Signal epidetection in third-harmonic generation microscopy of turbid media
Signal epidetection in third-harmonic generation microscopy of turbid media
复制标题
DOI：
10.1364/oe.15.008913
复制
发表时间：
2007-07-09
期刊：
影响因子：
3.8
通讯作者：
Beaurepaire, Emmanuel
中科院分区：
文献类型：
--
作者：
Debarre, Delphine;Olivier, Nicolas;Beaurepaire, Emmanuel
厚样品或大型生物体的三次谐波发生 (THG) 成像需要通过聚焦物镜采集 TH 光。在这项研究中，我们首先估计孤立物体产生的从后到前的 TH 辐射量，作为该物体尺寸和空间频率的函数。理论和模型实验表明，无法从嵌入透明介质中的（生物）介电结构中检测到显着信号。相比之下，从金属纳米颗粒中观察到反向发射，其中三次谐波部分是表面效应。然后我们解决嵌入在浑浊介质中的物体的情况。实验和蒙特卡罗模拟表明，当介质中谐波光的吸收平均自由程超过其减少的散射长度时，外探测是可能的，并且即使在浅深度，外探测效率也关键取决于显微镜视场，因为反向散射光本质上是扩散的。这些观察结果为优化厚组织三次谐波、二次谐波或 CARS 成像中的表观检测提供了指导。 (c) 2007 年美国光学学会。
Third-harmonic generation (THG) imaging of thick samples or large organisms requires TH light to be epicollected through the focusing objective. In this study we first estimate the amount of backward-to-forward TH radiation created by an isolated object as a function of size and spatial frequencies in the object. Theory and model experiments indicate that no significant signal can be epidetected from a (biological) dielectric structure embedded in a transparent medium. In contrast, backward emission is observed from metal nanoparticles where THG is partly a surface effect. We then address the case of an object embedded in a turbid medium. Experiments and Monte Carlo simulations show that epidetection is possible when the absorption mean free path of harmonic light in the medium exceeds its reduced scattering length, and that epicollection efficiency critically depends on the microscope field-of-view even at shallow depths, because backscattered light is essentially diffusive. These observations provide guidelines for optimizing epidetection in third-harmonic, second-harmonic, or CARS imaging of thick tissues. (c) 2007 Optical Society of America.