Characterizing Optical Fiber Transmission Matrices Using Metasurface Reflector Stacks for Lensless Imaging without Distal Access
Characterizing Optical Fiber Transmission Matrices Using Metasurface Reflector Stacks for Lensless Imaging without Distal Access
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DOI：
10.1103/physrevx.9.041050
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发表时间：
2019-12-09
影响因子：
12.5
通讯作者：
Bohndiek, Sarah E.
中科院分区：
文献类型：
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作者：
Gordon, George S. D.;Gataric, Milana;Bohndiek, Sarah E.
通过头发丝般细的光纤检索图像数据的能力有望在从生物医学成像到工业检测的一系列领域开辟新的应用。不幸的是，机械变形和温度的微小变化可以完全扰乱光学信息，扭曲任何产生的图像。这些动态变化的校正需要在成像之前立即原位测量光纤传输矩阵（TM），这通常需要同时接近光纤的近端和远端面。因此，TM校准在大多数现实使用场景中是不可行的，而不损害具有庞大远端光学器件的薄形状因子。在这里，我们介绍了一种新的方法来确定TM的多模或多芯光纤的反射模式配置，而不需要访问的远端面。我们建议在光纤的远端面处引入结构化超颖表面反射器的薄堆叠，以引入波长相关的空间非均匀反射分布。我们推导出一个一阶光纤模型，补偿这些波长相关的变化，在光纤TM和显示，因此，在三个波长的反射数据可以被用来明确地重建全TM的迭代优化算法。与以前的方法不同，我们的方法不要求光纤矩阵是单一的，这使得它适用于具有不可忽略的功率损耗的物理现实的光纤系统。我们演示TM重建和成像第一次使用模拟的非酉光纤和噪声反射矩阵，然后使用较大的实验测量TM的密集包装的多芯光纤（MCF），最后使用实验测量的多波长TM记录从阶跃折射率多模光纤（MMF）。多波长原位测量的并行化可以使实验表征时间与最先进的传输模式光纤TM实验相媲美。我们的研究结果铺平了道路，在线TM校准原位头发丝细的光纤。
The ability to retrieve image data through hair-thin optical fibers promises to open up new applications in a range of fields, from biomedical imaging to industrial inspection. Unfortunately, small changes in mechanical deformation and temperature can completely scramble optical information, distorting any resulting images. Correction of these dynamic changes requires measurement of the fiber transmission matrix (TM) in situ immediately before imaging, which typically requires access to both the proximal and distal facets of the fiber simultaneously. As a result, TM calibration is not feasible during most realistic usage scenarios without compromising the thin form factor with bulky distal optics. Here, we introduce a new approach to determine the TM of multimode or multicore optical fibers in a reflection-mode configuration, without requiring access to the distal facet. We propose introducing a thin stack of structured metasurface reflectors at the distal facet of the fiber, to introduce wavelength-dependent, spatially heterogeneous reflectance profiles. We derive a first-order fiber model that compensates these wavelength-dependent changes in the fiber TM and show that, consequently, the reflected data at three wavelengths can be used to unambiguously reconstruct the full TM by an iterative optimization algorithm. Unlike previous approaches, our method does not require the fiber matrix to be unitary, making it applicable to physically realistic fiber systems that have non-negligible power loss. We demonstrate TM reconstruction and imaging first using simulated nonunitary fibers and noisy reflection matrices, then using larger experimentally measured TMs of a densely packed multicore fiber (MCF), and finally using experimentally measured multiwavelength TMs recorded from a step-index multimode fiber (MMF). Parallelization of multiwavelength in situ measurements could enable experimental characterization times comparable with state-of-the-art transmission-mode fiber TM experiments. Our findings pave the way for online TM calibration in situ in hair-thin optical fibers.