Coherent beam combining(CBC) of fiber laser array is a promising technique to realize high output power while maintaining near diffraction-limited beam quality. To implement CBC, an appropriate phase control feedback ...Coherent beam combining(CBC) of fiber laser array is a promising technique to realize high output power while maintaining near diffraction-limited beam quality. To implement CBC, an appropriate phase control feedback structure should be established to realize phase-locking. In this paper, an innovative internal active phase control CBC fiber laser array based on photodetector array is proposed. The dynamic phase noises of the laser amplifiers are compensated before being emitted into free space. And the static phase difference compensation of emitting laser array is realized by interference measurement based on photodetector array. The principle of the technique is illustrated and corresponding simulations are carried out, and a CBC system with four laser channels is built to verify the technique. When the phase controllers are turned on, the phase deviation of the laser array is less than λ/20, and ~ 95% fringe contrast of the irradiation distribution is obtained. The technique proposed in this paper could provide a reference for the system design of a massive high-power CBC system.展开更多
In order to improve the bias stability of the micro-electro mechanical system（MEMS） gyroscope and reduce the impact on the bias from environmental temperature,a digital signal processing method is described for impr...In order to improve the bias stability of the micro-electro mechanical system（MEMS） gyroscope and reduce the impact on the bias from environmental temperature,a digital signal processing method is described for improving the accuracy of the drive phase in the gyroscope drive mode.Through the principle of bias signal generation,it can be concluded that the deviation of the drive phase is the main factor affecting the bias stability.To fulfill the purpose of precise drive phase control,a digital signal processing circuit based on the field-programmable gate array（FPGA） with the phase-lock closed-loop control method is described and a demodulation method for phase error suppression is given.Compared with the analog circuit,the bias drift is largely reduced in the new digital circuit and the bias stability is improved from 60 to 19 °/h.The new digital control method can greatly increase the drive phase accuracy,and thus improve the bias stability.展开更多
This paper investigates the control role of the relative phase between the probe and driving fields on the gain, dispersion and populations in an open A system with spontaneously generated coherence （SGC）. It shows ...This paper investigates the control role of the relative phase between the probe and driving fields on the gain, dispersion and populations in an open A system with spontaneously generated coherence （SGC）. It shows that by adjusting the value of the relative phase, a change from lasing with inversion to lasing without inversion can be realized; the values and frequency spectrum regions of the inversionless gain and dispersion can be obviously varied; high refractive index with zero absorption and electromagnetically induced transparency can be achieved. It is also found that when the driving field is resonant, the shapes of the dispersion and the gain curves versus the probe detuning are very similar if the relative phase of the dispersion lags π/2 than that of the gain, however for the off-resonant driving field the similarity will disappear; the gain, dispersion and populations are periodical functions of the relative phase, the modulation period is always 2π; the contribution of SGC to the inversionless gain and dispersion is much larger than that of the dynamically induced coherence.展开更多
A four-level quantum dot (QD) nanostructure interacting with four fields (two weak near-infrared (NIR) pulses and two control fields) forms the well-known double-cascade configuration.We investigate the cross-phase mo...A four-level quantum dot (QD) nanostructure interacting with four fields (two weak near-infrared (NIR) pulses and two control fields) forms the well-known double-cascade configuration.We investigate the cross-phase modulation (XPM) between the two NIR pulses.The results show,in such a closed-loop scheme,that the XPM can be greatly enhanced,while the linear absorption and two-photon absorption (gain) can be efficiently depressed by tuning the relative phase among the applied fields.This protocol may have potential applications in NIR all-optical switch design and quantum information processing with the solid-state materials.展开更多
We theoretically analyze the transient properties of a probe field absorption and dispersion in a coupled semiconductor double-quantum-dot nanostructure.We show that in the presence of the Gaussian laser beams,absorpt...We theoretically analyze the transient properties of a probe field absorption and dispersion in a coupled semiconductor double-quantum-dot nanostructure.We show that in the presence of the Gaussian laser beams,absorption and dispersion of the probe field can be dramatically influenced by the relative phase between applied fields and intensity of the Gaussian laser beams.Transient and steady-state behaviors of the probe field absorption and dispersion are discussed to estimate the required switching time.The estimated range is between 5-8 ps for subluminal to superluminal light propagation.展开更多
This paper theoretically investigates the coherent phase control in electron-argon scattering assisted by a bichro- matic laser field. The laser field is composed of a fundamental component and its second harmonic. Th...This paper theoretically investigates the coherent phase control in electron-argon scattering assisted by a bichro- matic laser field. The laser field is composed of a fundamental component and its second harmonic. The incoming and out going states of electron are described by the Volkov wave functions, and the electron-target interaction is treated as a screening potential. Numerical results for differential cross section of multiphoton processes vs the phase difference between the two components of laser field are discussed for several scattering angles and impact energies.展开更多
A novel scalable architecture for coherent beam combining with hybrid phase control involving passive phasing and active phasing in master oscillator-power amplifier configuration is presented. Wide-linewidth mutually...A novel scalable architecture for coherent beam combining with hybrid phase control involving passive phasing and active phasing in master oscillator-power amplifier configuration is presented. Wide-linewidth mutually injected passive phasing fibre laser arrays serve as master oscillators for the power amplifiers, and the active phasing using stochastic parallel gradient descent algorithm is induced. Wide-linewidth seed laser can suppress the stimulated Brillouin scattering effectively and improve the output power of the fibre laser amplifier, while hybrid phase control provides a robust way for in-phase mode coherent beam combining simultaneously. Experiment is performed by active phasing fibre laser amplifiers with passive phasing fibre ring laser array seed lasers. Power encircled in the main-lobe increases1.57 times and long-exposure fringe contrast is obtained to be 78% when the system evolves from passive phasing to hybrid phasing.展开更多
1T phase MoS_(2)(1T-MoS_(2)) is a promising substitute of platinum electrocatalyst for hydrogen evolution reaction(HER)due to its high intrinsic activity but suffering from thermodynamical instability.Although great e...1T phase MoS_(2)(1T-MoS_(2)) is a promising substitute of platinum electrocatalyst for hydrogen evolution reaction(HER)due to its high intrinsic activity but suffering from thermodynamical instability.Although great efforts have been made to synthesize 1T-MoS_(2) and enhance its stability,it remains a big challenge to realize the phase control and stabilization of 1T-MoS_(2).Herein,based on crystal field theory analysis,we propose a new solution by designing an electrocatalyst of 1T-MoS_(2) nanosheets anchoring on black TiO2-xnanotube arrays in-situ grown on Ti plate(1T-MoS_(2)/TiO_(2-x)@Ti).The black TiO_(2-x)substrate is expected to play as electron donors to increase the charge in Mo 4 d orbits of 1T-MoS_(2) and thus weaken the asymmetric occupation of electrons in the Mo 4 d orbits.Experimental results demonstrate that black TiO_(2-x)nanotubes shift electrons to MoS_(2) and induce MoS_(2) to generate more 1 T phase due to stabilizing the 1T-MoS_(2) nanosheets compared with a Ti substrate.Thus 1T-MoS_(2/)TiO_(2-x)@Ti shows much improved HER performance with a small Tafel slope of 42 m V dec^(-1) and excellent catalytic stability with negligible degradation for 24 h.Theoretical calculations confirm that the black TiO_(2-x)substrate can effectively stabilize metastable 1T-MoS_(2) due to electrons transferring from black TiO_(2-x)to Mo 4 d orbits.This work sheds light on the instability of 1T-MoS_(2) and provides an essential method to stabilize and efficiently utilize 1T-MoS_(2) for HER.展开更多
The design of phase control system in Shanghai Synchrotron Radiation Facility (SSRF) linac is presented in this paper. And digital phase detecting algorithm, the key for phase control system, is fully described. The t...The design of phase control system in Shanghai Synchrotron Radiation Facility (SSRF) linac is presented in this paper. And digital phase detecting algorithm, the key for phase control system, is fully described. The testing results for phase control system in 100MeV linac are discussed in detail.展开更多
The synthetic making test has been widely used in evaluating the break ability of high-voltage circuit breaker. However, the test research and application are still inadequate, especially in the condition of rated vol...The synthetic making test has been widely used in evaluating the break ability of high-voltage circuit breaker. However, the test research and application are still inadequate, especially in the condition of rated voltage. According to the realistic conditions of test stations in China, a control device based on pre-arcing current detection and phase control is proposed in this paper. A sample of the control device made up of DSP TMS320LF2407A is fabricated, in which the CPLD MAX7064 is used to transmit signals for EMC design. It can be applied in full voltage synthetic making test at a level of 126kV/63kA. The test results show that, it is accurate to control the making phase of the applied voltage, whether the closing is demanded at voltage peak or zero.展开更多
We propose an approach of long-term stabilization of optical fiber phase by controlling a piezo-based phase modulator and a Peltier component attached to the fiber via a phase-locked loop( PLL) circuit w ith dual prop...We propose an approach of long-term stabilization of optical fiber phase by controlling a piezo-based phase modulator and a Peltier component attached to the fiber via a phase-locked loop( PLL) circuit w ith dual proportional-integral- derivative( PID) adjustment. With this approach,we can suppress the fast disturbance and slow drifting of optical fiber to satisfy the requirements of optical phase long-term locking. In theory,a mathematical model of an optical fiber phase control system is established. The disturbance term induced by environment influence is considered into the PLL model. The monotonous and continuous changing environment disturbance w ill cause a steady-state error in this theory model. The experimental results accords w ell w ith the theory. The steady-state performance,adjusting time,and overshoot can be improved by using the dual PID control. As a result,the long-term,highly stable and low noise fiber phase locking is realized experimentally.展开更多
A novel technique to obtain injection locked oscillators phase tuning beyond 180° is demonstrated. The idea is to cascade injection locked oscillators together for phase change accumulation. A two stage injection...A novel technique to obtain injection locked oscillators phase tuning beyond 180° is demonstrated. The idea is to cascade injection locked oscillators together for phase change accumulation. A two stage injection locked oscillators can theoretically provide a maximum of 360?phase change within the locking range. This is particularly useful for phased array antenna applications.展开更多
The absorption–dispersion properties of a microwave-driven five-level atom embedded in an isotropic photonic bandgap(PBG) have been studied. Due to the singular density of modes(DOM) in the isotropic PBG and the dyna...The absorption–dispersion properties of a microwave-driven five-level atom embedded in an isotropic photonic bandgap(PBG) have been studied. Due to the singular density of modes(DOM) in the isotropic PBG and the dynamically coherence induced by the coupling fields, modified reservoir-induced transparency and quantum interference-induced transparency emerge simultaneously. Their interaction leads to ultra-narrow spectral structure. As a result of closed-loop configuration, these features can be manipulated by the amplitudes and relative phase of the coherently driven fields. The position and width of PBG also have an influence on the spectra. The theoretical studies can provide us with more efficient methods to control the atomic absorption–dispersion properties, which have applications in optical switching and slow light.展开更多
Machine learning has already shown promising potential in tiled-aperture coherent beam combining(CBC)to achieve versatile advanced applications.By sampling the spatially separated laser array before the combiner and d...Machine learning has already shown promising potential in tiled-aperture coherent beam combining(CBC)to achieve versatile advanced applications.By sampling the spatially separated laser array before the combiner and detuning the optical path delays,deep learning techniques are incorporated into filled-aperture CBC to achieve single-step phase control.The neural network is trained with far-field diffractive patterns at the defocus plane to establish one-to-one phase-intensity mapping,and the phase prediction accuracy is significantly enhanced thanks to the strategies of sin-cos loss function and two-layer output of the phase vector that are adopted to resolve the phase discontinuity issue.The results indicate that the trained network can predict phases with improved accuracy,and phase-locking of nine-channel filled-aperture CBC has been numerically demonstrated in a single step with a residual phase ofλ/70.To the best of our knowledge,this is the first time that machine learning has been made feasible in filled-aperture CBC laser systems.展开更多
Improved controllability and energy density of ignition agents are of great significance for the devel-opment of energetic composite materials.In this study,droplet microfluidics and emulsification tech-niques were co...Improved controllability and energy density of ignition agents are of great significance for the devel-opment of energetic composite materials.In this study,droplet microfluidics and emulsification tech-niques were combined to prepare HNS/CL-20 composite microspheres with polyglycidyl azide polymer(GAP)as the binder.The influence of binder content on the morphology of microspheres was investi-gated,and the microspheres were characterized and tested for particle size,crystal structure,thermal decomposition,dispersibility,mechanical sensitivity,combustion behavior and detonation performance.The results showed that microspheres prepared with a binder content of 3%had higher sphericity and particle size uniformity.The microspheres retained the crystal structure of both HNS and CL-20(ε-type).Compared with raw HNS,the microspheres had higher apparent activation energy,better safety per-formance,and good dispersibility.The ignition experiments and detonation performance tests show that HNS/CL-20 composite microspheres have excellent ignition performance,obvious combustion flame,and significant energy release effects,which are expected to achieve high energy and high-speed response of the igniter,thus improving the ignition reliability in special environments or systems.展开更多
Aqueous iron-ion batteries are regarded as one of the most promising candidates for grid applications owing to their low cost,high theoretical capacity,and excellent stability of iron in aqueous electrolytes.However,t...Aqueous iron-ion batteries are regarded as one of the most promising candidates for grid applications owing to their low cost,high theoretical capacity,and excellent stability of iron in aqueous electrolytes.However,the slow Fe(de)insertion caused by the high polarity of Fe^(2+)makes it difficult to match suitable cathode materials.Herein,defect-rich MoS_(2)with abundant 1T phase is synthesized and successfully applied in aqueous iron-ion batteries.Benefit from abundant active sites generated by the heteroatom incorporation and S vacancy,as well as the highly conductive 1T phase,it can deliver a specific capacity of 123 mAh/g at a current density of 100mA/g,and demonstrates an impressive capacity retention of 88%after 600 cycles at 200mA/g.This work presents a novel pathway for the advancement of cathode materials for aqueous iron-ion batteries.展开更多
We incorporate deep learning(DL)into tiled aperture coherent beam combining(CBC)systems for the first time,to the best of our knowledge.By using a well-trained convolutional neural network DL model,which has been cons...We incorporate deep learning(DL)into tiled aperture coherent beam combining(CBC)systems for the first time,to the best of our knowledge.By using a well-trained convolutional neural network DL model,which has been constructed at a non-focal-plane to avoid the data collision problem,the relative phase of each beamlet could be accurately estimated,and then the phase error in the CBC system could be compensated directly by a servo phase control system.The feasibility and extensibility of the phase control method have been demonstrated by simulating the coherent combining of different hexagonal arrays.This DL-based phase control method offers a new way of eliminating dynamic phase noise in tiled aperture CBC systems,and it could provide a valuable reference on alleviating the long-standing problem that the phase control bandwidth decreases as the number of array elements increases.展开更多
An optical phase locking method based on direct phase control is proposed.The core of this method is to synchronize the carrier by directly changing the phase of the local beam.The corresponding experimental device an...An optical phase locking method based on direct phase control is proposed.The core of this method is to synchronize the carrier by directly changing the phase of the local beam.The corresponding experimental device and the supporting algorithm were configured to verify the feasibility of this method.Phase locking can be completed without cycle skipping,and the acquisition time is 530 ns.Without an optical preamplifier,a sensitivity of-34.4 d Bm is obtained,and the bit error rate is 10^(-9) for 2.5 Gbit/s binary phase-shift keying modulation.The measured standard deviation of the phase error is 5.2805°.展开更多
A general method to realize arbitrary dual-band independent phase control is proposed and demonstrated in this paper.A double-layered C-shape reflective meta-atom is designed to realize independent phase control with ...A general method to realize arbitrary dual-band independent phase control is proposed and demonstrated in this paper.A double-layered C-shape reflective meta-atom is designed to realize independent phase control with high efficiency.As a proof of concept,we propose two functional metasurfaces in the microwave region;the first metasurface performs beam steering in different directions,and the second metasurface generates achromatic beam steering at two distinct frequencies.Both simulation and measurement results agree well with the theoretical pre-setting.The maximum measured efficiency is 88.7%and 92.3%at 6.8 GHz and 8.0 GHz,respectively,for one metasurface,and 91.0%and 89.8%at 6.9 GHz and8.6 GHz,respectively,for the other.展开更多
We experimentally demonstrated a cascaded internal phase control technique.A laser array with 12 channels was divided into three sub-arrays and a stage array,and phases of the sub-arrays and the stage array were locke...We experimentally demonstrated a cascaded internal phase control technique.A laser array with 12 channels was divided into three sub-arrays and a stage array,and phases of the sub-arrays and the stage array were locked by four phase controllers based on the stochastic parallel gradient descent(SPGD)algorithm,respectively.In this way,the phases of the whole array were locked,and the visibility of the interference pattern of the whole emitted laser array in the far field was∼93%.In addition,the technique has the advantage of element expanding and can be further used in the high-power coherent beam combination(CBC)system due to its compact spatial structure.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.62275272)the Training Program for Excellent Young Innovators of Changsha(Grant No.KQ2305025)。
文摘Coherent beam combining(CBC) of fiber laser array is a promising technique to realize high output power while maintaining near diffraction-limited beam quality. To implement CBC, an appropriate phase control feedback structure should be established to realize phase-locking. In this paper, an innovative internal active phase control CBC fiber laser array based on photodetector array is proposed. The dynamic phase noises of the laser amplifiers are compensated before being emitted into free space. And the static phase difference compensation of emitting laser array is realized by interference measurement based on photodetector array. The principle of the technique is illustrated and corresponding simulations are carried out, and a CBC system with four laser channels is built to verify the technique. When the phase controllers are turned on, the phase deviation of the laser array is less than λ/20, and ~ 95% fringe contrast of the irradiation distribution is obtained. The technique proposed in this paper could provide a reference for the system design of a massive high-power CBC system.
基金The National Natural Science Foundation of China (No.60974116)the Research Fund of Aeronautics Science (No. 20090869007)Specialized Research Fund for the Doctoral Program of Higher Education(No. 200802861063)
文摘In order to improve the bias stability of the micro-electro mechanical system（MEMS） gyroscope and reduce the impact on the bias from environmental temperature,a digital signal processing method is described for improving the accuracy of the drive phase in the gyroscope drive mode.Through the principle of bias signal generation,it can be concluded that the deviation of the drive phase is the main factor affecting the bias stability.To fulfill the purpose of precise drive phase control,a digital signal processing circuit based on the field-programmable gate array（FPGA） with the phase-lock closed-loop control method is described and a demodulation method for phase error suppression is given.Compared with the analog circuit,the bias drift is largely reduced in the new digital circuit and the bias stability is improved from 60 to 19 °/h.The new digital control method can greatly increase the drive phase accuracy,and thus improve the bias stability.
文摘This paper investigates the control role of the relative phase between the probe and driving fields on the gain, dispersion and populations in an open A system with spontaneously generated coherence （SGC）. It shows that by adjusting the value of the relative phase, a change from lasing with inversion to lasing without inversion can be realized; the values and frequency spectrum regions of the inversionless gain and dispersion can be obviously varied; high refractive index with zero absorption and electromagnetically induced transparency can be achieved. It is also found that when the driving field is resonant, the shapes of the dispersion and the gain curves versus the probe detuning are very similar if the relative phase of the dispersion lags π/2 than that of the gain, however for the off-resonant driving field the similarity will disappear; the gain, dispersion and populations are periodical functions of the relative phase, the modulation period is always 2π; the contribution of SGC to the inversionless gain and dispersion is much larger than that of the dynamically induced coherence.
基金Supported in part by the National Natural Science Foundation of China Grant Nos.10975054,60925021,11104210,and 61108016the Department of Education of China Grant No.200804870051
文摘A four-level quantum dot (QD) nanostructure interacting with four fields (two weak near-infrared (NIR) pulses and two control fields) forms the well-known double-cascade configuration.We investigate the cross-phase modulation (XPM) between the two NIR pulses.The results show,in such a closed-loop scheme,that the XPM can be greatly enhanced,while the linear absorption and two-photon absorption (gain) can be efficiently depressed by tuning the relative phase among the applied fields.This protocol may have potential applications in NIR all-optical switch design and quantum information processing with the solid-state materials.
文摘We theoretically analyze the transient properties of a probe field absorption and dispersion in a coupled semiconductor double-quantum-dot nanostructure.We show that in the presence of the Gaussian laser beams,absorption and dispersion of the probe field can be dramatically influenced by the relative phase between applied fields and intensity of the Gaussian laser beams.Transient and steady-state behaviors of the probe field absorption and dispersion are discussed to estimate the required switching time.The estimated range is between 5-8 ps for subluminal to superluminal light propagation.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10874169 and 10674125)the National Basic Research Program of China (Grant No. 2007CB925200)S.-M. Li is grateful to Deutscher Akademischer Austauschdienst and Deutsche Forschungsgemeinschaft for financial support during his stay in Germany
文摘This paper theoretically investigates the coherent phase control in electron-argon scattering assisted by a bichro- matic laser field. The laser field is composed of a fundamental component and its second harmonic. The incoming and out going states of electron are described by the Volkov wave functions, and the electron-target interaction is treated as a screening potential. Numerical results for differential cross section of multiphoton processes vs the phase difference between the two components of laser field are discussed for several scattering angles and impact energies.
基金supported by the Innovation Foundation for Graduates in National University of Defense Technology,China (GrantNo.B080702)
文摘A novel scalable architecture for coherent beam combining with hybrid phase control involving passive phasing and active phasing in master oscillator-power amplifier configuration is presented. Wide-linewidth mutually injected passive phasing fibre laser arrays serve as master oscillators for the power amplifiers, and the active phasing using stochastic parallel gradient descent algorithm is induced. Wide-linewidth seed laser can suppress the stimulated Brillouin scattering effectively and improve the output power of the fibre laser amplifier, while hybrid phase control provides a robust way for in-phase mode coherent beam combining simultaneously. Experiment is performed by active phasing fibre laser amplifiers with passive phasing fibre ring laser array seed lasers. Power encircled in the main-lobe increases1.57 times and long-exposure fringe contrast is obtained to be 78% when the system evolves from passive phasing to hybrid phasing.
基金supported by the New Zealand China Doctoral Research Scholarship (Grant no. 201706080124)support from the China Scholarships Council (CSC) for his study at the University of Auckland
文摘1T phase MoS_(2)(1T-MoS_(2)) is a promising substitute of platinum electrocatalyst for hydrogen evolution reaction(HER)due to its high intrinsic activity but suffering from thermodynamical instability.Although great efforts have been made to synthesize 1T-MoS_(2) and enhance its stability,it remains a big challenge to realize the phase control and stabilization of 1T-MoS_(2).Herein,based on crystal field theory analysis,we propose a new solution by designing an electrocatalyst of 1T-MoS_(2) nanosheets anchoring on black TiO2-xnanotube arrays in-situ grown on Ti plate(1T-MoS_(2)/TiO_(2-x)@Ti).The black TiO_(2-x)substrate is expected to play as electron donors to increase the charge in Mo 4 d orbits of 1T-MoS_(2) and thus weaken the asymmetric occupation of electrons in the Mo 4 d orbits.Experimental results demonstrate that black TiO_(2-x)nanotubes shift electrons to MoS_(2) and induce MoS_(2) to generate more 1 T phase due to stabilizing the 1T-MoS_(2) nanosheets compared with a Ti substrate.Thus 1T-MoS_(2/)TiO_(2-x)@Ti shows much improved HER performance with a small Tafel slope of 42 m V dec^(-1) and excellent catalytic stability with negligible degradation for 24 h.Theoretical calculations confirm that the black TiO_(2-x)substrate can effectively stabilize metastable 1T-MoS_(2) due to electrons transferring from black TiO_(2-x)to Mo 4 d orbits.This work sheds light on the instability of 1T-MoS_(2) and provides an essential method to stabilize and efficiently utilize 1T-MoS_(2) for HER.
文摘The design of phase control system in Shanghai Synchrotron Radiation Facility (SSRF) linac is presented in this paper. And digital phase detecting algorithm, the key for phase control system, is fully described. The testing results for phase control system in 100MeV linac are discussed in detail.
文摘The synthetic making test has been widely used in evaluating the break ability of high-voltage circuit breaker. However, the test research and application are still inadequate, especially in the condition of rated voltage. According to the realistic conditions of test stations in China, a control device based on pre-arcing current detection and phase control is proposed in this paper. A sample of the control device made up of DSP TMS320LF2407A is fabricated, in which the CPLD MAX7064 is used to transmit signals for EMC design. It can be applied in full voltage synthetic making test at a level of 126kV/63kA. The test results show that, it is accurate to control the making phase of the applied voltage, whether the closing is demanded at voltage peak or zero.
基金supported by the National Natural Science Foundation of China(Grant No.91436103)Research Programme of National University of Defense Technology(Grant No.JC15-02-03)
文摘We propose an approach of long-term stabilization of optical fiber phase by controlling a piezo-based phase modulator and a Peltier component attached to the fiber via a phase-locked loop( PLL) circuit w ith dual proportional-integral- derivative( PID) adjustment. With this approach,we can suppress the fast disturbance and slow drifting of optical fiber to satisfy the requirements of optical phase long-term locking. In theory,a mathematical model of an optical fiber phase control system is established. The disturbance term induced by environment influence is considered into the PLL model. The monotonous and continuous changing environment disturbance w ill cause a steady-state error in this theory model. The experimental results accords w ell w ith the theory. The steady-state performance,adjusting time,and overshoot can be improved by using the dual PID control. As a result,the long-term,highly stable and low noise fiber phase locking is realized experimentally.
文摘A novel technique to obtain injection locked oscillators phase tuning beyond 180° is demonstrated. The idea is to cascade injection locked oscillators together for phase change accumulation. A two stage injection locked oscillators can theoretically provide a maximum of 360?phase change within the locking range. This is particularly useful for phased array antenna applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11447232 and 11204367)
文摘The absorption–dispersion properties of a microwave-driven five-level atom embedded in an isotropic photonic bandgap(PBG) have been studied. Due to the singular density of modes(DOM) in the isotropic PBG and the dynamically coherence induced by the coupling fields, modified reservoir-induced transparency and quantum interference-induced transparency emerge simultaneously. Their interaction leads to ultra-narrow spectral structure. As a result of closed-loop configuration, these features can be manipulated by the amplitudes and relative phase of the coherently driven fields. The position and width of PBG also have an influence on the spectra. The theoretical studies can provide us with more efficient methods to control the atomic absorption–dispersion properties, which have applications in optical switching and slow light.
文摘Machine learning has already shown promising potential in tiled-aperture coherent beam combining(CBC)to achieve versatile advanced applications.By sampling the spatially separated laser array before the combiner and detuning the optical path delays,deep learning techniques are incorporated into filled-aperture CBC to achieve single-step phase control.The neural network is trained with far-field diffractive patterns at the defocus plane to establish one-to-one phase-intensity mapping,and the phase prediction accuracy is significantly enhanced thanks to the strategies of sin-cos loss function and two-layer output of the phase vector that are adopted to resolve the phase discontinuity issue.The results indicate that the trained network can predict phases with improved accuracy,and phase-locking of nine-channel filled-aperture CBC has been numerically demonstrated in a single step with a residual phase ofλ/70.To the best of our knowledge,this is the first time that machine learning has been made feasible in filled-aperture CBC laser systems.
基金supported by National Natural Science Foundation of China(grant No.22005275).
文摘Improved controllability and energy density of ignition agents are of great significance for the devel-opment of energetic composite materials.In this study,droplet microfluidics and emulsification tech-niques were combined to prepare HNS/CL-20 composite microspheres with polyglycidyl azide polymer(GAP)as the binder.The influence of binder content on the morphology of microspheres was investi-gated,and the microspheres were characterized and tested for particle size,crystal structure,thermal decomposition,dispersibility,mechanical sensitivity,combustion behavior and detonation performance.The results showed that microspheres prepared with a binder content of 3%had higher sphericity and particle size uniformity.The microspheres retained the crystal structure of both HNS and CL-20(ε-type).Compared with raw HNS,the microspheres had higher apparent activation energy,better safety per-formance,and good dispersibility.The ignition experiments and detonation performance tests show that HNS/CL-20 composite microspheres have excellent ignition performance,obvious combustion flame,and significant energy release effects,which are expected to achieve high energy and high-speed response of the igniter,thus improving the ignition reliability in special environments or systems.
基金supported by Shenzhen Fundamental Research Program(No.GXWD20201231165807007-20200802205241003).
文摘Aqueous iron-ion batteries are regarded as one of the most promising candidates for grid applications owing to their low cost,high theoretical capacity,and excellent stability of iron in aqueous electrolytes.However,the slow Fe(de)insertion caused by the high polarity of Fe^(2+)makes it difficult to match suitable cathode materials.Herein,defect-rich MoS_(2)with abundant 1T phase is synthesized and successfully applied in aqueous iron-ion batteries.Benefit from abundant active sites generated by the heteroatom incorporation and S vacancy,as well as the highly conductive 1T phase,it can deliver a specific capacity of 123 mAh/g at a current density of 100mA/g,and demonstrates an impressive capacity retention of 88%after 600 cycles at 200mA/g.This work presents a novel pathway for the advancement of cathode materials for aqueous iron-ion batteries.
基金supported by the National Natural Science Foundation of China(Nos.61705264 and 61705265)the Natural Science Foundation of Hunan Province,China(No.2019JJ10005).
文摘We incorporate deep learning(DL)into tiled aperture coherent beam combining(CBC)systems for the first time,to the best of our knowledge.By using a well-trained convolutional neural network DL model,which has been constructed at a non-focal-plane to avoid the data collision problem,the relative phase of each beamlet could be accurately estimated,and then the phase error in the CBC system could be compensated directly by a servo phase control system.The feasibility and extensibility of the phase control method have been demonstrated by simulating the coherent combining of different hexagonal arrays.This DL-based phase control method offers a new way of eliminating dynamic phase noise in tiled aperture CBC systems,and it could provide a valuable reference on alleviating the long-standing problem that the phase control bandwidth decreases as the number of array elements increases.
基金supported by the National Key R&D Program of China(No.2020YFB0408302)Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB43030400)+1 种基金National Natural Science Foundation of China(No.91938302)Key Project of Chinese Academy of Sciences(No.ZDRWKT-2019-1-01-0302)。
文摘An optical phase locking method based on direct phase control is proposed.The core of this method is to synchronize the carrier by directly changing the phase of the local beam.The corresponding experimental device and the supporting algorithm were configured to verify the feasibility of this method.Phase locking can be completed without cycle skipping,and the acquisition time is 530 ns.Without an optical preamplifier,a sensitivity of-34.4 d Bm is obtained,and the bit error rate is 10^(-9) for 2.5 Gbit/s binary phase-shift keying modulation.The measured standard deviation of the phase error is 5.2805°.
基金the support from National Natural Science Foundation of China(No.61771172)Open Project of Guangxi Key Laboratory of Wireless Wideband Communication and Signal ProcessingNatural Science Foundation of Heilongjiang Province(No.YQ2020F002)。
文摘A general method to realize arbitrary dual-band independent phase control is proposed and demonstrated in this paper.A double-layered C-shape reflective meta-atom is designed to realize independent phase control with high efficiency.As a proof of concept,we propose two functional metasurfaces in the microwave region;the first metasurface performs beam steering in different directions,and the second metasurface generates achromatic beam steering at two distinct frequencies.Both simulation and measurement results agree well with the theoretical pre-setting.The maximum measured efficiency is 88.7%and 92.3%at 6.8 GHz and 8.0 GHz,respectively,for one metasurface,and 91.0%and 89.8%at 6.9 GHz and8.6 GHz,respectively,for the other.
基金supported by the National Natural Science Foundation of China(Nos.62275272 and 62075242)the Natural Science Foundation of Hunan Province,China(No.2019JJ10005)+1 种基金the Training Program for Excellent Young Innovators of Changsha(No.kq2206003)the Postgraduate Scientific Research Innovation Project of Hunan Province(No.QL20220013).
文摘We experimentally demonstrated a cascaded internal phase control technique.A laser array with 12 channels was divided into three sub-arrays and a stage array,and phases of the sub-arrays and the stage array were locked by four phase controllers based on the stochastic parallel gradient descent(SPGD)algorithm,respectively.In this way,the phases of the whole array were locked,and the visibility of the interference pattern of the whole emitted laser array in the far field was∼93%.In addition,the technique has the advantage of element expanding and can be further used in the high-power coherent beam combination(CBC)system due to its compact spatial structure.
