Hybrid-material optical fibers enhance the capabilities of fiber-optics technologies, extending current functionalities to several emerging application areas. Such platforms rely on the integration of novel materials into the fiber core or cladding, thereby supporting hybrid modes with new characteristics. Here we present experiments that reveal hybrid mode interactions within a doped-core silica fiber containing a central high-index nanofluidic channel. Compared with a standard liquid-filled capillary, calculations predict modes with unique properties emerging as a result of the doped core/cladding interface, possessing a high power fraction inside and outside the nanofluidic channel. Our experiments directly reveal the beating pattern in the fluorescent liquid resulting from the excitation of the first two linearly polarized hybrid modes in this system, being in excellent agreement with theoretical predictions. The efficient excitation and beat of such modes in such an off-resonance situation distinguishes our device from regular directional mode couplers and can benefit applications that demand strong coupling between fundamental- and higher-order- modes, e.g. intermodal third-harmonic generation, bidirectional coupling, and nanofluidic sensing.

中文翻译：

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直接观察纳米流体纤维中的模态杂交[已邀请]

混合材料光纤增强了光纤技术的功能，将当前的功能扩展到了几个新兴的应用领域。这样的平台依靠将新型材料集成到光纤纤芯或包层中，从而支持具有新特性的混合模式。在这里，我们目前的实验揭示了在包含中央高折射率纳米流体通道的掺杂芯二氧化硅纤维内的混合模式相互作用。与标准的液体填充毛细管相比，计算可预测模式，这些模式具有独特的特性，这是由于掺杂的纤芯/覆层界面而产生的，在纳米流体通道的内部和外部都具有高功率分数。我们的实验直接揭示了荧光液中该系统中前两个线性极化混合模式的激发所产生的跳动模式，与理论预测非常吻合。在这样的失谐情况下，这种模式的有效激励和节拍使我们的设备与常规的定向模式耦合器区别开来，并且可以使需要基本模式与高阶模式之间强耦合的应用受益，例如，模态三次谐波产生，双向耦合，以及纳米流体传感。