We present an antiresonant hollow-core fiber-based bandpass optical filter. The device is realized by tapering down a section of tubular hollow-core fiber to a ratio of less than 0.5. Sweeping of the tube wall thickness-induced resonant bands in the down- and up-transition sections of the taper suppresses the blue side of the spectrum, while the red side filtering exploits the increased confinement loss at the taper waist that depends sharply on the wavelength-to-core-diameter ratio. These working principles of the filter make it possible to customize the location and width of the passband by tailoring the fiber design and taper profile. We achieve a 350-nm-wide bandpass filter with the minimum insertion loss of 1.3 dB in the passband and up to 40 dB suppression in the lossbands. We anticipate the filter to become one of the essential components in all-hollow-core fiberized optical systems.

中文翻译：

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在线空芯光纤带通滤波器

我们提出了一种基于反谐振空芯光纤的带通滤光器。该装置是通过将一段管状空心纤维逐渐缩小到小于 0.5 的比率来实现的。在锥形的向下和向上过渡部分扫描管壁厚度引起的共振带抑制了光谱的蓝色侧，而红色侧过滤利用了锥形腰部增加的限制损耗，这与波长密切相关芯径比。滤波器的这些工作原理可以通过定制光纤设计和锥度轮廓来定制通带的位置和宽度。我们实现了 350 纳米宽的带通滤波器，其通带中的最小插入损耗为 1.3 dB，损耗带中的抑制率高达 40 dB。