Frequency-tunable microwave signal generation is proposed and experimentally demonstrated with a dual-wavelength single-longitudinal-mode （SLM） erbium-doped fiber ring laser based on a digital Opto-DMD processor and...Frequency-tunable microwave signal generation is proposed and experimentally demonstrated with a dual-wavelength single-longitudinal-mode （SLM） erbium-doped fiber ring laser based on a digital Opto-DMD processor and four-wave mixing （FWM） in a high-nonlinear photonic crystal fiber （PCF）. The high-nonlinear PCF is employed for the generation of the FWM to obtain stable and uniform dual-wavelength oscillation. Two different short passive sub-ring cavities in the main ring cavity serve as mode filters to make SLM lasing. The two lasing wavelengths are electronically selected by loading different gratings on the Opto-DMD processor controlled with a computer. The wavelength spacing can be smartly adjusted from 0.165 nm to 1.08 nm within a tuning accuracy of 0.055 nm. Two microwave signals at 17.23 GHz and 27.47 GHz are achieved. The stability of the microwave signal is discussed. The system has the ability to generate a 137.36-GHz photonic millimeter signal at room temperature.展开更多
Laser shaping was introduced to maskless projection soft lithography by using digital micro-mirror device (DMD). The predesigned intensity pattern was imprinted onto the DMD and the input laser beam with a Gaussian or...Laser shaping was introduced to maskless projection soft lithography by using digital micro-mirror device (DMD). The predesigned intensity pattern was imprinted onto the DMD and the input laser beam with a Gaussian or quasi-Gaussian distribution will carry the pattern on DMD to etch the resin. It provides a method of precise control of laser beam shapes and?photon-induced curing behavior of resin. This technology provides an accurate micro-fabrication of microstructures used for micro-systems. As a virtual mask generator and a binary-amplitude spatial light modulator, DMD is equivalent to the masks in the conventional exposure system. As the virtual masks and shaped laser beam can be achieved flexibly, it is a good method of precision soft lithography for 2D/3D microstructures.展开更多
Multilayer of laser direct metal deposition（DMD）was prepared by depositing a gas atomized pre-alloyed powder with a composition close to Inconel 718 alloy on Inconel 718 high temperature alloy substrate.The effects ...Multilayer of laser direct metal deposition（DMD）was prepared by depositing a gas atomized pre-alloyed powder with a composition close to Inconel 718 alloy on Inconel 718 high temperature alloy substrate.The effects of the DMD parameters on the build-up rate and the structure of the deposited layer were studied.The laser DMD sample was further processed by a solution treatment.The microstructure and property of the laser DMD zone before and after heat treatment were investigated as well.The results show that the laser parameters of actual laser power of 650 W,scanning speed of 5.8 mm/s,beam diameter of 1 mm,powder feed rate of 6.45 g/min,with a corresponding specific energy of 90-130 J/mm2,can be recommended as optimum parameters for high build-up rate of Inconel 718 alloy.Under the condition of optimized parameters,a directional solidification microstructure was obtained and the average distance between the columnar crystals was 5-10 μm.The microcomposition segregation was found between the columnar crystal trunk and columnar crystal.The elements of Nb,Mo,Ti concentrated in the columnar crystal trunk.After the heat treatment,the segregation was greatly minimized,and the segregation ratios were close to 1.The hardness of the laser deposited layer did not show obvious difference along the height of the layer either for the as-deposited layer or for the heat treated layer.However,the microhardness of the laser DMD zone after heat treatment was obviously higher than that after the as-deposited treatment.During the heat treatment process,some Nb-and Mo-rich phases precipitated and strengthened DMD layer.展开更多
基金supported by the National Basic Research Program of China(Grant No.2010CB327605)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20120005120021)+2 种基金the Fundamental Research Funds for the Central Universities,China(Grant No.2013RC1202)the Program for New Century Excellent Talents in University,China(Grant No.NECT-11-0596)the Beijing Nova Program,China(Grant No.2011066)
文摘Frequency-tunable microwave signal generation is proposed and experimentally demonstrated with a dual-wavelength single-longitudinal-mode （SLM） erbium-doped fiber ring laser based on a digital Opto-DMD processor and four-wave mixing （FWM） in a high-nonlinear photonic crystal fiber （PCF）. The high-nonlinear PCF is employed for the generation of the FWM to obtain stable and uniform dual-wavelength oscillation. Two different short passive sub-ring cavities in the main ring cavity serve as mode filters to make SLM lasing. The two lasing wavelengths are electronically selected by loading different gratings on the Opto-DMD processor controlled with a computer. The wavelength spacing can be smartly adjusted from 0.165 nm to 1.08 nm within a tuning accuracy of 0.055 nm. Two microwave signals at 17.23 GHz and 27.47 GHz are achieved. The stability of the microwave signal is discussed. The system has the ability to generate a 137.36-GHz photonic millimeter signal at room temperature.
文摘Laser shaping was introduced to maskless projection soft lithography by using digital micro-mirror device (DMD). The predesigned intensity pattern was imprinted onto the DMD and the input laser beam with a Gaussian or quasi-Gaussian distribution will carry the pattern on DMD to etch the resin. It provides a method of precise control of laser beam shapes and?photon-induced curing behavior of resin. This technology provides an accurate micro-fabrication of microstructures used for micro-systems. As a virtual mask generator and a binary-amplitude spatial light modulator, DMD is equivalent to the masks in the conventional exposure system. As the virtual masks and shaped laser beam can be achieved flexibly, it is a good method of precision soft lithography for 2D/3D microstructures.
文摘Multilayer of laser direct metal deposition（DMD）was prepared by depositing a gas atomized pre-alloyed powder with a composition close to Inconel 718 alloy on Inconel 718 high temperature alloy substrate.The effects of the DMD parameters on the build-up rate and the structure of the deposited layer were studied.The laser DMD sample was further processed by a solution treatment.The microstructure and property of the laser DMD zone before and after heat treatment were investigated as well.The results show that the laser parameters of actual laser power of 650 W,scanning speed of 5.8 mm/s,beam diameter of 1 mm,powder feed rate of 6.45 g/min,with a corresponding specific energy of 90-130 J/mm2,can be recommended as optimum parameters for high build-up rate of Inconel 718 alloy.Under the condition of optimized parameters,a directional solidification microstructure was obtained and the average distance between the columnar crystals was 5-10 μm.The microcomposition segregation was found between the columnar crystal trunk and columnar crystal.The elements of Nb,Mo,Ti concentrated in the columnar crystal trunk.After the heat treatment,the segregation was greatly minimized,and the segregation ratios were close to 1.The hardness of the laser deposited layer did not show obvious difference along the height of the layer either for the as-deposited layer or for the heat treated layer.However,the microhardness of the laser DMD zone after heat treatment was obviously higher than that after the as-deposited treatment.During the heat treatment process,some Nb-and Mo-rich phases precipitated and strengthened DMD layer.
