Based on the dielectric continuum model and Loudon＇s uniaxial crystal model,quasi-confined （QC） optical phonon modes and electron-QC phonon coupling functions in quasi-one-dimensional （QID） wurtzite quantum well ...Based on the dielectric continuum model and Loudon＇s uniaxial crystal model,quasi-confined （QC） optical phonon modes and electron-QC phonon coupling functions in quasi-one-dimensional （QID） wurtzite quantum well wires （QWWs） are deduced and analyzed. Numerical calculations on an AIN/GaN/AIN wurtzite QWW are performed. The results reveal that the dispersions of the QC modes are quite obvious only when the free wavenumber kz in the z-direction and the azimuthal quantum number m are small. The reduced behavior of the QC modes in wurtzite quantum systems is clearly observed. Through the discussion of the electron-QC mode coupling functions,it is found that the lower-frequency QC modes in the high-frequency region play a more important role in the electron-QC phonon interactions. Moreover,our computations also prove that kz and m have a similar influence on the electron-QC phonon coupling properties.展开更多
We have investigated the transverse mode pattern and the optical field confinement factor of gallium nitride （GaN） laser diodes （LDs） theoretically. For the particular LD structure, composed of approximate 4 μm t...We have investigated the transverse mode pattern and the optical field confinement factor of gallium nitride （GaN） laser diodes （LDs） theoretically. For the particular LD structure, composed of approximate 4 μm thick n-GaN substrate layer, the maximum optical confinement factor was found to be corresponding to the 5^th order transverse mode, the so-called lasing mode. Moreover, the value of the maximum confinement factor varies periodically when increasing the n-side GaN layer thickness, which simultaneously changes and increases the oscillation mode order of the GaN LD caused by the effects of mode coupling. The effects of the thickness and the average composition of Al in the AlGaN/GaN superlat.tice on the optical confinement factor are also presented. Finally, the mode coupling and optimization of the layers in the GaN-based LD are discussed.展开更多
This paperdetails experimental work done to quantify stress measurements made optically utilizing ordinary single mode optical fibers. Strain-induced changes of birefringence for ordinary single mode optical fiber res...This paperdetails experimental work done to quantify stress measurements made optically utilizing ordinary single mode optical fibers. Strain-induced changes of birefringence for ordinary single mode optical fiber responses are characterized against standard stress measurements in a well understand configuration. The experimental scheme for this work and the results are presented in detaial. In this paper, POssible applications for this transverse stress character of single mode fibers are also proposed.展开更多
Within the framework of the macroscopic dielectric continuum model and Loudon＇s uniaxial crystal model, the phonon modes of a wurtzite/zinc-blende one-dimensional （1D） cylindrical nanowire （NW） are derived and st...Within the framework of the macroscopic dielectric continuum model and Loudon＇s uniaxial crystal model, the phonon modes of a wurtzite/zinc-blende one-dimensional （1D） cylindrical nanowire （NW） are derived and studied. The analytical phonon states of phonon modes are given. It is found that there exist two types of polar phonon modes, i.e. interface optical （IO） phonon modes and the quasi-confined （QC） phonon modes existing in 1D wurtzite/zinc-blende NWs. Via the standard procedure of field quantization, the Fr6hlich electron-phonon interaction Hamiltonians are obtained. Numerical calculations of dispersive behavior of these phonon modes on a wurtzite/zinc-blende ZnO/MgO NW are performed. The frequency ranges of the IO and QC phonon modes of the ZnO/MgO NWs are analyzed and discussed. It is found that the IO modes only exist in one frequency range, while QC modes may appear in three frequency ranges. The dispersive properties of the IO and QC modes on the free wave-number kz and the azimuthal quantum number m are discussed. The analytical Hamiltonians of electron-phonon interaction obtained here are quite useful for further investigating phonon influence on optoelectronics properties of wurtzite/zinc-blende 1D NW structures.展开更多
We proposed a fiber optic high temperature sensor based on the Mach-Zehnder interference(MZI)structure,which is composed of two lengths of multi-mode fibers(MMFs),a length of few-mode fiber(FMF)and two sections of sin...We proposed a fiber optic high temperature sensor based on the Mach-Zehnder interference(MZI)structure,which is composed of two lengths of multi-mode fibers(MMFs),a length of few-mode fiber(FMF)and two sections of single-mode fibers(SMFs).Firstly,the two sections of MMFs were spliced with two sections of SMFs.Then,the MMFs were fused to two ends of FMF to form a symmetrically structured fiber-optic MZI structure.In this structure,the MMF served as the optical mode field coupling element,and the cladding and core of the FMF are the interference arm and the reference arm of the MZI structure,respectively.We investigated the sensor's response characteristics of the temperature and strain.The experimental results indicate that the sensor is sensitive to temperature variation,and the temperature response sensitivity is up to 61.4 pm/℃ in the range of 40-250℃,while the sensor has weak strain sensitivity,its strain sensitivity is only-0.72 pm/μe in the strain range of 0-1400μe.Moreover,the sensor has good stability and repeatability.In brief,the proposed fiber optic high temperature sensor has good properties,such as high sensitivity,compact structure,good stability and repeatability,which can be used for monitoring the temperature of submerged oil electric pump units under oil wells.展开更多
In a recent study,Prof.Rui Min and collaborators published their paper in the journal of Opto-Electronic Science that is entitled"Smart photonic wristband for pulse wave monitoring".The paper introduces nove...In a recent study,Prof.Rui Min and collaborators published their paper in the journal of Opto-Electronic Science that is entitled"Smart photonic wristband for pulse wave monitoring".The paper introduces novel realization of a sensor that us-es a polymer optical multi-mode fiber to sense pulse wave bio-signal from a wrist by analyzing the specklegram mea-sured at the output of the fiber.Applying machine learning techniques over the pulse wave signal allowed medical diag-nostics and recognizing different gestures with accuracy rate of 95%.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
We theoretically investigate a two-cavity optomechanical system in which each optical cavity couples to a mechanical resonator via radiation pressure force,and the two optical cavities couple to each other via a dista...We theoretically investigate a two-cavity optomechanical system in which each optical cavity couples to a mechanical resonator via radiation pressure force,and the two optical cavities couple to each other via a distant waveguide.Our study shows that the multiple optomechanically induced transparency can be observed from the output field at the probe frequency.The number and width of the transparent windows can be tuned by the classical driving power Pl.We also analyze the distance of the two outermost transparency windows,which shows a linear relation with the parameters Pl andλ.Our approach is feasible for controlling multipartite induced transparency,which represents a valuable step towards quantum networks with photonic and phononic circuits.展开更多
The beams of 980nm high-power LDs are analyzed, and the reasons that aspect ratio of LD beams is high are explained. It is certified by the test that cylindrical lens can efficiently compress the perpendicular diverge...The beams of 980nm high-power LDs are analyzed, and the reasons that aspect ratio of LD beams is high are explained. It is certified by the test that cylindrical lens can efficiently compress the perpendicular divergence angle of the beam. Some typical and popular lensed fibers were compared and analyzed according to coupling characteristics. The factors which affect the coupling efficiency and tolerance of the wedged-shaped GRIN tipped lensed fiber are pointed out, and some methods to reduce the coupling loss of the lensed fibers are proposed finally.展开更多
The antiferromagnetic(AFM) interlayer coupling effective field in a ferromagnetic/non-magnetic/ferromagnetic(FM/NM/FM) sandwich structure, as a driving force, can dramatically enhance the ferromagnetic resonance(FMR) ...The antiferromagnetic(AFM) interlayer coupling effective field in a ferromagnetic/non-magnetic/ferromagnetic(FM/NM/FM) sandwich structure, as a driving force, can dramatically enhance the ferromagnetic resonance(FMR) frequency. Changing the non-magnetic spacer thickness is an effective way to control the interlayer coupling type and intensity, as well as the FMR frequency. In this study, Fe Co B/Ru/Fe Co B sandwich trilayers with Ru thickness(tRu) ranging from 1 A to 16 A are prepared by a compositional gradient sputtering(CGS) method. It is revealed that a stress-induced anisotropy is present in the Fe Co B films due to the B composition gradient in the samples. A tRu-dependent oscillation of interlayer coupling from FM to AFM with two periods is observed. An AFM coupling occurs in a range of 2 A ≤ tRu≤ 8 A and over 16 A, while an FM coupling is present in a range of tRu< 2 A and 9 A ≤ tRu≤ 14.5 A. It is interesting that an ultrahigh optical mode(OM) FMR frequency in excess of 20 GHz is obtained in the sample with tRu= 2.5 A under an AFM coupling. The dynamic coupling mechanism in trilayers is simulated, and the corresponding coupling types at different values of tRuare verified by Layadi’s rigid model. This study provides a controllable way to prepare and investigate the ultrahigh FMR films.展开更多
In the present work, vibrational and thermodynamic properties of XBi（X = B, Al, Ga, In） compounds are compared and investigated. The calculation is carried out using density functional theory（DFT） within the gener...In the present work, vibrational and thermodynamic properties of XBi（X = B, Al, Ga, In） compounds are compared and investigated. The calculation is carried out using density functional theory（DFT） within the generalized gradient approximation（GGA） in a plane wave basis, with ultrasoft pseudopotentials. The lattice dynamical properties are calculated using density functional perturbation theory（DFPT） as implemented in Quantum ESPRESSO（QE） code. Thermodynamic properties involving phonon density of states（DOS） and specific heat at constant volume are investigated using quasiharmonic approximation（QHA） package within QE. The phonon dispersion diagrams for InBi, GaBi, BBi, and AlBi indicate that there is no imaginary phonon frequency in the entire Brillouin zone, which proves the dynamical stability of these materials. BBi has the highest thermal conductivity and InBi has the lowest thermal conductivity. AlBi has the largest and GaBi has the smallest reststrahlen band which somehow suggests the polar property of XBi materials. The phonon gaps for InBi, GaBi, BBi and AlBi are about 160 cm^-1, 150 cm^-1, 300 cm^-1, and 150 cm^-1, respectively. For all compounds,the three acoustic modes near the gamma point have a linear behavior. C_V is a function of T-3 at low temperatures while for higher temperatures it asymptotically tends to a constant as expected.展开更多
Spatial quantum optics based on the high-order transverse mode is important for the super-resolution measurement and quantum image beyond the shot noise level. Quantum entanglement of the transverse plane Hermite–Gau...Spatial quantum optics based on the high-order transverse mode is important for the super-resolution measurement and quantum image beyond the shot noise level. Quantum entanglement of the transverse plane Hermite–Gauss TEM（01） mode has been demonstrated experimentally in this paper. Two squeezed TEM（01） modes, which are generated by a pair of degenerate optical parametric amplifiers（DOPA） with the nonlinear crystals of periodically poled KTi OPO4, have been combined to produce TEM（01） mode entanglement using a beam splitter. The 1.5 dB for the sum of amplitude and 1.2 dB for the difference of phase below shot-noise level is achieved with the measurement system of a Bell state detection.展开更多
Resonances are usually associated with finite systems—the vibrations of clamped strings in a guitar or the optical modes in a cavity defined by mirrors.In optics,resonances may be induced in infinite continuous media...Resonances are usually associated with finite systems—the vibrations of clamped strings in a guitar or the optical modes in a cavity defined by mirrors.In optics,resonances may be induced in infinite continuous media via periodic modulations of their optical properties.Here we demonstrate that periodic modulations of the permittivity of a featureless thin film can also act as a symmetry-breaking mechanism,allowing the excitation of photonic quasi-bound states in the continuum(qBICs).By interfering two ultrashort laser pulses in the unbounded film,transient resonances can be tailored through different parameters of the pump beams.We show that the system offers resonances tunable in wavelength and quality-factor,and spectrally selective enhancement of third-harmonic generation.Due to a fast decay of the permittivity asymmetry,we observe ultrafast dynamics,enabling time-selective near-field enhancement with picosecond precision.Optically induced permittivity asymmetries may be exploited in on-demand weak to ultrastrong light-matter interaction regimes and light manipulation at dynamically chosen wavelengths in lithography-free metasurfaces.展开更多
Identifying optical modes in chaotic cavities is crucial for exploring and understanding the physical mechanisms inside them.Compared with free spectral range estimation,the direct imaging technique has the capability...Identifying optical modes in chaotic cavities is crucial for exploring and understanding the physical mechanisms inside them.Compared with free spectral range estimation,the direct imaging technique has the capability of providing more precise mode information,but it is extremely time-consuming and susceptible to environmental perturbations.Here we report a high-speed imaging technique for visualizing field distributions in chaotic microcavities.When a silicon microdisk is excited by a femtosecond laser,free carriers are locally generated,thereby reducing the refractive index.Under a constant laser power,the spatial distribution of mode inside the silicon microdisk is proportional to its wavelength shift and can be precisely identified by comparing it with numerical simulation.With the assistance of a galvanometer,imaging a mode profile only takes a few hundred milliseconds to a few seconds,orders of magnitude faster than previous reports.The impacts of slight fabrication deviations on spectra have also been identified.展开更多
This paper investigates the use of artificial neural networks(ANNs)as a viable digital twin or alternative to the typical whispering gallery mode(WGM)optical sensors in engineering systems,especially in dynamic enviro...This paper investigates the use of artificial neural networks(ANNs)as a viable digital twin or alternative to the typical whispering gallery mode(WGM)optical sensors in engineering systems,especially in dynamic environments like robotics.Because of its fragility and limited endurance,the WGM sensor which is based on micro-optical resonators is inappropriate in these kinds of situations.In order to address these issues,the paper suggests an ANN that is specifically designed for the system and makes use of the WGM sensor’s high-quality factor(Q-factor).By extending the applicability and endurance to dynamic contexts and reducing fragility problems,the ANN seeks to give high-resolution measurement.In order to minimize post-processing requirements and maintain system robustness,the study goal is for the ANN to function as a representative predictor of the WGM sensor output.The GUCnoid 1.0 humanoid robot is used in the paper as an example to show how the WGM optical sensors may improve humanoid robot performance for a variety of applications.The results of the experiments demonstrate that the sensitivity,precision,and resolution of ANN outputs and actual WGM shifts are equivalent.As a consequence,current obstacles to the widespread use of high-precision sensing in the robotics industry are removed,and the potential of ANNs as virtual substitutes or the digital twin for genuine WGM sensors in robotics systems is validated.So,this paper can be very beneficial not only to the sensing technologies that are used in robotics,which are subjected to the dynamic environments,but also to the industrial automation and human-machine interface.展开更多
The increasing amount of data exchange requires higher-capacity optical communication links.Mode division multiplexing(MDM)is considered as a promising technology to support the higher data throughput.In an MDM system...The increasing amount of data exchange requires higher-capacity optical communication links.Mode division multiplexing(MDM)is considered as a promising technology to support the higher data throughput.In an MDM system,the mode generator and sorter are the backbone.However,most of the current schemes lack the programmability and universality,which makes the MDM link susceptible to the mode crosstalk and environmental disturbances.In this paper,we propose an intelligent multimode optical communication link using universal mode processing(generation and sorting)chips.The mode processor consists of a programmable 4×4 Mach Zehnder interferometer(MZI)network and can be intelligently configured to generate or sort both quasi linearly polarized(LP)modes and orbital angular momentum(OAM)modes in any desired routing state.We experimentally establish a chip-to-chip MDM communication system.The mode basis can be freely switched between four LP modes and four OAM modes.We also demonstrate the multimode optical communication capability at a data rate of 25 Gbit/s.The proposed scheme shows significant advantages in terms of universality,intelligence,programmability and resistance to mode crosstalk,environmental disturbances,and fabrication errors,demonstrating that the MZI-based reconfigurable mode processor chip has great potential in longdistance chip-to-chip multimode optical communication systems.展开更多
Guided modes in a hollow optical fiber are investigated using both scalar approximation and exact vectorial analysis. Effective indices of modes are seen to exhibit "nearly degenerate" groups. Besides provid...Guided modes in a hollow optical fiber are investigated using both scalar approximation and exact vectorial analysis. Effective indices of modes are seen to exhibit "nearly degenerate" groups. Besides providing an insight of modal characteristics, the analysis would prove to be useful to define design parameters for realizing components based on these fibers, and to explore new possibilities.展开更多
A novel slotted optical microdisk resonator, which significantly enhances light–matter interaction and provides a promising approach for increasing the sensitivity of sensors, is theoretically and numerically investi...A novel slotted optical microdisk resonator, which significantly enhances light–matter interaction and provides a promising approach for increasing the sensitivity of sensors, is theoretically and numerically investigated. In this slotted resonator, the mode splitting is generated due to reflection of the slot. Remarkably, effects of the slot width and angular position on the mode splitting are mainly studied. The results reveal that the mode splitting is a second function of the slot width, and the maximum mode splitting induced by the slot deformation is achieved with 2.7853 × 10~9Hz∕nm. Therefore, the slotted resonator is an excellent candidate for pressure and force sensing. Besides, the influence of the slot angular position on the mode splitting is a cosine curve with the highest sensitivity of 1.23 × 10^(11)Hz∕deg; thus, the optical characteristic demonstrates that the slotted resonator can be used for inertial measurements.展开更多
A wavelength filter with simple structure using multimode waveguide is proposed. The device uses mode conversion by a grating structure fabricated simultaneously with the multimode waveguide.
Overcoming the diffraction limit in optics is challenging and demands a profound understanding of light behavior under extreme confinement.The newly developed framework,termed singulonics,demonstrates the formation of...Overcoming the diffraction limit in optics is challenging and demands a profound understanding of light behavior under extreme confinement.The newly developed framework,termed singulonics,demonstrates the formation of sub-diffraction limit narwhal-shaped optical modes under specific conditions.Experimental implementation of this field confinement within a tiny sub-wavelength volume enables the acquisition of near-field super resolution images.展开更多
文摘Based on the dielectric continuum model and Loudon＇s uniaxial crystal model,quasi-confined （QC） optical phonon modes and electron-QC phonon coupling functions in quasi-one-dimensional （QID） wurtzite quantum well wires （QWWs） are deduced and analyzed. Numerical calculations on an AIN/GaN/AIN wurtzite QWW are performed. The results reveal that the dispersions of the QC modes are quite obvious only when the free wavenumber kz in the z-direction and the azimuthal quantum number m are small. The reduced behavior of the QC modes in wurtzite quantum systems is clearly observed. Through the discussion of the electron-QC mode coupling functions,it is found that the lower-frequency QC modes in the high-frequency region play a more important role in the electron-QC phonon interactions. Moreover,our computations also prove that kz and m have a similar influence on the electron-QC phonon coupling properties.
基金Project supported by the Wang Faculty Fellowship at Peking University,Beijing,China,2006-2007 through California State University (CSU) International Programs USAthe National Basic Research Program of China (Grant No 2007CB307004)+1 种基金the National High Technology Research and Development Program of China (Grant No 2006AA03A113)the National Natural Science Foundation of China (Grant Nos 60276034,60577030 and 60607003)
文摘We have investigated the transverse mode pattern and the optical field confinement factor of gallium nitride （GaN） laser diodes （LDs） theoretically. For the particular LD structure, composed of approximate 4 μm thick n-GaN substrate layer, the maximum optical confinement factor was found to be corresponding to the 5^th order transverse mode, the so-called lasing mode. Moreover, the value of the maximum confinement factor varies periodically when increasing the n-side GaN layer thickness, which simultaneously changes and increases the oscillation mode order of the GaN LD caused by the effects of mode coupling. The effects of the thickness and the average composition of Al in the AlGaN/GaN superlat.tice on the optical confinement factor are also presented. Finally, the mode coupling and optimization of the layers in the GaN-based LD are discussed.
文摘This paperdetails experimental work done to quantify stress measurements made optically utilizing ordinary single mode optical fibers. Strain-induced changes of birefringence for ordinary single mode optical fiber responses are characterized against standard stress measurements in a well understand configuration. The experimental scheme for this work and the results are presented in detaial. In this paper, POssible applications for this transverse stress character of single mode fibers are also proposed.
基金Supported by National Natural Science Foundation of China under Grant No.60906042by the National Basic Research Program of China under Grant No.2006CB921607
文摘Within the framework of the macroscopic dielectric continuum model and Loudon＇s uniaxial crystal model, the phonon modes of a wurtzite/zinc-blende one-dimensional （1D） cylindrical nanowire （NW） are derived and studied. The analytical phonon states of phonon modes are given. It is found that there exist two types of polar phonon modes, i.e. interface optical （IO） phonon modes and the quasi-confined （QC） phonon modes existing in 1D wurtzite/zinc-blende NWs. Via the standard procedure of field quantization, the Fr6hlich electron-phonon interaction Hamiltonians are obtained. Numerical calculations of dispersive behavior of these phonon modes on a wurtzite/zinc-blende ZnO/MgO NW are performed. The frequency ranges of the IO and QC phonon modes of the ZnO/MgO NWs are analyzed and discussed. It is found that the IO modes only exist in one frequency range, while QC modes may appear in three frequency ranges. The dispersive properties of the IO and QC modes on the free wave-number kz and the azimuthal quantum number m are discussed. The analytical Hamiltonians of electron-phonon interaction obtained here are quite useful for further investigating phonon influence on optoelectronics properties of wurtzite/zinc-blende 1D NW structures.
基金supported by the Scientific Research Program Funded by Shaanxi Provincial Education Department (No.15JK1573)the Postgraduate Innovation and Practice Ability Development Fund of Xi’an Shiyou University (No.YCS21211084)。
文摘We proposed a fiber optic high temperature sensor based on the Mach-Zehnder interference(MZI)structure,which is composed of two lengths of multi-mode fibers(MMFs),a length of few-mode fiber(FMF)and two sections of single-mode fibers(SMFs).Firstly,the two sections of MMFs were spliced with two sections of SMFs.Then,the MMFs were fused to two ends of FMF to form a symmetrically structured fiber-optic MZI structure.In this structure,the MMF served as the optical mode field coupling element,and the cladding and core of the FMF are the interference arm and the reference arm of the MZI structure,respectively.We investigated the sensor's response characteristics of the temperature and strain.The experimental results indicate that the sensor is sensitive to temperature variation,and the temperature response sensitivity is up to 61.4 pm/℃ in the range of 40-250℃,while the sensor has weak strain sensitivity,its strain sensitivity is only-0.72 pm/μe in the strain range of 0-1400μe.Moreover,the sensor has good stability and repeatability.In brief,the proposed fiber optic high temperature sensor has good properties,such as high sensitivity,compact structure,good stability and repeatability,which can be used for monitoring the temperature of submerged oil electric pump units under oil wells.
文摘In a recent study,Prof.Rui Min and collaborators published their paper in the journal of Opto-Electronic Science that is entitled"Smart photonic wristband for pulse wave monitoring".The paper introduces novel realization of a sensor that us-es a polymer optical multi-mode fiber to sense pulse wave bio-signal from a wrist by analyzing the specklegram mea-sured at the output of the fiber.Applying machine learning techniques over the pulse wave signal allowed medical diag-nostics and recognizing different gestures with accuracy rate of 95%.
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Project supported by the National Natural Science Foundation of China(Grant Nos.11704042 and 11674037)the LiaoNing Revitalization Talents Program(Grant No.XLYC1807206).
文摘We theoretically investigate a two-cavity optomechanical system in which each optical cavity couples to a mechanical resonator via radiation pressure force,and the two optical cavities couple to each other via a distant waveguide.Our study shows that the multiple optomechanically induced transparency can be observed from the output field at the probe frequency.The number and width of the transparent windows can be tuned by the classical driving power Pl.We also analyze the distance of the two outermost transparency windows,which shows a linear relation with the parameters Pl andλ.Our approach is feasible for controlling multipartite induced transparency,which represents a valuable step towards quantum networks with photonic and phononic circuits.
文摘The beams of 980nm high-power LDs are analyzed, and the reasons that aspect ratio of LD beams is high are explained. It is certified by the test that cylindrical lens can efficiently compress the perpendicular divergence angle of the beam. Some typical and popular lensed fibers were compared and analyzed according to coupling characteristics. The factors which affect the coupling efficiency and tolerance of the wedged-shaped GRIN tipped lensed fiber are pointed out, and some methods to reduce the coupling loss of the lensed fibers are proposed finally.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51871127 and 11674187)。
文摘The antiferromagnetic(AFM) interlayer coupling effective field in a ferromagnetic/non-magnetic/ferromagnetic(FM/NM/FM) sandwich structure, as a driving force, can dramatically enhance the ferromagnetic resonance(FMR) frequency. Changing the non-magnetic spacer thickness is an effective way to control the interlayer coupling type and intensity, as well as the FMR frequency. In this study, Fe Co B/Ru/Fe Co B sandwich trilayers with Ru thickness(tRu) ranging from 1 A to 16 A are prepared by a compositional gradient sputtering(CGS) method. It is revealed that a stress-induced anisotropy is present in the Fe Co B films due to the B composition gradient in the samples. A tRu-dependent oscillation of interlayer coupling from FM to AFM with two periods is observed. An AFM coupling occurs in a range of 2 A ≤ tRu≤ 8 A and over 16 A, while an FM coupling is present in a range of tRu< 2 A and 9 A ≤ tRu≤ 14.5 A. It is interesting that an ultrahigh optical mode(OM) FMR frequency in excess of 20 GHz is obtained in the sample with tRu= 2.5 A under an AFM coupling. The dynamic coupling mechanism in trilayers is simulated, and the corresponding coupling types at different values of tRuare verified by Layadi’s rigid model. This study provides a controllable way to prepare and investigate the ultrahigh FMR films.
文摘In the present work, vibrational and thermodynamic properties of XBi（X = B, Al, Ga, In） compounds are compared and investigated. The calculation is carried out using density functional theory（DFT） within the generalized gradient approximation（GGA） in a plane wave basis, with ultrasoft pseudopotentials. The lattice dynamical properties are calculated using density functional perturbation theory（DFPT） as implemented in Quantum ESPRESSO（QE） code. Thermodynamic properties involving phonon density of states（DOS） and specific heat at constant volume are investigated using quasiharmonic approximation（QHA） package within QE. The phonon dispersion diagrams for InBi, GaBi, BBi, and AlBi indicate that there is no imaginary phonon frequency in the entire Brillouin zone, which proves the dynamical stability of these materials. BBi has the highest thermal conductivity and InBi has the lowest thermal conductivity. AlBi has the largest and GaBi has the smallest reststrahlen band which somehow suggests the polar property of XBi materials. The phonon gaps for InBi, GaBi, BBi and AlBi are about 160 cm^-1, 150 cm^-1, 300 cm^-1, and 150 cm^-1, respectively. For all compounds,the three acoustic modes near the gamma point have a linear behavior. C_V is a function of T-3 at low temperatures while for higher temperatures it asymptotically tends to a constant as expected.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11504218 and 61108003)the Natural Science Foundation of Shanxi Province,China(Grant No.2013021005-2)
文摘Spatial quantum optics based on the high-order transverse mode is important for the super-resolution measurement and quantum image beyond the shot noise level. Quantum entanglement of the transverse plane Hermite–Gauss TEM（01） mode has been demonstrated experimentally in this paper. Two squeezed TEM（01） modes, which are generated by a pair of degenerate optical parametric amplifiers（DOPA） with the nonlinear crystals of periodically poled KTi OPO4, have been combined to produce TEM（01） mode entanglement using a beam splitter. The 1.5 dB for the sum of amplitude and 1.2 dB for the difference of phase below shot-noise level is achieved with the measurement system of a Bell state detection.
文摘Resonances are usually associated with finite systems—the vibrations of clamped strings in a guitar or the optical modes in a cavity defined by mirrors.In optics,resonances may be induced in infinite continuous media via periodic modulations of their optical properties.Here we demonstrate that periodic modulations of the permittivity of a featureless thin film can also act as a symmetry-breaking mechanism,allowing the excitation of photonic quasi-bound states in the continuum(qBICs).By interfering two ultrashort laser pulses in the unbounded film,transient resonances can be tailored through different parameters of the pump beams.We show that the system offers resonances tunable in wavelength and quality-factor,and spectrally selective enhancement of third-harmonic generation.Due to a fast decay of the permittivity asymmetry,we observe ultrafast dynamics,enabling time-selective near-field enhancement with picosecond precision.Optically induced permittivity asymmetries may be exploited in on-demand weak to ultrastrong light-matter interaction regimes and light manipulation at dynamically chosen wavelengths in lithography-free metasurfaces.
基金National Key Research and Development Program of China(2024YFB2809200)National Natural Science Foundation of China(12334016,12025402,62125501,62335005,12261131500,92250302)+2 种基金New Cornerstone Science Foundation(Xplorer Prize)Shenzhen Fundamental Research Projects(JCYJ20241202123719025,JCYJ20241202123729038)Fundamental Research Funds for the Central Universities(2022FRFK01013)。
文摘Identifying optical modes in chaotic cavities is crucial for exploring and understanding the physical mechanisms inside them.Compared with free spectral range estimation,the direct imaging technique has the capability of providing more precise mode information,but it is extremely time-consuming and susceptible to environmental perturbations.Here we report a high-speed imaging technique for visualizing field distributions in chaotic microcavities.When a silicon microdisk is excited by a femtosecond laser,free carriers are locally generated,thereby reducing the refractive index.Under a constant laser power,the spatial distribution of mode inside the silicon microdisk is proportional to its wavelength shift and can be precisely identified by comparing it with numerical simulation.With the assistance of a galvanometer,imaging a mode profile only takes a few hundred milliseconds to a few seconds,orders of magnitude faster than previous reports.The impacts of slight fabrication deviations on spectra have also been identified.
文摘This paper investigates the use of artificial neural networks(ANNs)as a viable digital twin or alternative to the typical whispering gallery mode(WGM)optical sensors in engineering systems,especially in dynamic environments like robotics.Because of its fragility and limited endurance,the WGM sensor which is based on micro-optical resonators is inappropriate in these kinds of situations.In order to address these issues,the paper suggests an ANN that is specifically designed for the system and makes use of the WGM sensor’s high-quality factor(Q-factor).By extending the applicability and endurance to dynamic contexts and reducing fragility problems,the ANN seeks to give high-resolution measurement.In order to minimize post-processing requirements and maintain system robustness,the study goal is for the ANN to function as a representative predictor of the WGM sensor output.The GUCnoid 1.0 humanoid robot is used in the paper as an example to show how the WGM optical sensors may improve humanoid robot performance for a variety of applications.The results of the experiments demonstrate that the sensitivity,precision,and resolution of ANN outputs and actual WGM shifts are equivalent.As a consequence,current obstacles to the widespread use of high-precision sensing in the robotics industry are removed,and the potential of ANNs as virtual substitutes or the digital twin for genuine WGM sensors in robotics systems is validated.So,this paper can be very beneficial not only to the sensing technologies that are used in robotics,which are subjected to the dynamic environments,but also to the industrial automation and human-machine interface.
基金National Natural Science Foundation of China(62275088,62075075,U21A20511)Innovation Project of Optics Valley Laboratory(Grant No.OVL2021BG001)+1 种基金Research Grants Council,University Grants Committee of Hong Kong SAR under Grant PolyU15301022Knowledge Innovation Program of Wuhan-Basic Research 2023010201010049.
文摘The increasing amount of data exchange requires higher-capacity optical communication links.Mode division multiplexing(MDM)is considered as a promising technology to support the higher data throughput.In an MDM system,the mode generator and sorter are the backbone.However,most of the current schemes lack the programmability and universality,which makes the MDM link susceptible to the mode crosstalk and environmental disturbances.In this paper,we propose an intelligent multimode optical communication link using universal mode processing(generation and sorting)chips.The mode processor consists of a programmable 4×4 Mach Zehnder interferometer(MZI)network and can be intelligently configured to generate or sort both quasi linearly polarized(LP)modes and orbital angular momentum(OAM)modes in any desired routing state.We experimentally establish a chip-to-chip MDM communication system.The mode basis can be freely switched between four LP modes and four OAM modes.We also demonstrate the multimode optical communication capability at a data rate of 25 Gbit/s.The proposed scheme shows significant advantages in terms of universality,intelligence,programmability and resistance to mode crosstalk,environmental disturbances,and fabrication errors,demonstrating that the MZI-based reconfigurable mode processor chip has great potential in longdistance chip-to-chip multimode optical communication systems.
文摘Guided modes in a hollow optical fiber are investigated using both scalar approximation and exact vectorial analysis. Effective indices of modes are seen to exhibit "nearly degenerate" groups. Besides providing an insight of modal characteristics, the analysis would prove to be useful to define design parameters for realizing components based on these fibers, and to explore new possibilities.
基金National Natural Science Foundation of China(NSFC)(61575014)Natural Science Foundation of Beijing Municipality(4162038)
文摘A novel slotted optical microdisk resonator, which significantly enhances light–matter interaction and provides a promising approach for increasing the sensitivity of sensors, is theoretically and numerically investigated. In this slotted resonator, the mode splitting is generated due to reflection of the slot. Remarkably, effects of the slot width and angular position on the mode splitting are mainly studied. The results reveal that the mode splitting is a second function of the slot width, and the maximum mode splitting induced by the slot deformation is achieved with 2.7853 × 10~9Hz∕nm. Therefore, the slotted resonator is an excellent candidate for pressure and force sensing. Besides, the influence of the slot angular position on the mode splitting is a cosine curve with the highest sensitivity of 1.23 × 10^(11)Hz∕deg; thus, the optical characteristic demonstrates that the slotted resonator can be used for inertial measurements.
文摘A wavelength filter with simple structure using multimode waveguide is proposed. The device uses mode conversion by a grating structure fabricated simultaneously with the multimode waveguide.
文摘Overcoming the diffraction limit in optics is challenging and demands a profound understanding of light behavior under extreme confinement.The newly developed framework,termed singulonics,demonstrates the formation of sub-diffraction limit narwhal-shaped optical modes under specific conditions.Experimental implementation of this field confinement within a tiny sub-wavelength volume enables the acquisition of near-field super resolution images.
