A technique is used to design the spectra in erbium doped superfluorescent fiber source experimentally and theoretically.In an erbium doped fiber with a 10m length and 300ppm concentration,a line width of about 42nm a...A technique is used to design the spectra in erbium doped superfluorescent fiber source experimentally and theoretically.In an erbium doped fiber with a 10m length and 300ppm concentration,a line width of about 42nm and high mean wavelength stability(<0.lppm/K,<0.2ppm/mW)were obtained by means of a suitable population distribution,and adjusting the ratio of backward to forward pump power.Also,its thermal characteristic is studied.These results will improve the performance of fiber optical gyroscope and fiber sensors,and will be applied in erbium doped fiber amplifier with flattening gain.展开更多
It is the core to improve the electron/ion transfer features of Li_(4)Ti_(5)O_(12) for achieving high-rate anode in lithium ion batteries.By directly using graphite oxide powder,nano-Li_(4)Ti_(5)O_(12)/reduced graphit...It is the core to improve the electron/ion transfer features of Li_(4)Ti_(5)O_(12) for achieving high-rate anode in lithium ion batteries.By directly using graphite oxide powder,nano-Li_(4)Ti_(5)O_(12)/reduced graphite oxide composite with mesopore-oriented porosity is prepared through one-pot facile ball-milling method in this work.Synthesis mechanism underlying the self-nucleophilic effect of oxygen-containing functional groups in graphite oxide is substantiated.Reactants can intercalate into graphite oxide bulk and in-situ generate nanoparticles.Subsequently,graphite oxide with nanoparticles generated inside can obtain a mesopore-oriented porous structure under ball-milling.Furthermore,the synergistic effects of Li_(4)Ti_(5)O_(12) nanoparticles and mesopore-oriented porosity strengthen composites with rapid Li^(+)diffusion and electron conductive frameworks.The obtained optimal LTO/GO-1.75 composite displays excellent high-rate capability(136 mA·h/g at 7000 mA/g)and good cycling stability(a capacity retention of 72%after 1000 cycles at 7000 mA/g).Additionally,the reactants concentration in this demonstrated strategy is as high as 30 wt%−40 wt%,which is over 6 times that of traditional methods with GO suspensions.It means that the strategy can significantly increase the yield,showing big potential for large-scale production.展开更多
A step index-type Nd^(3+) -doped polymer optical fiber(POF)was prepared by using bulk polymerization of solution of Nd^(3+) -octanoate(NOA)and methyl and methacrylate.A method of wide-angle x-ray diffraction was used ...A step index-type Nd^(3+) -doped polymer optical fiber(POF)was prepared by using bulk polymerization of solution of Nd^(3+) -octanoate(NOA)and methyl and methacrylate.A method of wide-angle x-ray diffraction was used to measure the solubility of NOA.In a high concentration Nd^(3+) doped POF,a residual absorption at 810nm could not be saturated,which is attributed to the high clustered ion rate in the Nd^(3+) POF.A model based on the rate equations to infer the clustered ion rate by the measurement of transmission is presented.展开更多
We propose and demonstrate a nanosecond square pulse ytterbium doped fiber laser in the 1060 nm band.The laser is based on the figure-8 structure and has a tunable pulse bandwidth from 3 ns to beyond 100 ns,showing ex...We propose and demonstrate a nanosecond square pulse ytterbium doped fiber laser in the 1060 nm band.The laser is based on the figure-8 structure and has a tunable pulse bandwidth from 3 ns to beyond 100 ns,showing excellent temporal tuning ability.The experimental results show that a steady square pulse can be generated when the parameters of the cavity are chosen appropriately.展开更多
The Judd-Ofelt theory was applied to optical-absorption transitions in an Nd^(3+)-doped polymer opticalfibre to obtain the intensity parameters (Ω_(2) = 0.83 x 10^(-20) cm^(2), 4 = 1.64 x 10^(-20) cm^(2), Ω_(6) = 4....The Judd-Ofelt theory was applied to optical-absorption transitions in an Nd^(3+)-doped polymer opticalfibre to obtain the intensity parameters (Ω_(2) = 0.83 x 10^(-20) cm^(2), 4 = 1.64 x 10^(-20) cm^(2), Ω_(6) = 4.04 x 10-20 cm^(2)), the radiative lifetime (371 μs) and the quantum efficiency (0.73) of the 4G5/2level, from which we found tlat the transition probability from 4G5/2 to 4I9/2 (Aij = 1995.7s^(-1)) is higher than others. Thus, in the polymer system, the traditional four-level laser system for Nd3+ was substituted by a three-level system. Furthermore, we have calculated the emission cross section (σeij = 2.45 × 10^(-21) cm^(2)), and solved the differential equations of the single-pass gain. In comparison with inorganic opticalfibres, an increased saturated intensity is observed.展开更多
By applying a strong coupling field between a lower state and the upper state of an allowed transition to ground,an enhancement of nondegenerate four wave mixing(NDFWM)with a resonantly enhanced third-order nonlinear ...By applying a strong coupling field between a lower state and the upper state of an allowed transition to ground,an enhancement of nondegenerate four wave mixing(NDFWM)with a resonantly enhanced third-order nonlinear susceptibility in a rare-earth doped fiber can be obtained.We have derived an expression for the third-order nonlinear susceptibility using quantum theory and discussed the conversion efficiency for NDFWM.The theoretical result shows that the conversion efficiency has a maximum value while the third-order nonlinear susceptibility shows constructive interference at the Rabi frequencyΩ_(23)=±-√Г2Г3.On account of phase-mismatch,the frequency conversion efficiency has a maximum value over a certain small range of frequency separation(such as 0<△f<30 GHz at the wavelengthλ_(c)=1.55μm),and the frequency conversion range increases with increase of the third-order nonlinear susceptibility.展开更多
Shearing interferometry of an ion-etched holographic double-frequency grating is used to measure the optical coherence of femtosecond pulsed lasers.The experimental results show that the optical coherence of the femto...Shearing interferometry of an ion-etched holographic double-frequency grating is used to measure the optical coherence of femtosecond pulsed lasers.The experimental results show that the optical coherence of the femtosecond light beam is not only related to the spectral width and size of the light source but is also related to the pulse duration and mode-locked laser state.The results of theoretical analysis and numerical calculation are also given.Application of this research is also discussed.展开更多
CaCu _(3)Ti_(4)O_(12)(CCTO)thin films were fabricated on ITO−covered MgO(100)substrates.The rectification characteristics were observed in the CCTO capacitance structure with Pt top electrodes at temperatures ranging ...CaCu _(3)Ti_(4)O_(12)(CCTO)thin films were fabricated on ITO−covered MgO(100)substrates.The rectification characteristics were observed in the CCTO capacitance structure with Pt top electrodes at temperatures ranging from 150 K to 330 K,which are attributed to the formation of a Schottky junction between n-type semiconducting CCTO and Pt due to the difference of their work functions.At low forward-bias voltage,the current-voltage characteristics of the Schottky junction follow J=JsD exp[qV/(k0T)].A strong decrease in ideality factor with the increasing temperature is obtained by linear fitting at the low bias voltage.展开更多
The boundary diffraction method is introduced to analyze the near-field diffraction of a subwavelength aperture. A self-consistent formula of boundary diffraction suitable to near field is derived. The near-field diff...The boundary diffraction method is introduced to analyze the near-field diffraction of a subwavelength aperture. A self-consistent formula of boundary diffraction suitable to near field is derived. The near-field diffraction patterns of slits and circular apertures are obtained. The influence of incident light polarization on these diffraction patterns is also shown. These results are in good agreement with other theoretical and experimental results.展开更多
基金Supported by the National Natural Science Foundation of China under Grand No.19674053.
文摘A technique is used to design the spectra in erbium doped superfluorescent fiber source experimentally and theoretically.In an erbium doped fiber with a 10m length and 300ppm concentration,a line width of about 42nm and high mean wavelength stability(<0.lppm/K,<0.2ppm/mW)were obtained by means of a suitable population distribution,and adjusting the ratio of backward to forward pump power.Also,its thermal characteristic is studied.These results will improve the performance of fiber optical gyroscope and fiber sensors,and will be applied in erbium doped fiber amplifier with flattening gain.
基金Project(21875283) supported by the the National Natural Science Foundation of China。
文摘It is the core to improve the electron/ion transfer features of Li_(4)Ti_(5)O_(12) for achieving high-rate anode in lithium ion batteries.By directly using graphite oxide powder,nano-Li_(4)Ti_(5)O_(12)/reduced graphite oxide composite with mesopore-oriented porosity is prepared through one-pot facile ball-milling method in this work.Synthesis mechanism underlying the self-nucleophilic effect of oxygen-containing functional groups in graphite oxide is substantiated.Reactants can intercalate into graphite oxide bulk and in-situ generate nanoparticles.Subsequently,graphite oxide with nanoparticles generated inside can obtain a mesopore-oriented porous structure under ball-milling.Furthermore,the synergistic effects of Li_(4)Ti_(5)O_(12) nanoparticles and mesopore-oriented porosity strengthen composites with rapid Li^(+)diffusion and electron conductive frameworks.The obtained optimal LTO/GO-1.75 composite displays excellent high-rate capability(136 mA·h/g at 7000 mA/g)and good cycling stability(a capacity retention of 72%after 1000 cycles at 7000 mA/g).Additionally,the reactants concentration in this demonstrated strategy is as high as 30 wt%−40 wt%,which is over 6 times that of traditional methods with GO suspensions.It means that the strategy can significantly increase the yield,showing big potential for large-scale production.
基金Supported by the National Natural Science Foundation of China under Grant No.19674053。
文摘A step index-type Nd^(3+) -doped polymer optical fiber(POF)was prepared by using bulk polymerization of solution of Nd^(3+) -octanoate(NOA)and methyl and methacrylate.A method of wide-angle x-ray diffraction was used to measure the solubility of NOA.In a high concentration Nd^(3+) doped POF,a residual absorption at 810nm could not be saturated,which is attributed to the high clustered ion rate in the Nd^(3+) POF.A model based on the rate equations to infer the clustered ion rate by the measurement of transmission is presented.
基金Supported by the National Natural Science Foundation of China under Grant No 10876038/A06the Key Laboratory of Environment Optics and Technology of Chinese Academy of Sciences.
文摘We propose and demonstrate a nanosecond square pulse ytterbium doped fiber laser in the 1060 nm band.The laser is based on the figure-8 structure and has a tunable pulse bandwidth from 3 ns to beyond 100 ns,showing excellent temporal tuning ability.The experimental results show that a steady square pulse can be generated when the parameters of the cavity are chosen appropriately.
基金Supported by the National Natural Science Foundation of China under Grant No.19974042the Research Fund for the Doctoral Programme of Higher Education No.1999035822。
文摘The Judd-Ofelt theory was applied to optical-absorption transitions in an Nd^(3+)-doped polymer opticalfibre to obtain the intensity parameters (Ω_(2) = 0.83 x 10^(-20) cm^(2), 4 = 1.64 x 10^(-20) cm^(2), Ω_(6) = 4.04 x 10-20 cm^(2)), the radiative lifetime (371 μs) and the quantum efficiency (0.73) of the 4G5/2level, from which we found tlat the transition probability from 4G5/2 to 4I9/2 (Aij = 1995.7s^(-1)) is higher than others. Thus, in the polymer system, the traditional four-level laser system for Nd3+ was substituted by a three-level system. Furthermore, we have calculated the emission cross section (σeij = 2.45 × 10^(-21) cm^(2)), and solved the differential equations of the single-pass gain. In comparison with inorganic opticalfibres, an increased saturated intensity is observed.
基金Supported by the National Natural Science Foundation of China under Grant No.19674053.
文摘By applying a strong coupling field between a lower state and the upper state of an allowed transition to ground,an enhancement of nondegenerate four wave mixing(NDFWM)with a resonantly enhanced third-order nonlinear susceptibility in a rare-earth doped fiber can be obtained.We have derived an expression for the third-order nonlinear susceptibility using quantum theory and discussed the conversion efficiency for NDFWM.The theoretical result shows that the conversion efficiency has a maximum value while the third-order nonlinear susceptibility shows constructive interference at the Rabi frequencyΩ_(23)=±-√Г2Г3.On account of phase-mismatch,the frequency conversion efficiency has a maximum value over a certain small range of frequency separation(such as 0<△f<30 GHz at the wavelengthλ_(c)=1.55μm),and the frequency conversion range increases with increase of the third-order nonlinear susceptibility.
基金Supported by the National Natural Science Foundation of China under Grant No.69577005。
文摘Shearing interferometry of an ion-etched holographic double-frequency grating is used to measure the optical coherence of femtosecond pulsed lasers.The experimental results show that the optical coherence of the femtosecond light beam is not only related to the spectral width and size of the light source but is also related to the pulse duration and mode-locked laser state.The results of theoretical analysis and numerical calculation are also given.Application of this research is also discussed.
基金by the National Key Basic Research Program of China under Grant No 2011CB301802.
文摘CaCu _(3)Ti_(4)O_(12)(CCTO)thin films were fabricated on ITO−covered MgO(100)substrates.The rectification characteristics were observed in the CCTO capacitance structure with Pt top electrodes at temperatures ranging from 150 K to 330 K,which are attributed to the formation of a Schottky junction between n-type semiconducting CCTO and Pt due to the difference of their work functions.At low forward-bias voltage,the current-voltage characteristics of the Schottky junction follow J=JsD exp[qV/(k0T)].A strong decrease in ideality factor with the increasing temperature is obtained by linear fitting at the low bias voltage.
基金the National Natural Science Foundation of China under Grant No.69577005。
文摘The boundary diffraction method is introduced to analyze the near-field diffraction of a subwavelength aperture. A self-consistent formula of boundary diffraction suitable to near field is derived. The near-field diffraction patterns of slits and circular apertures are obtained. The influence of incident light polarization on these diffraction patterns is also shown. These results are in good agreement with other theoretical and experimental results.
