The interaction effect of the fundamental mode in a special photonic crystal fiber (PCF) with a thin-film absorbing coating deposited on a surface of a fiber cladding on the optical transmission of the PCF is theoretically studied. It is shown that the transmission has a multi-peak spectrum that is determined by the resonance capture of the fundamental PCF mode energy by the coating. In some cases, this capture is explained by a resonance coupling between the fundamental core mode and leaky modes of the coating, or between the fundamental PCF mode and cladding modes located between PCF air channels and the coating. Examples are presented of using this effect to develop fiber-optic sensors of refractive index or pressure, and to sense a nanoscale adsorption layer of ammonia molecules deposited on a coating surface contacting air.

中文翻译：

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光子晶体光纤中的损耗模式共振

从理论上研究了特殊光子晶体光纤 (PCF) 中基模与沉积在光纤包层表面的薄膜吸收涂层对 PCF 光传输的相互作用影响。结果表明，传输具有多峰光谱，该光谱由涂层对基本 PCF 模式能量的共振捕获决定。在某些情况下，这种捕获是通过涂层的基本纤芯模式和泄漏模式之间，或基本 PCF 模式和位于 PCF 空气通道和涂层之间的包层模式之间的共振耦合来解释的。举例说明了使用这种效应开发折射率或压力的光纤传感器，并感测沉积在与空气接触的涂层表面上的氨分子的纳米级吸附层。