Mid-infrared (mid-IR) light scatters much less than shorter wavelengths, allowing greatly enhanced penetration depths for optical imaging techniques such as optical coherence tomography (OCT). However, both detection and broadband sources in the mid-IR are technologically challenging. Interfering entangled photons in a nonlinear interferometer enables sensing with undetected photons, making mid-IR sources and detectors obsolete. Here we implement mid-IR frequency-domain OCT based on ultra-broadband entangled photon pairs spanning from 3.3 to 4.3 µm. We demonstrate 10 µm axial and 20 µm lateral resolution 2D and 3D imaging of strongly scattering ceramic and paint samples. By intrinsically being limited only by shot noise, we observe ${10^6}$ times more sensitivity per integration time and power of the probe light. Together with the vastly reduced footprint and technical complexity, our technique can outperform conventional approaches with classical mid-IR light sources.

中文翻译：

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具有未检测到的中红外光子的频域光学相干断层扫描

中红外（mid-IR）的散射比短波长的散射少得多，从而大大提高了光学成像技术（如光学相干断层扫描（OCT））的穿透深度。但是，中红外的检测和宽带源在技术上都具有挑战性。非线性干涉仪中纠缠的纠缠光子可以利用未检测到的光子进行传感，从而使中红外源和检测器变得过时。在这里，我们基于跨度从3.3到4.3 µm的超宽带纠缠光子对实现中红外频域OCT。我们演示了强散射陶瓷和油漆样品的10 µm轴向分辨率和20 µm横向分辨率2D和3D成像。通过本质上仅受散粒噪声的限制，我们观察到$ {10 ^ 6} $积分时间和探测光功率的灵敏度提高两倍。加上大大减少的占位面积和技术复杂性，我们的技术可以超越传统中红外光源的传统方法。