Optical antennas play an important role in optical field manipulation.Among them,nanoscale bowtie antennas have been extensively studied for its high confinement and enhancement.In this mini-review,we start with a bri...Optical antennas play an important role in optical field manipulation.Among them,nanoscale bowtie antennas have been extensively studied for its high confinement and enhancement.In this mini-review,we start with a brief introduction of bowtie antennas and underlying physics.Then we review the applications with respect to optically and electrically excited nanoscale bowtie antennas.Optically driven bowtie antennas enable a set of optical applications such as near-field imaging/trapping,nonlinear response,nanolithography,photon generation and detection.Finally,we put emphasis on the principle and applications of electrically driven bowtie antennas,an emerging method of generating ultrafast and broadband tunable nanosources.In a word,nanoscale bowtie antennas still have great potential research value to explore.展开更多
Optical data storage(ODS)is a low-cost and high-durability counterpart of traditional electronic or mag-netic storage.As a means of enhancing ODS capacity,the multiple recording layer(MRL)method is more promising than...Optical data storage(ODS)is a low-cost and high-durability counterpart of traditional electronic or mag-netic storage.As a means of enhancing ODS capacity,the multiple recording layer(MRL)method is more promising than other approaches such as reducing the recording volume and multiplexing technology.However,the architecture of current MRLs is identical to that of recording data into physical layers with rigid space,which leads to either severe interlayer crosstalk or finite recording layers constrained by the short working distances of the objectives.Here,we propose the concept of hybrid-layer ODS,which can record optical information into a physical layer and multiple virtual layers by using high-orthogonality random meta-channels.In the virtual layer,32 images are experimentally reconstructed through holog-raphy,where their holographic phases are encoded into 16 printed images and complementary images in the physical layer,yielding a capacity of 2.5 Tbit cm^(-3).A higher capacity is achievable with more virtual layers,suggesting hybrid-layer ODS as a possible candidate for next-generation ODS.展开更多
We report the optical response characteristics of A1/Ti bilayer transition edge sensors （TESs）, which are mainly comprised of A1/Ti bilayer thermometers and suspended SiN membranes for thermal isolation. The measure...We report the optical response characteristics of A1/Ti bilayer transition edge sensors （TESs）, which are mainly comprised of A1/Ti bilayer thermometers and suspended SiN membranes for thermal isolation. The measurement was performed in a 3He sorption refrigerator and the device＇s response to optical pulses was investigated using a pulsed laser source. Based on these measurements, we obtained the effective recovery time （τeff） of the devices at different biases and discussed the dependence of Veff on the bias. The device with a 940 μm × 940 μm continuous suspended SiN membrane demonstrated a fast response speed with τeff = 3.9 μs, which indicates a high temperature sensitivity （a = T/R·dR/dT = 326）. The results also showed that the TES exhibits good linearity under optical pulses of variable widths.展开更多
An effective method to fabricate two-helix long-period fiber gratings （TH-LFGs） is presented. Based on the coupling mode theory, the conversion of optical vortices （OVs） in TH-LFGs are analyzed in detail. The conv...An effective method to fabricate two-helix long-period fiber gratings （TH-LFGs） is presented. Based on the coupling mode theory, the conversion of optical vortices （OVs） in TH-LFGs are analyzed in detail. The conversions of OVs with different topological charges： 0 → ±2 and 1 → 3 are simulated as three examples and the conversion efficiency higher than 98% can be realized.展开更多
We report on a wide-band and stable mode-locked all-polarization-maintaining fiber laser configuration using a nonlinear optical loop mirror. The central wavelength of the laser is 1080.14nm and the 3dB bandwidth is 2...We report on a wide-band and stable mode-locked all-polarization-maintaining fiber laser configuration using a nonlinear optical loop mirror. The central wavelength of the laser is 1080.14nm and the 3dB bandwidth is 20.29nm. The repetition rate of the pulse is 3.28 MHz and the pulse width is 848ps. By tuning the pump power, which is centered at 980nrn, from 300mW to 380mW, we obtain a linearly changed output power from 6row to 7.12roW. The all-polarization-mMntaining fiber configuration is fundamental to the stability of the output power.展开更多
Lead halide perovskites have attracted considerable attention as potential candidates for high-performance nano/microlasers,owing to their outstanding optical properties.However,the further development of perovskite m...Lead halide perovskites have attracted considerable attention as potential candidates for high-performance nano/microlasers,owing to their outstanding optical properties.However,the further development of perovskite microlaser arrays(especially based on polycrystalline thin films)produced by the conventional processing techniques is hindered by the chemical instability and surface roughness of the perovskite structures.Herein,we demonstrate a laser patterning of large-scale,highly crystalline perovskite single-crystal films to fabricate reproducible perovskite single-crystal-based microlaser arrays.Perovskite thin films were directly ablated by femtosecond-laser in multiple low-power cycles at a minimum machining line width of approximately 300 nm to realize high-precision,chemically clean,and repeatable fabrication of microdisk arrays.The surface impurities generated during the process can be washed away to avoid external optical loss due to the robustness of the single-crystal film.Moreover,the high-quality,large-sized perovskite single-crystal films can significantly improve the quality of microcavities,thereby realizing a perovskite microdisk laser with narrow linewidth(0.09 nm)and low threshold(5.1µJ/cm2).Benefiting from the novel laser patterning method and the large-sized perovskite single-crystal films,a high power and high color purity laser display with single-mode microlasers as pixels was successfully fabricated.Thus,this study may offer a potential platform for mass-scale and reproducible fabrication of microlaser arrays,and further facilitate the development of highly integrated applications based on perovskite materials.展开更多
Enhancement of uorescent radiation is of great importance for applications including biological imaging,high-sensitivity detectors,and integrated light sources.Strong electromagnetic elds can be created around metalli...Enhancement of uorescent radiation is of great importance for applications including biological imaging,high-sensitivity detectors,and integrated light sources.Strong electromagnetic elds can be created around metallic nanoparticles or in gap of nanostructures,where the local state density of radiating mode is then dramatically enhanced.While enhanced uorescent emission has been demonstrated in many metallic nanoparticles and nanoparticle pairs,simultaneous mediation of absorption and emission processes of uorescent emitters remains challenging in metallic nanostructures.Here,we investigate uorescent emission mediated by metal-dielectric-metal fishnet metasurface,in which localized surface plasmon(LSP)and magnetic plasmon polaritons(MPPs)modes are coupled with absorption and emission processes,respectively.For absorption process,coupling of the LSP mode enables spatially-selective excitation of the uorescent emitters by rotating the polarization of the pump laser beam.In addition,the polarization-dependent MPP mode enables manipulation of both polarization and wavelength of the uorescent emission by introducing a rectangular fishnet structure.All the experimental observations are further corroborated by nite-difference time-domain simulations.The structure reported here has great potential for application to color light-emitting devices and nanoscale integrated light sources.展开更多
In this work, an all-fiber-based mode converter for generating orbital angular momentum （OAM） beams is proposed and numerically investigated. Its structure is constructed by cascading a mode selective coupler （MSC...In this work, an all-fiber-based mode converter for generating orbital angular momentum （OAM） beams is proposed and numerically investigated. Its structure is constructed by cascading a mode selective coupler （MSC） and an inner elliptical cladding fiber （IECF）. OAM modes refer to a combination of two orthogonal LPlm modes with a phase difference of ±π/2. By adjusting the parameters and controlling the splicing angle of MSC and IECF appropriately, higher-order OAM modes with topological charges of l = ±1, ±2, ±3 can be obtained with the injection of the fundamental mode LP01, resulting in a mode-conversion efficiency of almost 100%. This achievement may pave the way towards the realization of a compact, all-fiber, and high-efficiency device for increasing the transmission capacity and spectral efficiency in optical communication systems with OAM mode multiplexing.展开更多
In this paper,a solution for speckle reduction using phase plate array(PPA)and lens array(LA)in a motionless way is proposed.The specially designed PPA is composed of sub-phase plates,which are constituted by phase pa...In this paper,a solution for speckle reduction using phase plate array(PPA)and lens array(LA)in a motionless way is proposed.The specially designed PPA is composed of sub-phase plates,which are constituted by phase patterns formed by Hadamard sub-matrices.Each component of the proposed optical system should satisfy the stated relationships.The incident laser beam will be incoherent after passing through PPA,and superpose on the screen under the action of LA and main lens.Speckle reduction can be achieved by the averaging of the incoherent speckle patterns.Because of abandoning the mechanical movement,it will be suitable for laser displays and images.展开更多
Two physical interpretations of chirp transform related to Fresnel diffraction and Wigner distribution function are given. The chirp transform can be regarded as a Fresnel diffraction observed on a spherical tangent t...Two physical interpretations of chirp transform related to Fresnel diffraction and Wigner distribution function are given. The chirp transform can be regarded as a Fresnel diffraction observed on a spherical tangent to the diffraction plane, or a rotation and stretching transformation of the Wigner distribution function space. A general fast algorithm for the numerical calculation of chirp transform is developed by employing two fast Fourier transform algorithms. The algorithm, by which a good evaluation can be achieved, unifies the calculations of Fresnel diffraction, arbitrary fractional- order Fourier transforms and other scalar diffraction systems. The algorithm is used to calculate the Fourier transform of a Gaussian function and the Fourier transform, the Fresnel transform, the Fractional-order Fourier transforms of a rectangle function to evaluate the performance of this algorithm. The calculated results are in good agreement with the analytical results, both in the amplitude and phase.展开更多
We introduce a corrected sinusoidal-wave drag force method （SDFM） into optical tweezers to calibrate the trapping stiffness of the optical trap and conversion factor （CF） of photodetectors. First, the theoretical ...We introduce a corrected sinusoidal-wave drag force method （SDFM） into optical tweezers to calibrate the trapping stiffness of the optical trap and conversion factor （CF） of photodetectors. First, the theoretical analysis and experimental result demonstrate that the correction of SDFM is necessary, especially the error of no correction is up to 11.25% for a bead of 5μm in diameter. Second, the simulation results demonstrate that the SDFM has a better performance in the calibration of optical tweezers than the triangular-wave drag force method （TDFM） and power spectrum density method （PSDM） at the same signal-to-noise ratio or trapping stiffness. Third, in experiments, the experimental standard deviations of calibration of trapping stiffness and CF with the SDFM are about less than 50% of TDFM and PSDM especially at low laser power. Finally, the experiments of stretching DNA verify that the in situ calibration with the SDFM improves the measurement stability and accuracy.展开更多
The influence of a vacuum on the laser-induced breakdown spectroscopy （LIBS） of carbon in the ultraviolet wavelength range is studied. Experiments are performed with graphite using a LIBS system, which consists of a...The influence of a vacuum on the laser-induced breakdown spectroscopy （LIBS） of carbon in the ultraviolet wavelength range is studied. Experiments are performed with graphite using a LIBS system, which consists of a 1064 nm Nd：YAG laser, a vacuum pump, a spectrometer and a vacuum chamber. The vacuum varies from 10 Pa to 1 atm. Atomic lines as well as singly and doubly charged ions are confirmed under the vacuums. A temporal evolution analysis of intensity is performed for the atomic lines of C I 193.09 nm and C I 247.86 nm under different vacuum conditions. Both time-integrated and time-resolved intensity evolutions under vacuums are achieved. The lifetimes of the two atomic lines have similar trends, which supports the point of view of a ＇soft spot＇. Variations of plasma temperature and electron density under different vacuums are measured. This study is helpful for research on carbon detection using LIBS under vacuum conditions.展开更多
Broadband nonlinear frequency conversions of optical waves are widely employed in multiple areas of optics and photonics. However, the broadening of conversion bandwidth is often at a cost of reduction in efficiency, ...Broadband nonlinear frequency conversions of optical waves are widely employed in multiple areas of optics and photonics. However, the broadening of conversion bandwidth is often at a cost of reduction in efficiency, which may induce a limitation on practical applications. Here we theoretically propose a novel design of LiNbO_(3) ridge waveguides on LiTaO_(3) substrates which can be used for efficient and broadband second harmonic generation. Through group velocity engineering of the ridge waveguides, acceptance bandwidth over 20 nm with a high conversion efficiency of > 25%W^(-1)·cm^(-2) is achieved at telecom-band.展开更多
We propose a new method to separate different orders of an all-fiber passive Q-switching stimulated Brillouin scattering（SBS） laser. We use two fiber Bragg gratings connected by two circulators for the filtering. We...We propose a new method to separate different orders of an all-fiber passive Q-switching stimulated Brillouin scattering（SBS） laser. We use two fiber Bragg gratings connected by two circulators for the filtering. We obtain a stabilized pulse laser and measure the pulse width of different orders. The first order of SBS has a central wavelength of 1549.75 nm, an average output power of 9 mW, and a pulse width of 400 ns. The pulse width of SBS is reduced by the higher-order signals with the larger fluctuations.展开更多
A simple scheme based on the uniform distribution for the placement of numerous laser beams in the context o~ fiber-based laser fusion is proposed. It is theoretically demonstrated that all modes of the geometrical fa...A simple scheme based on the uniform distribution for the placement of numerous laser beams in the context o~ fiber-based laser fusion is proposed. It is theoretically demonstrated that all modes of the geometrical factor can be eliminated if sufflcient laser beams are uniformly distributed on the sphere. In the case of a finite number of laser beams, a quasi-uniform distribution of beams can be achieved based on the equal area subdivision algorithm. Numerical simulations indicate that with the increasing number of laser beams, the order of the dominant geometrical mode increases, and the irradiation nonuniformity decreases accordingly.展开更多
In the fabrication of surface relief gratings （SRGs） on azobenzene polymer films with a zeroth-order suppressed diffraction phase mask, it is found that the SRGs＇ relief figure and period change with the irradiatio...In the fabrication of surface relief gratings （SRGs） on azobenzene polymer films with a zeroth-order suppressed diffraction phase mask, it is found that the SRGs＇ relief figure and period change with the irradiation time, and the period is doubled after a critical time. The time dependence of the changes in the SRG forming process is investigated by theoretical analysis and experiments. An optimum time range for inscription of the sub-micron SInGs is determined to be 5-8 rain in terms of both the theoretical and experimental results.展开更多
Supercritical lens(SCL)can break the diffraction limit in the far field and has been demonstrated for high-resolution scanning confocal imaging.Its capability in sharper focusing and needle-like long focal depth shoul...Supercritical lens(SCL)can break the diffraction limit in the far field and has been demonstrated for high-resolution scanning confocal imaging.Its capability in sharper focusing and needle-like long focal depth should allow high-resolution lithography at violet or ultraviolet(UV)wavelength,however,this has never been experimentally demonstrated.As a proof of concept,in this paper SCLs operating at 405 nm(h-line)wavelength with smaller full-width-at-half-maximum focal spot and longer depth of focus than conventional Fresnel zone lens while maintaining controlled side lobes are designed for direct laser writing(DLW)lithography.Aluminum nitride(AlN)with a high refractive index and low loss in UVvisible range is used to fabricate nanopillar-based metasurfaces structure for the metalens.Grating arrays with improved pitch resolution are fabricated using the SCLs with sub-diffraction-limit focusing capability.The AlN-based metasurface for SCLs at short wavelength for DLW could extend further to UV or deep UV lithography and might be of great interest to both the research and industry applications.展开更多
Since RGD peptides （R： arginine; G： glycine; D： aspartic acid） are found to promote cell adhesion, they are modified at numerous materials surface for medical applications such as drug delivery and regenerative m...Since RGD peptides （R： arginine; G： glycine; D： aspartic acid） are found to promote cell adhesion, they are modified at numerous materials surface for medical applications such as drug delivery and regenerative medicine. Peptide-cell surface interactions play a key role in the above applications. In this letter, we study the adhesion force between the RGD-coated bead and Hela cell surface by optical tweezes. The adhesion is dominated by the binding of α5β1 and RGD-peptide with higher adhesion probability and stronger adhesion strength compared with the adhesion of bare bead and cell surface. The binding force for a single α5β1 -GRGDSP pair is determined to be 16.8 pN at a loading rate of 1.5 nN/s. The unstressed off-rate is 1.65 × 10^-2s^-1 and the distance of transition state for the rigid binding model is 3.0 nm.展开更多
We demonstrate the post-compression of the GW-level femtosecond pulse in a solid-state multi-pass cell(MPC) by the pre-chirp management method. When the laser pulse is positively pre-chirped, the 200 μJ 170 fs input ...We demonstrate the post-compression of the GW-level femtosecond pulse in a solid-state multi-pass cell(MPC) by the pre-chirp management method. When the laser pulse is positively pre-chirped, the 200 μJ 170 fs input pulse is compressed to 163 μJ 44 fs at the output, corresponding to a transmission of 81% and a pulse shortening factor of 3.86. When the laser pulse is negatively pre-chirped, the spectral evolution, as the pulse propagates in the MPC, is characterized and, eventually, the pulse duration is compressed to 51 fs, corresponding to a pulse shortening factor of 3.3. After the driving laser goes through the pre-chirp managed MPC device, the power stability and beam quality are almost preserved. The experimental results offer a viable path toward the post-compression of high-peak-power laser pulses.展开更多
Phase carried by two orthogonal polarizations can be manipulated independently by controlling both the geometric size and orientation of the dielectric nanopost.With this characteristic,we demonstrate a novel multifun...Phase carried by two orthogonal polarizations can be manipulated independently by controlling both the geometric size and orientation of the dielectric nanopost.With this characteristic,we demonstrate a novel multifunctional metasurface,which converts part of the incident linearly polarized light into its cross-polarization and encodes the phase of the two orthogonal polarizations independently.A beam splitter and a bifocal metalens were realized in a single-layer dielectric metasurface by this approach.We fabricated the bifocal metalens and demonstrated that two focal spots in orthogonal polarizations can be separated transversely or longitudinally at will.The proposed approach shows a new route to design multifunctional metasurfaces with various applications in holography and three-dimensional display.展开更多
基金This work is supported by National Key Research and Development Program of China(2018YFB2200900)the Key R&D Program of Anhui(Grant No.202004A05020077)National Natural Science Foundation of China(61775206).The nanofabrication was carried out at the USTC Center for Micro and Nanoscale Research and Fabrication.We also thank Prof.Xianfan Xu of Purdue University for his warm-hearted discussion.
文摘Optical antennas play an important role in optical field manipulation.Among them,nanoscale bowtie antennas have been extensively studied for its high confinement and enhancement.In this mini-review,we start with a brief introduction of bowtie antennas and underlying physics.Then we review the applications with respect to optically and electrically excited nanoscale bowtie antennas.Optically driven bowtie antennas enable a set of optical applications such as near-field imaging/trapping,nonlinear response,nanolithography,photon generation and detection.Finally,we put emphasis on the principle and applications of electrically driven bowtie antennas,an emerging method of generating ultrafast and broadband tunable nanosources.In a word,nanoscale bowtie antennas still have great potential research value to explore.
基金the National Key Research and Development Program of China(2022YFB3607300)the National Natural Science Foundation of China(62322512 and 12134013)+3 种基金the Chinese Acad-emy of Sciences Project for Young Scientists in Basic Research(YSBR-049)support from the University of Science and Technology of China’s Center for Micro and Nanoscale Research and Fabricationsupported by the China Postdoctoral Science Foundation(2023M743364)supercomputing system in Hefei Advanced Computing Center and the Supercomputing Center of University of Science and Technology of China.
文摘Optical data storage(ODS)is a low-cost and high-durability counterpart of traditional electronic or mag-netic storage.As a means of enhancing ODS capacity,the multiple recording layer(MRL)method is more promising than other approaches such as reducing the recording volume and multiplexing technology.However,the architecture of current MRLs is identical to that of recording data into physical layers with rigid space,which leads to either severe interlayer crosstalk or finite recording layers constrained by the short working distances of the objectives.Here,we propose the concept of hybrid-layer ODS,which can record optical information into a physical layer and multiple virtual layers by using high-orthogonality random meta-channels.In the virtual layer,32 images are experimentally reconstructed through holog-raphy,where their holographic phases are encoded into 16 printed images and complementary images in the physical layer,yielding a capacity of 2.5 Tbit cm^(-3).A higher capacity is achievable with more virtual layers,suggesting hybrid-layer ODS as a possible candidate for next-generation ODS.
基金supported by the National Basic Research Program of China(Grant No.2011CBA00304)Tsinghua University Initiative Scientific Research Program,China(Grant No.20131089314)the National Natural Science Foundation of China(Grant Nos.60836001 and 11273023)
文摘We report the optical response characteristics of A1/Ti bilayer transition edge sensors （TESs）, which are mainly comprised of A1/Ti bilayer thermometers and suspended SiN membranes for thermal isolation. The measurement was performed in a 3He sorption refrigerator and the device＇s response to optical pulses was investigated using a pulsed laser source. Based on these measurements, we obtained the effective recovery time （τeff） of the devices at different biases and discussed the dependence of Veff on the bias. The device with a 940 μm × 940 μm continuous suspended SiN membrane demonstrated a fast response speed with τeff = 3.9 μs, which indicates a high temperature sensitivity （a = T/R·dR/dT = 326）. The results also showed that the TES exhibits good linearity under optical pulses of variable widths.
基金Supported by the National Natural Science Foundation of China under Grant No 61275049
文摘An effective method to fabricate two-helix long-period fiber gratings （TH-LFGs） is presented. Based on the coupling mode theory, the conversion of optical vortices （OVs） in TH-LFGs are analyzed in detail. The conversions of OVs with different topological charges： 0 → ±2 and 1 → 3 are simulated as three examples and the conversion efficiency higher than 98% can be realized.
文摘We report on a wide-band and stable mode-locked all-polarization-maintaining fiber laser configuration using a nonlinear optical loop mirror. The central wavelength of the laser is 1080.14nm and the 3dB bandwidth is 20.29nm. The repetition rate of the pulse is 3.28 MHz and the pulse width is 848ps. By tuning the pump power, which is centered at 980nrn, from 300mW to 380mW, we obtain a linearly changed output power from 6row to 7.12roW. The all-polarization-mMntaining fiber configuration is fundamental to the stability of the output power.
基金the support from the National Natural Science Foundation of China (No. 61925506)the Natural Science Foundation of Shanghai (No. 20JC1414605)+1 种基金Hangzhou Science and Technology Bureau of Zhejiang Province (No. TD2020002)the Academic/Technology Research Leader Program of Shanghai (23XD1404500)
文摘Lead halide perovskites have attracted considerable attention as potential candidates for high-performance nano/microlasers,owing to their outstanding optical properties.However,the further development of perovskite microlaser arrays(especially based on polycrystalline thin films)produced by the conventional processing techniques is hindered by the chemical instability and surface roughness of the perovskite structures.Herein,we demonstrate a laser patterning of large-scale,highly crystalline perovskite single-crystal films to fabricate reproducible perovskite single-crystal-based microlaser arrays.Perovskite thin films were directly ablated by femtosecond-laser in multiple low-power cycles at a minimum machining line width of approximately 300 nm to realize high-precision,chemically clean,and repeatable fabrication of microdisk arrays.The surface impurities generated during the process can be washed away to avoid external optical loss due to the robustness of the single-crystal film.Moreover,the high-quality,large-sized perovskite single-crystal films can significantly improve the quality of microcavities,thereby realizing a perovskite microdisk laser with narrow linewidth(0.09 nm)and low threshold(5.1µJ/cm2).Benefiting from the novel laser patterning method and the large-sized perovskite single-crystal films,a high power and high color purity laser display with single-mode microlasers as pixels was successfully fabricated.Thus,this study may offer a potential platform for mass-scale and reproducible fabrication of microlaser arrays,and further facilitate the development of highly integrated applications based on perovskite materials.
基金supported by the National Nature Science Foundation of China(No.11674303 and No.11574293)the USTC Center for Micro and Nanoscale Research and Fabrication
文摘Enhancement of uorescent radiation is of great importance for applications including biological imaging,high-sensitivity detectors,and integrated light sources.Strong electromagnetic elds can be created around metallic nanoparticles or in gap of nanostructures,where the local state density of radiating mode is then dramatically enhanced.While enhanced uorescent emission has been demonstrated in many metallic nanoparticles and nanoparticle pairs,simultaneous mediation of absorption and emission processes of uorescent emitters remains challenging in metallic nanostructures.Here,we investigate uorescent emission mediated by metal-dielectric-metal fishnet metasurface,in which localized surface plasmon(LSP)and magnetic plasmon polaritons(MPPs)modes are coupled with absorption and emission processes,respectively.For absorption process,coupling of the LSP mode enables spatially-selective excitation of the uorescent emitters by rotating the polarization of the pump laser beam.In addition,the polarization-dependent MPP mode enables manipulation of both polarization and wavelength of the uorescent emission by introducing a rectangular fishnet structure.All the experimental observations are further corroborated by nite-difference time-domain simulations.The structure reported here has great potential for application to color light-emitting devices and nanoscale integrated light sources.
基金This work was supported by National Natural Science Foundation of China （Grant No. 61275049）.
文摘In this work, an all-fiber-based mode converter for generating orbital angular momentum （OAM） beams is proposed and numerically investigated. Its structure is constructed by cascading a mode selective coupler （MSC） and an inner elliptical cladding fiber （IECF）. OAM modes refer to a combination of two orthogonal LPlm modes with a phase difference of ±π/2. By adjusting the parameters and controlling the splicing angle of MSC and IECF appropriately, higher-order OAM modes with topological charges of l = ±1, ±2, ±3 can be obtained with the injection of the fundamental mode LP01, resulting in a mode-conversion efficiency of almost 100%. This achievement may pave the way towards the realization of a compact, all-fiber, and high-efficiency device for increasing the transmission capacity and spectral efficiency in optical communication systems with OAM mode multiplexing.
文摘In this paper,a solution for speckle reduction using phase plate array(PPA)and lens array(LA)in a motionless way is proposed.The specially designed PPA is composed of sub-phase plates,which are constituted by phase patterns formed by Hadamard sub-matrices.Each component of the proposed optical system should satisfy the stated relationships.The incident laser beam will be incoherent after passing through PPA,and superpose on the screen under the action of LA and main lens.Speckle reduction can be achieved by the averaging of the incoherent speckle patterns.Because of abandoning the mechanical movement,it will be suitable for laser displays and images.
文摘Two physical interpretations of chirp transform related to Fresnel diffraction and Wigner distribution function are given. The chirp transform can be regarded as a Fresnel diffraction observed on a spherical tangent to the diffraction plane, or a rotation and stretching transformation of the Wigner distribution function space. A general fast algorithm for the numerical calculation of chirp transform is developed by employing two fast Fourier transform algorithms. The algorithm, by which a good evaluation can be achieved, unifies the calculations of Fresnel diffraction, arbitrary fractional- order Fourier transforms and other scalar diffraction systems. The algorithm is used to calculate the Fourier transform of a Gaussian function and the Fourier transform, the Fresnel transform, the Fractional-order Fourier transforms of a rectangle function to evaluate the performance of this algorithm. The calculated results are in good agreement with the analytical results, both in the amplitude and phase.
基金supported by the National Natural Science Foundation of China(Grant Nos.11302220,11374292,and 31100555)the National Basic Research Program of China(Grant No.2011CB910402)
文摘We introduce a corrected sinusoidal-wave drag force method （SDFM） into optical tweezers to calibrate the trapping stiffness of the optical trap and conversion factor （CF） of photodetectors. First, the theoretical analysis and experimental result demonstrate that the correction of SDFM is necessary, especially the error of no correction is up to 11.25% for a bead of 5μm in diameter. Second, the simulation results demonstrate that the SDFM has a better performance in the calibration of optical tweezers than the triangular-wave drag force method （TDFM） and power spectrum density method （PSDM） at the same signal-to-noise ratio or trapping stiffness. Third, in experiments, the experimental standard deviations of calibration of trapping stiffness and CF with the SDFM are about less than 50% of TDFM and PSDM especially at low laser power. Finally, the experiments of stretching DNA verify that the in situ calibration with the SDFM improves the measurement stability and accuracy.
基金supported by the National Special Fund for the Development of Major Research Equipment and Instruments of China(No.2014YQ120351)
文摘The influence of a vacuum on the laser-induced breakdown spectroscopy （LIBS） of carbon in the ultraviolet wavelength range is studied. Experiments are performed with graphite using a LIBS system, which consists of a 1064 nm Nd：YAG laser, a vacuum pump, a spectrometer and a vacuum chamber. The vacuum varies from 10 Pa to 1 atm. Atomic lines as well as singly and doubly charged ions are confirmed under the vacuums. A temporal evolution analysis of intensity is performed for the atomic lines of C I 193.09 nm and C I 247.86 nm under different vacuum conditions. Both time-integrated and time-resolved intensity evolutions under vacuums are achieved. The lifetimes of the two atomic lines have similar trends, which supports the point of view of a ＇soft spot＇. Variations of plasma temperature and electron density under different vacuums are measured. This study is helpful for research on carbon detection using LIBS under vacuum conditions.
文摘Broadband nonlinear frequency conversions of optical waves are widely employed in multiple areas of optics and photonics. However, the broadening of conversion bandwidth is often at a cost of reduction in efficiency, which may induce a limitation on practical applications. Here we theoretically propose a novel design of LiNbO_(3) ridge waveguides on LiTaO_(3) substrates which can be used for efficient and broadband second harmonic generation. Through group velocity engineering of the ridge waveguides, acceptance bandwidth over 20 nm with a high conversion efficiency of > 25%W^(-1)·cm^(-2) is achieved at telecom-band.
基金Supported by the National Natural Science Foundation of China under Grant No 61675188the Open Fund of Key Laboratory Pulse Power Laser Technology of China under Grant No SKL2016KF03
文摘We propose a new method to separate different orders of an all-fiber passive Q-switching stimulated Brillouin scattering（SBS） laser. We use two fiber Bragg gratings connected by two circulators for the filtering. We obtain a stabilized pulse laser and measure the pulse width of different orders. The first order of SBS has a central wavelength of 1549.75 nm, an average output power of 9 mW, and a pulse width of 400 ns. The pulse width of SBS is reduced by the higher-order signals with the larger fluctuations.
文摘A simple scheme based on the uniform distribution for the placement of numerous laser beams in the context o~ fiber-based laser fusion is proposed. It is theoretically demonstrated that all modes of the geometrical factor can be eliminated if sufflcient laser beams are uniformly distributed on the sphere. In the case of a finite number of laser beams, a quasi-uniform distribution of beams can be achieved based on the equal area subdivision algorithm. Numerical simulations indicate that with the increasing number of laser beams, the order of the dominant geometrical mode increases, and the irradiation nonuniformity decreases accordingly.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50703038, 50773075 and 50533040, the Knowledge Innovation Project of Chinese Academy of Sciences （KJCX3.SYW.H02 and KJCX2-YW-M11）, China Postdoctoral Science Foundation （No 20100470038）, and the National Basic Research Program of China under Grant No 2006cb302900.
文摘In the fabrication of surface relief gratings （SRGs） on azobenzene polymer films with a zeroth-order suppressed diffraction phase mask, it is found that the SRGs＇ relief figure and period change with the irradiation time, and the period is doubled after a critical time. The time dependence of the changes in the SRG forming process is investigated by theoretical analysis and experiments. An optimum time range for inscription of the sub-micron SInGs is determined to be 5-8 rain in terms of both the theoretical and experimental results.
基金financially supported by A*STAR under IRG program(Grant No.A2083c0058)and the MTC Programmatic(Grant No.M22L1b0110)Z Wang thanks the GAP Funding(I21D1AG010)+4 种基金the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-049)the National Natural Science Foundation of China(Grant Nos.12134013 and 62322512)the National Key Research and Development Program of China(Grant No.2022YFB3607300)the CAS Pioneer Hundred Talents Program,and support from the University of Science and Technology of China’s Centre for MicroNanoscale Research and Fabrication.
文摘Supercritical lens(SCL)can break the diffraction limit in the far field and has been demonstrated for high-resolution scanning confocal imaging.Its capability in sharper focusing and needle-like long focal depth should allow high-resolution lithography at violet or ultraviolet(UV)wavelength,however,this has never been experimentally demonstrated.As a proof of concept,in this paper SCLs operating at 405 nm(h-line)wavelength with smaller full-width-at-half-maximum focal spot and longer depth of focus than conventional Fresnel zone lens while maintaining controlled side lobes are designed for direct laser writing(DLW)lithography.Aluminum nitride(AlN)with a high refractive index and low loss in UVvisible range is used to fabricate nanopillar-based metasurfaces structure for the metalens.Grating arrays with improved pitch resolution are fabricated using the SCLs with sub-diffraction-limit focusing capability.The AlN-based metasurface for SCLs at short wavelength for DLW could extend further to UV or deep UV lithography and might be of great interest to both the research and industry applications.
基金supported by the National "863" Program of China (Nos. 2007AA021811 and 2007AA021809)the National Natural Science Foundation of China (No. 31100555)the Chinese Universities Scientific Fund (Nos. WK2030020016 and WK2030380002)
文摘Since RGD peptides （R： arginine; G： glycine; D： aspartic acid） are found to promote cell adhesion, they are modified at numerous materials surface for medical applications such as drug delivery and regenerative medicine. Peptide-cell surface interactions play a key role in the above applications. In this letter, we study the adhesion force between the RGD-coated bead and Hela cell surface by optical tweezes. The adhesion is dominated by the binding of α5β1 and RGD-peptide with higher adhesion probability and stronger adhesion strength compared with the adhesion of bare bead and cell surface. The binding force for a single α5β1 -GRGDSP pair is determined to be 16.8 pN at a loading rate of 1.5 nN/s. The unstressed off-rate is 1.65 × 10^-2s^-1 and the distance of transition state for the rigid binding model is 3.0 nm.
基金supported by the National Natural Science Foundation of China(Nos.12388102,62205351,61925507,62075227 and 22227901)the Youth Innovation Promotion Association CAS(No.2020248)+1 种基金the Shanghai Sailing Program(No.20YF1455000)the Shanghai Rising-Star Program(No.21QA1410200)
文摘We demonstrate the post-compression of the GW-level femtosecond pulse in a solid-state multi-pass cell(MPC) by the pre-chirp management method. When the laser pulse is positively pre-chirped, the 200 μJ 170 fs input pulse is compressed to 163 μJ 44 fs at the output, corresponding to a transmission of 81% and a pulse shortening factor of 3.86. When the laser pulse is negatively pre-chirped, the spectral evolution, as the pulse propagates in the MPC, is characterized and, eventually, the pulse duration is compressed to 51 fs, corresponding to a pulse shortening factor of 3.3. After the driving laser goes through the pre-chirp managed MPC device, the power stability and beam quality are almost preserved. The experimental results offer a viable path toward the post-compression of high-peak-power laser pulses.
基金the National Natural Science Foundation of China(NSFC)(Nos.11674303 and 11574293)the Anhui Provincial Science andTechnology Major Projects(No.18030901005)。
文摘Phase carried by two orthogonal polarizations can be manipulated independently by controlling both the geometric size and orientation of the dielectric nanopost.With this characteristic,we demonstrate a novel multifunctional metasurface,which converts part of the incident linearly polarized light into its cross-polarization and encodes the phase of the two orthogonal polarizations independently.A beam splitter and a bifocal metalens were realized in a single-layer dielectric metasurface by this approach.We fabricated the bifocal metalens and demonstrated that two focal spots in orthogonal polarizations can be separated transversely or longitudinally at will.The proposed approach shows a new route to design multifunctional metasurfaces with various applications in holography and three-dimensional display.
