Stimulated Raman scattering （SRS） effect is considered to be one of the main obstacles for power scaling in general-type fber lasers. Different from previous techniques that aim at suppressing SRS, nonlinear fiber a...Stimulated Raman scattering （SRS） effect is considered to be one of the main obstacles for power scaling in general-type fber lasers. Different from previous techniques that aim at suppressing SRS, nonlinear fiber amplifier （NFA）, which manipulates and employs the SRS for power scaling in rare-earth-doped fiber, is under intensive research in recent years. In this paper, the authors will present an all-round study on this new kind of high-power fiber amplifier. A theoretical model is proposed based on the rate equation and amplified spontaneous emission （ASE）, with random noise taken into account. By numerical solving of the theoretical model, the power scaling potential, heat analysis and advantages in suppressing the undesired backscattering light are quantificationally analyzed for the first time. Then two different types of high-power NFAs are demonstrated individually. Firstly, a laser diode pumped NFA has reached kilowatt output power, and the results agree well with theoretical predictions. Secondly, a tandem-pumped NFA is proposed for the first time and validated experimentally, in which 1.5 kW output power has been achieved. The authors also briefly discuss several new issues relating to the complex nonlinear dynamics that occur in high-power NFAs, which might be interesting topics for future endeavors.展开更多
Direct writing of graphene patterns and devices may significantly facilitate the application of graphene-based flexible electronics. In terms of scalability and cost efficiency, inkjet printing is very competitive ove...Direct writing of graphene patterns and devices may significantly facilitate the application of graphene-based flexible electronics. In terms of scalability and cost efficiency, inkjet printing is very competitive over other existing direct- writing methods. However, it has been challenging to obtain highly stable and clog-free graphene-based ink. Here, we report an alternative and highly efficient technique to directly print a reducing reagent on graphene oxide film to form conductive graphene patterns. By this ＂inkjet reduction＂ method, without using any other microfabrication technique, conductive graphene patterns and devices for various applications are obtained. The ionic nature of the reductant ink makes it clog-free and stable for continuous and large-area printing. The method shows self-limited reduction feature, which enables electrical conductivity of graphene patterns to be tuned within 5 orders of magnitude, reaching as high as 8,000 S.m-1. Furthermore, this method can be extended to produce noble metal/graphene composite patterns. The devices, including transistors, biosensors, and surface- enhanced Raman scattering substrates, demonstrate excellent functionalities. This work provides a new strategy to prepare large-area graphene-based devices that is low-cost and highly efficient, promising to advance research on graphene- based flexible electronics.展开更多
Amorphous chalcogenide thin films were fabricated by the pulsed laser deposition technique. Thereafter, the stacks of multilayered thin films for reflectors and microcavity were designed for telecommunication waveleng...Amorphous chalcogenide thin films were fabricated by the pulsed laser deposition technique. Thereafter, the stacks of multilayered thin films for reflectors and microcavity were designed for telecommunication wavelength. The prepared multilayered thin films for reflectors show good compatibility. The microcavity structure consists of Ge_(25)Ga)5Sb_(10)S_(65)(doped with Er^(3+)) spacer layer surrounded by two 5-layer As_(40)Se_(60)/Ge_(25)Sb_(5)S_(70) reflectors. Scanning/transmission electron microscopy results show good periodicity, great adherence and smooth interfaces between the alternating dielectric layers, which confirms a suitable compatibility between different materials. The results demonstrate that the chalcogenides can be used for preparing vertical Bragg reflectors and microcavity with high quality.展开更多
基金supported by the Natural Science Foundation of Hunan Province,China(No.2018JJ2474)the Huo Yingdong Education Foundation of China
文摘Stimulated Raman scattering （SRS） effect is considered to be one of the main obstacles for power scaling in general-type fber lasers. Different from previous techniques that aim at suppressing SRS, nonlinear fiber amplifier （NFA）, which manipulates and employs the SRS for power scaling in rare-earth-doped fiber, is under intensive research in recent years. In this paper, the authors will present an all-round study on this new kind of high-power fiber amplifier. A theoretical model is proposed based on the rate equation and amplified spontaneous emission （ASE）, with random noise taken into account. By numerical solving of the theoretical model, the power scaling potential, heat analysis and advantages in suppressing the undesired backscattering light are quantificationally analyzed for the first time. Then two different types of high-power NFAs are demonstrated individually. Firstly, a laser diode pumped NFA has reached kilowatt output power, and the results agree well with theoretical predictions. Secondly, a tandem-pumped NFA is proposed for the first time and validated experimentally, in which 1.5 kW output power has been achieved. The authors also briefly discuss several new issues relating to the complex nonlinear dynamics that occur in high-power NFAs, which might be interesting topics for future endeavors.
文摘Direct writing of graphene patterns and devices may significantly facilitate the application of graphene-based flexible electronics. In terms of scalability and cost efficiency, inkjet printing is very competitive over other existing direct- writing methods. However, it has been challenging to obtain highly stable and clog-free graphene-based ink. Here, we report an alternative and highly efficient technique to directly print a reducing reagent on graphene oxide film to form conductive graphene patterns. By this ＂inkjet reduction＂ method, without using any other microfabrication technique, conductive graphene patterns and devices for various applications are obtained. The ionic nature of the reductant ink makes it clog-free and stable for continuous and large-area printing. The method shows self-limited reduction feature, which enables electrical conductivity of graphene patterns to be tuned within 5 orders of magnitude, reaching as high as 8,000 S.m-1. Furthermore, this method can be extended to produce noble metal/graphene composite patterns. The devices, including transistors, biosensors, and surface- enhanced Raman scattering substrates, demonstrate excellent functionalities. This work provides a new strategy to prepare large-area graphene-based devices that is low-cost and highly efficient, promising to advance research on graphene- based flexible electronics.
基金supported by the National Natural Science Foundation of China(No.61308092)the Natural Science Foundation of Liaoning Province of China(No.2013010590-401/20131116)
文摘Amorphous chalcogenide thin films were fabricated by the pulsed laser deposition technique. Thereafter, the stacks of multilayered thin films for reflectors and microcavity were designed for telecommunication wavelength. The prepared multilayered thin films for reflectors show good compatibility. The microcavity structure consists of Ge_(25)Ga)5Sb_(10)S_(65)(doped with Er^(3+)) spacer layer surrounded by two 5-layer As_(40)Se_(60)/Ge_(25)Sb_(5)S_(70) reflectors. Scanning/transmission electron microscopy results show good periodicity, great adherence and smooth interfaces between the alternating dielectric layers, which confirms a suitable compatibility between different materials. The results demonstrate that the chalcogenides can be used for preparing vertical Bragg reflectors and microcavity with high quality.
