -1) and a Coherent 899-21 dye laser as light sources and using a monochromator and a phase-locking amplifier, the optical properties of Eu 3+∶Y_2SiO_5 crystal were detected. Persistent spectral hole burning (PSHB) were also observed in 5D_0-7F_0 transition in the crystal at the temperature of 16 K. For 15 mW dye laser (Wavelength: 579.62 nm) burning the crystal for 0.1 s a spectral hole with about 80 MHz hole width were detected and the hole can been keep for longer than 10 h.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFC0601602)the Fundamental Research Funds for the Central Universities,China(Grant Nos.2017FZA3005 and 2018FZA3005)
文摘Ellipse fitting is a useful tool to obtain the differential signal of two atom interference gravimeters. The quality standard of ellipse fitting should be the deviation between the true phase and the fitting phase of the interference fringe. In this paper, we present a new algorithm to fit the ellipse. The algorithm is to minimize the differential noise of two interference gravimeters and obtain a more accurate value of the gravity gradient. We have theoretically derived the expression of the differential-mode noise and implemented the ellipse fitting in the program. This new algorithm is also compared with the classical methods.
文摘Based on auditory peripheral simulation model,a new Sound Quality Objective Evaluation(SQOE)method is presented,which can be used to model and analyze the impacts of head,shoulder and other parts of human body on sound wave trans-mission.This method employs the artificial head technique,in which the head related transfer function was taken into account tothe outer ear simulation phase.First,a bionic artificial head was designed as the outer ear model with considering the outersound field in view of theory and physical explanations.Then the auditory peripheral simulation model was built,which mimicsthe physiological functions of the human hearing,simulating the acoustic signal transfer process and conversion mechanismsfrom the free field to the peripheral auditory system.Finally,performance comparison was made between the proposed SQOEmethod and ArtemiS software,and the verifications of subjective and objective related analysis were made.Results show thatthe proposed method was economical,simple,and with good evaluation quality.
基金supported by National Natural Science Foundation of China(Nos.31571110 and 81771877)Natural Science Foundation of Zhejiang Province of China(LZ17F050001)the Fundamental Research Funds for the Central Universities.
文摘Two-photon microscopy normally suffers from the scattering of the tissue in biological imaging.Multidither coberent optical adaptive technique(COAT)can correct the scattered wavefront in parallel.However,the determination of the corrective phases may not be completely accurate using conventional method,which undermines the performance of this technique.In this paper,we theoretically demonstrate a method that can obtain more accurate corrective phases by determining the phase values from the square root of the fuorescence signal.A numnerical simulation model is established to study the performance of adaptive optics in two-photon micros-copy by combining scalar diffraction theory with vector diffraction theory.The results show that the distortion of the wavefront can be corrected more thoroughly with our method in two-photon imaging.In our simulation,with the scattering from a 450-mn-thick mouse brain tissue,excitation focal spots with higher peak-to background ratio(PBR)and images with higher contrast can be obtained.Hence,further enhancement of the multidither COAT correction performance in two-photon imaging can be expected.
