Opt Lett. 2018 Oct 15;43(20):5017-5020. doi: 10.1364/OL.43.005017.
We demonstrate superconducting nanowire single-photon detectors (SNSPDs) based on a fractal design of the nanowires to reduce the polarization sensitivity of detection efficiency. We patterned niobium titanium nitride thin films into Peano curves with a linewidth of 100 nm and integrated the nanowires with optical microcavities to enhance their optical absorption. At a base temperature of 2.6 K, the fractal SNSPD exhibited a polarization-maximum device efficiency of 67% and a polarization-minimum device efficiency of 61% at a wavelength of 1550 nm. Therefore, the polarization sensitivity, defined as their ratio, was 1.1, lower than the polarization sensitivity of the SNSPDs in the meander design. The reduced polarization sensitivity of the detector could be maintained for higher-order spatial modes in multimode optical fibers and could tolerate misalignment between the optical mode and the detector. This fractal design is applicable to both amorphous and polycrystalline materials that are commonly used for making SNSPDs.
我们展示了基于纳米线分形设计的超导纳米线单光子探测器 (SNSPD)，以降低探测效率的偏振灵敏度。我们将氮化钛铌薄膜图案化成线宽为 100nm 的彭罗斯曲线，并将纳米线与光学微腔集成，以增强它们的光吸收。在基底温度为 2.6K 的情况下，分形 SNSPD 在 1550nm 波长处表现出偏振最大值器件效率为 67%，偏振最小值器件效率为 61%。因此，偏振灵敏度（定义为两者之比）为 1.1，低于蛇形设计的 SNSPD 的偏振灵敏度。探测器的偏振灵敏度降低可用于多模光纤中的更高阶空间模式，并可容忍光学模式和探测器之间的失准。这种分形设计适用于通常用于制造 SNSPD 的非晶态和多晶态材料。
