In this paper, a novel method of a subwavelength binary simple periodic rectangular structure is presented to realize even beam splitting by combining the rigorous couple-wave analysis with the genetic algorithm. Seve...In this paper, a novel method of a subwavelength binary simple periodic rectangular structure is presented to realize even beam splitting by combining the rigorous couple-wave analysis with the genetic algorithm. Several even splitters in the terahertz region were designed and one of the silicon-based beam splitters designed to separate one incident beam into four emergent beams has total efficiency up to 92.23 %. Zero-order diffraction efficiency was reduced to less than 0.192 % and the error of uniformity decreased to 6.51 9 10-6. These results break the limitation of even beam splitting based on the traditional scalar theory. In addition, the effects of the incident angle, wavelength, as well as the polarizing angle on the diffraction efficiency and uniformity were also investigated.展开更多
In turbomachinery,strong secondary flow can produce significant losses of total pressure near the endwall and reduce the efficiency of the considered turbomachine.In this study,splitters located at different positions...In turbomachinery,strong secondary flow can produce significant losses of total pressure near the endwall and reduce the efficiency of the considered turbomachine.In this study,splitters located at different positions with respect to the main blade have been used to reduce such losses and improve the efficiency of the outlet guide vane(OGV).Three different relative positions have been considered assuming a NACA 65-010 profile for both the main blade and the splitter.The numerical results indicate that splitters can effectively reduce the total pressure loss by suppressing the secondary flow around the main blade,but the splitters themselves also produce flow losses,which are caused by flow separation effects.展开更多
In this paper, we construct photon-added f-deformed coherent states (PAf-DCSs) for nonlinear bosonic fields by discussing Klauder's minimal set of conditions required to obtain coherent states. Using this set of no...In this paper, we construct photon-added f-deformed coherent states (PAf-DCSs) for nonlinear bosonic fields by discussing Klauder's minimal set of conditions required to obtain coherent states. Using this set of nonlinear states, we propose a very useful scheme for generating the maximal amount of entanglement via unitary beam splitters for different strength regimes of the input field α, deformation q and excitation number m. Therefore, the possibility to create highly entangled states and to control the entanglement is proposed. Moreover, the condition for a maximal and separable output beam state is obtained. Finally, we examine the statistical properties of the PAf-DCSs through the Mandel parameter and exploit a connection between this quantity and the behavior variation of the output state entanglement. Our result may open new perspectives in different tasks of quantum information processing.展开更多
The production of maxima and minima by the superposition of two or more light signals provides fundamental support for the wave nature of light. This result is based on the study of wave interference phenomena which r...The production of maxima and minima by the superposition of two or more light signals provides fundamental support for the wave nature of light. This result is based on the study of wave interference phenomena which remains the only approach to explain the production of those maxima and minima. In a system that is prepared to work with only one photon at a time, any detector can signal only one or zero. In 1986, a rigorously controlled experiment was designed by Grangier, G. Roger, and A. Aspect, [Europhys Lett. 1(4), p. 173, 1986] that guaranteed a single-photon beam. The explanation of the experimental results implied the interference of the wave function of a single-photon with itself. Thus, the explanation of interference that is accepted for an ensemble of photons was assumed to be valid for a single photon. In this study, we prepare a Mach-Zehnder interferometer using the same type of beam splitters used by Grangier et al. to test the assumption mentioned above. Our results allow us to explain the results of Grangier et al. because of the interaction between light and the beam splitters. Our results also verify that their wave interpretation of the results is not valid. Here, we present the essential findings of the extensive experimental evidence that supports our ideas.展开更多
Separating lights into different, paths according to the polarization states while keeping their respective path's polarizations with high purification is keen for polarization multiplex in optical communications....Separating lights into different, paths according to the polarization states while keeping their respective path's polarizations with high purification is keen for polarization multiplex in optical communications. Metallic nanowire gratings with multi-slits in a period are proposed to achieve polarized beam splitters (PBSs) in reflection and diffraction. The setting of multi-slits largely reduces the reflection of photons with a transverse magnetific field via the plasmonic waveguiding effect, which leads to highly polarized output lights with extinction ratio larger than 20 dB in each channel. The proposed reflection/diffraction PBSs enrich the approaches to control the polarization states with the advantages of wide incident angles and flexible beam splitting angles.展开更多
Two types of 1×2 multi-mode interference (MMI) splitters with splitting ratios of 85:15 and 72:28 are designed. On the basis of a numerical simulation, an optimal length of the MMI section is obtained. Subseq...Two types of 1×2 multi-mode interference (MMI) splitters with splitting ratios of 85:15 and 72:28 are designed. On the basis of a numerical simulation, an optimal length of the MMI section is obtained. Subsequently, the devices are fabricated and tested. The footprints of the rectangular MMI regions are only 3×18.2 and 3×14.3 (#m). The minimum excess losses are 1.4 and 1.1 dB. The results of the test on the splitting ratios are consistent with designed values. The devices can be applied in ultra-compact photonic integrated circuits to realize the "tap" function.展开更多
The soft X-ray interferometry is completed by the Mach-Zehnder interferometer using a soft X-ray laser, and it is also an important method to measure the electron densities of a laser-produced plasma near the critical...The soft X-ray interferometry is completed by the Mach-Zehnder interferometer using a soft X-ray laser, and it is also an important method to measure the electron densities of a laser-produced plasma near the critical surface. It is apparently demonstrated in this paper that the incident angle of each optical element in the soft X-ray Mach- Zehnder interferometer should be near normal incidence based on the polarized characteristics of the soft X-ray mul-tilayers, and the product of reflectivity and transmission of the beam splitter should be taken as a standard of design according to the structure of the soft X-ray Mach-Zehnder interferometer. The beam splitters used in the soft X-ray interferometry at 13.9 nm are fabricated using the ion beam sputtering. The figure error of the beam splitter has reached the nanometer magnitude, in which the product of reflectiv-ity and transmission of the beam splitter is more than 1.6%.展开更多
Beam splitters play a crucial role in a wide range of optical systems.A typical beam splitter consists of several transport channels,and an input beam from one channel is split into multiple output beams coupled into ...Beam splitters play a crucial role in a wide range of optical systems.A typical beam splitter consists of several transport channels,and an input beam from one channel is split into multiple output beams coupled into other channels.For traditional beam splitters,their transportation channels(either in free space or waveguides)are reciprocal,being sensitive to various perturbations caused by defects and obstacles.展开更多
A novel polarization beam splitter(PBS)based on dual-core photonic crystal fiber(DC-PCF)is proposed in this work.The proposed DC-PCF PBS contains two kinds of lattices and three kinds of air holes to form the asymmetr...A novel polarization beam splitter(PBS)based on dual-core photonic crystal fiber(DC-PCF)is proposed in this work.The proposed DC-PCF PBS contains two kinds of lattices and three kinds of air holes to form the asymmetrical elliptic dual-core structure.By using the full-vector finite element method,the propagation characteristics of the proposed DC-PCF PBS are investigated.The simulation results show that the bandwidth of the proposed DC-PCF PBS can reach to 340 nm,which covers the S+C+L+U communication bands,the shortest splitting length is 1.97 mm,and the maximum extinction ratio appears near wavelength 1550 nm.Moreover,the insertion loss of the proposed DC-PCF PBS is very low.It is believed that the proposed DC-PCF PBS has important applications in the field of all-optical communication and network.展开更多
Polarizing beam splitter has rather significant applications in polarization diversity circuits and polarization multiplexing systems.In this paper,we present an asymmetric polarizing beam splitter utilizing hybrid pl...Polarizing beam splitter has rather significant applications in polarization diversity circuits and polarization multiplexing systems.In this paper,we present an asymmetric polarizing beam splitter utilizing hybrid plasmonic waveguide.The special hybrid structure with a hybrid waveguide and a dielectric waveguide can limit the energy of TE and TM modes to a different layer.Therefore,we can achieve beam splitting by adjusting the corresponding parameters of the two waveguides.First,we studied the influences of different structure parameters on the real part of the effective mode refractive index of the two waveguides,and obtained a set of parameters that satisfy the condition of strong coupling of TM mode and weak coupling of TE mode.Then,the performance of our proposed polarizing beam splitter is evaluated numerically.The length of the coupling section is only 4.1μm,and the propagation loss of TM and TE modes is 0.0025 d B/μm and 0.0031 d B/μm respectively.Additionally,the extinction ratios of TM and TE modes are 10.62 d B and 12.55 d B,respectively.Particularly,the proposed device has excellent wavelength insensitivity.Over the entire C-band,the fluctuation of the whole normalized output power is less than 0.03.In short,our proposed asymmetric polarizing beam splitter features ultra-compactness,low propagation loss,and broad bandwidth,which would provide promising applications in polarization multiplexing system and polarization diversity circuits relevant to optical interconnection.展开更多
An ultra-broadband polarization splitter based on graphene layer-filled dual-core photonic crystal fiber (GDC-PCF) that can work in a wavelength range from 1120 nm to 1730 nm is proposed in this paper. Through optim...An ultra-broadband polarization splitter based on graphene layer-filled dual-core photonic crystal fiber (GDC-PCF) that can work in a wavelength range from 1120 nm to 1730 nm is proposed in this paper. Through optimizing fiber configuration, the polarization splitter has an extinction ratio of-56.3 dB at 1.55 μm with a fiber length of 4.8 mm. Compared with the photonic crystal fiber reported splitters, to our knowledge, the GDC-PCF splitter with the extinction ratio below-20 dB has a super wide bandwidth of 610 nm. Due to the excellent splitting characteristics, the GDC-PCF will be used in coherent optical communication systems in a wavelength range from infrared to mid-infraed.展开更多
A novel optimal design of sub-wavelength metal rectangular gratings for the polarizing beam splitter (PBS) is proposed. The method is based on effective medium theory and the method of designing single layer antiref...A novel optimal design of sub-wavelength metal rectangular gratings for the polarizing beam splitter (PBS) is proposed. The method is based on effective medium theory and the method of designing single layer antireflection coating. The polarization performance of PBS is discussed by rigorous couple-wave analysis (RCWA) method at a wavelength of 1550 nm. The result shows that sub-wavelength metal rectangular grating is characterized by a high reflectivity, like metal films for TE polarization, and high transmissivity, like dielectric films for TM polarization. The optimal design accords well with the results simulated by RCWA method.展开更多
We fabricated a new type of two-dimensional photonic crystal slab filter. The resonant cavities were directly put into the waveguide arms. The optical transmissions of the filters were measured and the results show th...We fabricated a new type of two-dimensional photonic crystal slab filter. The resonant cavities were directly put into the waveguide arms. The optical transmissions of the filters were measured and the results show that the optimized two-channel filters give good intensity distribution at the output ports of the waveguide. A minimum wavelength spacing of 5 nm of the filter outputs is realized by accurately controlling the size of the resonant cavities.展开更多
Cavitation will reduce the turbine performance and even damage the turbine components.To verify the effects of splitter blades on improving the cavitation performance,the cavitation flow inside a Francis turbine runne...Cavitation will reduce the turbine performance and even damage the turbine components.To verify the effects of splitter blades on improving the cavitation performance,the cavitation flow inside a Francis turbine runner with splitter blades was numerically simulated by using the Singhal cavitation model and the standard k-ε turbulence model.The distributions of static pressure and gas volume fractions on the surface of the runner blades were predicated under different conditions,and the cavitation in the flow field of the runner was analyzed.The results show that the static pressure and gas volume fractions are more uniformly distributed on the short blades than those on the long blades in Francis turbines with splitter blades,and there is almost no cavitation on the short blades;their distributions are more uniform under small flow conditions than those under large flow conditions;and large gas volume fractions are concentrated at the outlet tip near the band on the suction side of the long blade.The installation of splitter blades can improve the cavitation performance of conventional Francis turbines.展开更多
Analysis on the inner flow field of a centrifugal pump impeller with splitter blades is carfled out by numerical simulation. Based on this analysis, the principle of increasing pump head and efficiency are discussed. ...Analysis on the inner flow field of a centrifugal pump impeller with splitter blades is carfled out by numerical simulation. Based on this analysis, the principle of increasing pump head and efficiency are discussed. New results are obtained from the analysis of turbulence kinetic energy and relative velocity distribution: Firstly, unreasonable length or deviation design of the splitter blades may cause great turbulent fluctuation in impeller channel, which has a great effect on the stability of impeller outlet flow; Secondly, it is found that the occurrence of flow separation can be decreased or delayed with splitter blades from the analysis of blade loading; Thirdly, the effect of splitter blades on reforming the structure of "jet-wake" is explained from the relative velocity distribution at different flow cross-sections, which shows the flow process in the impeller. The inner flow analysis verifies the results of performance tests results and the PIV test.展开更多
We have proposed a novel kind of photonic crystal fiber which contains two asymmetric cores. The bireti'ingence and the dispersion are numerically analyzed based on finite element method when the size of the air hole...We have proposed a novel kind of photonic crystal fiber which contains two asymmetric cores. The bireti'ingence and the dispersion are numerically analyzed based on finite element method when the size of the air holes and the pitch of two adjacent air holes are changed. It is shown that the proposed photonic crystal fiber has high birefringence up to the order of 10-2 and double-zero dispersion points are at the wavelengths of 1310 nm and 800 rim, simultaneously. At the same time, the normalized power and the extinction ratios of the proposed photonic crystal fiber have been simulated. It is demonstrated that, at the wavelength of 1310 rim, the x-polarized mode and the y-polarized mode are separated when the propagation distance is 2.481 ram.展开更多
We report an experimental demonstration of a new scheme to split cold atoms on an atom chip. The atom chip consists of a U-wire and a Z-wire. The cold atom cloud is initially loaded and prepared in the Z-trap, which i...We report an experimental demonstration of a new scheme to split cold atoms on an atom chip. The atom chip consists of a U-wire and a Z-wire. The cold atom cloud is initially loaded and prepared in the Z-trap, which is split into two separate parts by switching on the current of the U-wire. The two separate atom clouds have a distance more than one millimeter apart from each other and show almost symmetrical profiles, corresponding to about a 50/50 splitting ratio.展开更多
X-ray speckle tracking based methods can provide results with best reported angular accuracy up to 2 nrad. However,duo to the multi-frame requirement for phase retrieval and the possible instability of the x-ray beam,...X-ray speckle tracking based methods can provide results with best reported angular accuracy up to 2 nrad. However,duo to the multi-frame requirement for phase retrieval and the possible instability of the x-ray beam, mechanical and background vibration, the actual accuracy will inevitably be degraded by these time-dependent fluctuations. Therefore,not only spatial position, but also temporal features of the speckle patterns need to be considered in order to maintain the superiority of the speckle-based methods. In this paper, we propose a parallel acquisition method with advantages of real time and high accuracy, which has potential applicability to dynamic samples imaging as well as on-line beam monitoring.Through simulations, we demonstrate that the proposed method can reduce the phase error caused by the fluctuations to1% at most compared with current speckle tracking methods. Meanwhile, it can keep the accuracy deterioration within0.03 nrad, making the high theoretical accuracy a reality. Also, we find that waveforms of the incident beam have a little impact on the phase retrieved and will not influence the actual accuracy, which relaxes the requirements for speckle-based experiments.展开更多
基金supported by grants from the Natural Science Foundation of China(Nos.61275167,60878036and 60178023)the Basic Research Project of Shenzhen(Nos.JCYJ20130329103020637,JCYJ20120613112628842,JCYJ20140418095735591 and JC201005280533A)
文摘In this paper, a novel method of a subwavelength binary simple periodic rectangular structure is presented to realize even beam splitting by combining the rigorous couple-wave analysis with the genetic algorithm. Several even splitters in the terahertz region were designed and one of the silicon-based beam splitters designed to separate one incident beam into four emergent beams has total efficiency up to 92.23 %. Zero-order diffraction efficiency was reduced to less than 0.192 % and the error of uniformity decreased to 6.51 9 10-6. These results break the limitation of even beam splitting based on the traditional scalar theory. In addition, the effects of the incident angle, wavelength, as well as the polarizing angle on the diffraction efficiency and uniformity were also investigated.
基金the Natural Science Foundation from Hubei Province of China[Grant No.2019CFC866]the Guiding Project of Scientific Research Plan of Hubei Education Department of China[Grant No.B2020227]+2 种基金the Collaborative Innovation Team of Discipline Characteristics of Jianghan University[Grant No.03100061]the Research Start-up Funds of Jianghan University[Grant No.101906320001]and the Research Start-up Funds of Jianghan University[101906270002].
文摘In turbomachinery,strong secondary flow can produce significant losses of total pressure near the endwall and reduce the efficiency of the considered turbomachine.In this study,splitters located at different positions with respect to the main blade have been used to reduce such losses and improve the efficiency of the outlet guide vane(OGV).Three different relative positions have been considered assuming a NACA 65-010 profile for both the main blade and the splitter.The numerical results indicate that splitters can effectively reduce the total pressure loss by suppressing the secondary flow around the main blade,but the splitters themselves also produce flow losses,which are caused by flow separation effects.
文摘In this paper, we construct photon-added f-deformed coherent states (PAf-DCSs) for nonlinear bosonic fields by discussing Klauder's minimal set of conditions required to obtain coherent states. Using this set of nonlinear states, we propose a very useful scheme for generating the maximal amount of entanglement via unitary beam splitters for different strength regimes of the input field α, deformation q and excitation number m. Therefore, the possibility to create highly entangled states and to control the entanglement is proposed. Moreover, the condition for a maximal and separable output beam state is obtained. Finally, we examine the statistical properties of the PAf-DCSs through the Mandel parameter and exploit a connection between this quantity and the behavior variation of the output state entanglement. Our result may open new perspectives in different tasks of quantum information processing.
文摘The production of maxima and minima by the superposition of two or more light signals provides fundamental support for the wave nature of light. This result is based on the study of wave interference phenomena which remains the only approach to explain the production of those maxima and minima. In a system that is prepared to work with only one photon at a time, any detector can signal only one or zero. In 1986, a rigorously controlled experiment was designed by Grangier, G. Roger, and A. Aspect, [Europhys Lett. 1(4), p. 173, 1986] that guaranteed a single-photon beam. The explanation of the experimental results implied the interference of the wave function of a single-photon with itself. Thus, the explanation of interference that is accepted for an ensemble of photons was assumed to be valid for a single photon. In this study, we prepare a Mach-Zehnder interferometer using the same type of beam splitters used by Grangier et al. to test the assumption mentioned above. Our results allow us to explain the results of Grangier et al. because of the interaction between light and the beam splitters. Our results also verify that their wave interpretation of the results is not valid. Here, we present the essential findings of the extensive experimental evidence that supports our ideas.
基金supported by the National Natural Science Foundation of China(Nos.61775136 and 11721091)
文摘Separating lights into different, paths according to the polarization states while keeping their respective path's polarizations with high purification is keen for polarization multiplex in optical communications. Metallic nanowire gratings with multi-slits in a period are proposed to achieve polarized beam splitters (PBSs) in reflection and diffraction. The setting of multi-slits largely reduces the reflection of photons with a transverse magnetific field via the plasmonic waveguiding effect, which leads to highly polarized output lights with extinction ratio larger than 20 dB in each channel. The proposed reflection/diffraction PBSs enrich the approaches to control the polarization states with the advantages of wide incident angles and flexible beam splitting angles.
基金supported in part by the National Natural Science Foundation of China (No. 60977050)the National "973" Program of China (Nos. 2009CB320302 and 2011CB301704)
文摘Two types of 1×2 multi-mode interference (MMI) splitters with splitting ratios of 85:15 and 72:28 are designed. On the basis of a numerical simulation, an optimal length of the MMI section is obtained. Subsequently, the devices are fabricated and tested. The footprints of the rectangular MMI regions are only 3×18.2 and 3×14.3 (#m). The minimum excess losses are 1.4 and 1.1 dB. The results of the test on the splitting ratios are consistent with designed values. The devices can be applied in ultra-compact photonic integrated circuits to realize the "tap" function.
文摘The soft X-ray interferometry is completed by the Mach-Zehnder interferometer using a soft X-ray laser, and it is also an important method to measure the electron densities of a laser-produced plasma near the critical surface. It is apparently demonstrated in this paper that the incident angle of each optical element in the soft X-ray Mach- Zehnder interferometer should be near normal incidence based on the polarized characteristics of the soft X-ray mul-tilayers, and the product of reflectivity and transmission of the beam splitter should be taken as a standard of design according to the structure of the soft X-ray Mach-Zehnder interferometer. The beam splitters used in the soft X-ray interferometry at 13.9 nm are fabricated using the ion beam sputtering. The figure error of the beam splitter has reached the nanometer magnitude, in which the product of reflectiv-ity and transmission of the beam splitter is more than 1.6%.
文摘Beam splitters play a crucial role in a wide range of optical systems.A typical beam splitter consists of several transport channels,and an input beam from one channel is split into multiple output beams coupled into other channels.For traditional beam splitters,their transportation channels(either in free space or waveguides)are reciprocal,being sensitive to various perturbations caused by defects and obstacles.
基金Project supported by the National Key Research and Development Project of China(Grant No.2019YFB2204001)。
文摘A novel polarization beam splitter(PBS)based on dual-core photonic crystal fiber(DC-PCF)is proposed in this work.The proposed DC-PCF PBS contains two kinds of lattices and three kinds of air holes to form the asymmetrical elliptic dual-core structure.By using the full-vector finite element method,the propagation characteristics of the proposed DC-PCF PBS are investigated.The simulation results show that the bandwidth of the proposed DC-PCF PBS can reach to 340 nm,which covers the S+C+L+U communication bands,the shortest splitting length is 1.97 mm,and the maximum extinction ratio appears near wavelength 1550 nm.Moreover,the insertion loss of the proposed DC-PCF PBS is very low.It is believed that the proposed DC-PCF PBS has important applications in the field of all-optical communication and network.
基金supported by the Shenzhen Science and Technology Program(JCYJ20210324093806017)the ShenzhenHong Kong Joint Innovation Foundation(SGDX20190919094401725)。
文摘Polarizing beam splitter has rather significant applications in polarization diversity circuits and polarization multiplexing systems.In this paper,we present an asymmetric polarizing beam splitter utilizing hybrid plasmonic waveguide.The special hybrid structure with a hybrid waveguide and a dielectric waveguide can limit the energy of TE and TM modes to a different layer.Therefore,we can achieve beam splitting by adjusting the corresponding parameters of the two waveguides.First,we studied the influences of different structure parameters on the real part of the effective mode refractive index of the two waveguides,and obtained a set of parameters that satisfy the condition of strong coupling of TM mode and weak coupling of TE mode.Then,the performance of our proposed polarizing beam splitter is evaluated numerically.The length of the coupling section is only 4.1μm,and the propagation loss of TM and TE modes is 0.0025 d B/μm and 0.0031 d B/μm respectively.Additionally,the extinction ratios of TM and TE modes are 10.62 d B and 12.55 d B,respectively.Particularly,the proposed device has excellent wavelength insensitivity.Over the entire C-band,the fluctuation of the whole normalized output power is less than 0.03.In short,our proposed asymmetric polarizing beam splitter features ultra-compactness,low propagation loss,and broad bandwidth,which would provide promising applications in polarization multiplexing system and polarization diversity circuits relevant to optical interconnection.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61405096 and 61504058)the Introduction of Talent Research and Research Fund of Nanjing University of Posts and Telecommunications,China(Grant No.NY214158)+1 种基金the Open Fund of Laboratory of Solid State Microstructures,Nanjing University,China(Grant No.M28035)the Open Fund of State Key Laboratory of Transient Optics and Photonics,Chinese Academy of Sciences(Grant No.SKLST201404)
文摘An ultra-broadband polarization splitter based on graphene layer-filled dual-core photonic crystal fiber (GDC-PCF) that can work in a wavelength range from 1120 nm to 1730 nm is proposed in this paper. Through optimizing fiber configuration, the polarization splitter has an extinction ratio of-56.3 dB at 1.55 μm with a fiber length of 4.8 mm. Compared with the photonic crystal fiber reported splitters, to our knowledge, the GDC-PCF splitter with the extinction ratio below-20 dB has a super wide bandwidth of 610 nm. Due to the excellent splitting characteristics, the GDC-PCF will be used in coherent optical communication systems in a wavelength range from infrared to mid-infraed.
基金Project supported by Science Foundation of the Chongqing Committee of Education,China (Grant No KJ071205)
文摘A novel optimal design of sub-wavelength metal rectangular gratings for the polarizing beam splitter (PBS) is proposed. The method is based on effective medium theory and the method of designing single layer antireflection coating. The polarization performance of PBS is discussed by rigorous couple-wave analysis (RCWA) method at a wavelength of 1550 nm. The result shows that sub-wavelength metal rectangular grating is characterized by a high reflectivity, like metal films for TE polarization, and high transmissivity, like dielectric films for TM polarization. The optimal design accords well with the results simulated by RCWA method.
基金Project supported by the National Key Basic Research and Development Programme of China (Grant No 2001CB6104), the National Center for Nanoscience and Technology, China (Grant No 2003CB7169) and the National Natural Science Foundation of China (Grant No 10474036).
文摘We fabricated a new type of two-dimensional photonic crystal slab filter. The resonant cavities were directly put into the waveguide arms. The optical transmissions of the filters were measured and the results show that the optimized two-channel filters give good intensity distribution at the output ports of the waveguide. A minimum wavelength spacing of 5 nm of the filter outputs is realized by accurately controlling the size of the resonant cavities.
基金Comprehensive Health Management Promotion Center of Xihua University(kgl2018-019)Scientific Research Project of the Education Department of Sichuan,China(18ZB0560)National Natural Science Foundation of China(51279172)
文摘Cavitation will reduce the turbine performance and even damage the turbine components.To verify the effects of splitter blades on improving the cavitation performance,the cavitation flow inside a Francis turbine runner with splitter blades was numerically simulated by using the Singhal cavitation model and the standard k-ε turbulence model.The distributions of static pressure and gas volume fractions on the surface of the runner blades were predicated under different conditions,and the cavitation in the flow field of the runner was analyzed.The results show that the static pressure and gas volume fractions are more uniformly distributed on the short blades than those on the long blades in Francis turbines with splitter blades,and there is almost no cavitation on the short blades;their distributions are more uniform under small flow conditions than those under large flow conditions;and large gas volume fractions are concentrated at the outlet tip near the band on the suction side of the long blade.The installation of splitter blades can improve the cavitation performance of conventional Francis turbines.
基金This project is supported by Foundation of National College Doctoral Prog-ram of China(No.20050299006).
文摘Analysis on the inner flow field of a centrifugal pump impeller with splitter blades is carfled out by numerical simulation. Based on this analysis, the principle of increasing pump head and efficiency are discussed. New results are obtained from the analysis of turbulence kinetic energy and relative velocity distribution: Firstly, unreasonable length or deviation design of the splitter blades may cause great turbulent fluctuation in impeller channel, which has a great effect on the stability of impeller outlet flow; Secondly, it is found that the occurrence of flow separation can be decreased or delayed with splitter blades from the analysis of blade loading; Thirdly, the effect of splitter blades on reforming the structure of "jet-wake" is explained from the relative velocity distribution at different flow cross-sections, which shows the flow process in the impeller. The inner flow analysis verifies the results of performance tests results and the PIV test.
基金Project supported by the National Natural Science Foundation of China(Grant No.61178026)the Natural Science Foundation of Hebei Province,China(Grant No.E2012203035)
文摘We have proposed a novel kind of photonic crystal fiber which contains two asymmetric cores. The bireti'ingence and the dispersion are numerically analyzed based on finite element method when the size of the air holes and the pitch of two adjacent air holes are changed. It is shown that the proposed photonic crystal fiber has high birefringence up to the order of 10-2 and double-zero dispersion points are at the wavelengths of 1310 nm and 800 rim, simultaneously. At the same time, the normalized power and the extinction ratios of the proposed photonic crystal fiber have been simulated. It is demonstrated that, at the wavelength of 1310 rim, the x-polarized mode and the y-polarized mode are separated when the propagation distance is 2.481 ram.
基金supported by the State Key Basic Research Program of China(Grant No.2011CB921504)the National Natural Science Foundation of China(Grant No.91536107)
文摘We report an experimental demonstration of a new scheme to split cold atoms on an atom chip. The atom chip consists of a U-wire and a Z-wire. The cold atom cloud is initially loaded and prepared in the Z-trap, which is split into two separate parts by switching on the current of the U-wire. The two separate atom clouds have a distance more than one millimeter apart from each other and show almost symmetrical profiles, corresponding to about a 50/50 splitting ratio.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11675253 and 11505278)。
文摘X-ray speckle tracking based methods can provide results with best reported angular accuracy up to 2 nrad. However,duo to the multi-frame requirement for phase retrieval and the possible instability of the x-ray beam, mechanical and background vibration, the actual accuracy will inevitably be degraded by these time-dependent fluctuations. Therefore,not only spatial position, but also temporal features of the speckle patterns need to be considered in order to maintain the superiority of the speckle-based methods. In this paper, we propose a parallel acquisition method with advantages of real time and high accuracy, which has potential applicability to dynamic samples imaging as well as on-line beam monitoring.Through simulations, we demonstrate that the proposed method can reduce the phase error caused by the fluctuations to1% at most compared with current speckle tracking methods. Meanwhile, it can keep the accuracy deterioration within0.03 nrad, making the high theoretical accuracy a reality. Also, we find that waveforms of the incident beam have a little impact on the phase retrieved and will not influence the actual accuracy, which relaxes the requirements for speckle-based experiments.