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测量了高功率976nm InGaAs量子阱半导体激光器在低于1/30阈值电流下的低频电噪声,提出了以1/f噪声时域信号小波系数相关性与电流的关系来分析噪声来源的方法.结合1/f噪声源理论模型及小波变换系数的特性,完成了不同偏置电流下纯1/f噪声、加白噪声后的1/f噪声两种情况下的对比实验.实验结果表明:所测的低频噪声表现为明显的1/f噪声,对于纯1/f噪声,噪声幅度和小波系数相关性在判断噪声来源时具有相同的结果;对于加白噪声后的1/f噪声,噪声幅度变化很大且不能正确表征1/f噪声来源,而部分尺度下的小波系数相关性仍能作为判断噪声来源的可靠参量. 相似文献
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结合伪逆关联成像和迭代去噪关联成像,提出了关联成像目标重构的伪逆迭代方法.该方法以伪逆关联成像重构结果为初始值,选取合适的与噪声干扰相关的阈值,通过迭代运算逼近实际的噪声干扰,最终抑制噪声并提高重构图像的峰值信噪比.以峰值信噪比和相关系数为衡量标准,将伪逆迭代关联成像的重构结果与差分关联成像、伪逆关联成像进行对比分析.仿真实验结果表明,伪逆迭代方法的峰值信噪比较伪逆关联成像方法、差分关联成像方法分别高出约1.0dB、3.1dB,同时其相关系数、视觉效果也有所改善,验证了该方法的有效性. 相似文献
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根据微腔原理运用传输矩阵法对构成微腔有机电致发光器件(MOLED)谐振腔的两个反射镜进行模拟计算并比较,可观察到:随金属反射镜的反射率增大,微腔器件的电致发光(PL)谱的半峰全宽(FWHM)逐渐窄化;峰值逐渐蓝移至设计的谐振峰值520nm处;峰值强度和光谱积分强度逐渐增强。结果表明:金属反射镜反射率越大越好。随DBR反射镜的周期数从1增加到9,EL的峰值均为520nm,半峰全宽逐渐窄化,积分强度逐渐减弱;峰值强度由弱增强再减弱,4个周期时峰值强度最大,所以设计微腔器件时,DBR的周期是一项很重要的参数。DBR反射率太大不利于出光,太小微腔效应小。需要根据制作目的和需要进行合理选择。 相似文献
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用Gobin Yvon hr800拉曼光谱仪及与之相连接的Linkam,Thms600加热装置,测量了含9个C-C共轭双键的β胡萝卜素分子在二甲基亚砜中在25~73℃范围内的拉曼光谱.结果表明,短链多烯生物分子β胡萝卜素在液体中有很大的拉曼散射截面[6.5×10-23cm2/(molecule·Sr)],除共振效应外,β胡萝卜素分子结构有序产生较强的弱阻尼C-C键相干振动,是获得大拉曼散射截面的重要因素.温度对多烯类链状线性分子结构有序性影响很大.温度升高,分子结构有序性下降,C-C键弱阻尼相干振动减弱,C-C键长变短,各C-C键键长略有不同,使拉曼散射截面减少,拉曼光谱谱线蓝移,振动频率成分增加使线宽增加. 相似文献
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Polycrystalline silicon (poly-Si) thin film has been prepared by means of nickel-disilicide (NiSi2) assisted excimer laser crystallization (ELC). The process to prepare a sample includes two steps. One step consists of the formation of NiSi2 precipitates by heat-treating the dehydrogenated amorphous silicon (a-Si) coated with a thin layer of Ni. And the other step consists of the formation of poly-Si grains by means of ELC. According to the test results of scanning electron microscopy (SEM), another grain growth model named two-interface grain growth has been proposed to contrast with the conventional Ni-metal-induced lateral crystallization (Ni-MILC) model and the ELC model. That is, an additional grain growth interface other than that in conventional ELC is formed, which consists of NiSi2 precipitates and a-Si. The processes for grain growth according to various excimer laser energy densities delivered to the a-Si film have been discussed. It is discovered that grains with needle shape and most of a uniform orientation are formed which grow up with NiSi2 precipitates as seeds. The reason for the formation of such grains which are different from that of Ni-MILC without migration of Ni atoms is not clear. Our model and analysis point out a method to prepare grains with needle shape and mostly of a uniform orientation. If such grains are utilized to make thin-film transistor, its characteristics may be improved. 相似文献
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