论文标题
在线近距离声音和光束中时域brillouin散射的相互直觉特征
Contra-Intuitive Features of Time-Domain Brillouin Scattering in Collinear Paraxial Sound and Light Beams
论文作者
论文摘要
时间域Brillouin散射是一种用于评估透明材料的光学光学探针技术。在样品皮秒连贯的声音脉冲中，通过光声转换发射通过光声转换发射的Ultrashort泵激光脉冲。时间延迟的超时探针激光脉冲通过光弹性效应监测相干声脉冲的传播，从而诱导光散射。光电探测器会收集声学散射的光，并反射出异性疾病的样品结构所反映的探针光。散射的探针载体在相干声学脉冲的当前位置中有关材料的声学，光学和声学参数的信息。因此，除其他应用外，时域布里鲁因散射是一种用于三维成像的技术。相干的声脉冲和探针激光脉冲的急剧聚焦可能会增加成像的横向空间分辨率，但可能会减少成像的深度。然而，在本手稿中介绍的理论分析表明，时间域的布里群散射成像的深度和光谱分辨率，共同传播的近距离声音和光束，完全不依赖于声音的焦点/衍射。时间域Brillouin散射信号的幅度的变化仅是由于光聚焦/衍射引起的探针光振幅的变化。尽管声学光的光的幅度与局部声学和探测光场的乘积成正比，但幅度域brillouin散射信号振幅的时间动力学与相干声学脉冲幅度的动力学无关。
Time-domain Brillouin scattering is an opto-acousto-optical probe technique for the evaluation of the transparent materials. Ultrashort pump laser pulses via optoacoustic conversion launch in the sample picosecond coherent acoustic pulses. The time-delayed ultrashort probe laser pulses monitor the propagation of the coherent acoustic pulses via photo-elastic effect, which induces light scattering. A photodetector collects acoustically scattered light and the probe light reflected by the sample structure for the heterodyning. The scattered probe light carriers the information on the acoustical, optical and acousto-optical parameters of the material in the current position of the coherent acoustic pulse. Thus, among other applications, the time-domain Brillouin scattering is a technique for three-dimensional imaging. Sharp focusing of the coherent acoustic pulses and probe laser pulses could increase lateral spatial resolution of imaging, but could potentially diminish the depth of imaging. However, the theoretical analysis presented in this manuscript contra-intuitively demonstrates that the depth and spectral resolution of the time-domain Brillouin scattering imaging, with collinearly propagating paraxial sound and light beams, do not depend at all on the focusing/diffraction of sound. The variations of the amplitude of the time-domain Brillouin scattering signal are only due to the variations of the probe light amplitude caused by light focusing/diffraction. Although the amplitude of the acoustically scattered light is proportional to the product of the local acoustical and probe light field amplitudes the temporal dynamics of the time-domain Brillouin scattering signal amplitude is independent of the dynamics of the coherent acoustic pulse amplitude.
