Narrowband absorption spectrum is usually a critically important factor for a plasmonic absorber that is worked as a biosensor, for narrower bandwidth refers to higher sensitivity of sensor. To realize plasmonic biosensor of narrow bandwidth, absorption property of plasmonic absorber has been usually investigated under normally incident light with transverse magnetic polarization. Here we present numerically a structure of graphene-based metasurface to obtain reflection spectrum of narrow bandwidth, while incident light is at oblique angle and with transverse electric polarization in the infrared range. The presented structure includes a dielectric layer on top side, a buffer dielectric layer, graphene film, a dielectric layer of high refractive index with high-aspect-ratio nanotrench array, and a metal substrate. As a plasmonic absorber, its absorption bandwidth is 0.5 nm wide, and its peak absorption reaches 97% at the resonant wavelength. As a refractive index sensor, its bulk sensitivity and figure of merit are 500 nm/RIU and 1000/ RIU (“RIU” is abbreviation of “Refractive Index Unit” and as unit of refractive index), respectively. It shows a novel configuration of obtaining narrow bandwidth plasmonic absorbers using transverse electric polarized incident light at oblique incidence angle.} The presented graphene-based structure has a strong potential in biosensing applications, such as platform for sensing refractive index variation on the nanoscale while probing neural stem cell activities in the period of cell development.

中文翻译：

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基于石墨烯的窄带吸收平台和红外范围内的斜入射

窄带吸收光谱通常是作为生物传感器工作的等离子体吸收器的一个至关重要的因素，因为更窄的带宽是指传感器的更高灵敏度。为了实现窄带宽的等离子体生物传感器，通常研究等离子体吸收体在具有横向磁极化的垂直入射光下的吸收特性。在这里，我们在数值上提出了一种基于石墨烯的超表面结构，以获得窄带宽的反射光谱，而入射光是倾斜的，并且在红外范围内具有横向电极化。所提出的结构包括顶部的介电层、缓冲介电层、石墨烯膜、具有高纵横比纳米沟槽阵列的高折射率介电层和金属基板。作为等离子体吸收体，其吸收带宽为 0.5 nm 宽，在共振波长处其峰值吸收达到 97%。作为折射率传感器，其体积灵敏度和品质因数分别为 500 nm/RIU 和 1000/RIU（“RIU”是“Refractive Index Unit”的缩写，作为折射率的单位）。它展示了一种使用斜入射角的横向电偏振入射光获得窄带宽等离子体吸收体的新配置。}所提出的基于石墨烯的结构在生物传感应用中具有强大的潜力，例如在探测时传感纳米级折射率变化的平台细胞发育时期的神经干细胞活动。其体积灵敏度和品质因数分别为 500 nm/RIU 和 1000/RIU（“RIU”是“折射率单位”的缩写，是折射率单位）。它展示了一种使用斜入射角的横向电偏振入射光获得窄带宽等离子体吸收体的新配置。}所提出的基于石墨烯的结构在生物传感应用中具有强大的潜力，例如在探测时传感纳米级折射率变化的平台细胞发育时期的神经干细胞活动。其体积灵敏度和品质因数分别为 500 nm/RIU 和 1000/RIU（“RIU”是“Refractive Index Unit”的缩写，是折射率的单位）。它展示了一种使用斜入射角的横向电偏振入射光获得窄带宽等离子体吸收体的新配置。}所提出的基于石墨烯的结构在生物传感应用中具有强大的潜力，例如在探测时传感纳米级折射率变化的平台细胞发育时期的神经干细胞活动。