Department of Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden.
ACS Nano. 2023 Feb 28;17(4):3401-3411. doi: 10.1021/acsnano.2c08947. Epub 2023 Feb 17.
Perfect absorption and strong coupling are two highly sought-after regimes of light-matter interactions. Both regimes have been studied as separate phenomena in excitonic 2D materials, particularly in MoS. However, the structures used to reach these regimes often require intricate nanofabrication. Here, we demonstrate the occurrence of perfect absorption and strong coupling in thin MoS multilayers supported by a glass substrate. We measure reflection spectra of mechanically exfoliated MoS flakes at various angles beyond the light-line via Fourier plane imaging and spectroscopy and find that absorption in MoS monolayers increases up to 74% at the C-exciton by illuminating at the critical angle. Perfect absorption is achieved for ultrathin MoS flakes (4-8 layers) with a notable angle and frequency sensitivity to the exact number of layers. By calculating zeros and poles of the scattering matrix in the complex frequency plane, we identify perfect absorption (zeros) and strong coupling (poles) conditions for thin (<10 layers) and thick (>10 layers) limits. Our findings reveal rich physics of light-matter interactions in bare MoS flakes, which could be useful for nanophotonic and light harvesting applications.
完美吸收和强耦合是两种备受关注的光物质相互作用模式。这两种模式都被作为单独的现象在激子二维材料中进行了研究，特别是在 MoS 中。然而，为了达到这些模式，所使用的结构通常需要复杂的纳米制造。在这里，我们证明了在玻璃衬底支撑的薄 MoS 多层中存在完美吸收和强耦合。我们通过傅里叶平面成像和光谱法测量了在超越光线路的各种角度下机械剥离的 MoS 薄片的反射光谱，并发现通过在临界角处照明，MoS 单层中的吸收在 C-激子处增加到 74%。对于超薄 MoS 薄片（4-8 层），通过计算散射矩阵在复频平面上的零点和极点，我们确定了完美吸收（零点）和强耦合（极点）条件对于薄（<10 层）和厚（>10 层）极限。我们的发现揭示了裸 MoS 薄片中光物质相互作用的丰富物理特性，这对于纳米光子学和光收集应用可能是有用的。
