A polarization-maintaining （PM） fiber Mach-Zehnder （MZ） interferometer has been established to measure the EO effect of very thin film materials with optical anisotropy. Unlike a common MZ interferometer, all the ...A polarization-maintaining （PM） fiber Mach-Zehnder （MZ） interferometer has been established to measure the EO effect of very thin film materials with optical anisotropy. Unlike a common MZ interferometer, all the components are connected via polarization-maintaining fibers. At the same time, a polarized DFB laser with a maximum power output of 10mW is adopted as the light source to induce a large extinction ratio. Here,we take it to determine the electro-optical coefficients of a very thin superlattice structure with GaAs, KTP, and GaN as comparative samples. The measured EO coefficients show good comparability with the others.展开更多
We investigate the tunable bistable behavior of a hybrid nano-electro-optomechanical system(NEOMS) composed of S-shaped in the presence of two-level atoms, trapped inside a Fabry–Pérot cavity, and driven by a st...We investigate the tunable bistable behavior of a hybrid nano-electro-optomechanical system(NEOMS) composed of S-shaped in the presence of two-level atoms, trapped inside a Fabry–Pérot cavity, and driven by a strong driving field and a weak probe field. The bistable behavior of the steady-state photon number and the mechanical steady-state positions are discussed. Further, we tune bistability by tuning all the coupling frequencies involved in the system and amplitude of the driving field. The present study provides the possibility of realization of a controllable optical switch depending on atom-field coupling, optomechanical coupling, electrostatic Coulomb coupling, and threshold power. In addition, we discuss that the non-linear effect of the hybrid NEOMS generates the four-wave mixing(FWM) process. Moreover, we show that the FWM process can be suppressed by the atom-field detuning and cavity-field detuning, which exhibits low photon transmission.展开更多
Liquid crystals （LCs） and polymers are extensively used in various electro-optical applications. In this paper, normal mode polymer stabilized cholesteric LC film is prepared and studied. The effects of chiral dopan...Liquid crystals （LCs） and polymers are extensively used in various electro-optical applications. In this paper, normal mode polymer stabilized cholesteric LC film is prepared and studied. The effects of chiral dopant and monomer concentrations on the electro-optical properties, such as contrast ratio, driving voltage, hysteresis width and response time, are investigated. The reasons of electro-optical properties influenced by the concentrations of the materials are discussed. Through the proper material recipe, the electro-optical properties of polymer stabilized cholesteric LC film can be optimized.展开更多
The novel BaTiO3/BiFeO3/TiO2 multilayer heterojunction is prepared on a fluorine-doped tinoxide(FTO) substrate by the sol–gel method. The results indicate that the Pt/Ba TiO3/BiFeO3/TiO2/FTO heterojunction exhibits s...The novel BaTiO3/BiFeO3/TiO2 multilayer heterojunction is prepared on a fluorine-doped tinoxide(FTO) substrate by the sol–gel method. The results indicate that the Pt/Ba TiO3/BiFeO3/TiO2/FTO heterojunction exhibits stable bipolar resistive switching characteristic, good retention performance, and reversal characteristic. Under different pulse voltages and light fields, four stable resistance states can also be realized. The analysis shows that the main conduction mechanism of the resistive switching characteristic of the heterojunction is space charge limited current(SCLC) effect. After the comprehensive analysis of the band diagram and the P–E ferroelectric property of the multilayer heterojunction, we can deduce that the SCLC is formed by the effect of the oxygen vacancy which is controlled by ferroelectric polarizationmodulated change of interfacial barrier. And the effective photo-generated carrier also plays a regulatory role in resistance state(RS), which is formed by the double ferroelectric layer Ba TiO3/BiFeO3 under different light fields. This research is of potential application values for developing the multi-state non-volatile resistance random access memory(RRAM) devices based on ferroelectric materials.展开更多
We report the specification of a compact and stable side diode-pumped Q-switched pulsed Nd：YAG laser. We ex- perimentally study and compare the performance of the pulsed Nd：YAG laser in the free-running and Q-switch...We report the specification of a compact and stable side diode-pumped Q-switched pulsed Nd：YAG laser. We ex- perimentally study and compare the performance of the pulsed Nd：YAG laser in the free-running and Q-switched modes at different pulse repetition rates from 1 Hz to 100 Hz. The laser output energy is stabilized by using a special configu- ration of the optical resonator. In this laser, an unsymmetrical concave-concave resonator is used and this structure helps the mode volume to be nearly fixed when the pulse repetition rate is increased. According to the experimental results in the Q-switched operation, the laser output energy is nearly constant around 70 mJ with an FWHM pulse width of 7 ns at 100 Hz. The optical-to-optical conversion efficiency in the Q-switched regime is 17.5%.展开更多
Transparent relaxor ferroelectric ceramics of the system lanthanum modified lead magnesium niobate have been investigated for a variety of electro-optic properties could make these materials alternatives to (Pb,La)(Zr...Transparent relaxor ferroelectric ceramics of the system lanthanum modified lead magnesium niobate have been investigated for a variety of electro-optic properties could make these materials alternatives to (Pb,La)(Zr,Ti)O3. However, a study that relates the properties in function stoichiometric formula, it has not been analyzed heretofore. Therefore, in this work the effect of A-site substitution of La+3 in the characterization microstructural, structural, optical and electro-optical on (1-x)[Pb(1-3/2y)Lay(Mg1/3Nb2/3)O3]-xPbTiO3 and (1-z)[(1-x)Pb(Mg1/3Nb2/3)O3+xPbTiO3]+zLa2O3 has been performed. It was observed that the properties according to the stoichiometric formula and the PT had a maximum whose behavior was related to the addition of lanthanum in each stoichiometries.展开更多
In this work, we studied the electro-optical properties of high-aligned carbon nanotubes deposited at room temperature. For this, we used the High Density Plasma Chemical Vapor Deposition system. This system uses a ne...In this work, we studied the electro-optical properties of high-aligned carbon nanotubes deposited at room temperature. For this, we used the High Density Plasma Chemical Vapor Deposition system. This system uses a new concept of plasma generation: a planar coil is coupled to an RF system for plasma generation. This was used together with an electrostatic shield, for plasma densification, thereby obtaining high-density plasmas. The carbon nanotubes were deposited using pure methane plasmas. Three methods were used for the surface modification of the sample: reference substrate (silicon wafer only submitted to a chemical cleaning), silicon wafer with surface roughness generated by plasma etching, silicon wafer with a thin iron film and silicon wafer with diamond nano powder used as precursor materials. For each kind of silicon wafer surface, the carbon nanotubes were deposited with two different deposition times (two and three hours). The carbon nanotubes structural characteristics were analyzed by Atomic Force Microscope and Scanning Electronic Microscope. The carbon nanotubes electrical characteristics were observed by Raman Spectroscopy and the carbon nanotubes electro-optical properties were analyzed by current vs voltage electrical measurements and photo-luminescence spectroscopy measurements. The photoelectric effect in the carbon nanotubes were determined by photo-induced current measurements. In this work, we obtained carbon nanotubes with semiconductor properties and carbon nanotubes with metallic properties. The electro-optical effects depend strongly on the substrate preparation and the deposition parameters of the carbon nanotubes. The carbon nanotubes are high aligned and show singular properties that can be used for many applications.展开更多
Liquid crystal（LC） compound with isothiocyanate and naphthyl group is an attractive high birefringence LC material,and can be used in optical devices. In this paper, the electro-optical properties of a series of thi...Liquid crystal（LC） compound with isothiocyanate and naphthyl group is an attractive high birefringence LC material,and can be used in optical devices. In this paper, the electro-optical properties of a series of this type of LC compounds were investigated. The melting points and enthalpy values of these LC compounds were higher than those of corresponding compounds with the phenyl group. These compounds exhibited high birefringence with a maximum value of 0.66. Fluorine substitution in the molecular almost does not affect the birefringence value. When these LC compounds with the naphthyl group were dissolved in a commercial LC mixture, the electro-optical properties depending on temperature were investigated. In the low-temperature region, LC mixtures with the naphthyl-group LC compounds exhibited higher viscosity than pure commercial LCs. In the high-temperature region, viscosity values very closely approached each other. When response performance was investigated, figure-of-merit（FoM） values were measured. The Fo M values of LC mixtures containing LC compounds with naphthyl group were lower than those of reference benzene LCs in the low-temperature region. However, in the high-temperature region, the results were reversed. These isothiocyanate LC compounds with naphthyl group can be applied in special fast-response LC device, particularly the ones used under high-temperature conditions.展开更多
The electro-optical payloads on mobile platforms generally suffer undesirable vibrations generated by maneuvers and turbulence.These vibrations are in six degrees of freedom and cause line-of-sight jitters,resulting i...The electro-optical payloads on mobile platforms generally suffer undesirable vibrations generated by maneuvers and turbulence.These vibrations are in six degrees of freedom and cause line-of-sight jitters,resulting in image blurring and loss of tracking accuracy.In this paper,a Hexapod Vibration Isolation System(HVIS)is proposed and optimized to solve this problem.The optimization aims to centralize and minimize the natural frequencies of HVIS,for expanding the vibration isolation bandwidth and improving the vibration isolation in the higher frequency band.Considering that the design space for HVIS is limited and interfered with the frames of the mobile platform,a non-collision algorithm is proposed and applied in the optimization to obtain the feasible optimal design.The optimization result shows that the natural frequency bandwidth has been reduced by 42.9%,and the maximum natural frequency is reduced by 30.2%.The prototypes of initial and optimal designs are manufactured and tested.Both simulated and experimental results demonstrate the validity of the optimization,and the optimal design provides a maximum of 15 dB more isolation in rotation direction than the initial design.展开更多
Fluorinated smectic liquid crystals each with a biphenyl benzoate rigid core are investigated. Molecular structures of the studied compounds have difference only in fluorine position and the length of the carbon chain...Fluorinated smectic liquid crystals each with a biphenyl benzoate rigid core are investigated. Molecular structures of the studied compounds have difference only in fluorine position and the length of the carbon chain. Dielectric relaxation study and electro-optical measurements are carried out with the classical SSFLC geometry. The field-induced phase transitions are studied and the（E,T） phase diagram is established.展开更多
A bunch arrival-time monitor(BAM) based on an electro-optical intensity modulation scheme is currently under development at Shanghai Soft X-ray Free-Electron Laser to meet the high-resolution requirements for bunch st...A bunch arrival-time monitor(BAM) based on an electro-optical intensity modulation scheme is currently under development at Shanghai Soft X-ray Free-Electron Laser to meet the high-resolution requirements for bunch stability. The BAM uses a radio frequency signal generated by a pickup cavity to modulate the reference laser pulses in an electro-optical intensity modulator(EOM), and the bunch arrival-time information is derived from the amplitude change of the laser pulse after laser pulse modulation.EOM is a key optical component in the BAM system.Through the basic principle analysis of BAM, many parameters of the EOM are observed to affect the measurement resolution of the BAM system. Therefore, a systematic analysis of the EOM is crucial. In this paper, we present two schemes to compare and analyze an EOM and provide a reference for selecting a new version of the EOM.展开更多
The liquid crystal composite materials consist of microdroplets of liquid crystals which are spontaneously formed in a matrix of a polymer at the time of its polymerization. The director configuration in liquid crysta...The liquid crystal composite materials consist of microdroplets of liquid crystals which are spontaneously formed in a matrix of a polymer at the time of its polymerization. The director configuration in liquid crystal droplets, the model of orientation of droplets, and the contrast ratios of a cell are investigated. Droplet size, spacing and distribution are readily controlled in these materials to allow optimization of displays based upon electrically controlled light scattering from the liquid crystal droplets. Preliminary experimental and theoretical studies of the light scattering and electro-optic response of new material show that these materials can offer new features suitable for large area displays and light valves.展开更多
Electro-Optic Sampling(EOS)detection technique has been widely used in terahertz science and tech⁃nology,and it also can measure the field time waveform of the few-cycle laser pulse.Its frequency response and band lim...Electro-Optic Sampling(EOS)detection technique has been widely used in terahertz science and tech⁃nology,and it also can measure the field time waveform of the few-cycle laser pulse.Its frequency response and band limitation are determined directly by the electro-optic crystal and duration of the probe laser pulse.Here,we investigate the performance of the EOS with thin GaSe crystal in the measurement of the mid-infrared few-cycle la⁃ser pulse.The shift of the central frequency and change of the bandwidth induced by the EOS detection are calcu⁃lated,and then the pulse distortions induced in this detection process are discussed.It is found that this technique produces a red-shift of the central frequency and narrowing of the bandwidth.These changings decrease when the laser wavelength increases from 2μm to 10μm.This work can help to estimate the performance of the EOS de⁃tection technique in the mid-infrared band and offer a reference for the related experiment as well.展开更多
The unique arrangement of panels and folds in origami structures provides distinct mechanical properties,such as the ability to achieve multiple stable states,reconfigure shapes,and adjust performance.However,combinin...The unique arrangement of panels and folds in origami structures provides distinct mechanical properties,such as the ability to achieve multiple stable states,reconfigure shapes,and adjust performance.However,combining movement and control functions into a simple yet efficient origami-based system remains a challenge.This study introduces a practical and efficient bistable origami mechanism,realized through lightweight and tailored designs in two bio-inspired applications.The mechanism is constructed from two thin materials:a PET sheet with precisely cut flexible hinges and a pre-tensioned elastic band.Its mechanical behavior is studied using nonlinear spring models.These components can be rearranged to create new bistable structures,enabling the integration of movement and partial control features.Inspired by natural systems,the mechanism is applied to two examples:a passive origami gripper that can quickly and precisely grasp moving objects in less than 100 ms,and an active magnetic-driven fish tail capable of high-speed swimming in multiple modes,reaching a maximum straight-line speed of 3.35 body lengths per second and a turning speed of 2.3 radians per second.This bistable origami mechanism highlights its potential for flexible design and high performance,offering useful insights for developing origami-based robotic systems.展开更多
Pneumatic soft robots have undergone significant advancements in recent years.However,the majority of robot motion control still relies on electronic computers to regulate the valves and air pumps.Despite the potentia...Pneumatic soft robots have undergone significant advancements in recent years.However,the majority of robot motion control still relies on electronic computers to regulate the valves and air pumps.Despite the potential reduction in controller dependency by utilizing soft pneumatic oscillators,challenges such as low flow rates,complex manufacturing processes,and lack of adjustment ability persist.Inspired by the geckos'spine,we propose a Spinal Bistable Oscillator(SBO)that operates without discrete components or electronic control hardware,achieving stable oscillatory motion under constant air pressure.This oscillator employs a soft control valve and lagging pin,which can switch the direction of airflow conduction based on the oscillation angle of the spine.Different types of actuators can be controlled using a series connection.In this study,the effective working range of the soft control valve,influence of the spring pretension force on the torque during oscillation,and effect of different throttle tube lengths on the oscillation frequency were investigated.Furthermore,a self-crawling robot was developed.Experimental results demonstrate that the robot can crawl at speeds ranging from 3.6 to 5.7 mm/s(or 3.1 to 4.9 body length/min)and overcome its own gravity(with a weight of 165 g)to climb vertically.The SBO proposed in this study exhibits characteristics of lightweight,low cost,high oscillation torque,and tunable frequency.It holds promise for application in joint control of future pneumatic soft robots.展开更多
Mechanical metamaterials are artificial materials that control their macroscopic properties using repetitive units rather than chemical constituents.Through rational design and spatial arrangement of the unit cells,me...Mechanical metamaterials are artificial materials that control their macroscopic properties using repetitive units rather than chemical constituents.Through rational design and spatial arrangement of the unit cells,mechanical metamaterials can realize a range of counterintuitive properties on a larger scale.In this work,a type of mechanical metamaterial unit cell is proposed,exhibiting both compression-twist coupling behavior and bistability that can be programmed.The design involves linking two cylindrical frames with topology-designed inclined beams.Under uniaxial loading,the structure undergoes a compression-twist deformation,along with buckling at two joints of the inclined beams.Through a rational design of the unit's geometric parameters,the structure can retain its deformed state once the applied displacement surpasses a specified threshold,showing a programmed bistable characteristic.We investigated the influence of the involved parameters on the mechanical response of the unit cells numerically,which agrees well with our experimental results.Since the inclined beams dominate the elastic deformation of unit cells,the two cylindrical frames are almost independent of the bistable response and can therefore be designed in any shape for various arrangements of unit cells in multi-dimensional space.展开更多
The fluorine-containing organic polymer was synthesized from 3, 3＇, 4, 4＇-Bisphenyltetracarboxylic （BPDA）, and 2,2-Bis （3-amino-4-hydroxyyphenyl） hexafluoropropane （6FHP）. It is a first-step preparation of a p...The fluorine-containing organic polymer was synthesized from 3, 3＇, 4, 4＇-Bisphenyltetracarboxylic （BPDA）, and 2,2-Bis （3-amino-4-hydroxyyphenyl） hexafluoropropane （6FHP）. It is a first-step preparation of a preimided hydroxy-containing polyimide, followed by the covalent bonding of an active chromophore, dispersed red 19 （DR19）, onto the backbone of the polyimide via the Mitsunobu reaction. The nonlinear optical （NLO） containing polyimide was synthesized. The differential scanning calorimeter （DSC）and thermal gravimetric analysis （TGA） exhibited Tg and the temperature Tg at which 5 % mass losses occurring of polymer were 248 and 309 ℃, respectively. A reflective electro-optic （EO） modulator using this polymer was fabricated. The optical nonlinearities were determined to be d33 = 5. 209×10^-9 esu （poling voltage of 3.6 kV, 205 ℃） and d33 =7. 418×10^-9esu （poling voltage of 3. 8 kV, 210 ℃） by the second harmonic generation method in in-situ condition at a fundamental wavelength of 1 064 nm. The EO coefficients 733 of the polymer layer in the EO modulator were determined to be 2. 182 pm/V （poling voltage of 3.6 kV, 205 ℃） and 3. 107 pm/V （poling voltage of 3.8 kV, 210 ℃） at 1064 nm by an attenuated-total-reflection （ATR） method.展开更多
We propose and analyze a novel Si-based electro-optic modulator with an improved metal-oxide-semiconductor （MOS） capacitor configuration integrated into silicon-on-insulator （SOl）. Three gate-oxide layers embedded...We propose and analyze a novel Si-based electro-optic modulator with an improved metal-oxide-semiconductor （MOS） capacitor configuration integrated into silicon-on-insulator （SOl）. Three gate-oxide layers embedded in the silicon waveguide constitute a triple MOS capacitor structure, which boosts the modulation efficiency compared with a single MOS capacitor. The simulation results demonstrate that the Vπ Lπ product is 2. 4V · cm. The rise time and fall time of the proposed device are calculated to be 80 and 40ps from the transient response curve, respectively,indicating a bandwidth of 8GHz. The phase shift efficiency and bandwidth can be enhanced by rib width scaling.展开更多
The AgTCNQ thin-film was prepared by vacuum vapor co-deposition and characterized by infrared spectral analysis,and then a uniform AgTCNQ （TCNQ-- 7,7,8,8-tetracyanoquinodimethane） thin-film layer was sandwiched in a...The AgTCNQ thin-film was prepared by vacuum vapor co-deposition and characterized by infrared spectral analysis,and then a uniform AgTCNQ （TCNQ-- 7,7,8,8-tetracyanoquinodimethane） thin-film layer was sandwiched in a Ti/AgTCNQ/Ati crossbar structure array as organic bistable devices （OBD）.A reversible and reproducible memory switching property,caused by intermolecular charge transfer （CT） in the AgTCNQ thin-film, was observed in the organic bista- ble devices. The positive threshold voltage from the high impedance state to the low impedance was about 3.8-5V, with the reverse phenomenon occurring at a negative voltage of - 3.5- - 4. 4V,lower than that with a CuTCNQ active layer. The crossbar array of OBDs with AgTCNQ is promising for nonvolatile organic memory applications.展开更多
文摘A polarization-maintaining （PM） fiber Mach-Zehnder （MZ） interferometer has been established to measure the EO effect of very thin film materials with optical anisotropy. Unlike a common MZ interferometer, all the components are connected via polarization-maintaining fibers. At the same time, a polarized DFB laser with a maximum power output of 10mW is adopted as the light source to induce a large extinction ratio. Here,we take it to determine the electro-optical coefficients of a very thin superlattice structure with GaAs, KTP, and GaN as comparative samples. The measured EO coefficients show good comparability with the others.
文摘We investigate the tunable bistable behavior of a hybrid nano-electro-optomechanical system(NEOMS) composed of S-shaped in the presence of two-level atoms, trapped inside a Fabry–Pérot cavity, and driven by a strong driving field and a weak probe field. The bistable behavior of the steady-state photon number and the mechanical steady-state positions are discussed. Further, we tune bistability by tuning all the coupling frequencies involved in the system and amplitude of the driving field. The present study provides the possibility of realization of a controllable optical switch depending on atom-field coupling, optomechanical coupling, electrostatic Coulomb coupling, and threshold power. In addition, we discuss that the non-linear effect of the hybrid NEOMS generates the four-wave mixing(FWM) process. Moreover, we show that the FWM process can be suppressed by the atom-field detuning and cavity-field detuning, which exhibits low photon transmission.
基金Project partially supported by the National Natural Science Foundation of China （Grant Nos. 60736042, 60578035 and 50703039） and the Science Foundation of Jilin Province of China （Grant Nos. 20050520 and 20050321-2）.
文摘Liquid crystals （LCs） and polymers are extensively used in various electro-optical applications. In this paper, normal mode polymer stabilized cholesteric LC film is prepared and studied. The effects of chiral dopant and monomer concentrations on the electro-optical properties, such as contrast ratio, driving voltage, hysteresis width and response time, are investigated. The reasons of electro-optical properties influenced by the concentrations of the materials are discussed. Through the proper material recipe, the electro-optical properties of polymer stabilized cholesteric LC film can be optimized.
基金Project supported by the Scientific Research Program of Hunan Provincial Education Department,China(Grant No.18C0232)the International Cooperative Extension Program of Changsha University of Science and Technology,China(Grant No.2019IC35)
文摘The novel BaTiO3/BiFeO3/TiO2 multilayer heterojunction is prepared on a fluorine-doped tinoxide(FTO) substrate by the sol–gel method. The results indicate that the Pt/Ba TiO3/BiFeO3/TiO2/FTO heterojunction exhibits stable bipolar resistive switching characteristic, good retention performance, and reversal characteristic. Under different pulse voltages and light fields, four stable resistance states can also be realized. The analysis shows that the main conduction mechanism of the resistive switching characteristic of the heterojunction is space charge limited current(SCLC) effect. After the comprehensive analysis of the band diagram and the P–E ferroelectric property of the multilayer heterojunction, we can deduce that the SCLC is formed by the effect of the oxygen vacancy which is controlled by ferroelectric polarizationmodulated change of interfacial barrier. And the effective photo-generated carrier also plays a regulatory role in resistance state(RS), which is formed by the double ferroelectric layer Ba TiO3/BiFeO3 under different light fields. This research is of potential application values for developing the multi-state non-volatile resistance random access memory(RRAM) devices based on ferroelectric materials.
文摘We report the specification of a compact and stable side diode-pumped Q-switched pulsed Nd：YAG laser. We ex- perimentally study and compare the performance of the pulsed Nd：YAG laser in the free-running and Q-switched modes at different pulse repetition rates from 1 Hz to 100 Hz. The laser output energy is stabilized by using a special configu- ration of the optical resonator. In this laser, an unsymmetrical concave-concave resonator is used and this structure helps the mode volume to be nearly fixed when the pulse repetition rate is increased. According to the experimental results in the Q-switched operation, the laser output energy is nearly constant around 70 mJ with an FWHM pulse width of 7 ns at 100 Hz. The optical-to-optical conversion efficiency in the Q-switched regime is 17.5%.
基金CAPES,FAPESP and CNPq for the financial support.
文摘Transparent relaxor ferroelectric ceramics of the system lanthanum modified lead magnesium niobate have been investigated for a variety of electro-optic properties could make these materials alternatives to (Pb,La)(Zr,Ti)O3. However, a study that relates the properties in function stoichiometric formula, it has not been analyzed heretofore. Therefore, in this work the effect of A-site substitution of La+3 in the characterization microstructural, structural, optical and electro-optical on (1-x)[Pb(1-3/2y)Lay(Mg1/3Nb2/3)O3]-xPbTiO3 and (1-z)[(1-x)Pb(Mg1/3Nb2/3)O3+xPbTiO3]+zLa2O3 has been performed. It was observed that the properties according to the stoichiometric formula and the PT had a maximum whose behavior was related to the addition of lanthanum in each stoichiometries.
文摘In this work, we studied the electro-optical properties of high-aligned carbon nanotubes deposited at room temperature. For this, we used the High Density Plasma Chemical Vapor Deposition system. This system uses a new concept of plasma generation: a planar coil is coupled to an RF system for plasma generation. This was used together with an electrostatic shield, for plasma densification, thereby obtaining high-density plasmas. The carbon nanotubes were deposited using pure methane plasmas. Three methods were used for the surface modification of the sample: reference substrate (silicon wafer only submitted to a chemical cleaning), silicon wafer with surface roughness generated by plasma etching, silicon wafer with a thin iron film and silicon wafer with diamond nano powder used as precursor materials. For each kind of silicon wafer surface, the carbon nanotubes were deposited with two different deposition times (two and three hours). The carbon nanotubes structural characteristics were analyzed by Atomic Force Microscope and Scanning Electronic Microscope. The carbon nanotubes electrical characteristics were observed by Raman Spectroscopy and the carbon nanotubes electro-optical properties were analyzed by current vs voltage electrical measurements and photo-luminescence spectroscopy measurements. The photoelectric effect in the carbon nanotubes were determined by photo-induced current measurements. In this work, we obtained carbon nanotubes with semiconductor properties and carbon nanotubes with metallic properties. The electro-optical effects depend strongly on the substrate preparation and the deposition parameters of the carbon nanotubes. The carbon nanotubes are high aligned and show singular properties that can be used for many applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61378075,61377032,11604327,and 61475152)the Science Foundation of State Key Laboratory of Applied Optics,China
文摘Liquid crystal（LC） compound with isothiocyanate and naphthyl group is an attractive high birefringence LC material,and can be used in optical devices. In this paper, the electro-optical properties of a series of this type of LC compounds were investigated. The melting points and enthalpy values of these LC compounds were higher than those of corresponding compounds with the phenyl group. These compounds exhibited high birefringence with a maximum value of 0.66. Fluorine substitution in the molecular almost does not affect the birefringence value. When these LC compounds with the naphthyl group were dissolved in a commercial LC mixture, the electro-optical properties depending on temperature were investigated. In the low-temperature region, LC mixtures with the naphthyl-group LC compounds exhibited higher viscosity than pure commercial LCs. In the high-temperature region, viscosity values very closely approached each other. When response performance was investigated, figure-of-merit（FoM） values were measured. The Fo M values of LC mixtures containing LC compounds with naphthyl group were lower than those of reference benzene LCs in the low-temperature region. However, in the high-temperature region, the results were reversed. These isothiocyanate LC compounds with naphthyl group can be applied in special fast-response LC device, particularly the ones used under high-temperature conditions.
基金supported by the National Key R&D Program of China(No.2021YFA1003503)。
文摘The electro-optical payloads on mobile platforms generally suffer undesirable vibrations generated by maneuvers and turbulence.These vibrations are in six degrees of freedom and cause line-of-sight jitters,resulting in image blurring and loss of tracking accuracy.In this paper,a Hexapod Vibration Isolation System(HVIS)is proposed and optimized to solve this problem.The optimization aims to centralize and minimize the natural frequencies of HVIS,for expanding the vibration isolation bandwidth and improving the vibration isolation in the higher frequency band.Considering that the design space for HVIS is limited and interfered with the frames of the mobile platform,a non-collision algorithm is proposed and applied in the optimization to obtain the feasible optimal design.The optimization result shows that the natural frequency bandwidth has been reduced by 42.9%,and the maximum natural frequency is reduced by 30.2%.The prototypes of initial and optimal designs are manufactured and tested.Both simulated and experimental results demonstrate the validity of the optimization,and the optimal design provides a maximum of 15 dB more isolation in rotation direction than the initial design.
文摘Fluorinated smectic liquid crystals each with a biphenyl benzoate rigid core are investigated. Molecular structures of the studied compounds have difference only in fluorine position and the length of the carbon chain. Dielectric relaxation study and electro-optical measurements are carried out with the classical SSFLC geometry. The field-induced phase transitions are studied and the（E,T） phase diagram is established.
基金supported by the National Key R&D Plan(No.2016YFA0401900)
文摘A bunch arrival-time monitor(BAM) based on an electro-optical intensity modulation scheme is currently under development at Shanghai Soft X-ray Free-Electron Laser to meet the high-resolution requirements for bunch stability. The BAM uses a radio frequency signal generated by a pickup cavity to modulate the reference laser pulses in an electro-optical intensity modulator(EOM), and the bunch arrival-time information is derived from the amplitude change of the laser pulse after laser pulse modulation.EOM is a key optical component in the BAM system.Through the basic principle analysis of BAM, many parameters of the EOM are observed to affect the measurement resolution of the BAM system. Therefore, a systematic analysis of the EOM is crucial. In this paper, we present two schemes to compare and analyze an EOM and provide a reference for selecting a new version of the EOM.
文摘The liquid crystal composite materials consist of microdroplets of liquid crystals which are spontaneously formed in a matrix of a polymer at the time of its polymerization. The director configuration in liquid crystal droplets, the model of orientation of droplets, and the contrast ratios of a cell are investigated. Droplet size, spacing and distribution are readily controlled in these materials to allow optimization of displays based upon electrically controlled light scattering from the liquid crystal droplets. Preliminary experimental and theoretical studies of the light scattering and electro-optic response of new material show that these materials can offer new features suitable for large area displays and light valves.
基金Supported by the National Natural Science Foundation of China(12064028)Jiangxi Provincial Natural Science Foundation(20232BAB201045).
文摘Electro-Optic Sampling(EOS)detection technique has been widely used in terahertz science and tech⁃nology,and it also can measure the field time waveform of the few-cycle laser pulse.Its frequency response and band limitation are determined directly by the electro-optic crystal and duration of the probe laser pulse.Here,we investigate the performance of the EOS with thin GaSe crystal in the measurement of the mid-infrared few-cycle la⁃ser pulse.The shift of the central frequency and change of the bandwidth induced by the EOS detection are calcu⁃lated,and then the pulse distortions induced in this detection process are discussed.It is found that this technique produces a red-shift of the central frequency and narrowing of the bandwidth.These changings decrease when the laser wavelength increases from 2μm to 10μm.This work can help to estimate the performance of the EOS de⁃tection technique in the mid-infrared band and offer a reference for the related experiment as well.
基金supported in part by the Fundamental Research Funds for the Central Universities under Grant CSA-TS202404in part by the National Natural Science Foundation of China under Grant 12172226.
文摘The unique arrangement of panels and folds in origami structures provides distinct mechanical properties,such as the ability to achieve multiple stable states,reconfigure shapes,and adjust performance.However,combining movement and control functions into a simple yet efficient origami-based system remains a challenge.This study introduces a practical and efficient bistable origami mechanism,realized through lightweight and tailored designs in two bio-inspired applications.The mechanism is constructed from two thin materials:a PET sheet with precisely cut flexible hinges and a pre-tensioned elastic band.Its mechanical behavior is studied using nonlinear spring models.These components can be rearranged to create new bistable structures,enabling the integration of movement and partial control features.Inspired by natural systems,the mechanism is applied to two examples:a passive origami gripper that can quickly and precisely grasp moving objects in less than 100 ms,and an active magnetic-driven fish tail capable of high-speed swimming in multiple modes,reaching a maximum straight-line speed of 3.35 body lengths per second and a turning speed of 2.3 radians per second.This bistable origami mechanism highlights its potential for flexible design and high performance,offering useful insights for developing origami-based robotic systems.
基金supported by Sichuan Provincial Department of Science and Technology Key Research and Development Program in High-Tech Fields(2022YFG0240).
文摘Pneumatic soft robots have undergone significant advancements in recent years.However,the majority of robot motion control still relies on electronic computers to regulate the valves and air pumps.Despite the potential reduction in controller dependency by utilizing soft pneumatic oscillators,challenges such as low flow rates,complex manufacturing processes,and lack of adjustment ability persist.Inspired by the geckos'spine,we propose a Spinal Bistable Oscillator(SBO)that operates without discrete components or electronic control hardware,achieving stable oscillatory motion under constant air pressure.This oscillator employs a soft control valve and lagging pin,which can switch the direction of airflow conduction based on the oscillation angle of the spine.Different types of actuators can be controlled using a series connection.In this study,the effective working range of the soft control valve,influence of the spring pretension force on the torque during oscillation,and effect of different throttle tube lengths on the oscillation frequency were investigated.Furthermore,a self-crawling robot was developed.Experimental results demonstrate that the robot can crawl at speeds ranging from 3.6 to 5.7 mm/s(or 3.1 to 4.9 body length/min)and overcome its own gravity(with a weight of 165 g)to climb vertically.The SBO proposed in this study exhibits characteristics of lightweight,low cost,high oscillation torque,and tunable frequency.It holds promise for application in joint control of future pneumatic soft robots.
基金supported by the National Natural Science Foundation of China(Grant Numbers:12125205,12321002,12072316,12132014)the Zhejiang Provincial Natural Science Foundation of China(LD22A020001).
文摘Mechanical metamaterials are artificial materials that control their macroscopic properties using repetitive units rather than chemical constituents.Through rational design and spatial arrangement of the unit cells,mechanical metamaterials can realize a range of counterintuitive properties on a larger scale.In this work,a type of mechanical metamaterial unit cell is proposed,exhibiting both compression-twist coupling behavior and bistability that can be programmed.The design involves linking two cylindrical frames with topology-designed inclined beams.Under uniaxial loading,the structure undergoes a compression-twist deformation,along with buckling at two joints of the inclined beams.Through a rational design of the unit's geometric parameters,the structure can retain its deformed state once the applied displacement surpasses a specified threshold,showing a programmed bistable characteristic.We investigated the influence of the involved parameters on the mechanical response of the unit cells numerically,which agrees well with our experimental results.Since the inclined beams dominate the elastic deformation of unit cells,the two cylindrical frames are almost independent of the bistable response and can therefore be designed in any shape for various arrangements of unit cells in multi-dimensional space.
基金Jiangsu Planned Projects for Postdoctoral ResearchFunds(No0602037B)the Natural Science Foundation of Higher Edu-cation Institutions of Jiangsu Province (No05KJB150016)+1 种基金the Nation-al Natural Science Foundation of China (No50377005)the Fund ofJiangsu University (No06JDG015)
文摘The fluorine-containing organic polymer was synthesized from 3, 3＇, 4, 4＇-Bisphenyltetracarboxylic （BPDA）, and 2,2-Bis （3-amino-4-hydroxyyphenyl） hexafluoropropane （6FHP）. It is a first-step preparation of a preimided hydroxy-containing polyimide, followed by the covalent bonding of an active chromophore, dispersed red 19 （DR19）, onto the backbone of the polyimide via the Mitsunobu reaction. The nonlinear optical （NLO） containing polyimide was synthesized. The differential scanning calorimeter （DSC）and thermal gravimetric analysis （TGA） exhibited Tg and the temperature Tg at which 5 % mass losses occurring of polymer were 248 and 309 ℃, respectively. A reflective electro-optic （EO） modulator using this polymer was fabricated. The optical nonlinearities were determined to be d33 = 5. 209×10^-9 esu （poling voltage of 3.6 kV, 205 ℃） and d33 =7. 418×10^-9esu （poling voltage of 3. 8 kV, 210 ℃） by the second harmonic generation method in in-situ condition at a fundamental wavelength of 1 064 nm. The EO coefficients 733 of the polymer layer in the EO modulator were determined to be 2. 182 pm/V （poling voltage of 3.6 kV, 205 ℃） and 3. 107 pm/V （poling voltage of 3.8 kV, 210 ℃） at 1064 nm by an attenuated-total-reflection （ATR） method.
文摘We propose and analyze a novel Si-based electro-optic modulator with an improved metal-oxide-semiconductor （MOS） capacitor configuration integrated into silicon-on-insulator （SOl）. Three gate-oxide layers embedded in the silicon waveguide constitute a triple MOS capacitor structure, which boosts the modulation efficiency compared with a single MOS capacitor. The simulation results demonstrate that the Vπ Lπ product is 2. 4V · cm. The rise time and fall time of the proposed device are calculated to be 80 and 40ps from the transient response curve, respectively,indicating a bandwidth of 8GHz. The phase shift efficiency and bandwidth can be enhanced by rib width scaling.
文摘The AgTCNQ thin-film was prepared by vacuum vapor co-deposition and characterized by infrared spectral analysis,and then a uniform AgTCNQ （TCNQ-- 7,7,8,8-tetracyanoquinodimethane） thin-film layer was sandwiched in a Ti/AgTCNQ/Ati crossbar structure array as organic bistable devices （OBD）.A reversible and reproducible memory switching property,caused by intermolecular charge transfer （CT） in the AgTCNQ thin-film, was observed in the organic bista- ble devices. The positive threshold voltage from the high impedance state to the low impedance was about 3.8-5V, with the reverse phenomenon occurring at a negative voltage of - 3.5- - 4. 4V,lower than that with a CuTCNQ active layer. The crossbar array of OBDs with AgTCNQ is promising for nonvolatile organic memory applications.
