InGaN-based green light-emitting diodes （LEDs） with different growth temperatures of superlattice grown on Si （111） substrates are investigated by temperature-dependent electroluminescence between 100 K and 350K. ...InGaN-based green light-emitting diodes （LEDs） with different growth temperatures of superlattice grown on Si （111） substrates are investigated by temperature-dependent electroluminescence between 100 K and 350K. It is observed that with the decrease of the growth temperature of the superlattice from 895℃ to 855℃, the forward voltage decreases, especially at low temperature. We presume that this is due to the existence of the larger average size of V-shaped pits, which is determined by secondary ion mass spectrometer measurements. Meanwhile, the sample with higher growth temperature of superlattice shows a severer efficiency droop at cryogenic temperatures （about 100 K-150 K）. Electron overflow into p-GaN is considered to be the cause of such phenomena, which is relevant to the poorer hole injection into multiple quantum wells and the more reduced effective active volume in the active region.展开更多
We report the investigation on the performance of an amplification assisted difference frequency generation(AA-DFG) system driven by pulsed pump and continuous-wave primary signal lasers. A monolithic tandem lithium n...We report the investigation on the performance of an amplification assisted difference frequency generation(AA-DFG) system driven by pulsed pump and continuous-wave primary signal lasers. A monolithic tandem lithium niobate superlattice was employed as the nonlinear crystal with a uniform grating section for the DFG process, followed by a chirp section for the optical parametric amplification process. The impacts of pump pulse shape, primary signal power, input beam diameter, and crystal structure on the pump-to-idler conversion efficiency of the AA-DFG system were comprehensively studied by numerically solving the coupled wave equations. It is concluded that square pump pulse and high primary signal power are beneficial to high pump-to-idler conversion efficiency. In addition, tighter input beam focus and smaller DFG length proportion could redeem the reduction in conversion efficiency resulting from wider acceptance bandwidths for the input lasers. We believe that such systems combining the merits of high stability inherited from cavity-free configuration and high efficiency attributed from the cascaded nonlinear conversion should be of great interest to a wide community,especially when the pulse shaping technique is incorporated.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 61334001the National Key Research and Development Program of China under Grant Nos 2016YFB0400600,2016YFB0400601 and 2016YFB0400100+1 种基金the National Science Foundation for Young Scientists of China under Grant No 21405076the Fund for Less Developed Regions of the National Natural Science Foundation of China under Grant No 11364034
文摘InGaN-based green light-emitting diodes （LEDs） with different growth temperatures of superlattice grown on Si （111） substrates are investigated by temperature-dependent electroluminescence between 100 K and 350K. It is observed that with the decrease of the growth temperature of the superlattice from 895℃ to 855℃, the forward voltage decreases, especially at low temperature. We presume that this is due to the existence of the larger average size of V-shaped pits, which is determined by secondary ion mass spectrometer measurements. Meanwhile, the sample with higher growth temperature of superlattice shows a severer efficiency droop at cryogenic temperatures （about 100 K-150 K）. Electron overflow into p-GaN is considered to be the cause of such phenomena, which is relevant to the poorer hole injection into multiple quantum wells and the more reduced effective active volume in the active region.
基金National Natural Science Foundation of China(NSFC)(61505236)Key Laboratory Foundation of Chinese Academy of Sciences(CAS)(CXJJ-15S099,CXJJ-17S026)Innovation Foundation of Shanghai Institute of Technical Physics(CX-54)
文摘We report the investigation on the performance of an amplification assisted difference frequency generation(AA-DFG) system driven by pulsed pump and continuous-wave primary signal lasers. A monolithic tandem lithium niobate superlattice was employed as the nonlinear crystal with a uniform grating section for the DFG process, followed by a chirp section for the optical parametric amplification process. The impacts of pump pulse shape, primary signal power, input beam diameter, and crystal structure on the pump-to-idler conversion efficiency of the AA-DFG system were comprehensively studied by numerically solving the coupled wave equations. It is concluded that square pump pulse and high primary signal power are beneficial to high pump-to-idler conversion efficiency. In addition, tighter input beam focus and smaller DFG length proportion could redeem the reduction in conversion efficiency resulting from wider acceptance bandwidths for the input lasers. We believe that such systems combining the merits of high stability inherited from cavity-free configuration and high efficiency attributed from the cascaded nonlinear conversion should be of great interest to a wide community,especially when the pulse shaping technique is incorporated.
