A Smith-Purcell （SP） free electron laser （FEL） ,composed of a metallic diffraction flat grating,an open cylindrical mirror cavity and a relativistic sheet electron beam with moderate energy, is presented. The char...A Smith-Purcell （SP） free electron laser （FEL） ,composed of a metallic diffraction flat grating,an open cylindrical mirror cavity and a relativistic sheet electron beam with moderate energy, is presented. The characteristics of this device are studied by theoretical analysis,experimental measurements and particle-in-cell （PIO） simulation method. Results indicate that the coherent radiation with an output peak power up to 50 MW at millimeter wavelengths can be generated by using relativistic electron beam of moderate energy.展开更多
An opportunity to use laser radiation as a means to reduce negative aftermath of acute and prolonged exposure to ionizing radiation was checked. The mice were exposed to γ- rays of ^60Co （whole body irradiation） in...An opportunity to use laser radiation as a means to reduce negative aftermath of acute and prolonged exposure to ionizing radiation was checked. The mice were exposed to γ- rays of ^60Co （whole body irradiation） in the dose of 7 Gy （the transitional clinical form of the acute radiation sickness）. The dose rate at acute irradiation was 1.14 Gy/min, and at prolonged exposure, 0.027 Gy/min. Laser radiation in the dose l mJ/cm^2 was used to irradiate only the back of a mouse. First, the mice were exposed to γ-radiation, then to laser radiation. The time interval between two types of irradiation did not exceed 30 min. It was shown that the radiation protection of mice with laser radiation is possible at exposure to ionizing radiation in a wide dose interval and can reduce negative after-effects of both the acute and prolonged radiation exposure.展开更多
The development of cleaning optics and deposition-mitigating techniques is a key factor in the construction and operation of optical diagnostics in ITER. The cleaning of optical surface by pulsed radiation from a fibe...The development of cleaning optics and deposition-mitigating techniques is a key factor in the construction and operation of optical diagnostics in ITER. The cleaning of optical surface by pulsed radiation from a fiber laser is an effective method that can recover optical properties of the mirror surface. The possibility of cleaning metallic mirrors from films with complex composition by pulsed radiation from a fiber laser has been experimentally researched. It has been shown that the high initial reflection characteristics of optical elements can be recovered by choosing regimes of radiation effect on the deposited surface. Efficient cleaning is ensured by radiation with the power density of less than 107 W/cm2. At this relatively low power density, pollutions are removed in a solid phase and the thermal effect on the mirror is insignificant. Preliminary experiments of the metal mirrors cleaning by fiber laser radiation have demonstrated the possibility of hardware implementation techniques.展开更多
The characteristics of low frequency electrical noise, voltage current ( V I ) and electrical derivation for 980 nm InGaAsP/InGaAs/GaAs high power double quantum well lasers(DQWLs) are measured under different conditi...The characteristics of low frequency electrical noise, voltage current ( V I ) and electrical derivation for 980 nm InGaAsP/InGaAs/GaAs high power double quantum well lasers(DQWLs) are measured under different conditions. The correlation of the low frequency electrical noise with surface non radiative current of devices is discussed. The results indicate the low frequency electrical noise of 980 nm DQWLs with high power is mainly 1/ f noise and has good relation with the device surface current at low injection.展开更多
The Ho^(3+)/Pr^(3+) co-doped Na YF4 single crystals with various Pr^(3+) concentrations and constant Ho^(3+) molar percentage of ~1% were grown by an improved Bridgman method.Compared with the Ho^(3+) single-doped Na ...The Ho^(3+)/Pr^(3+) co-doped Na YF4 single crystals with various Pr^(3+) concentrations and constant Ho^(3+) molar percentage of ~1% were grown by an improved Bridgman method.Compared with the Ho^(3+) single-doped Na YF4 crystal,an obviously enhanced emission band at 2.85 μm is observed under 640 nm excitation.The Judd-Ofelt strength parameters(?2,?4 and ?6) are calculated,the radiative transition probabilities(A),the fluorescence branching ratios(β) and the radiative lifetime(τrad) are obtained in the meantime.The energy transfer from Pr^(3+) to Ho^(3+) and the optimum fluorescence emission of Ho^(3+) ions around 2.85 μm are investigated.Moreover,the maximum emission cross section of above samples at 2.85 μm is calculated to be 0.72×10^(-20) cm2 for the Na YF4 single crystal with Ho^(3+) molar percentage of 1% and Pr^(3+) molar percentage of 0.5% according to the measured absorption spectrum.All results suggest that the Ho^(3+)/Pr^(3+) co-doped Na YF4 single crystal may have potential applications in mid-infrared lasers.展开更多
A new scheme for fabricating a kind of flexible semiconductor micro-laser is put forward.And the optical properties of this kind of flexible semiconductor laser are investigated by the finite difference time domain(FD...A new scheme for fabricating a kind of flexible semiconductor micro-laser is put forward.And the optical properties of this kind of flexible semiconductor laser are investigated by the finite difference time domain(FDTD) method.The results show that the light should be localized by photonic crystals(PCs),and the interaction between light and gain medium should be enhanced,while the mode of laser should be modulated.These results indicate that the PCs could control the spontaneous emission,and lead the radiation emission to the needed frequency.展开更多
文摘A Smith-Purcell （SP） free electron laser （FEL） ,composed of a metallic diffraction flat grating,an open cylindrical mirror cavity and a relativistic sheet electron beam with moderate energy, is presented. The characteristics of this device are studied by theoretical analysis,experimental measurements and particle-in-cell （PIO） simulation method. Results indicate that the coherent radiation with an output peak power up to 50 MW at millimeter wavelengths can be generated by using relativistic electron beam of moderate energy.
文摘An opportunity to use laser radiation as a means to reduce negative aftermath of acute and prolonged exposure to ionizing radiation was checked. The mice were exposed to γ- rays of ^60Co （whole body irradiation） in the dose of 7 Gy （the transitional clinical form of the acute radiation sickness）. The dose rate at acute irradiation was 1.14 Gy/min, and at prolonged exposure, 0.027 Gy/min. Laser radiation in the dose l mJ/cm^2 was used to irradiate only the back of a mouse. First, the mice were exposed to γ-radiation, then to laser radiation. The time interval between two types of irradiation did not exceed 30 min. It was shown that the radiation protection of mice with laser radiation is possible at exposure to ionizing radiation in a wide dose interval and can reduce negative after-effects of both the acute and prolonged radiation exposure.
文摘The development of cleaning optics and deposition-mitigating techniques is a key factor in the construction and operation of optical diagnostics in ITER. The cleaning of optical surface by pulsed radiation from a fiber laser is an effective method that can recover optical properties of the mirror surface. The possibility of cleaning metallic mirrors from films with complex composition by pulsed radiation from a fiber laser has been experimentally researched. It has been shown that the high initial reflection characteristics of optical elements can be recovered by choosing regimes of radiation effect on the deposited surface. Efficient cleaning is ensured by radiation with the power density of less than 107 W/cm2. At this relatively low power density, pollutions are removed in a solid phase and the thermal effect on the mirror is insignificant. Preliminary experiments of the metal mirrors cleaning by fiber laser radiation have demonstrated the possibility of hardware implementation techniques.
文摘The characteristics of low frequency electrical noise, voltage current ( V I ) and electrical derivation for 980 nm InGaAsP/InGaAs/GaAs high power double quantum well lasers(DQWLs) are measured under different conditions. The correlation of the low frequency electrical noise with surface non radiative current of devices is discussed. The results indicate the low frequency electrical noise of 980 nm DQWLs with high power is mainly 1/ f noise and has good relation with the device surface current at low injection.
基金supported by the National Natural Science Foundation of China(No.51272109)the Natural Science Foundation of Ningbo City(No.201401A6105016)the K.C.Wong Magna Fund in Ningbo University
文摘The Ho^(3+)/Pr^(3+) co-doped Na YF4 single crystals with various Pr^(3+) concentrations and constant Ho^(3+) molar percentage of ~1% were grown by an improved Bridgman method.Compared with the Ho^(3+) single-doped Na YF4 crystal,an obviously enhanced emission band at 2.85 μm is observed under 640 nm excitation.The Judd-Ofelt strength parameters(?2,?4 and ?6) are calculated,the radiative transition probabilities(A),the fluorescence branching ratios(β) and the radiative lifetime(τrad) are obtained in the meantime.The energy transfer from Pr^(3+) to Ho^(3+) and the optimum fluorescence emission of Ho^(3+) ions around 2.85 μm are investigated.Moreover,the maximum emission cross section of above samples at 2.85 μm is calculated to be 0.72×10^(-20) cm2 for the Na YF4 single crystal with Ho^(3+) molar percentage of 1% and Pr^(3+) molar percentage of 0.5% according to the measured absorption spectrum.All results suggest that the Ho^(3+)/Pr^(3+) co-doped Na YF4 single crystal may have potential applications in mid-infrared lasers.
基金supported by the National Natural Science Foundation of China (Nos.60768001 and 60808019)the Natural Science Foundation of Jiangxi Province (No. 2010gzw0045)
文摘A new scheme for fabricating a kind of flexible semiconductor micro-laser is put forward.And the optical properties of this kind of flexible semiconductor laser are investigated by the finite difference time domain(FDTD) method.The results show that the light should be localized by photonic crystals(PCs),and the interaction between light and gain medium should be enhanced,while the mode of laser should be modulated.These results indicate that the PCs could control the spontaneous emission,and lead the radiation emission to the needed frequency.
