Ultrasonics without a source: Thermal fluctuation correlations at MHz frequencies
Ultrasonics without a source: Thermal fluctuation correlations at MHz frequencies
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DOI：
10.1103/physrevlett.87.134301
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发表时间：
2001-09-24
影响因子：
8.6
通讯作者：
Lobkis, OI
中科院分区：
文献类型：
--
作者：
Weaver, RL;Lobkis, OI
由换能器和放大器组成的超声波接收电路中产生的噪声通常被忽略，或被视为滋扰。在这里，有人认为，声学热波动，位移振幅为3调频，包含大量的超声信息。它示出的噪声自相关函数是波形，将获得在一个直接的脉冲/回波测量。该论文在实验中证明了直接测量相比，相关函数。产生这些相关性的弹性动力学噪声的热性质通过其强度的绝对测量（基本上是样品温度的测量）来确认。
Noise generated in an ultrasonic receiver circuit consisting of transducer and amplifier is usually ignored, or treated as a nuisance. Here it is argued that acoustic thermal fluctuations, with displacement amplitudes of 3 fm, contain substantial ultrasonic information. It is shown that the noise autocorrelation function is the waveform that would be obtained in a direct pulse/echo measurement. That thesis is demonstrated in experiments in which direct measurements are compared to correlation functions. The thermal nature of the elastodynamic noise that generates these correlations is confirmed by an absolute measurement of their strength, essentially a measurement of the sample temperature.