Fundamental power couplers are crucial components for feeding radio frequency power to accelerating cavities. Couplers must be tested and conditioned on a room-temperature test stand to evaluate and potentially improv...Fundamental power couplers are crucial components for feeding radio frequency power to accelerating cavities. Couplers must be tested and conditioned on a room-temperature test stand to evaluate and potentially improve their performance before being installed in an accelerating cavity. A new test system has been designed and is under construction at the institute of modern physics.For this test system, multiple conditioning modes, including the pulse mode, CW mode, and amplitude-sweeping mode, have been embedded in the low-level radio frequency system of the test stand. All of these conditioning modes can be run manually or automatically. In addition, a novel test cavity is proposed and has been designed, which facilitates non-contact conditioning and a multi-purpose test stand.展开更多
Two-mode converters at 1.3μm, aiming at applications in mode-division multiplexing in Ethernet systems, are proposed and experimentally demonstrated. Based on multimode interference couplers, the two-mode converters ...Two-mode converters at 1.3μm, aiming at applications in mode-division multiplexing in Ethernet systems, are proposed and experimentally demonstrated. Based on multimode interference couplers, the two-mode converters with 50% and 66% mode conversion efficiencies are designed and fabricated on InP substrates. AIode conver- sion from the fundamental mode （TEo） to the first order mode （TE1） is successfully demonstrated within the wavelength range of 1280-1320nm. The 1.3-μm mode converters should be important devices in mode-division multiplexing systems in Ethernet systems.展开更多
A novel grating coupler with a stair-step blaze profile is proposed. The coupler is a CMOS process compatible device and can be used for light coupling in optical communication. The blaze profile can be optimized to o...A novel grating coupler with a stair-step blaze profile is proposed. The coupler is a CMOS process compatible device and can be used for light coupling in optical communication. The blaze profile can be optimized to obtain a high efficiency of 66.7% for the out-of-plane coupling at the centre wavelength of 1595 nm with a 1 dB bandwidth of 41 nm. Five key parameters of the stair-step blaze grating and their effects on the coupling are discussed for the application in L band telecommunication.展开更多
Grating couplers are widely investigated as coupling interfaces between silicon-on-insulator waveguides and optical fibers.In this work,a high-efficiency and complementary metal-oxide-semiconductor（CMOS） process com...Grating couplers are widely investigated as coupling interfaces between silicon-on-insulator waveguides and optical fibers.In this work,a high-efficiency and complementary metal-oxide-semiconductor（CMOS） process compatible grating coupler is proposed.The poly-Si layer used as a gate in the CMOS metal-oxide-semiconductor field effect transistor（MOSFET） is combined with a normal fully etched grating coupler,which greatly enhances its coupling efficiency.With optimal structure parameters,a coupling efficiency can reach as high as ～ 70% at a wavelength of 1550 nm as indicated by simulation.From the angle of fabrication,all masks and etching steps are shared between MOSFETs and grating couplers,thereby making the high performance grating couplers easily integrated with CMOS circuits.Fabrication errors such as alignment shift are also simulated,showing that the device is quite tolerant in fabrication.展开更多
We demonstrate visible-light all-fiber vortex lasers by incorporating the home-made mode selective couplers (MSCs). The MSC at green or red wavebands is fabricated by specially designing and fusing a single-mode fiber...We demonstrate visible-light all-fiber vortex lasers by incorporating the home-made mode selective couplers (MSCs). The MSC at green or red wavebands is fabricated by specially designing and fusing a single-mode fiber (SMF) and a few-mode fiber (FMF). The MSCs inserted into visible fiber cavities act as power splitters and mode converters from the LP01 to LP11 mode at green and red wavelengths, respectively. The red-light all-fiber vortex laser is formed by a 10-cm Pr3+/Yb3+:ZBLAN fiber, a fiber Bragg grating, a fiber end-facet mirror and the MSC at 635 nm, which generates vortex beams with OAM±1 at 634.4 nm and an output power of 13 mW. The green-light all-fiber vortex laser consists of a 12-cm Ho3+:ZBLAN fiber, two fiber pigtail mirrors, and the MSC at 550 nm, which generates vortex beams with OAM±1 at 548.9 nm and an output power of 3 mW.展开更多
An explanation of optical unitary transformation is presented for general nonoverlapping-image multimode interference(MMI)couplers with any number of input and output ports.The light transformation in the MMI coupler ...An explanation of optical unitary transformation is presented for general nonoverlapping-image multimode interference(MMI)couplers with any number of input and output ports.The light transformation in the MMI coupler can be considered as an optical field matrix acting on an input light column vector.We investigate the general phase principle of output light image.The complete proof of nonoverlapping-image MMI coupler’s optical unitarity along with the phase analysis of matrix element is provided.Based on a two-dimensional finite-difference time-domain(2 D-FDTD)simulation,the unitary transformation is obtained for a 4×4 nonoverlapping-image MMI coupler within a deviation of 4×10-2 for orthogonal invariance and 8×10-2 for transvection invariance in the C-band spectral range.A compact 1×4 splitter based on cascaded MMI coupler is proposed,showing a phase deviation less than 5.4°while maintaining a low-loss performance in C-band spectra.展开更多
Weakly-coupled mode division multiplexing(MDM)technique is considered a promising candidate to enhance the capacity of an optical transmission system,in which mode multiplexers/demultiplexers(MMUX/MDEMUX)with low inse...Weakly-coupled mode division multiplexing(MDM)technique is considered a promising candidate to enhance the capacity of an optical transmission system,in which mode multiplexers/demultiplexers(MMUX/MDEMUX)with low insertion loss and modal crosstalk are the key components.In this paper,a low-modal-crosstalk 4-mode MMUX/MDEMUX for the weakly-coupled triple-ring-core few-mode fiber(TRC-FMF)is designed and fabricated with side-polishing processing.The measurement results show that a pair of MMUX/MDEMUX and 25 km weakly-coupled TRC-FMF MDM link achieve low modal crosstalk of lower than−17.5 dB and insertion loss of lower than 11.56 dB for all the four modes.Based on the TRC-FMF and all-fiber MMUX/MDEMUX,an experiment for 25 km real-time 4-mode 3-λwavelength division multiplexing(WDM)-MDM transmission is conducted using commercial 400G optical transport network(OTN)transceivers.The experimental results prove weakly-coupled MDM techniques facilitate a smooth upgrade of the optical transmission system.展开更多
To validate the design rationality of the power coupler for the RFQ cavity and minimize cavity contamination,we designed a low-loss offline conditioning cavity and conducted high-power testing.This offline cavity feat...To validate the design rationality of the power coupler for the RFQ cavity and minimize cavity contamination,we designed a low-loss offline conditioning cavity and conducted high-power testing.This offline cavity features two coupling ports and two tuners,operating at a frequency of 162.5 MHz with a tuning range of 3.2 MHz.Adjusting the installation angle of the coupling ring and the insertion depth of the tuner helps minimize cavity losses.We performed electromagnetic structural and multiphysics simulations,revealing a minimal theoretical power loss of 4.3%.However,when the cavity frequency varied by110 kHz,theoretical power losses increased to10%,necessitating constant tuner adjustments during conditioning.Multiphysics simulations indicated that increased cavity temperature did not affect frequency variation.Upon completion of the offline high-power conditioning platform,we measured the transmission performance,revealing a power loss of 6.3%,exceeding the theoretical calculation.Conditioning utilized efficient automatic range scanning and standing wave resonant methods.To fully condition the power coupler,a 15°phase difference between two standing wave points in the condition-ing system was necessary.Notably,the maximum continuous wave power surpassed 20 kW,exceeding the expected target.展开更多
The coupling efficiency of the pump coupler determines the pump light injection capacity of a laser system. Experi- mental analysis of the influences of different factors on the pump coupling efficiency is in accordan...The coupling efficiency of the pump coupler determines the pump light injection capacity of a laser system. Experi- mental analysis of the influences of different factors on the pump coupling efficiency is in accordance with this conclusion. We use two Nufern fibers （400 Ixrn/440 p.m with NA = 0.22） as pump arm, one Nufern fiber （20 μm/400 μm with NA = 0.06/0.46） as a main fiber to make a side-pumping （2 ＋ 1） × 1 coupler. The experimental result shows that the total output power of this （2 ＋ 1） × 1 coupler is about 1160 W, corresponding to a coupling efficiency as high as 98.6%. The loss of signal light is less than 1%.展开更多
A rigorous analysis of a broad wall slot coupler composed of two crossed rectangular waveguides by using FDTD method is presented. Two types of slots, a longitudinal/transverse slot and a centered-inclined slot, are a...A rigorous analysis of a broad wall slot coupler composed of two crossed rectangular waveguides by using FDTD method is presented. Two types of slots, a longitudinal/transverse slot and a centered-inclined slot, are analyzed. Coupling slot characteristics are obtained, including scattering parameters and the resonant length for different waveguide dimensions and frequencies. The numerical results are all in good agreement with those by the method of moments. A coupler system with a short circuit port is also analyzed to help designing the slot array.展开更多
A two-dimensional apodized grating coupler for interfacing between single-mode fiber and photonic circuit is demonstrated in order to bridge the mode gap between the grating coupler and optical fiber. The grating groo...A two-dimensional apodized grating coupler for interfacing between single-mode fiber and photonic circuit is demonstrated in order to bridge the mode gap between the grating coupler and optical fiber. The grating grooves of the grating couplers are realized by columns of fully etched nanostructures, which are utilized to digitally tailor the effective refractive index of each groove in order to obtain the Gaussian-like output diffractive mode and then enhance the coupling efficiency.Compared with that of the uniform grating coupler, the coupling efficiency of the apodized grating coupler is increased by 4.3% and 5.7%, respectively, for the nanoholes and nanorectangles as refractive index tunes layer.展开更多
We fnrther study theoretically the properties of switching and Fano resonance in a hybrid nanosystem consisting of two quantum dots （QDs） and a metal nanowire via exciton-plasmon interaction. The transmission of the...We fnrther study theoretically the properties of switching and Fano resonance in a hybrid nanosystem consisting of two quantum dots （QDs） and a metal nanowire via exciton-plasmon interaction. The transmission of the single plasmon can be switched on or off in a wide-frequency region by adjusting the transition frequencies of the QDs and the phase of the propagating plasmon. Specifically, the dynamical mechanism of Fano-type transmission is further revealed and analyzed in detail.展开更多
Power measurement is necessary for an electron cyclotron resonance heating(ECRH)system.The directional coupler method has been put forward to monitor high-power microwave from gyrotrons in real time.A multi-hole direc...Power measurement is necessary for an electron cyclotron resonance heating(ECRH)system.The directional coupler method has been put forward to monitor high-power microwave from gyrotrons in real time.A multi-hole directional coupler has been designed and manufactured for the 105 GHz/500 kW ECRH system on the J-TEXT tokamak.During the design process,we established the relationships between hole parameters and coupling characteristics based on the multi-hole coupling method and small-hole coupling theory.High-power tests have been carried out.The results indicated the reasonability of the theoretical design and practicality of the fabricated directional coupler.Sources of test errors have been discussed in detail,and the influences of spurious modes on the directional couplers have been emphatically analyzed.展开更多
Flexible strain sensors play an important role in electronic skins,wearable medical devices,and advanced robots.Herein,a highly sensitive and fast response optical strain sensor with two evanescently coupled optical m...Flexible strain sensors play an important role in electronic skins,wearable medical devices,and advanced robots.Herein,a highly sensitive and fast response optical strain sensor with two evanescently coupled optical micro/nanofibers(MNFs)embedded in a polydimethylsiloxane(PDMS)film is proposed.The strain sensor exhibits a gauge factor as high as 64.5 for strain≤0.5%and a strain resolution of 0.0012%which corresponds to elongation of 120 nm on a 1 cm long device.As a proof-of-concept,highly sensitive fingertip pulse measurement is realized.The properties of fast temporal frequency response up to 30 kHz and a pressure sensitivity of 102 kPa^(−1) enable the sensor for sound detection.Such versatile sensor could be of great use in physiological signal monitoring,voice recognition and micro-displacement detection.展开更多
Coupling plane wave into a single-mode fiber （SMF） with high and steady coupling efficiency is crucial for fiber- based free-space laser systems, where random angular jitters are the main influencing factors of fibe...Coupling plane wave into a single-mode fiber （SMF） with high and steady coupling efficiency is crucial for fiber- based free-space laser systems, where random angular jitters are the main influencing factors of fiber coupling. In this paper, we verified a new adaptive-optic device named adaptive fiber coupler （AFC） which could compensate angular jitters and improve the SMF coupling efficiency in some degree. Experiments of SMF coupling under the angular jitter situation using AFC have been achieved. Stochastic parallel gradient descent （SPGD） algorithm is employed as the control strategy, of which the iteration rate is 625 Hz. In closed loop, the coupling efficiency keeps above 65% when angular errors are below 80/3tad. The compensation bandwidth is 35 Hz at sine-jitter of 15 ~rad amplitude with average coupling efficiency of above 60%. Also, experiments with simulated turbulence have been studied. The average coupling efficiency increases from 31.97% in open loop to 61.33% in closed loop, and mean square error （MSE） of coupling efficiency drops from 7.43% to 1.75%.展开更多
An S-band high-gradient accelerating structure is designed for a proton therapy linear accelerator(linac)to accommodate the new development of compact,singleroom facilities and ultra-high dose rate(FLASH)radiotherapy....An S-band high-gradient accelerating structure is designed for a proton therapy linear accelerator(linac)to accommodate the new development of compact,singleroom facilities and ultra-high dose rate(FLASH)radiotherapy.To optimize the design,an efficient optimization scheme is applied to improve the simulation efficiency.An S-band accelerating structure with 2856 MHz is designed with a low beta of 0.38,which is a difficult structure to achieve for a linac accelerating proton particles from 70 to 250 MeV,as a high gradient up to 50 MV/m is required.A special design involving a dual-feed coupler eliminates the dipole field effect.This paper presents all the details pertaining to the design,fabrication,and cold test results of the S-band high-gradient accelerating structure.展开更多
The Shanghai High Repetition Rate XFEL and Extreme Light Facility(SHINE)project will use 6001.3 GHz fundamental power couplers,which are modified based on TTF-Ⅲ power couplers,for continuous-wave operation with input...The Shanghai High Repetition Rate XFEL and Extreme Light Facility(SHINE)project will use 6001.3 GHz fundamental power couplers,which are modified based on TTF-Ⅲ power couplers,for continuous-wave operation with input power up to approximately 7 kW.The first batch of 20 sets of 1.3 GHz coupler prototypes was fabricated from three domestic manufacturers for the SHINE project.To better characterize the radio frequency conditioning phenomena for validating the performance of power couplers,a room temperature test stand was designed,constructed,and commissioned for the SHINE 1.3 GHz power couplers.In addition,a horizontal test cryostat was built to test the 1.3 GHz superconducting cavities,fundamental power couplers,tuners,and other components as a set.The results of these tests indicate that the 1.3 GHz couplers are capable of handling up to 14 kW continuous waves.Herein,the main aspects of the radio frequency design and construction of the test stand,along with the test results of the high-power conditioning of the 1.3 GHz couplers,are described.展开更多
Once operating trains are disabled on the railway lines,an efficient manner is to utilize the train for train rescue.Owning to the different train and coupler types,it is difficult to formulate uniform regulations for...Once operating trains are disabled on the railway lines,an efficient manner is to utilize the train for train rescue.Owning to the different train and coupler types,it is difficult to formulate uniform regulations for train to train rescue.In this paper,the longitudinal train dynamics of electric multiple units under rescue were analyzed by field and laboratory tests.The angling behavior of the brakinginduced coupler under compressed in-train forces was analyzed.A dynamic model for the train and draft gear system was developed considering accurate boundary limitations and braking characteristics.The safety indices and their limits for the coupled rescue train were defined.Thedynamic evaluations of different train to train rescue scenarios were analyzed.It is indicated that the coupler vertical rotation occurs during the emergency braking applied by the assisting train.The vertical force components of intrain forces lead to the carbody pitch behavior and even cause local destructions to the coupler system.The carbody pitch motion can arise the inference of in-train devices.Based on the safety evaluation of train and coupler system,the regulations for typical train to train rescue scenarios were formulated.展开更多
The proton beam with energy around 100 MeV has seen wide applications in modern scientific research and in various fields.However,proton sources in China fall short for meeting experimental needs owing to the vast siz...The proton beam with energy around 100 MeV has seen wide applications in modern scientific research and in various fields.However,proton sources in China fall short for meeting experimental needs owing to the vast size and expensive traditional proton accelerators.The Institute of Nuclear Science and Technology of Sichuan University proposed to build a 3 GHz side-coupled cavity linac(SCL)for re-accelerating a 26 MeV proton beam extracted from a CS-30 cyclotron to 120 MeV.We carried out investigations into several vital factors of S-band SCL for proton acceleration,such as optimization of SCL cavity geometry,end cell tuning,and bridge coupler design.Results demonstrated that the effective shunt impedance per unit length ranged from 22.5 to 59.8 MX/m throughout the acceleration process,and the acceleration gradient changed from 11.5 to 15.7 MV/m when the maximum surface electric field was equivalent to Kilpatrick electric field.We obtained equivalent circuit parameters of the biperiodic structures and applied them to the end cell tuning;results of the theoretical analysis agreed well with the 3D simulation.We designed and optimized a bridge coupler based on the previously obtained biperiodic structure parameters,and the field distribution un-uniformness was\1.5%for a two-tank module.The radio frequency power distribution system of the linac was obtained based on the preliminary beam dynamics design.展开更多
基金supported by the National Key Basic Research Program of China(973 Program)(No.2014CB845504)
文摘Fundamental power couplers are crucial components for feeding radio frequency power to accelerating cavities. Couplers must be tested and conditioned on a room-temperature test stand to evaluate and potentially improve their performance before being installed in an accelerating cavity. A new test system has been designed and is under construction at the institute of modern physics.For this test system, multiple conditioning modes, including the pulse mode, CW mode, and amplitude-sweeping mode, have been embedded in the low-level radio frequency system of the test stand. All of these conditioning modes can be run manually or automatically. In addition, a novel test cavity is proposed and has been designed, which facilitates non-contact conditioning and a multi-purpose test stand.
基金Supported by the National Basic Research Program of China under Grant No 2014CB340102the National Natural Science Foundation of China under Grant Nos 61474111 and 61274046
文摘Two-mode converters at 1.3μm, aiming at applications in mode-division multiplexing in Ethernet systems, are proposed and experimentally demonstrated. Based on multimode interference couplers, the two-mode converters with 50% and 66% mode conversion efficiencies are designed and fabricated on InP substrates. AIode conver- sion from the fundamental mode （TEo） to the first order mode （TE1） is successfully demonstrated within the wavelength range of 1280-1320nm. The 1.3-μm mode converters should be important devices in mode-division multiplexing systems in Ethernet systems.
基金Project supported by the National Natural Science Foundation of China (Grant No.60877036)the National Basic Research Program of China (Grant Nos.2006CB302803 and 2011CB301701)+1 种基金the State Key Laboratory of Advanced Optical Communication Systems and Networks,China (Grant No.2008SH02)the Knowledge Innovation Program of Institute of Semiconductors,Chinese Academy of Sciences (Grant No.ISCAS2008T10)
文摘A novel grating coupler with a stair-step blaze profile is proposed. The coupler is a CMOS process compatible device and can be used for light coupling in optical communication. The blaze profile can be optimized to obtain a high efficiency of 66.7% for the out-of-plane coupling at the centre wavelength of 1595 nm with a 1 dB bandwidth of 41 nm. Five key parameters of the stair-step blaze grating and their effects on the coupling are discussed for the application in L band telecommunication.
基金Project supported by the Natural Science Foundation of Shanghai,China (Grant No. 11ZR1443700)the Funds from the Science and Technology Commission of Shanghai Municipality,China (Grant Nos. 10DJ1400400 and 10706200500)the National Natural Science Foundation of China (Grant No. 61106051)
文摘Grating couplers are widely investigated as coupling interfaces between silicon-on-insulator waveguides and optical fibers.In this work,a high-efficiency and complementary metal-oxide-semiconductor（CMOS） process compatible grating coupler is proposed.The poly-Si layer used as a gate in the CMOS metal-oxide-semiconductor field effect transistor（MOSFET） is combined with a normal fully etched grating coupler,which greatly enhances its coupling efficiency.With optimal structure parameters,a coupling efficiency can reach as high as ～ 70% at a wavelength of 1550 nm as indicated by simulation.From the angle of fabrication,all masks and etching steps are shared between MOSFETs and grating couplers,thereby making the high performance grating couplers easily integrated with CMOS circuits.Fabrication errors such as alignment shift are also simulated,showing that the device is quite tolerant in fabrication.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91750115 and 91750108)the Equipment Pre-research Project of Equipment Development Department of Central Military Commission,China(Grant No.61404140112)the Science and Technology Planning Project of Xiamen City,China(Grant No.3502Z20183003).
文摘We demonstrate visible-light all-fiber vortex lasers by incorporating the home-made mode selective couplers (MSCs). The MSC at green or red wavebands is fabricated by specially designing and fusing a single-mode fiber (SMF) and a few-mode fiber (FMF). The MSCs inserted into visible fiber cavities act as power splitters and mode converters from the LP01 to LP11 mode at green and red wavelengths, respectively. The red-light all-fiber vortex laser is formed by a 10-cm Pr3+/Yb3+:ZBLAN fiber, a fiber Bragg grating, a fiber end-facet mirror and the MSC at 635 nm, which generates vortex beams with OAM±1 at 634.4 nm and an output power of 13 mW. The green-light all-fiber vortex laser consists of a 12-cm Ho3+:ZBLAN fiber, two fiber pigtail mirrors, and the MSC at 550 nm, which generates vortex beams with OAM±1 at 548.9 nm and an output power of 3 mW.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB2200202)the National Natural Science Foundation of China(Grant No.61804148)
文摘An explanation of optical unitary transformation is presented for general nonoverlapping-image multimode interference(MMI)couplers with any number of input and output ports.The light transformation in the MMI coupler can be considered as an optical field matrix acting on an input light column vector.We investigate the general phase principle of output light image.The complete proof of nonoverlapping-image MMI coupler’s optical unitarity along with the phase analysis of matrix element is provided.Based on a two-dimensional finite-difference time-domain(2 D-FDTD)simulation,the unitary transformation is obtained for a 4×4 nonoverlapping-image MMI coupler within a deviation of 4×10-2 for orthogonal invariance and 8×10-2 for transvection invariance in the C-band spectral range.A compact 1×4 splitter based on cascaded MMI coupler is proposed,showing a phase deviation less than 5.4°while maintaining a low-loss performance in C-band spectra.
基金supported in part by the ZTE Industry-University-Institute Cooperation Funds.
文摘Weakly-coupled mode division multiplexing(MDM)technique is considered a promising candidate to enhance the capacity of an optical transmission system,in which mode multiplexers/demultiplexers(MMUX/MDEMUX)with low insertion loss and modal crosstalk are the key components.In this paper,a low-modal-crosstalk 4-mode MMUX/MDEMUX for the weakly-coupled triple-ring-core few-mode fiber(TRC-FMF)is designed and fabricated with side-polishing processing.The measurement results show that a pair of MMUX/MDEMUX and 25 km weakly-coupled TRC-FMF MDM link achieve low modal crosstalk of lower than−17.5 dB and insertion loss of lower than 11.56 dB for all the four modes.Based on the TRC-FMF and all-fiber MMUX/MDEMUX,an experiment for 25 km real-time 4-mode 3-λwavelength division multiplexing(WDM)-MDM transmission is conducted using commercial 400G optical transport network(OTN)transceivers.The experimental results prove weakly-coupled MDM techniques facilitate a smooth upgrade of the optical transmission system.
基金supported by the Chinese initiative accelerator driven subcritical system and the hundred talents plan of the Chinese Academy of Sciences(No.E129841Y).
文摘To validate the design rationality of the power coupler for the RFQ cavity and minimize cavity contamination,we designed a low-loss offline conditioning cavity and conducted high-power testing.This offline cavity features two coupling ports and two tuners,operating at a frequency of 162.5 MHz with a tuning range of 3.2 MHz.Adjusting the installation angle of the coupling ring and the insertion depth of the tuner helps minimize cavity losses.We performed electromagnetic structural and multiphysics simulations,revealing a minimal theoretical power loss of 4.3%.However,when the cavity frequency varied by110 kHz,theoretical power losses increased to10%,necessitating constant tuner adjustments during conditioning.Multiphysics simulations indicated that increased cavity temperature did not affect frequency variation.Upon completion of the offline high-power conditioning platform,we measured the transmission performance,revealing a power loss of 6.3%,exceeding the theoretical calculation.Conditioning utilized efficient automatic range scanning and standing wave resonant methods.To fully condition the power coupler,a 15°phase difference between two standing wave points in the condition-ing system was necessary.Notably,the maximum continuous wave power surpassed 20 kW,exceeding the expected target.
基金Project supported by the National Natural Science Foundation of China(Grant No.61307057)the Fund from the State Key Laboratory of Tribology,Tsinghua University(Grant No.SKLT12B08)
文摘The coupling efficiency of the pump coupler determines the pump light injection capacity of a laser system. Experi- mental analysis of the influences of different factors on the pump coupling efficiency is in accordance with this conclusion. We use two Nufern fibers （400 Ixrn/440 p.m with NA = 0.22） as pump arm, one Nufern fiber （20 μm/400 μm with NA = 0.06/0.46） as a main fiber to make a side-pumping （2 ＋ 1） × 1 coupler. The experimental result shows that the total output power of this （2 ＋ 1） × 1 coupler is about 1160 W, corresponding to a coupling efficiency as high as 98.6%. The loss of signal light is less than 1%.
文摘A rigorous analysis of a broad wall slot coupler composed of two crossed rectangular waveguides by using FDTD method is presented. Two types of slots, a longitudinal/transverse slot and a centered-inclined slot, are analyzed. Coupling slot characteristics are obtained, including scattering parameters and the resonant length for different waveguide dimensions and frequencies. The numerical results are all in good agreement with those by the method of moments. A coupler system with a short circuit port is also analyzed to help designing the slot array.
基金supported by the National Natural Science Foundation of China(Grant Nos.61222501,61335004,and 61505003)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20111103110019)+1 种基金the Postdoctoral Science Foundation of Beijing Funded Project,China(Grant No.Q6002012201502)the Science and Technology Research Project of Jiangxi Provincial Education Department,China(Grant No.GJJ150998)
文摘A two-dimensional apodized grating coupler for interfacing between single-mode fiber and photonic circuit is demonstrated in order to bridge the mode gap between the grating coupler and optical fiber. The grating grooves of the grating couplers are realized by columns of fully etched nanostructures, which are utilized to digitally tailor the effective refractive index of each groove in order to obtain the Gaussian-like output diffractive mode and then enhance the coupling efficiency.Compared with that of the uniform grating coupler, the coupling efficiency of the apodized grating coupler is increased by 4.3% and 5.7%, respectively, for the nanoholes and nanorectangles as refractive index tunes layer.
基金supported by the National Natural Science Foundation of China(Grant No.11174372)
文摘We fnrther study theoretically the properties of switching and Fano resonance in a hybrid nanosystem consisting of two quantum dots （QDs） and a metal nanowire via exciton-plasmon interaction. The transmission of the single plasmon can be switched on or off in a wide-frequency region by adjusting the transition frequencies of the QDs and the phase of the propagating plasmon. Specifically, the dynamical mechanism of Fano-type transmission is further revealed and analyzed in detail.
基金supported by the National Key Research and Development Program of China (Nos.2017YFE0300200 and 2017YFE0300204)in part by National Natural Science Foundation of China(No.51821005).
文摘Power measurement is necessary for an electron cyclotron resonance heating(ECRH)system.The directional coupler method has been put forward to monitor high-power microwave from gyrotrons in real time.A multi-hole directional coupler has been designed and manufactured for the 105 GHz/500 kW ECRH system on the J-TEXT tokamak.During the design process,we established the relationships between hole parameters and coupling characteristics based on the multi-hole coupling method and small-hole coupling theory.High-power tests have been carried out.The results indicated the reasonability of the theoretical design and practicality of the fabricated directional coupler.Sources of test errors have been discussed in detail,and the influences of spurious modes on the directional couplers have been emphatically analyzed.
基金We are grateful for financial supports from the National Natural Science Foundation of China(No.61975173)the National Key Research and Development Program of China(No.SQ2019YFC170311)+3 种基金the Major Scientific Research Project of Zhejiang Lab(No.2019MC0AD01)the Key Research and Development Project of Zhejiang Province(No.2021C05003)the Quantum Joint Funds of the Natural Foundation of Shandong Province(No.ZR2020LLZ007)the CIE-Tencent Robotics X Rhino-Bird Focused Research Program(No.2020-01-006).
文摘Flexible strain sensors play an important role in electronic skins,wearable medical devices,and advanced robots.Herein,a highly sensitive and fast response optical strain sensor with two evanescently coupled optical micro/nanofibers(MNFs)embedded in a polydimethylsiloxane(PDMS)film is proposed.The strain sensor exhibits a gauge factor as high as 64.5 for strain≤0.5%and a strain resolution of 0.0012%which corresponds to elongation of 120 nm on a 1 cm long device.As a proof-of-concept,highly sensitive fingertip pulse measurement is realized.The properties of fast temporal frequency response up to 30 kHz and a pressure sensitivity of 102 kPa^(−1) enable the sensor for sound detection.Such versatile sensor could be of great use in physiological signal monitoring,voice recognition and micro-displacement detection.
基金Project supported by the National Natural Science Foundation of China （Grant No. 61205069）.
文摘Coupling plane wave into a single-mode fiber （SMF） with high and steady coupling efficiency is crucial for fiber- based free-space laser systems, where random angular jitters are the main influencing factors of fiber coupling. In this paper, we verified a new adaptive-optic device named adaptive fiber coupler （AFC） which could compensate angular jitters and improve the SMF coupling efficiency in some degree. Experiments of SMF coupling under the angular jitter situation using AFC have been achieved. Stochastic parallel gradient descent （SPGD） algorithm is employed as the control strategy, of which the iteration rate is 625 Hz. In closed loop, the coupling efficiency keeps above 65% when angular errors are below 80/3tad. The compensation bandwidth is 35 Hz at sine-jitter of 15 ~rad amplitude with average coupling efficiency of above 60%. Also, experiments with simulated turbulence have been studied. The average coupling efficiency increases from 31.97% in open loop to 61.33% in closed loop, and mean square error （MSE） of coupling efficiency drops from 7.43% to 1.75%.
基金This work was supported by the Alliance of International Science Organizations(No.ANSO-CR-KP-2020-16).
文摘An S-band high-gradient accelerating structure is designed for a proton therapy linear accelerator(linac)to accommodate the new development of compact,singleroom facilities and ultra-high dose rate(FLASH)radiotherapy.To optimize the design,an efficient optimization scheme is applied to improve the simulation efficiency.An S-band accelerating structure with 2856 MHz is designed with a low beta of 0.38,which is a difficult structure to achieve for a linac accelerating proton particles from 70 to 250 MeV,as a high gradient up to 50 MV/m is required.A special design involving a dual-feed coupler eliminates the dipole field effect.This paper presents all the details pertaining to the design,fabrication,and cold test results of the S-band high-gradient accelerating structure.
基金supported by Shanghai Municipal Science and Technology Major Project(No.2017SHZDZX02)。
文摘The Shanghai High Repetition Rate XFEL and Extreme Light Facility(SHINE)project will use 6001.3 GHz fundamental power couplers,which are modified based on TTF-Ⅲ power couplers,for continuous-wave operation with input power up to approximately 7 kW.The first batch of 20 sets of 1.3 GHz coupler prototypes was fabricated from three domestic manufacturers for the SHINE project.To better characterize the radio frequency conditioning phenomena for validating the performance of power couplers,a room temperature test stand was designed,constructed,and commissioned for the SHINE 1.3 GHz power couplers.In addition,a horizontal test cryostat was built to test the 1.3 GHz superconducting cavities,fundamental power couplers,tuners,and other components as a set.The results of these tests indicate that the 1.3 GHz couplers are capable of handling up to 14 kW continuous waves.Herein,the main aspects of the radio frequency design and construction of the test stand,along with the test results of the high-power conditioning of the 1.3 GHz couplers,are described.
基金supported by the National Natural Science Foundation of China [No.U1334206]the National Key R&D Program of China [No.2016YFB1200500]
文摘Once operating trains are disabled on the railway lines,an efficient manner is to utilize the train for train rescue.Owning to the different train and coupler types,it is difficult to formulate uniform regulations for train to train rescue.In this paper,the longitudinal train dynamics of electric multiple units under rescue were analyzed by field and laboratory tests.The angling behavior of the brakinginduced coupler under compressed in-train forces was analyzed.A dynamic model for the train and draft gear system was developed considering accurate boundary limitations and braking characteristics.The safety indices and their limits for the coupled rescue train were defined.Thedynamic evaluations of different train to train rescue scenarios were analyzed.It is indicated that the coupler vertical rotation occurs during the emergency braking applied by the assisting train.The vertical force components of intrain forces lead to the carbody pitch behavior and even cause local destructions to the coupler system.The carbody pitch motion can arise the inference of in-train devices.Based on the safety evaluation of train and coupler system,the regulations for typical train to train rescue scenarios were formulated.
基金supported by the National Natural Science Foundation of China(Nos.11375122 and 11875197)
文摘The proton beam with energy around 100 MeV has seen wide applications in modern scientific research and in various fields.However,proton sources in China fall short for meeting experimental needs owing to the vast size and expensive traditional proton accelerators.The Institute of Nuclear Science and Technology of Sichuan University proposed to build a 3 GHz side-coupled cavity linac(SCL)for re-accelerating a 26 MeV proton beam extracted from a CS-30 cyclotron to 120 MeV.We carried out investigations into several vital factors of S-band SCL for proton acceleration,such as optimization of SCL cavity geometry,end cell tuning,and bridge coupler design.Results demonstrated that the effective shunt impedance per unit length ranged from 22.5 to 59.8 MX/m throughout the acceleration process,and the acceleration gradient changed from 11.5 to 15.7 MV/m when the maximum surface electric field was equivalent to Kilpatrick electric field.We obtained equivalent circuit parameters of the biperiodic structures and applied them to the end cell tuning;results of the theoretical analysis agreed well with the 3D simulation.We designed and optimized a bridge coupler based on the previously obtained biperiodic structure parameters,and the field distribution un-uniformness was\1.5%for a two-tank module.The radio frequency power distribution system of the linac was obtained based on the preliminary beam dynamics design.
