共查询到18条相似文献,搜索用时 531 毫秒
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半导体激光器的线宽通常采用激光外差测量技术,通过差拍信号的功率谱密度函数来确定,受傅里叶变换方法的限制,得到的均是在一定时间段内的静态平均线宽。为了获得半导体激光器在电流调谐过程中的瞬时线宽特性,提出了利用时变功率谱获知调谐瞬时线宽的相干和非相干测量方法,并分别进行了理论分析和实验验证。首先对半导体激光器输出光信号及差拍信号进行了时间-频率域下的数学描述,确定了时变功率谱与调谐瞬时线宽的关系;其次,针对差拍信号的趋向性特征,提出了趋势局部均值分解方法,并研究了利用分解出的乘积函数建立差拍信号及激光器输出光信号的时变功率谱的方法;最后利用非相干和相干测量法分别获得了分布反馈式半导体激光器在50~51及50~100 mA锯齿波电流调谐过程中的瞬时线宽。 相似文献
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动态光散射图像法测量纳米颗粒粒度研究 总被引:4,自引:0,他引:4
提出了一种基于动态光散射原理的图像法测量纳米颗粒粒径的新方法,采用面阵CCD数以万计的像素同时并行测量处于布朗运动的纳米颗粒空间分布的动态散射光信号,对测得的信号进行数据处理,得到了纳米颗粒粒径。对27、79、482、948nm 4种不同粒径的纳米标准颗粒进行了实验研究,针对面阵CCD拍摄帧率远低于光电倍增管测量频率的特点,采用质量分数为55%高粘度甘油水溶液作为分散介质,在CCD拍摄帧率为8290frame/s时,27nm颗粒的测量误差从以水为分散介质时的15.1%降至1.9%。与目前动态光散射纳米颗粒测量方法相比,该方法大幅度减少了测量时间,仅为现有方法的1%以下,并可大幅度简化测量装置。 相似文献
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随机振动试验是振动环境试验常用的一项重要试验方法。开展随机振动控制算法研究,将有助于提高随机振动试验技术水平。随机振动控制原理如图1所示,其系统的主要功能模块可分为:测量信号的自功率谱密度(PSD)计算;驱动信号的PSD更新;驱动信号相位随机化,转换成FFT谱;IFFT变换生成时域帧信号;时域帧信号搭接。 相似文献
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提出了一种基于图像动态光散射原理测量二维纳米颗粒粒度的新方法,称为平移转动-图像动态光散射(TR-IDLS)法。采用会聚的偏振高斯光束照射样品池中处于布朗运动的二维纳米粒子,分别采集纳米粒子的水平偏振散射光信号和垂直偏振散射光信号。根据两个偏振方向上散射光光强波动的时间相关函数,计算出纳米颗粒的平移和转动扩散系数的分布,进而从扩散系数中获得颗粒的长宽比、等效直径和厚度的分布。采用该方法测量了球形标准纳米颗粒和片状云母颗粒的粒径。采用电镜获得了片状云母颗粒的形状和等效直径,并与TR-IDLS方法的实验结果进行比较,验证了TR-IDLS方法的可行性。 相似文献
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K. V. Kozadaev 《Journal of Applied Spectroscopy》2011,78(5):692-697
Two-factor dependences of the maximum and half-width of a surface plasmon resonance band on both the average diameter of nanoparticles
and the scatter in their particle-size distributions were defined for colloidal silver and gold aqueous solutions based on
modeling the extinction effectiveness factor by Mie theory. The obtained three-dimensional surfaces determined the shape of
calibration curves used to define the average particle diameters and the scatter in their particle-size distributions from
measurements of the maximum and half-width of the surface plasmon resonance band in spectra of the silver and gold colloidal
solutions. The calibration curves were correlated with experimental samples of aqueous ultradispersed media containing silver
and gold nanoparticles. 相似文献
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The size of nanoparticles is measured by laser diode self-mixing interferometry, which employs a sensitive, compact, and simple optical setup. However, the signal processing of the interferometry is slow or expensive. In this article, a fast and economic signal processing technique is introduced, in which the self-mixing AC signal is transformed into DC signals with an analog circuit consisting of 16 channels. These DC signals are obtained as a spectrum from which the size of nanoparticles can be retrieved. The technique is examined by measuring the standard nanoparticles. Further experiments are performed to compare the skimmed milk and whole milk, and also the fresh skimmed milk and rotten skimmed milk. 相似文献
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The self-mixing vibration signals are observed in the laser diode when the optical beam is back-scattered into the laser cavity which causes laser output power modulated. Based on these properties, a laser diode self-mixing vibrometer with wide dynamic range is proposed. This current investigation further reports new work to improve the accuracy and range of the measured vibration signals. Numerical simulations and experimental results are given and discussed. The experimental results show that the frequency measurement range can be achieved up to 22 kHz with 0.241% maximum relative error while utilizing the reflecting film. For amplitude measurement utilizing the same reflecting film, the error of measurement result is 4.77 nm which has approached nanometer order of magnitude. 相似文献
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We propose a novel and practical method to exactly measure the transient reflectance spectra (TRS) of the adaptive filters based on dynamic population gratings. The modulating signals applied to the laser source play an important role. We specially designed a train of triangular amplitude modulated pulses with a small duty to modulate the laser frequency, and then the TRS was obtained from the grating responses to this pulse train. The measured half-zero-point bandwidths of the filter with and without 2.6 m cavity length are 20 and 60 MHz, respectively. Our research also indicates that the relatively high input power and a short cavity length may enhance the antiperturbation ability of lasers. 相似文献
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基于颗粒物米氏散射特性、激光自混合三镜腔理论和激光器稳态条件,推导出在大气颗粒物光反馈下激光器频率、功率、线宽的理论表达式,建立了大气颗粒物光反馈下的激光自混合理论模型。同时,数值模拟和分析了大气颗粒物物理参数对激光自混合干涉信号的影响。结果表明,在一定粒径范围内,激光自混合反馈强度随大气颗粒物粒径增大先增大后减小,且反馈强度峰值出现的位置随颗粒物折射率实部的增大、虚部的减小向粒径较大处移动;自混合系统的外腔长度影响自混合干涉信号的波动深度,激光器输出光信号的幅值随外腔长度增大呈指数衰减;自混合干涉信号波动频率与大气颗粒物运动速度呈线性关系。分析结果对基于激光自混合效应的大气颗粒物多物理参数传感具有重要作用。 相似文献
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Laser-induced breakdown detection (LIBD) is a well established technique for measuring size and concentration of inorganic
colloids in liquids. However, most applications of LIBD are restricted to the measurement of mean sizes, which is problematic
in cases of wide colloid size distributions (PSD) as typically is the case in natural systems. Evaluation of PSDs from LIBD
is possible but requires detailed control of the power density within the laser focus. In the present work we describe the
mathematical treatment how to calculate this power density from the beam characteristics of the light source and the optical
properties of the focusing optics. The results are compared to measured spatial distributions of breakdown events of three
LIBD setups. 相似文献
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N. Prosperini 《Physica A》2007,383(2):595-602
In this contribution, particle size distributions (PSD) of soil samples are analyzed by fractal methods. Different scaling domains, characterizing different ranges of particle sizes, are identified. Numerical models based on cellular automata are presented with the aim to understand the basic mechanisms responsible for the occurrence of multiple scaling domains in soil PSD. Numerical simulations are in good agreement with natural data and furnish a conceptual framework to explain the features observed in the PSD of studied soil samples. 相似文献