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Laser shaping and optical power limiting of pulsed Laguerre–Gaussian laser beams of high-order radial modes in fullerene C60 被引量:1
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作者 李杰 管文慧 +3 位作者 袁烁 赵亚男 孙玉萍 刘纪彩 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第2期273-280,共8页
We study the strong nonlinear optical dynamics of nanosecond pulsed Laguerre–Gaussian laser beams of high-order radial modes with zero orbital angular momentum propagating in the fullerene C60molecular medium. It is ... We study the strong nonlinear optical dynamics of nanosecond pulsed Laguerre–Gaussian laser beams of high-order radial modes with zero orbital angular momentum propagating in the fullerene C60molecular medium. It is found that the spatiotemporal profile of the incident pulsed Laguerre–Gaussian laser beam is strongly reshaped during its propagation in the C60molecular medium. The centrosymmetric temporal profile of the incident pulse gradually evolves into a noncentrosymmetric meniscus shape, and the on-axis pulse duration is clearly depressed. Furthermore, the field intensity is distinctly attenuated due to the field-intensity-dependent reverse saturable absorption, and clear optical power limiting behavior is observed for different orders of the input pulsed Laguerre–Gaussian laser beams before the takeover of the saturation effect;the lower the order of the Laguerre–Gaussian beam, the lower the energy transmittance. 展开更多
关键词 pulsed Laguerre–Gaussian laser beams high-order radial mode optical power limiting reverse saturable absorption
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Optical power limiting of ultrashort hyper-Gaussian pulses in cascade three-level system 被引量:1
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作者 Ji-Cai Liu Fen-Fen Guo +1 位作者 Ya-Nan Zhao Xing-Zhe Li 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第10期357-361,共5页
Propagation of strong femtosecond hyper-Gaussian pulses in a cascade three-level molecular system is studied by solving numerically the Maxwell–Bloch equations by the iterative predictor-corrector finite-difference t... Propagation of strong femtosecond hyper-Gaussian pulses in a cascade three-level molecular system is studied by solving numerically the Maxwell–Bloch equations by the iterative predictor-corrector finite-difference time-domain method.Optical power limiting behavior induced by strong nonlinear two-photon absorption is observed for different orders of the femtosecond hyper-Gaussian pulses. Pulses of a higher order temporal profile are found to have a wider power range of optical limiting but a larger output saturation intensity. Both the output saturation value and the damage threshold of optical power limiting decrease with pulse duration increasing. The decrease of the pulse area along the pulse propagation is much slower than that obtained from the two-photon area theorem due to invalidity of the slowly varying amplitude approximation and the monochromatic field hypothesis. 展开更多
关键词 optical power limiting two-photon absorption ultrashort hyper-Gaussian pulse cascade three-level system
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Thiophene-fluorene derivatives with high three-photon absorption activities and their application to optical power limiting
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作者 马文波 吴谊群 +3 位作者 韩俊鹤 刘军辉 顾冬红 干福熹 《Chinese Physics B》 SCIE EI CAS CSCD 2006年第4期750-755,共6页
The three-photon absorption (3PA) properties of two thiophene-fluorene derivatives (abbreviated as MOTFTBr and ATFTBr) have been determined by using a Q-switched Nd:YAG laser pumped with 38ps pulses at 1064nm in ... The three-photon absorption (3PA) properties of two thiophene-fluorene derivatives (abbreviated as MOTFTBr and ATFTBr) have been determined by using a Q-switched Nd:YAG laser pumped with 38ps pulses at 1064nm in DMF. The measured 3PA cross-sections are 152×10^-78cm^6s^2 and 139× 10^-78cm^6s^2, respectively. The optimized structures were obtained by AM1 calculations and the results indicate that these two molecules show nonplanar structures, and attaching different donors has different effects on the molecular structure. The charge density distributions during the excitation were also systematically studied by using AM1 method. In addition, an obvious optical power limiting effect induced by 3PA has been demonstrated for both derivatives. 展开更多
关键词 three-photon absorption thiophene-fluorene derivative AM1 optical power limiting
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A Multi-mode Electronic Load Sensing Control Scheme with Power Limitation and Pressure Cut-off for Mobile Machinery
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作者 Min Cheng Bolin Sun +1 位作者 Ruqi Ding Bing Xu 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2023年第1期157-170,共14页
In mobile machinery,hydro-mechanical pumps are increasingly replaced by electronically controlled pumps to improve the automation level,but diversified control functions(e.g.,power limitation and pressure cut-off)are ... In mobile machinery,hydro-mechanical pumps are increasingly replaced by electronically controlled pumps to improve the automation level,but diversified control functions(e.g.,power limitation and pressure cut-off)are integrated into the electronic controller only from the pump level,leading to the potential instability of the overall system.To solve this problem,a multi-mode electrohydraulic load sensing(MELS)control scheme is proposed especially considering the switching stability from the system level,which includes four working modes of flow control,load sensing,power limitation,and pressure control.Depending on the actual working requirements,the switching rules for the different modes and the switching direction(i.e.,the modes can be switched bilaterally or unilaterally)are defined.The priority of different modes is also defined,from high to low:pressure control,power limitation,load sensing,and flow control.When multiple switching rules are satisfied at the same time,the system switches to the control mode with the highest priority.In addition,the switching stability between flow control and pressure control modes is analyzed,and the controller parameters that guarantee the switching stability are obtained.A comparative study is carried out based on a test rig with a 2-ton hydraulic excavator.The results show that the MELS controller can achieve the control functions of proper flow supplement,power limitation,and pressure cut-off,which has good stability performance when switching between different control modes.This research proposes the MELS control method that realizes the stability of multi-mode switching of the hydraulic system of mobile machinery under different working conditions. 展开更多
关键词 Hydraulic control Load sensing MULTI-MODE power limitation Mobile machinery
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Flexible Power Regulation and Limitation of Voltage Source Inverters under Unbalanced Grid Faults 被引量:2
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作者 Peng Cheng Kongyuan Li +2 位作者 Chao Wu Jing Ma Limin Jia 《CES Transactions on Electrical Machines and Systems》 CSCD 2022年第2期153-161,共9页
This paper develops a flexible power regulation and limitation strategy of voltage source inverters(VSIs)under unbalanced grid faults.When the classical power theory is used under unbalanced grid faults,the power osci... This paper develops a flexible power regulation and limitation strategy of voltage source inverters(VSIs)under unbalanced grid faults.When the classical power theory is used under unbalanced grid faults,the power oscillations and current distortions are inevitable.In the proposed strategy,the extended power theory is introduced to compute the power feedbacks together with the classical power theory.Based on the combination of the classical and extended power theory,the proposed strategy can achieve the sinusoidal current provision and the flexible regulation between three common targets,i.e.,constant active power,balanced current,and constant reactive power.Meanwhile,the proposed strategy is associated with a power limiter,which is capable to keep the currents under the pre-defined threshold and to compute the maximum apparent power for better utilization of the inverter capacity.With this power limiter,the rated inverter capacity is fully used for both the active and reactive power provisions under unbalanced grid faults.Using the proposed power regulation and limitation,the VSI can avoid overcurrent tripping and flexibly regulate its power under unbalanced grid faults.All the conclusions are verified by the real-time hardware-in-loop tests. 展开更多
关键词 Flexible power regulation power limiter Voltage source inverter Unbalanced faults
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Analysis and design of over-current limit control strategies applied in aeronautical power supplies 被引量:1
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作者 王林兵 何湘宁 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2007年第2期287-291,共5页
Some Over-Current Limit Control strategies are analyzed and designed to meet the demands of high reliability and rapid dynamic response in the aeronautical power supply applications. The control schemes are both effec... Some Over-Current Limit Control strategies are analyzed and designed to meet the demands of high reliability and rapid dynamic response in the aeronautical power supply applications. The control schemes are both effective in DC-DC converters and DC-AC converters. Controller models are set up, and the over-current limit operation principles of analogy and digital control are analyzed too. An 800VA aeronautical power supply bas been constructed to verify the performance of the proposed control strategy in various cases such as the sudden load change and the constant load. The analysis and experiments confirm the advantages of the proposed over-current limit strategies as follows: simple,effective and reliable. 展开更多
关键词 over-current limit control: power converter aeronautical power supply
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Fujian Provincial Electric Power Limited Company Formally Established
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《Electricity》 2000年第2期54-55,共2页
关键词 Grid Fujian Provincial Electric power Limited Company Formally Established
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Fuel Cells as Energy Systems: Efficiency, Power Limits and Thermodynamic Behavior
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作者 S. Sieniutycz 《Journal of Energy and Power Engineering》 2011年第1期17-28,共12页
Steady-state model of a high-temperature solid oxide fuel cell (SOFC) is considered, which refers to constant chemical potentials of incoming hydrogen fuel and oxidant. Lowering of the cell voltage below its reversi... Steady-state model of a high-temperature solid oxide fuel cell (SOFC) is considered, which refers to constant chemical potentials of incoming hydrogen fuel and oxidant. Lowering of the cell voltage below its reversible value is attributed to polarizations and imperfect conversions of reactions. An imperfect power formula summarizes the effect of transport laws, irreversible polarizations and efficiency of power yield. Reversible electrochemical theory is extended to the case with dissipative chemical reactions; this case includes systems with incomplete conversions, characterized by "reduced affinities" and an idle run voltage. Efficiency drop is linked with thermodynamic and electrochemical irreversibilities expressed in terms of polarizations (activation, concentration and ohmic). Effect of incomplete conversions is modeled by assuming that substrates can be remained after the reaction and that side reactions may occur. Optimum and feasibility conditions are discussed for basic input parameters of the cell. Calculations of maximum power show that the data differ for power generated and consumed and depend on current intensity, number of mass transfer units, polarizations, electrode surface area, average chemical rate, etc.. These data provide bounds for SOFC energy generators, which are more exact and informative than reversible bounds for electrochemical transformation. 展开更多
关键词 power limits ENTROPY engines thermal efficiency fuel cells.
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Small Thermal Power Must be Limited
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《Electricity》 1997年第3期25-25,共1页
关键词 Small Thermal power Must be Limited
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The first limited recourse of financing power project without government's guarantee in China runs well
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《Electricity》 2001年第4期50-50,共1页
关键词 The first limited recourse of financing power project without government’s guarantee in China runs well
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海上运输的脱碳:土耳其船队的案例研究
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作者 Berna Kanberoğlu Eda Turan Görkem Kökkülünk 《哈尔滨工程大学学报(英文版)》 CSCD 2023年第4期716-727,共12页
Climate change and global warming are among the most severe threats to the global ecosystem,caused by greenhouse gas emissions.Therefore,all industries that cause environmental emissions should collaborate in the stru... Climate change and global warming are among the most severe threats to the global ecosystem,caused by greenhouse gas emissions.Therefore,all industries that cause environmental emissions should collaborate in the struggle against climate change.In this context,the International Maritime Organization(IMO)approved the initial greenhouse gas strategy at the MEPC 72 session in April 2018 to achieve targets for 2050.With this strategy,the IMO aims to create and improve new regulations that can enhance energy efficiency to achieve their short-term,midterm,and long-term goals.In this study,one of the novel terms,energy efficiency existing ship index(EEXI)values,has been calculated for the Turkish fleet to guide the maritime sector.The Turkish fleet in the study refers to the Turkish-owned vessels both sailing with a national or international flag.In accordance with this regulation,the number of Turkish fleets that were identified as either above or below the IMO reference lines has been determined.Additionally,EEXI values have been recalculated using the engine power limitation(EPL)method for ships that exceed the required limits,and the success rate of this method has been estimated.As a result,the application of EPL increased the number of ships below the Phase 2 reference line from 15.6%to 53.1%.To the best of our knowledge,this research,which has been carried out on all Turkish-owned ships,is the first study intended to serve as a guide for other ship owners in the global maritime industry regarding energy efficiency management. 展开更多
关键词 Energy efficiency existing ship index Energy efficiency EMISSIONS CO_(2) Engine power limitation Decarbonization
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Stability Study of a 23 MVA Turbine Generator
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作者 Godwin Effiong Priye Kenneth Ainah Nduka W. Aguiyi 《Energy and Power Engineering》 CAS 2022年第8期313-326,共14页
Power system stability is a very important issue in power system engineering because a decrease in the stability margins can cause unacceptable operating conditions, which leads to frequent failures. In this paper, SK... Power system stability is a very important issue in power system engineering because a decrease in the stability margins can cause unacceptable operating conditions, which leads to frequent failures. In this paper, SKM POWER TOOLS PTW-32 Version 4.5.2.0 was used to study different Stability recovery tests after a medium voltage short circuit fault on a turbine generator in the power system. The analysis focused on the generator electrical and mechanical powers stability recovery test, generator speed stability recovery test, excitation voltage stability recovery test, bus voltage and bus frequency stability recovery test. In our study, when the introduced fault was cleared after 0.5 s, it reveals that the recovery rate of electrical power was much faster than that of mechanical power. Also, the results reveal that it took about 10 seconds for the turbine speed to stabilize while it took fewer seconds for the frequency to stabilize. 展开更多
关键词 power System Stability Turbine Generator power System Limit
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A Pragmatic Method to Determine Transient Stability Constrained with Interface Real Power Flow Limits via Power System Scenario Similarity 被引量:1
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作者 Xianzhuang Liu Yong Min +3 位作者 Lei Chen Xiaohua Zhang Changyou Feng Wei Hu 《CSEE Journal of Power and Energy Systems》 SCIE CSCD 2020年第1期131-141,共11页
In practical power systems,operators generally keep interface flowing under the transient stability constrained with interface real power flow limits(TS-IRPFL)to guarantee transient stability of the system.Many method... In practical power systems,operators generally keep interface flowing under the transient stability constrained with interface real power flow limits(TS-IRPFL)to guarantee transient stability of the system.Many methods of computing TS-IRPFL have been proposed.However,in practice,the method widely used to determine TS-IRPFL is based on selection and analysis of typical scenarios as well as scenario matching.First,typical scenarios are selected and analyzed to obtain accurate limits,then the scenario to be analyzed is matched with a certain typical scenario,whose limit is adopted as the forecast limit.In this paper,following the steps described above,a pragmatic method to determine TS-IRPFL is proposed.The proposed method utilizes data-driven tools to improve the steps of scenario selection and matching.First of all,we formulate a clear model of power system scenario similarity.Based on the similarity model,we develop a typical scenario selector by clustering and a scenario matcher by nearest neighbor algorithm.The proposed method is pragmatic because it does not change the existing procedure.Moreover,it is much more reasonable than the traditional method.Test results verify the validity of the method. 展开更多
关键词 Clustering data-driven nearest neighbor power system scenario similarity transient stability constrained interface real power flow limit(TSC-IRPFL) typical scenario.
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A micro-power LDO with piecewise voltage foldback current limit protection 被引量:1
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作者 魏海龙 刘佑宝 +1 位作者 郭仲杰 廖雪 《Journal of Semiconductors》 EI CAS CSCD 2012年第11期121-125,共5页
To achieve a constant current limit,low power consumption and high driving capability,a micro-power LDO with a piecewise voltage-foldback current-limit circuit is presented.The current-limit threshold is dynamically a... To achieve a constant current limit,low power consumption and high driving capability,a micro-power LDO with a piecewise voltage-foldback current-limit circuit is presented.The current-limit threshold is dynamically adjusted to achieve a maximum driving capability and lower quiescent current of only 300 nA.To increase the loop stability of the proposed LDO,a high impedance transconductance buffer under a micro quiescent current is designed for splitting the pole that exists at the gate of the pass transistor to the dominant pole,and a zero is designed for the purpose of the second pole phase compensation.The proposed LDO is fabricated in a BiCMOS process. The measurement results show that the short-circuit current of the LDO is 190 mA,the constant limit current under a high drop-out voltage is 440 mA,and the maximum load current under a low drop-out voltage is up to 800 mA. In addition,the quiescent current of the LDO is only 7μA,the load regulation is about 0.56%on full scale,the line regulation is about 0.012%/V,the PSRR at 120 Hz is 58 dB and the drop-out voltage is only 70 mV when the load current is 250 mA. 展开更多
关键词 power protection voltage foldback current limit micro-power LDO
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Design methodology of permanent magnet generators for fixed-pitch tidal turbines with overspeed power limitation strategy
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作者 Sofiane Djebarri Jean Frédéric Charpentier +1 位作者 Frank Scuiller Mohamed Benbouzid 《Journal of Ocean Engineering and Science》 SCIE 2020年第1期73-83,共11页
This paper deals with a design methodology of permanent magnets(PM)generators used for fixed-pitch tidal turbines in a marine renewable energy context.In the case of underwater turbines,fixed-pitch tidal turbines coul... This paper deals with a design methodology of permanent magnets(PM)generators used for fixed-pitch tidal turbines in a marine renewable energy context.In the case of underwater turbines,fixed-pitch tidal turbines could be very attractive and interesting to reduce maintenance operation by avoiding using such a complex electromechanical system for blade-pitching.In this technological case,one of the main control challenges is to ensure power limitation at high tidal current velocities.This control mode can be achieved using the generator flux-weakening.In this context,this paper proposes an original and systemic design methodology to optimize the generator design taking into account the tidal turbine power limitation for high tidal currents velocities. 展开更多
关键词 Tidal turbine Fixed-pitch turbine Direct-drive PM generator Design methodology Flux-weakening power limitation.
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Energy Method in Stretch Reducing Process of Steel Tube 被引量:2
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作者 ZHANG Fang-ping SUN Bin-yu WANG Jian-mei 《Journal of Iron and Steel Research International》 SCIE EI CAS CSCD 2008年第6期39-43,共5页
According to the theories for stretch reducing process and steel tube plastic deformation, the energy method was used to mesh the rolled deformation zone of the steel tube into the upper limit elements, and an admissi... According to the theories for stretch reducing process and steel tube plastic deformation, the energy method was used to mesh the rolled deformation zone of the steel tube into the upper limit elements, and an admissible velocity field was constructed to deduce a series of formulas of the inner virtual power consumption of deformed bodies. The roiling force during the stretch reducing process could be obtained by optimizing the upper limit power, which could provide guidelines for a proper choice of the stretch reducing process and devices for steel tube companies, as well as new products and devices. 展开更多
关键词 upper limit power rolling force velocity field
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A Novel Design of Hybrid Energy Storage System for Electric Vehicles 被引量:6
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作者 Xiangyang Xia Xinxin Zhao +1 位作者 Heqing Zeng Xiaoyong Zeng 《Chinese Journal of Electrical Engineering》 CSCD 2018年第1期45-51,共7页
In order to provide long distance endurance and ensure the minimization of a cost function for electric vehicles,a new hybrid energy storage system for electric vehicle is designed in this paper.For the hybrid energy ... In order to provide long distance endurance and ensure the minimization of a cost function for electric vehicles,a new hybrid energy storage system for electric vehicle is designed in this paper.For the hybrid energy storage system,the paper proposes an optimal control algorithm designed using a Li-ion battery power dynamic limitation rule-based control based on the SOC of the super-capacitor.At the same time,the magnetic integration technology adding a second-order Bessel low-pass filter is introduced to DC-DC converters of electric vehicles.As a result,the size of battery is reduced,and the power quality of the hybrid energy storage system is optimized.Finally,the effectiveness of the proposed method is validated by simulation and experiment. 展开更多
关键词 Hybrid energy storage system integrated magnetic structure electric vehicles DC-DC converter power dynamic limitation
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Concept and design of super junction devices 被引量:4
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作者 Bo Zhang Wentong Zhang +2 位作者 Ming Qiao Zhenya Zhan Zhaoji Li 《Journal of Semiconductors》 EI CAS CSCD 2018年第2期1-12,共12页
The super junction(SJ) has been recognized as the "milestone" of the power MOSFET, which is the most important innovation concept of the voltage-sustaining layer(VSL). The basic structure of the SJ is a typical ... The super junction(SJ) has been recognized as the "milestone" of the power MOSFET, which is the most important innovation concept of the voltage-sustaining layer(VSL). The basic structure of the SJ is a typical junction-type VSL(J-VSL) with the periodic N and P regions. However, the conventional VSL is a typical resistance-type VSL(R-VSL) with only an N or P region. It is a qualitative change of the VSL from the R-VSL to the JVSL, introducing the bulk depletion to increase the doping concentration and optimize the bulk electric field of the SJ. This paper firstly summarizes the development of the SJ, and then the optimization theory of the SJ is discussed for both the vertical and the lateral devices, including the non-full depletion mode, the minimum specific on-resistance optimization method and the equivalent substrate model. The SJ concept breaks the conventional"silicon limit" relationship of R_(on)∝V_B^(2.5), showing a quasi-linear relationship of R_(on)∝V_B^(1.03). 展开更多
关键词 super junction silicon limit power semiconductor device design theory
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Three-photon absorption in a push-pull type chromophore containing tricyanofuran acceptor
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作者 Yan Ji Ying Qian +2 位作者 Zhi Qiang Zhou Wei Lu Yi Ping Cui 《Chinese Chemical Letters》 SCIE CAS CSCD 2012年第7期757-760,共4页
Three-photon absorption(3PA) of a push-pull chromophore,2-(3-cyano-(3-(4-(dimethylamino)styryl)-5,5-dimethylcyclohex- 2-enylidene)methyl)-5,5-dimethylfuran-2-ylidene) malononitrile(CFM) including TCF grou... Three-photon absorption(3PA) of a push-pull chromophore,2-(3-cyano-(3-(4-(dimethylamino)styryl)-5,5-dimethylcyclohex- 2-enylidene)methyl)-5,5-dimethylfuran-2-ylidene) malononitrile(CFM) including TCF group was measured by the nonlinear transmission method using a femto-second Ti:Sapphire oscillator-amplifier laser system.Its three-photon absorption cross-sections at 1300 ran were 36.8×10^-79 cm^6 s^2 in the solution of DMF and 12.3×10^-79 cm^6 s^2 in the solution of CH_2Cl_2,respectively.The large values were got by experiments in this paper,which is a new exploration for these kinds of materials.The molecule has the potential application foreground of 3PA areas and optical power limiting. 展开更多
关键词 Three-photon absorption Optical power limiting Nonlinear transmission method Push-pull chromophore TCF
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