Single-Fundamental-Mode 850 nm Surface Relief VCSEL

The performance of the oxide-confined surface-relief(SR)structure vertical-cavity surface-emitting laser(VCSEL)is simulated and analyzed by using the three-dimensional finite-difference time-domain(FDTD)method.The impacts of the device structure parameters on the far-field characteristics are researched.A single-fundamental-mode SR VCSEL with an oxide-aperture of 15μm is designed and produced.The single-mode power of the VCSEL is 5 mW,the threshold current is 2.5 mA,far-field divergent angles range from 7.8°to 10.8°and the side-mode suppression ratio is over 30 dB.The optical and electrical properties of the device are in agreement with the results of FDTD simulation,which shows that the SR technology can effectively suppress the higher-order-mode lasing,and make the SR VCSEL work in a single mode under a larger oxide aperture.

丛枝菌根真菌降低辣椒镉吸收和果实镉积累的机制

【目的】丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)与作物存在互利共生关系,可增强宿主对镉(Cd)的耐受能力。研究AMF对不同Cd积累型辣椒Cd吸收积累的影响,探索AMF降低辣椒可食部位Cd的生理生化机制。【方法】采用盆栽试验,供试土壤为石灰性黄壤,该土壤上已连续种植辣椒8年。丛枝菌根处理包括接菌(+AMF)和不接菌(−AMF);Cd浓度包括3个水平:0、5、10 mg/kg,分别记作Cd0、Cd5、Cd10;辣椒品种包括Cd高积累型‘辣研101’和Cd低积累型‘辣研201’,3个因素共组成12个处理。辣椒移栽90天后收获,分别测定了辣椒根、地上部和果实干重、Cd含量,以及根际土壤养分含量、根系分泌物成分。【结果】Cd处理抑制了辣椒生长,随施Cd浓度的增加,株高、地上部和根部生物量显著下降;Cd10处理下,与−AMF处理相比,+AMF处理‘辣研101’地上部生物量增加了31.72%,‘辣研201’增加了20.09%;‘辣研101’根部Cd含量显著降低了30.75%;‘辣研201’增加了41.93%;+AMF处理下‘辣研101’Cd的转运系数(地上部/根部)显著增加了48.96%,而‘辣研201’降低了24.04%。+AMF处理降低了各Cd浓度下两品种辣椒果实Cd的富集系数,改变了辣椒根系分泌物化学组成及相对含量,不同品种间有所差异。结构方程模型分析表明,接菌、根部Cd含量对辣椒果实Cd含量表现出显著负向调节作用。【结论】在Cd胁迫条件下,AMF通过减少低积累型辣椒(辣研201)根部Cd向地上部的转运,降低可食部位Cd积累;通过减少高积累型辣椒(辣研101)地上部Cd向果实的转运,降低可食部位Cd积累。