Replication Data for: Terahertz sensing of 7 nm dielectric film with bound states in the continuum metasurfaces

The fingerprint spectral response of several materials with terahertz electromagnetic radiation indicates that terahertz technology is an effective tool for sensing applications. However, sensing few nanometer thin-films of dielectrics with much longer terahertz waves (1 THz = 0.3 mm) is challenging. Here, we demonstrate a quasibound state in the continuum (BIC) resonance for sensing of a nanometer scale thin analyte deposited on a flexible metasurface. The large sensitivity originates from the strong local field confinement of the quasi-BIC Fano resonance state and extremely low absorption loss of a low-index cyclic olefin copolymer substrate. A minimum thickness of 7 nm thin-film of germanium is sensed on the metasurface, which corresponds to a deep subwavelength scale of λ/43 000, where λ is the resonance wavelength. The low-loss, flexible, and large mechanical strength of the quasi-BIC microstructured metamaterial sensor could be an ideal platform for developing ultrasensitive wearable terahertz sensors.多种材料在太赫兹电磁波下的指纹光谱响应表明，太赫兹（terahertz）技术是传感应用的有效工具。然而，利用波长长得多的太赫兹波（1太赫兹=0.3毫米）传感数纳米厚度的电介质薄膜仍颇具挑战。本研究展示了一种连续域中准束缚态（quasibound state in the continuum, BIC）共振现象，可用于检测沉积在柔性超表面（metasurface）上的纳米级超薄分析物。该传感器的高灵敏度源于准BIC法诺（Fano）共振态的强局域场限域效应，以及低折射率环烯烃共聚物（cyclic olefin copolymer）基底极低的吸收损耗。我们在该超表面上成功检测到厚度仅7纳米的锗（germanium）薄膜，其对应深亚波长尺度λ/43000（λ为共振波长）。这种低损耗、柔性且机械强度优异的准BIC微结构超材料（metamaterial）传感器，有望成为开发超灵敏可穿戴太赫兹传感器的理想平台。