Multi-channel polarization optical technology is increasingly used for prompt monitoring of water systems.Optical devices during the assessment of water quality determine the intensity of light through the studied aqu...Multi-channel polarization optical technology is increasingly used for prompt monitoring of water systems.Optical devices during the assessment of water quality determine the intensity of light through the studied aquatic environment.Spectrophotometric devices measure the spectrum of weakening of light through the aquatic environment.Spectroellipsometric devices receive spectra in vertical and horizontal polarizations.The presented article develops an adaptive optical hardware and image system for monitoring water bodies.The system is combined.It consists of 2 parts:1)automated spectrophotometer-refractometer,and 2)adaptive spectroellipsometer.The system is equipped with a corresponding algorithmic and software,including algorithms for identifying spectral curves,databases and knowledge of spectral curves algorithms for solving reverse problems.The presented system is original since it differs from modern foreign systems by a new method of spectrophotometric and spectroellipsometric measurements,an original elemental base of polarization optics and a comprehensive mathematical approach to assessing the quality of a water body.There are no rotating polarization elements in the system.Therefore,this makes it possible to increase the signal-to-noise ratio and,as a result,improve measurement stability and simplify multichannel spectrophotometers and spectroellipsometers.The proposed system can be used in various water systems where it is necessary to assess water quality or identify the presence of a certain set of chemical elements.展开更多
Just like an electronic diode that allows the electrical current to flow in one direction only, a kind of chiral metamaterial structure with a similar functionality for the electromagnetic wave is proposed. The design...Just like an electronic diode that allows the electrical current to flow in one direction only, a kind of chiral metamaterial structure with a similar functionality for the electromagnetic wave is proposed. The designed nanostructure that consists of twisted metallic split-ring resonators on both sides of a dielectric substrate achieves asymmetric transmission for a forward and backward propagating linearly polarized wave by numerical simulation in near-infrared band. Difference in transmission efficiency of the optimized structure between the same polarized waves incident from opposite directions can reach a maximum at the communication wavelength （1.55 μm）. Moreover, the simulation results of this structure also exhibit strong optical activity and circular dichroism.展开更多
The intensity distribution in the focal region of a high-NA lens for the incident azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram is studied on the basis of the vector ...The intensity distribution in the focal region of a high-NA lens for the incident azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram is studied on the basis of the vector diffraction theory. Here we report a new method used to generate a needle of transversely polarized light beam with sub diffraction beam size of 0.366A that propagates without divergence over a long distance of about 22A in free space. We also expect that such a light needle of transversely polarized beam may find its applications in utilizing optical materials or instruments responsive to the transversal field only.展开更多
A new method to visualize the large-scale crystal grain morphology of organic polycrystalline films is proposed. First,optical anisotropic transmittance images of polycrystalline zinc phthalocyanine（Zn Pc） films vac...A new method to visualize the large-scale crystal grain morphology of organic polycrystalline films is proposed. First,optical anisotropic transmittance images of polycrystalline zinc phthalocyanine（Zn Pc） films vacuum deposited by weak epitaxial growth（WEG） method were acquired with polarized optical microscopy（POM）. Then morphology properties including crystal grain size, distribution, relative orientation, and crystallinity were derived from these images by fitting with a transition dipole model. At last, atomic force microscopy（AFM） imaging was carried out to confirm the fitting and serve as absolute references. This method can be readily generalized to other organic polycrystalline films, thus providing an efficient way to access the large-scale morphologic properties of organic polycrystalline films, which may prove to be useful in industry as a film quality monitoring method.展开更多
Due to the large exciton binding energy,two-dimensional(2D)transition metal dichalcogenides(TMDCs)provide an ideal platform for studying excitonic states and related photonics and optoelectronics.Polarization states l...Due to the large exciton binding energy,two-dimensional(2D)transition metal dichalcogenides(TMDCs)provide an ideal platform for studying excitonic states and related photonics and optoelectronics.Polarization states lead to distinct light-matter interactions which are of great importance for device applications.In this work,we study polarized photoluminescence spectra from intralayer exciton and indirect exciton in WS_(2) and WSe_(2) atomic layers,and interlayer exciton in WS_(2)/WSe_(2) heterostructures by radially and azimuthally polarized cylindrical vector laser beams.We demonstrated the same in-plane and out-of-plane polarization behavior from the intralayer and indirect exciton.Moreover,with these two laser modes,we obtained interlayer exciton in WS_(2)/WSe_(2) heterostructures with stronger out-of-plane polarization,due to the formation of vertical electric dipole moment.展开更多
A transverse relaxation determination of spin-exchange relaxation free （SERF） magnetometer based on polarization modulation technique is proposed. Compared with the radio-frequency （RF） excitation and light intens...A transverse relaxation determination of spin-exchange relaxation free （SERF） magnetometer based on polarization modulation technique is proposed. Compared with the radio-frequency （RF） excitation and light intensity excitation meth- ods used in SERF magnetometer, the light polarization modulation method has a high stability in low-frequency range, which indicates a more accurate transverse relaxation measurement.展开更多
This paper reports that the designed optical polarization mode dispersion compensator shows a good performance under the real-time variation of differential group delay, state of polarization and principal state of po...This paper reports that the designed optical polarization mode dispersion compensator shows a good performance under the real-time variation of differential group delay, state of polarization and principal state of polarization in a （40×43）-Gb/s dense-wavelength-multiplexing, 1200-km enhanced return-to-zero differential-quadrature-phase-shift- keying （RZ-DQPSK） system. The polarization mode dispersion tolerance of the system is improved by 26 ps using the optical polarization mode dispersion compensator. The short and long time stabilities are tested with the bit error ratio recorded.展开更多
The properties of polar optical phonon vibrations in a quasi-zero- dimensional （QOD） anisotropic wurtzite cylindrical quantum dot （QD） are analyzed based on the dielectric continuum model and Loudon＇s uniaxial cr...The properties of polar optical phonon vibrations in a quasi-zero- dimensional （QOD） anisotropic wurtzite cylindrical quantum dot （QD） are analyzed based on the dielectric continuum model and Loudon＇s uniaxial crystal model. The analytical electrostatic potentials of the phonon vibrations in the systems are deduced and solved exactly. The result shows that there exist four types of polar mixing optical phonon modes in the QOD wurtzite cylindrical QD systems. The dispersive equations and electron-phonon coupling function for the quasi-confined-half-space （QC-HS） mixing modes are derived and discussed. It is found that once the radius or the height of the QD approach infinity, the dispersive equations of the QC-HS mixing modes in the QOD cylindrical QD can naturally reduce to those of the QC and HS modes in Q2D QWs or Q1D QWWs systems. This has been analyzed reasonably from both of physicM and mathematical viewpoints.展开更多
A wideband tunable frequency-doubling optoelectronic oscillator （FD-OEO） is proposed and experimentally demonstrated based on a polarization modulator and an optical bandpass filter （OBPF）. The central frequency o...A wideband tunable frequency-doubling optoelectronic oscillator （FD-OEO） is proposed and experimentally demonstrated based on a polarization modulator and an optical bandpass filter （OBPF）. The central frequency of the correspondingly fundamental OEO could be adjusted by tuning the bandwidth and central frequency of the OBPF, which could also be regarded as a photonic-assisted tunable microwave filter. The frequency tuning range of the FD-OEO covers from 9.5 to 32.8？GHz, and the single sideband phase noise of the fundamental signal is lower than -100dBc/Hz at an offset of 10？kHz. Moreover, the frequency stability of the generated signal is investigated by measuring its Allan deviation. The Allan deviation of the generated fundamental signal at 10？GHz is 2.39×10^-9.展开更多
Two new series (A & B) of three materials each based on the aroyl hydrazinato-nickel (II) complex were synthesized and characterized. The core molecule in these series consists of two 4-benzoyloxy benzylidene moie...Two new series (A & B) of three materials each based on the aroyl hydrazinato-nickel (II) complex were synthesized and characterized. The core molecule in these series consists of two 4-benzoyloxy benzylidene moieties and two benzene rings attached at the azomethine moiety. These latter benzene rings have one or two alkoxy chains comprised of either 10, 12, 16 or 18 carbon atoms. The characterization of these two series by polarized optical microscopy and differential scanning calorimetry is described herein. Upon cooling from the Isotropic phase, three of the six materials display a monophasic columnar phase and the other three possess a biphasic nematic and columnar phases. Upon heating, all six materials have a clearance point at high temperatures without displaying mesomorphic behavior. In series B mesogens, it was observed that the longer the hydrocarbon tail length, the lower the clearance point.展开更多
The mesogenic properties of a homologous series of aromatic ester materials are investigated. Single tail and double tail materials were synthesized to compare with other series we prepared and published earlier. The ...The mesogenic properties of a homologous series of aromatic ester materials are investigated. Single tail and double tail materials were synthesized to compare with other series we prepared and published earlier. The phase sequences and transition temperatures were obtained by polarized light microscopy and differential scanning calorimetry. Only the single tail materials with the ester attached to naphthalene at position 2 display mesogenicbehavior. Two materials (ZH 29 & ZH 32) possess a monophasic nematic phase and another two materials (ZH 14 & ZH 35) display biphasic nematic and smectic (A) phases.展开更多
A model of an optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis is presented. Different coordinate frames for nuclear spin polarization vector are introduced, and ...A model of an optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis is presented. Different coordinate frames for nuclear spin polarization vector are introduced, and theoretical calculation is conducted to analyze this model. We demonstrate that when the optical pumping nuclear magnetic resonance system rotates in a plane parallel to the quantization axis, it will maintain a steady state with respect to the quantization axis which is independent of rotational speed and direction.展开更多
Four different states of Si15Sb85 and Ge2Sb2Te5 phase change memory thin films are obtained by crystallization degree modulation through laser initialization at different powers or annealing at different temperatures....Four different states of Si15Sb85 and Ge2Sb2Te5 phase change memory thin films are obtained by crystallization degree modulation through laser initialization at different powers or annealing at different temperatures. The polarization characteristics of these two four-level phase change recording media are analyzed systematically. A simple and effective readout scheme is then proposed, and the readout signal is numerically simulated. The results show that a high-contrast polarization readout can be obtained in an extensive wavelength range for the four-level phase change recording media using common phase change materials. This study will help in-depth understanding of the physical mechanisms and provide technical approaches to multilevel phase change recording.展开更多
Manipulating the polarization of light at the nanoscale is essential for the development of nano-optical devices. Owing to its corrugated honeycomb structure, two-dimensional （2D） layered black phosphorus （BP） exh...Manipulating the polarization of light at the nanoscale is essential for the development of nano-optical devices. Owing to its corrugated honeycomb structure, two-dimensional （2D） layered black phosphorus （BP） exhibits outstanding in-plane optical anisotropy with distinct linear dichroism and optical birefringence in the visible region, which are superior characteristics for ultrathin polarizing optics. Herein, taking advantage of polarized Raman spectroscopy, we demonstrate that layered BP with a nanometer thickness can remarkably alter the polarization state of a linearly-polarized laser and behave as an ultrathin optical polarization element in a BP-Bi2Se3 stacking structure by inducing the exceptionally polarized Raman scattering of isotropic Bi2Se3. Our findings provide a promising alternative for designing novel polarization optics based on 2D anisotropic materials, which can be easily integrated in micro- sized all-optical and optoelectronic devices.展开更多
A vectorial optical field generator(VOF-Gen) based on two reflective phase-only liquid crystal spatial light modulators enables the creation of an arbitrary optical complex field. In this work, the capabilities of the...A vectorial optical field generator(VOF-Gen) based on two reflective phase-only liquid crystal spatial light modulators enables the creation of an arbitrary optical complex field. In this work, the capabilities of the VOF-Gen in terms of manipulating the spatial distributions of phase, amplitude, and polarization are experimentally demonstrated by generating a radially polarized optical field consisted of five annular rings, the focusing properties of which are also numerically studied with vectorial diffraction theory. By carefully adjusting the relative amplitude and phase between the adjacent rings, an optical needle field with purely longitudinal polarization can be produced in the focal region of a high numerical aperture lens. The versatile method presented in this work can be easily extended to the generation of a vectorial optical field with any desired complex distributions.展开更多
Vortex and vector terahertz(THz)beams with inhomogeneous polarization states have become a considerable hot topic in the last decade due to their important roles in multiplexed wireless data transmission.However,the t...Vortex and vector terahertz(THz)beams with inhomogeneous polarization states have become a considerable hot topic in the last decade due to their important roles in multiplexed wireless data transmission.However,the technical instruments to form and evaluate such beams are rather limited,as they are mainly collected in the visible range.The emergence of coded metasurfaces has reinvigorated the design of functional devices with multiple degrees of freedom.Here,we demonstrate a versatile design inspired by a binary encoding approach for generating off-axis vectorial THz beams on all-silicon metasurfaces.Experimentally,simultaneous manipulation of the encoding method within the orthogonal circularly polarized(CP)channel provides strong support for developing versatility in vector THz beams,including the generation of arbitrary polarization profiles and the directional emission of multiplexed vector vortex beams(VVBs)with specified polarization states.The introduction of the latitudinal polarization control factor guarantees that continuously rotating or independently designed vector polarization profiles can be obtained on a pre-defined focal plane.Subsequently,a universal parametric theoretical model is developed to analyze the evolutionary trend of off-axis VVB in detail.Notably,the proposed monolayer vector metasurface bypasses the requirement of multiple cascaded optical elements,further inducing the advancement of ultra-thin vector THz sources,and also facilitating the generation of vector fields with tailored polarization distributions in 3D space.展开更多
As an intrinsic nature of light,polarization plays a critical role in the vectorial characteristic of optical fields.Vector optical fields with an inhomogeneous polarization distribution show many exotic phenomena and...As an intrinsic nature of light,polarization plays a critical role in the vectorial characteristic of optical fields.Vector optical fields with an inhomogeneous polarization distribution show many exotic phenomena and applications not existing in scalar optical fields.Existing polarization optics,however,mainly focuses on the manipulation of polarization distribution on a single transverse plane.Here,we propose a synthetic approach to realize polarization manipulation with spatial and temporal degrees.The underlying mechanism relies on decoupling two orthogonal polarization states through asymmetric photonic spin-orbit interactions to obtain customer-tailored phase and amplitude difference in both transverse and longitudinal space,thereby changing the resulting polarization distribution at will in three-dimensional(3 D)space.Remarkably,a longitudinally varied cylindrical vector field is experimentally demonstrated by a monolayer metasurface,in which the polarization distribution switches continuously and periodically between radial and azimuthal polarization.Furthermore,the vector field can be dynamically tuned by rotating the incident polarization state.Our work extends polarization optics from two-dimensional space to 3 D space,allowing the arbitrary generation and manipulation of 3D vector optical fields with temporal tunability.展开更多
Two-dimensional （2D） layered materials, transition-metal dichalcogenides, and black phosphorus have attracted considerable interest from the viewpoints of fundamental physics and device applications. The establishme...Two-dimensional （2D） layered materials, transition-metal dichalcogenides, and black phosphorus have attracted considerable interest from the viewpoints of fundamental physics and device applications. The establishment of new functionalities in anisotropic layered 2D materials is a challenging but rewarding frontier, owing to the remarkable optical properties of these materials and their prospects for new devices. Herein, we report the anisotropic and thickness- dependent optical properties of a 2D layered monochalcogenide of germanium sulfide （GeS）. Three Raman-scattering peaks corresponding to the B3g,, A1g, and A2g modes with a strong polarization dependence are demonstrated in the GeS flakes, which validates polarized Raman spectroscopy as an effective method for identifying the crystal orientation of anisotropic layered GeS. Photoluminescence （PL） is observed with a peak at -1.66 eV that originates from the direct optical transition in GeS at room temperature. The polarization-dependent characteristics of the PL, which are revealed for the first time, along with the demonstration of anisotropic absorption, indicate an obvious anisotropic optical transition near the band edge of GeS, which is supported by density functional theory calculations. The significantly thickness-dependent PL is observed and discussed. This anisotropic layered GeS presents opportunities for the discovery of new physical phenomena and will find applications that exploit its anisotropic properties, such as polarization-sensitive photodetectors.展开更多
Scattering phenomena affect light propagation through any kind of medium from free space to biological tissues.Finding appropriate strategies to increase the robustness to scattering is the common requirement in devel...Scattering phenomena affect light propagation through any kind of medium from free space to biological tissues.Finding appropriate strategies to increase the robustness to scattering is the common requirement in developing both communication protocols and imaging systems.Recently,structured light has attracted attention due to its seeming scattering resistance in terms of transmissivity and spatial behavior.Moreover,correlation between optical polarization and orbital angular momentum(OAM),which characterizes the so-called vector vortex beams(VVBs)states,seems to allow for the preservation of the polarization pattern.We extend the analysis by investigating both the spatial features and the polarization structure of vectorial optical vortexes propagating in scattering media with different concentrations.Among the observed features,we find a sudden swift decrease in contrast ratio for Gaussian,OAM,and VVB modes for concentrations of the adopted scattering media exceeding 0.09%.Our analysis provides a more general and complete study on the propagation of structured light in dispersive and scattering media.展开更多
Background:The retina has been used to study the pathophysiology of multiple sclerosis(MS).Peripapillary retinal nerve fiber layer(pRNFL)thinning has been suggested as an ocular biomarker of neurodegeneration in MS.Th...Background:The retina has been used to study the pathophysiology of multiple sclerosis(MS).Peripapillary retinal nerve fiber layer(pRNFL)thinning has been suggested as an ocular biomarker of neurodegeneration in MS.The goal of this project was to determine the birefringence of the pRNFL by measuring the fiber birefringence using polarization sensitive optical coherence tomography(PS-OCT).Methods:Sixty-six MS patients without history of optic neuritis(age:39.9±11.0 yrs.old,53 females and 13 males)and 66 age-and gender-matched normal controls(age:40.7±11.4 yrs.old)were recruited.Custom built PS-OCT was used to measure phase retardation per unit depth(PR/UD,proportional to the birefringence)and pRNFL thickness in each quadrant of the pRNFL.In addition,clinical manifestation was used to correlate with the pRNFL birefringence.Results:The pRNFL was thinner in the temporal and inferior quadrants in MS patients compared with normal controls(P<0.05).The PR/UD of the pRNFL was significantly decreased in MS patients(P<0.05)in all quadrants except for the nasal quadrant.In both groups,the PR/UD from all four quadrants was not related to the averaged pRNFL thickness(P>0.05).In MS patients,the PR/UD was not related to the expanded disability status scale(EDSS)nor disease duration(r ranged from−0.17 to 0.02,P>0.05).Conclusion:This is the first study using PS-OCT to study the pRNFL birefringence in MS patients.Decreased birefringence of the pRNFL may indicate microtubule abnormality,and could be a potential biomarker for detecting early neurodegeneration in MS.展开更多
基金Supported By The Russian Science Foundation Grant No.23-21-00115,https://rscf.ru/en/project/23-21-00115/.
文摘Multi-channel polarization optical technology is increasingly used for prompt monitoring of water systems.Optical devices during the assessment of water quality determine the intensity of light through the studied aquatic environment.Spectrophotometric devices measure the spectrum of weakening of light through the aquatic environment.Spectroellipsometric devices receive spectra in vertical and horizontal polarizations.The presented article develops an adaptive optical hardware and image system for monitoring water bodies.The system is combined.It consists of 2 parts:1)automated spectrophotometer-refractometer,and 2)adaptive spectroellipsometer.The system is equipped with a corresponding algorithmic and software,including algorithms for identifying spectral curves,databases and knowledge of spectral curves algorithms for solving reverse problems.The presented system is original since it differs from modern foreign systems by a new method of spectrophotometric and spectroellipsometric measurements,an original elemental base of polarization optics and a comprehensive mathematical approach to assessing the quality of a water body.There are no rotating polarization elements in the system.Therefore,this makes it possible to increase the signal-to-noise ratio and,as a result,improve measurement stability and simplify multichannel spectrophotometers and spectroellipsometers.The proposed system can be used in various water systems where it is necessary to assess water quality or identify the presence of a certain set of chemical elements.
基金Project supported by the National Natural Science Foundation of China(Grant No.61078060)the Fund from the Ningbo Optoelectronic Materials and Devices Creative Team,China(Grant No.2009B21007)partially sponsored by K.C.Wong Magna Fund in Ningbo University
文摘Just like an electronic diode that allows the electrical current to flow in one direction only, a kind of chiral metamaterial structure with a similar functionality for the electromagnetic wave is proposed. The designed nanostructure that consists of twisted metallic split-ring resonators on both sides of a dielectric substrate achieves asymmetric transmission for a forward and backward propagating linearly polarized wave by numerical simulation in near-infrared band. Difference in transmission efficiency of the optimized structure between the same polarized waves incident from opposite directions can reach a maximum at the communication wavelength （1.55 μm）. Moreover, the simulation results of this structure also exhibit strong optical activity and circular dichroism.
文摘The intensity distribution in the focal region of a high-NA lens for the incident azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram is studied on the basis of the vector diffraction theory. Here we report a new method used to generate a needle of transversely polarized light beam with sub diffraction beam size of 0.366A that propagates without divergence over a long distance of about 22A in free space. We also expect that such a light needle of transversely polarized beam may find its applications in utilizing optical materials or instruments responsive to the transversal field only.
基金Project supported by the National Natural Science Foundation of China(Grant No.20933010)the National Basic Research Program of China(Grant No.2013CB834800)
文摘A new method to visualize the large-scale crystal grain morphology of organic polycrystalline films is proposed. First,optical anisotropic transmittance images of polycrystalline zinc phthalocyanine（Zn Pc） films vacuum deposited by weak epitaxial growth（WEG） method were acquired with polarized optical microscopy（POM）. Then morphology properties including crystal grain size, distribution, relative orientation, and crystallinity were derived from these images by fitting with a transition dipole model. At last, atomic force microscopy（AFM） imaging was carried out to confirm the fitting and serve as absolute references. This method can be readily generalized to other organic polycrystalline films, thus providing an efficient way to access the large-scale morphologic properties of organic polycrystalline films, which may prove to be useful in industry as a film quality monitoring method.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91850116,51772084,52022029,and U19A2090)Hunan Provincial Natural Science Foundation of China(Grant Nos.2018RS3051 and 2018WK4004)the Key Program of the Hunan Provincial Science and Technology Department,China(Grant No.2019XK2001).
文摘Due to the large exciton binding energy,two-dimensional(2D)transition metal dichalcogenides(TMDCs)provide an ideal platform for studying excitonic states and related photonics and optoelectronics.Polarization states lead to distinct light-matter interactions which are of great importance for device applications.In this work,we study polarized photoluminescence spectra from intralayer exciton and indirect exciton in WS_(2) and WSe_(2) atomic layers,and interlayer exciton in WS_(2)/WSe_(2) heterostructures by radially and azimuthally polarized cylindrical vector laser beams.We demonstrated the same in-plane and out-of-plane polarization behavior from the intralayer and indirect exciton.Moreover,with these two laser modes,we obtained interlayer exciton in WS_(2)/WSe_(2) heterostructures with stronger out-of-plane polarization,due to the formation of vertical electric dipole moment.
基金Project supported by the National Natural Science Foundation of China(Grant No.61227902)the National Key R&D Program of China(Grant No.2017YFB0503100)the Natural Science Foundation of Beijing Municipality,China(Grant No.4162038)
文摘A transverse relaxation determination of spin-exchange relaxation free （SERF） magnetometer based on polarization modulation technique is proposed. Compared with the radio-frequency （RF） excitation and light intensity excitation meth- ods used in SERF magnetometer, the light polarization modulation method has a high stability in low-frequency range, which indicates a more accurate transverse relaxation measurement.
基金Project supported by the Huawei Technology Project (Grant No.YBON2008014)the National "863" High Technology Projects (Grant No.2009AA01Z224)
文摘This paper reports that the designed optical polarization mode dispersion compensator shows a good performance under the real-time variation of differential group delay, state of polarization and principal state of polarization in a （40×43）-Gb/s dense-wavelength-multiplexing, 1200-km enhanced return-to-zero differential-quadrature-phase-shift- keying （RZ-DQPSK） system. The polarization mode dispersion tolerance of the system is improved by 26 ps using the optical polarization mode dispersion compensator. The short and long time stabilities are tested with the bit error ratio recorded.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 60276004 and 60390073 and the Natural Science Foundation of Guangzhou Education Bureau under Grant No. 2060
文摘The properties of polar optical phonon vibrations in a quasi-zero- dimensional （QOD） anisotropic wurtzite cylindrical quantum dot （QD） are analyzed based on the dielectric continuum model and Loudon＇s uniaxial crystal model. The analytical electrostatic potentials of the phonon vibrations in the systems are deduced and solved exactly. The result shows that there exist four types of polar mixing optical phonon modes in the QOD wurtzite cylindrical QD systems. The dispersive equations and electron-phonon coupling function for the quasi-confined-half-space （QC-HS） mixing modes are derived and discussed. It is found that once the radius or the height of the QD approach infinity, the dispersive equations of the QC-HS mixing modes in the QOD cylindrical QD can naturally reduce to those of the QC and HS modes in Q2D QWs or Q1D QWWs systems. This has been analyzed reasonably from both of physicM and mathematical viewpoints.
基金Supported by the National Natural Science Foundation of China under Grant No 61675196the National Basic Research Program of China under Grant No 2014CB340102+1 种基金the National High-Tech Research and Development Program of China under Grant No 2015AA016903the Open Research of Beijing University of Posts and Telecommunications under Grant No IOOC2013A002
文摘A wideband tunable frequency-doubling optoelectronic oscillator （FD-OEO） is proposed and experimentally demonstrated based on a polarization modulator and an optical bandpass filter （OBPF）. The central frequency of the correspondingly fundamental OEO could be adjusted by tuning the bandwidth and central frequency of the OBPF, which could also be regarded as a photonic-assisted tunable microwave filter. The frequency tuning range of the FD-OEO covers from 9.5 to 32.8？GHz, and the single sideband phase noise of the fundamental signal is lower than -100dBc/Hz at an offset of 10？kHz. Moreover, the frequency stability of the generated signal is investigated by measuring its Allan deviation. The Allan deviation of the generated fundamental signal at 10？GHz is 2.39×10^-9.
文摘Two new series (A & B) of three materials each based on the aroyl hydrazinato-nickel (II) complex were synthesized and characterized. The core molecule in these series consists of two 4-benzoyloxy benzylidene moieties and two benzene rings attached at the azomethine moiety. These latter benzene rings have one or two alkoxy chains comprised of either 10, 12, 16 or 18 carbon atoms. The characterization of these two series by polarized optical microscopy and differential scanning calorimetry is described herein. Upon cooling from the Isotropic phase, three of the six materials display a monophasic columnar phase and the other three possess a biphasic nematic and columnar phases. Upon heating, all six materials have a clearance point at high temperatures without displaying mesomorphic behavior. In series B mesogens, it was observed that the longer the hydrocarbon tail length, the lower the clearance point.
文摘The mesogenic properties of a homologous series of aromatic ester materials are investigated. Single tail and double tail materials were synthesized to compare with other series we prepared and published earlier. The phase sequences and transition temperatures were obtained by polarized light microscopy and differential scanning calorimetry. Only the single tail materials with the ester attached to naphthalene at position 2 display mesogenicbehavior. Two materials (ZH 29 & ZH 32) possess a monophasic nematic phase and another two materials (ZH 14 & ZH 35) display biphasic nematic and smectic (A) phases.
基金Project supported by the National Natural Science Foundation of China(Grant No.61475192)
文摘A model of an optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis is presented. Different coordinate frames for nuclear spin polarization vector are introduced, and theoretical calculation is conducted to analyze this model. We demonstrate that when the optical pumping nuclear magnetic resonance system rotates in a plane parallel to the quantization axis, it will maintain a steady state with respect to the quantization axis which is independent of rotational speed and direction.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61178059 and 61137002)the Key Program of the Science and Technology Commission of Shanghai Municipality,China(Grant No.11jc1413300)
文摘Four different states of Si15Sb85 and Ge2Sb2Te5 phase change memory thin films are obtained by crystallization degree modulation through laser initialization at different powers or annealing at different temperatures. The polarization characteristics of these two four-level phase change recording media are analyzed systematically. A simple and effective readout scheme is then proposed, and the readout signal is numerically simulated. The results show that a high-contrast polarization readout can be obtained in an extensive wavelength range for the four-level phase change recording media using common phase change materials. This study will help in-depth understanding of the physical mechanisms and provide technical approaches to multilevel phase change recording.
文摘Manipulating the polarization of light at the nanoscale is essential for the development of nano-optical devices. Owing to its corrugated honeycomb structure, two-dimensional （2D） layered black phosphorus （BP） exhibits outstanding in-plane optical anisotropy with distinct linear dichroism and optical birefringence in the visible region, which are superior characteristics for ultrathin polarizing optics. Herein, taking advantage of polarized Raman spectroscopy, we demonstrate that layered BP with a nanometer thickness can remarkably alter the polarization state of a linearly-polarized laser and behave as an ultrathin optical polarization element in a BP-Bi2Se3 stacking structure by inducing the exceptionally polarized Raman scattering of isotropic Bi2Se3. Our findings provide a promising alternative for designing novel polarization optics based on 2D anisotropic materials, which can be easily integrated in micro- sized all-optical and optoelectronic devices.
文摘A vectorial optical field generator(VOF-Gen) based on two reflective phase-only liquid crystal spatial light modulators enables the creation of an arbitrary optical complex field. In this work, the capabilities of the VOF-Gen in terms of manipulating the spatial distributions of phase, amplitude, and polarization are experimentally demonstrated by generating a radially polarized optical field consisted of five annular rings, the focusing properties of which are also numerically studied with vectorial diffraction theory. By carefully adjusting the relative amplitude and phase between the adjacent rings, an optical needle field with purely longitudinal polarization can be produced in the focal region of a high numerical aperture lens. The versatile method presented in this work can be easily extended to the generation of a vectorial optical field with any desired complex distributions.
基金supported by the National Key Research and Development Program of China(Grant Nos.2021YFB2800703,and 2017YFA0700202)the National Natural Science Foundation of China(Grant Nos.61675147,61975146,62075159,62105240,and 91838301).
文摘Vortex and vector terahertz(THz)beams with inhomogeneous polarization states have become a considerable hot topic in the last decade due to their important roles in multiplexed wireless data transmission.However,the technical instruments to form and evaluate such beams are rather limited,as they are mainly collected in the visible range.The emergence of coded metasurfaces has reinvigorated the design of functional devices with multiple degrees of freedom.Here,we demonstrate a versatile design inspired by a binary encoding approach for generating off-axis vectorial THz beams on all-silicon metasurfaces.Experimentally,simultaneous manipulation of the encoding method within the orthogonal circularly polarized(CP)channel provides strong support for developing versatility in vector THz beams,including the generation of arbitrary polarization profiles and the directional emission of multiplexed vector vortex beams(VVBs)with specified polarization states.The introduction of the latitudinal polarization control factor guarantees that continuously rotating or independently designed vector polarization profiles can be obtained on a pre-defined focal plane.Subsequently,a universal parametric theoretical model is developed to analyze the evolutionary trend of off-axis VVB in detail.Notably,the proposed monolayer vector metasurface bypasses the requirement of multiple cascaded optical elements,further inducing the advancement of ultra-thin vector THz sources,and also facilitating the generation of vector fields with tailored polarization distributions in 3D space.
基金supported by the National Key Research and Development Program of China(Grant No.2019YFF0216400)Sichuan Science and Technology Program(Grant No.2021ZYCD002)+1 种基金China Postdoctoral Science Foundation(Grant No.2021T140670)National Natural Science Foundation of China(Grant Nos.62175242,and U20A20217)。
文摘As an intrinsic nature of light,polarization plays a critical role in the vectorial characteristic of optical fields.Vector optical fields with an inhomogeneous polarization distribution show many exotic phenomena and applications not existing in scalar optical fields.Existing polarization optics,however,mainly focuses on the manipulation of polarization distribution on a single transverse plane.Here,we propose a synthetic approach to realize polarization manipulation with spatial and temporal degrees.The underlying mechanism relies on decoupling two orthogonal polarization states through asymmetric photonic spin-orbit interactions to obtain customer-tailored phase and amplitude difference in both transverse and longitudinal space,thereby changing the resulting polarization distribution at will in three-dimensional(3 D)space.Remarkably,a longitudinally varied cylindrical vector field is experimentally demonstrated by a monolayer metasurface,in which the polarization distribution switches continuously and periodically between radial and azimuthal polarization.Furthermore,the vector field can be dynamically tuned by rotating the incident polarization state.Our work extends polarization optics from two-dimensional space to 3 D space,allowing the arbitrary generation and manipulation of 3D vector optical fields with temporal tunability.
文摘Two-dimensional （2D） layered materials, transition-metal dichalcogenides, and black phosphorus have attracted considerable interest from the viewpoints of fundamental physics and device applications. The establishment of new functionalities in anisotropic layered 2D materials is a challenging but rewarding frontier, owing to the remarkable optical properties of these materials and their prospects for new devices. Herein, we report the anisotropic and thickness- dependent optical properties of a 2D layered monochalcogenide of germanium sulfide （GeS）. Three Raman-scattering peaks corresponding to the B3g,, A1g, and A2g modes with a strong polarization dependence are demonstrated in the GeS flakes, which validates polarized Raman spectroscopy as an effective method for identifying the crystal orientation of anisotropic layered GeS. Photoluminescence （PL） is observed with a peak at -1.66 eV that originates from the direct optical transition in GeS at room temperature. The polarization-dependent characteristics of the PL, which are revealed for the first time, along with the demonstration of anisotropic absorption, indicate an obvious anisotropic optical transition near the band edge of GeS, which is supported by density functional theory calculations. The significantly thickness-dependent PL is observed and discussed. This anisotropic layered GeS presents opportunities for the discovery of new physical phenomena and will find applications that exploit its anisotropic properties, such as polarization-sensitive photodetectors.
基金This project received funding from the European Union’s Horizon 2020 research and innovation program(Future and Emerging Technologies)under Grant Agreement No.828978.
文摘Scattering phenomena affect light propagation through any kind of medium from free space to biological tissues.Finding appropriate strategies to increase the robustness to scattering is the common requirement in developing both communication protocols and imaging systems.Recently,structured light has attracted attention due to its seeming scattering resistance in terms of transmissivity and spatial behavior.Moreover,correlation between optical polarization and orbital angular momentum(OAM),which characterizes the so-called vector vortex beams(VVBs)states,seems to allow for the preservation of the polarization pattern.We extend the analysis by investigating both the spatial features and the polarization structure of vectorial optical vortexes propagating in scattering media with different concentrations.Among the observed features,we find a sudden swift decrease in contrast ratio for Gaussian,OAM,and VVB modes for concentrations of the adopted scattering media exceeding 0.09%.Our analysis provides a more general and complete study on the propagation of structured light in dispersive and scattering media.
基金Supported by the National Multiple Sclerosis Society,NIH Center Grant P30 EY014801a grant from Research to Prevent Blindness(RPB).
文摘Background:The retina has been used to study the pathophysiology of multiple sclerosis(MS).Peripapillary retinal nerve fiber layer(pRNFL)thinning has been suggested as an ocular biomarker of neurodegeneration in MS.The goal of this project was to determine the birefringence of the pRNFL by measuring the fiber birefringence using polarization sensitive optical coherence tomography(PS-OCT).Methods:Sixty-six MS patients without history of optic neuritis(age:39.9±11.0 yrs.old,53 females and 13 males)and 66 age-and gender-matched normal controls(age:40.7±11.4 yrs.old)were recruited.Custom built PS-OCT was used to measure phase retardation per unit depth(PR/UD,proportional to the birefringence)and pRNFL thickness in each quadrant of the pRNFL.In addition,clinical manifestation was used to correlate with the pRNFL birefringence.Results:The pRNFL was thinner in the temporal and inferior quadrants in MS patients compared with normal controls(P<0.05).The PR/UD of the pRNFL was significantly decreased in MS patients(P<0.05)in all quadrants except for the nasal quadrant.In both groups,the PR/UD from all four quadrants was not related to the averaged pRNFL thickness(P>0.05).In MS patients,the PR/UD was not related to the expanded disability status scale(EDSS)nor disease duration(r ranged from−0.17 to 0.02,P>0.05).Conclusion:This is the first study using PS-OCT to study the pRNFL birefringence in MS patients.Decreased birefringence of the pRNFL may indicate microtubule abnormality,and could be a potential biomarker for detecting early neurodegeneration in MS.
