Verma Sagar Kumar, Srivastava Sachin K
Department of Physics, Indian Institute of Technology Roorkee, Roorkee, Haridwar, Uttarakhand 247667 India.
Plasmonics. 2022;17(2):653-663. doi: 10.1007/s11468-021-01551-1. Epub 2021 Oct 19.
In the present study, we report giant extra-ordinary transmission of near infrared (NIR) light, more than 90%, through a seemingly opaque plasmonic metasurface, which consists of two metal nano-slits arrays (MNSAs) with alternate opening arrangements. By using perfect coupling of the plasmonic modes formed between the sharp edges of the upper and lower MNSAs of silver, a giant, wavelength selective transmission could be obtained. The study is accompanied by optimization of electromagnetic (EM) field coupling for different interlayer spacings and lateral overlap between the two MNSAs to understand their significance in light transmission through the metasurface. The interlayer spacing between the MNSAs works as the transmitting channel for light. The optimization of performance with different fill factors and plasmonic metals was performed as well. Because of the excitation of extended surface plasmons (ESPs) generated at both the MNSAs, the metasurface can be used for refractive index (RI) sensing as one of its applications by using a transparent and flexible polymer, such as polydimethylsiloxane (PDMS), as substrate. The maximum sensitivity which could be achieved for the optimal configuration of the metasurface was 1435.71 nm/RIU, with a figure of merit (FOM) of 80 RIU for 90.45% optical transmission of light for the refractive index variation of analyte medium from 1.33 to 1.38 RIU. The present study strengthens the concept of light funneling through subwavelength structures due to plasmons, which are responsible for light transmission through this seemingly opaque metasurface and finds use in highly sensitive, flexible, and cost-effective EOT-based sensors.
在本研究中，我们报道了近红外（NIR）光通过一个看似不透明的等离子体超表面实现了超过90%的巨大超常传输，该超表面由两个具有交替开口排列的金属纳米狭缝阵列（MNSA）组成。通过利用银的上下MNSA锐边之间形成的等离子体模式的完美耦合，可以获得巨大的、波长选择性的传输。该研究还伴随着针对不同层间距和两个MNSA之间的横向重叠对电磁场（EM）耦合进行优化，以了解它们在光通过超表面传输中的重要性。MNSA之间的层间距充当光的传输通道。还对不同填充因子和等离子体金属进行了性能优化。由于在两个MNSA处都激发了扩展表面等离子体（ESP），该超表面可以使用透明且柔性的聚合物（如聚二甲基硅氧烷（PDMS））作为基底，将其用作折射率（RI）传感的应用之一。对于超表面的最佳配置，可实现的最大灵敏度为1435.71 nm/RIU，品质因数（FOM）为80 RIU，对于分析物介质折射率从1.33到1.38 RIU变化时，光的光学传输率为90.45%。本研究强化了由于等离子体导致光通过亚波长结构进行光漏斗效应的概念，等离子体负责光通过这个看似不透明的超表面的传输，并在基于超常传输（EOT）的高灵敏度、柔性且经济高效的传感器中得到应用。
