Optical fiber bundles have been widely used in microendoscopic biomedical imaging, Raman microscopy, and depth-resolved imaging due to their flexibility, long-distance transmission, and high spatial resolution. However, there are few reports on fiber bundles in the terahertz (THz) band, which significantly limits the applications in the biomedical field and nondestructive imaging. Although sapphire dielectric fiber-based bundles have shown promising applications in THz imaging, it is difficult to achieve long-distance and high-quality imaging due to the high absorption coefficient and uneven arrangements of fibers. Here, we propose a copper hollow-core waveguide bundle with a hexagonal arrangement, which is fabricated by a low-cost extrusion and stacking method. Simulation results demonstrate that transmission loss of the TE₁₁ mode increases with the decrease of the inner radius of metallic waveguides, which is consistent with the experimental results. Moreover, under liquid nitrogen conditions, the metallic waveguide bundle exhibits higher output power under different biasing currents of THz quantum cascade lasers (QCLs). The effect of the inner radius of the waveguide on the bundle’s spatial resolution has been thoroughly analyzed theoretically and experimentally with a maximum spatial resolution of ∼400 μm, indicating the accuracy of fabrication. In addition, different square tablets with four different mixed ratios of polytetrafluoroethylene powders and silver nanoparticles are well distinguished by the THz waveguide bundle-based transmission images. Moreover, the imaging performance of the THz waveguide bundle is simulated and such a bundle with a length of 6 cm is employed to experimentally demonstrate the remarkable terahertz imaging capabilities. The THz waveguide bundle in this work is well integrated with QCLs to enable long-distance submillimeter near-field terahertz imaging, especially in applications with cryogenic environments.

中文翻译：

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用于低温环境下太赫兹成像的低损耗空心波导束


光纤束因其灵活性、长距离传输和高空间分辨率而广泛应用于微内窥镜生物医学成像、拉曼显微镜和深度分辨成像。然而，关于太赫兹（THz）波段光纤束的报道很少，这极大地限制了其在生物医学领域和无损成像中的应用。尽管基于蓝宝石介质光纤的光纤束在太赫兹成像中显示出了良好的应用前景，但由于光纤的高吸收系数和不均匀排列，很难实现长距离高质量成像。在这里，我们提出了一种具有六边形排列的铜空心波导束，它是通过低成本挤压和堆叠方法制造的。仿真结果表明，TE ₁₁ 模式的传输损耗随着金属波导内半径的减小而增大，这与实验结果一致。此外，在液氮条件下，金属波导束在太赫兹量子级联激光器（QCL）的不同偏置电流下表现出更高的输出功率。波导内半径对光纤束空间分辨率的影响已经在理论上和实验上得到了深入的分析，最大空间分辨率可达~400μm，表明了制造的准确性。此外，基于太赫兹波导束的传输图像可以很好地区分具有四种不同比例的聚四氟乙烯粉末和银纳米颗粒的不同方形片。此外，还模拟了太赫兹波导束的成像性能，并采用长度为6 cm的太赫兹波导束通过实验证明了其卓越的太赫兹成像能力。 这项工作中的太赫兹波导束与 QCL 良好集成，可实现长距离亚毫米近场太赫兹成像，特别是在低温环境应用中。