Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apdo. Postal 70-543, Ciudad de México, 04510, Mexico.
Tecnologico de Monterrey, Escuela de Ingeniería y Ciencias, Ave. Eugenio Garza Sada 2501, Monterrey, N.L., 64849, Mexico.
Sci Rep. 2019 Jun 20;9(1):8954. doi: 10.1038/s41598-019-45088-0.
Optical-coherence tomography (OCT) is a technique that employs light in order to measure the internal structure of semitransparent, e.g. biological, samples. It is based on the interference pattern of low-coherence light. Quantum-OCT (QOCT), instead, employs the correlation properties of entangled photon pairs, for example, generated by the process of spontaneous parametric downconversion (SPDC). The usual QOCT scheme uses photon pairs characterised by a joint-spectral amplitude with strict spectral anti-correlations. It has been shown that, in contrast with its classical counterpart, QOCT provides resolution enhancement and dispersion cancellation. In this paper, we revisit the theory of QOCT and extend the theoretical model so as to include photon pairs with arbitrary spectral correlations. We present experimental results that complement the theory and explain the physical underpinnings appearing in the interference pattern. In our experiment, we utilize a pump for the SPDC process ranging from continuous wave to pulsed in the femtosecond regime, and show that cross-correlation interference effects appearing for each pair of layers may be directly suppressed for a sufficiently large pump bandwidth. Our results provide insights and strategies that could guide practical implementations of QOCT.
光学相干断层扫描（OCT）是一种利用光来测量半透明，例如生物，样本的内部结构的技术。它基于低相干光的干涉图案。相反，量子光学相干断层扫描（QOCT）利用纠缠光子对的相关特性，例如由自发参量下转换（SPDC）过程产生的光子对。通常的 QOCT 方案使用具有严格光谱反相关的联合光谱幅度特征的光子对。已经表明，与经典对应物相比，QOCT 提供了分辨率增强和色散消除。在本文中，我们重新审视了 QOCT 的理论，并扩展了理论模型，以便包括具有任意光谱相关性的光子对。我们提出了实验结果来补充理论并解释干涉图案中出现的物理基础。在我们的实验中，我们利用从连续波到飞秒脉冲的泵浦来进行 SPDC 过程，并表明对于每对层出现的交叉相关干涉效应可以直接抑制对于足够大的泵浦带宽。我们的结果提供了见解和策略，可指导 QOCT 的实际实现。
