窄线宽激光器的线宽表征方式通常采用延时自外差法测量技术。该技术是通过延时光纤差拍产生一个与待测激光线宽相关的洛伦兹频谱,因此该频谱只具有单一的线宽表现形式。为了能够观察到激光器的线宽和频率噪声在其傅里叶频率分布下的完...窄线宽激光器的线宽表征方式通常采用延时自外差法测量技术。该技术是通过延时光纤差拍产生一个与待测激光线宽相关的洛伦兹频谱,因此该频谱只具有单一的线宽表现形式。为了能够观察到激光器的线宽和频率噪声在其傅里叶频率分布下的完整特性,报道了一种基于β算法计算窄线宽激光器线宽的方法。该方法是结合频率噪声中的白噪声和1/ f 噪声分别诱导不同激光线型的理论,从而确定激光线宽。首先,对β算法的基本原理进行了详细的分析说明。通过基于维纳-辛钦定理,分析了窄线宽激光器不同频率范围内的频率噪声和激光线宽的依赖关系。阐明了在截止频率趋于0和无穷大的两个范围条件时,激光频谱特性从高斯线型向洛伦兹线型演变。同时推导出使两种线型转换的截止频率表达式,并将其转换为频率噪声函数,该函数定义为β分子线。此时频率噪声分量中高斯线型的总和即为激光线宽计算公式;其次,对窄线宽激光器的频率噪声和激光线型进行数值仿真。将通过OEwaves公司的OE4000互相关零差相位/频率噪声自动测试系统测得的频率噪声谱密度,带入β算法理论公式中。结果显示: 1/ f 噪声导致激光呈现高斯线型,线宽随截止频率的增加而增大。而白噪声将导致洛伦兹线型,线宽不再随截止频率而改变。此外,在低频区域,频率噪声电平远大于其傅里叶频率,噪声调制系数较高,该部分噪声可以决定线宽大小。因此,高斯线型区域对应的频率噪声的积分,即为待测激光器的线宽;在高频区域,频率噪声电平与其傅里叶频率相差较小,频率波动较快,噪声对线宽影响可以忽略。并且频率带宽在截止频率范围内,计算的线宽误差较小。最后,实验上运用β算法对RIO公司的1 550 nm低噪声窄线宽激光器的频率噪声功率谱密度进行积分计算,成功获得了其不同傅里叶频率�展开更多
随着降低成本及高端传输的需求，COB（Chip on Board，载芯片板）技术越来越受到PCB用户的欢迎，但COB技术对PCB产品的金面质量、洁净度及镀层厚度都有着诸多苛刻要求。文章针对FPC产品本身材质特性及加工工艺特性，探讨了挠性基材、补...随着降低成本及高端传输的需求，COB（Chip on Board，载芯片板）技术越来越受到PCB用户的欢迎，但COB技术对PCB产品的金面质量、洁净度及镀层厚度都有着诸多苛刻要求。文章针对FPC产品本身材质特性及加工工艺特性，探讨了挠性基材、补强压合工艺及激光外形工艺对COB性能的影响，总结出柔性基材承受能力及金面污染是影响FPC产品COB性能的主要因素，并在此基础上提出通过建立FPc选材规则、优化补强压合工艺及激光外形后处理等改善措施，从而提高FPC产品的COB性能。展开更多
The use of multi-segmented Position Sensitive Photodiodes (PSD) to measure microcantilever deflections have been found to produce nonlinear signal output, especially when the dynamic range is large. The reflected beam...The use of multi-segmented Position Sensitive Photodiodes (PSD) to measure microcantilever deflections have been found to produce nonlinear signal output, especially when the dynamic range is large. The reflected beam of the microcantilever may undergo intensity and shape modifications prior to reaching the PSD. In a multi-microcantilever sensor system the variation in the size of the individual spots plays an additional role contributing to the nonlinearities of detector output. Irrespective of the range of operation the merits of intensity normalization have been discussed. We show that the output is proportional to the width of the spot along the split line of the detector. This enables the determination of the shape of a spot. We show that the microcantilever vibrational spectrum can be obtained just using a single segment photodetector instead of using multiple segmented PSDs. These concepts will greatly facilitate interpretation of sensor data acquired from either single or multi-microcantilever experimental platforms.展开更多
文摘窄线宽激光器的线宽表征方式通常采用延时自外差法测量技术。该技术是通过延时光纤差拍产生一个与待测激光线宽相关的洛伦兹频谱,因此该频谱只具有单一的线宽表现形式。为了能够观察到激光器的线宽和频率噪声在其傅里叶频率分布下的完整特性,报道了一种基于β算法计算窄线宽激光器线宽的方法。该方法是结合频率噪声中的白噪声和1/ f 噪声分别诱导不同激光线型的理论,从而确定激光线宽。首先,对β算法的基本原理进行了详细的分析说明。通过基于维纳-辛钦定理,分析了窄线宽激光器不同频率范围内的频率噪声和激光线宽的依赖关系。阐明了在截止频率趋于0和无穷大的两个范围条件时,激光频谱特性从高斯线型向洛伦兹线型演变。同时推导出使两种线型转换的截止频率表达式,并将其转换为频率噪声函数,该函数定义为β分子线。此时频率噪声分量中高斯线型的总和即为激光线宽计算公式;其次,对窄线宽激光器的频率噪声和激光线型进行数值仿真。将通过OEwaves公司的OE4000互相关零差相位/频率噪声自动测试系统测得的频率噪声谱密度,带入β算法理论公式中。结果显示: 1/ f 噪声导致激光呈现高斯线型,线宽随截止频率的增加而增大。而白噪声将导致洛伦兹线型,线宽不再随截止频率而改变。此外,在低频区域,频率噪声电平远大于其傅里叶频率,噪声调制系数较高,该部分噪声可以决定线宽大小。因此,高斯线型区域对应的频率噪声的积分,即为待测激光器的线宽;在高频区域,频率噪声电平与其傅里叶频率相差较小,频率波动较快,噪声对线宽影响可以忽略。并且频率带宽在截止频率范围内,计算的线宽误差较小。最后,实验上运用β算法对RIO公司的1 550 nm低噪声窄线宽激光器的频率噪声功率谱密度进行积分计算,成功获得了其不同傅里叶频率�
文摘随着降低成本及高端传输的需求，COB（Chip on Board，载芯片板）技术越来越受到PCB用户的欢迎，但COB技术对PCB产品的金面质量、洁净度及镀层厚度都有着诸多苛刻要求。文章针对FPC产品本身材质特性及加工工艺特性，探讨了挠性基材、补强压合工艺及激光外形工艺对COB性能的影响，总结出柔性基材承受能力及金面污染是影响FPC产品COB性能的主要因素，并在此基础上提出通过建立FPc选材规则、优化补强压合工艺及激光外形后处理等改善措施，从而提高FPC产品的COB性能。
文摘The use of multi-segmented Position Sensitive Photodiodes (PSD) to measure microcantilever deflections have been found to produce nonlinear signal output, especially when the dynamic range is large. The reflected beam of the microcantilever may undergo intensity and shape modifications prior to reaching the PSD. In a multi-microcantilever sensor system the variation in the size of the individual spots plays an additional role contributing to the nonlinearities of detector output. Irrespective of the range of operation the merits of intensity normalization have been discussed. We show that the output is proportional to the width of the spot along the split line of the detector. This enables the determination of the shape of a spot. We show that the microcantilever vibrational spectrum can be obtained just using a single segment photodetector instead of using multiple segmented PSDs. These concepts will greatly facilitate interpretation of sensor data acquired from either single or multi-microcantilever experimental platforms.
