Massachusetts Institute of Technology, Research Laboratory of Electronics, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Sci Rep. 2013;3:2406. doi: 10.1038/srep02406.
Plasmonic structures open novel avenues in photodetector development. Optimized illumination configurations are reported to improve p-polarized light absorptance in superconducting-nanowire single-photon detectors (SNSPDs) comprising short- and long-periodic niobium-nitride (NbN) stripe-patterns. In OC-SNSPDs consisting of ~quarter-wavelength dielectric layer closed by a gold reflector the highest absorptance is attainable at perpendicular incidence onto NbN patterns in P-orientation due to E-field concentration at the bottom of nano-cavities. In NCAI-SNSPDs integrated with nano-cavity-arrays consisting of vertical and horizontal gold segments off-axis illumination in S-orientation results in polar-angle-independent perfect absorptance via collective resonances in short-periodic design, while in long-periodic NCAI-SNSPDs grating-coupled surface waves promote EM-field transportation to the NbN stripes and result in local absorptance maxima. In NCDAI-SNSPDs integrated with nano-cavity-deflector-array consisting of longer vertical gold segments large absorptance maxima appear in 3p-periodic designs due to E-field enhancement via grating-coupled surface waves synchronized with the NbN stripes in S-orientation, which enable to compensate fill-factor-related retrogression.
等离子体结构为光电探测器的发展开辟了新途径。据报道，优化的照明配置可以提高由短周期和长周期铌氮化物（NbN）条带图案组成的超导纳米线单光子探测器（SNSPD）的 p 偏振光吸收率。在由金反射器封闭的约四分之一波长介电层组成的 OC-SNSPD 中，由于在纳米腔底部的电场集中，在 P 取向的 NbN 图案上垂直入射时可获得最高吸收率。在与由垂直和水平金段组成的纳米腔阵列集成的 NCAI-SNSPD 中，通过短周期设计中的集体共振，在 S 取向的离轴照明下实现了与极角无关的完美吸收率，而在长周期 NCAI-SNSPD 中，光栅耦合表面波促进 EM 场传输到 NbN 条带，并导致局部吸收率最大值。在与由更长的垂直金段组成的纳米腔偏转器阵列集成的 NCDAI-SNSPD 中，由于与 S 取向的 NbN 条带同步的光栅耦合表面波增强了电场，在 3p 周期设计中出现了较大的吸收率最大值，这使得能够补偿与填充因子相关的退化。
