论文标题
频域中的斑点记忆效应和时间反转实验的稳定性
Speckle Memory Effect in the Frequency Domain and Stability in Time-Reversal Experiments
论文作者
论文摘要
当波通过像湍流大气这样的复杂介质传播时，波场就变得不连贯，波强度形成了复杂的斑点图案。在本文中，我们研究了频域中的斑点记忆效应及其某些后果。这种效果意味着，当移动照明频率时，通过波传递通过随机散射介质产生的斑点图案的某些特性。通过对四个不同频率的随机携带绿色功能的四阶矩进行详细的新颖分析来表征斑点记忆效应。我们得出了频率记忆效应的精确表征以及什么控制了内存强度。作为一种应用，我们量化了通过在携带或梁状态下的随机散射培养基重新聚焦的时间反转波的统计稳定性。时间逆转是指将传输波场记录在时间反射镜上，然后倒转并回到复杂介质中的情况。然后重新定位的波场在原始源点重新集中。我们计算重新聚焦波的平均值，并根据时间反向镜的半径，元素的大小，源带宽和随机培养基波动的统计数据来确定其方差的新颖定量描述。
When waves propagate through a complex medium like the turbulent atmosphere the wave field becomes incoherent and the wave intensity forms a complex speckle pattern. In this paper we study a speckle memory effect in the frequency domain and some of its consequences. This effect means that certain properties of the speckle pattern produced by wave transmission through a randomly scattering medium is preserved when shifting the frequency of the illumination. The speckle memory effect is characterized via a detailed novel analysis of the fourth-order moment of the random paraxial Green's function at four different frequencies. We arrive at a precise characterization of the frequency memory effect and what governs the strength of the memory. As an application we quantify the statistical stability of time-reversal wave refocusing through a randomly scattering medium in the paraxial or beam regime. Time reversal refers to the situation when a transmitted wave field is recorded on a time-reversal mirror then time reversed and sent back into the complex medium. The reemitted wave field then refocuses at the original source point. We compute the mean of the refocused wave and identify a novel quantitative description of its variance in terms of the radius of the time-reversal mirror, the size of its elements, the source bandwidth and the statistics of the random medium fluctuations.
