利用平面式雙曲超穎材料達到二維原子層材料二 硫化鉬之自發輻射增益

Abstract

單層二維材料二硫化鉬擁有垂直能隙半導體材料，被視為新興光電元件材料，目前需 要改善的缺點是量子效率仍低於主流垂直能係半導體材料，本研究探討利用平面式雙 曲超穎材料結合新穎的二維原子層材料二硫化鉬達成結構與材料耦合進而達到自發輻 射增益效果。在此研究中，第一部分，相較於傳統超穎雙曲材料，我們選擇設計平面 式一維的雙曲超穎材料結構，優點在於能與鋪在表面的僅有原子層厚的二維材料達到 更強的光物質交互作用，並結合超穎雙曲材料的優勢，使得光能在結構中有非等相性 的介電常數，進而達到平面的耦合及共振效果，第二部分，則著重於探討把原本的一 維結構彎曲成同心圓狀的雙曲超穎材料，把原本一維的共振效果轉變為環形共振，不 僅藉由更好的共振及更強的耦合達到更高的自發輻射增益，也利用彎曲的雙曲超穎材 料原理，能夠控制光能量匯聚在內圈及小面積的區域中，由於材料和結構都是低維度 及次波長，因此能夠整合到光學元件上，發展出極小光學元件之應用。

Recently, increasing attentions are paid to the two-dimensional materials especially TMDCs due to its direct band gap light emission. It was view as a next generation semiconductor materials which would apply to the optoelectronic device. However, challenging of TMDCs was that they suffered weak quantum yield. Therefore, in this study, we demonstrated the spontaneous emmission enhancement of MoS2 on the planar hyperbolic metamaterials (P- HMMs). In the first part, we designed the planar P-HMM at the PL wavelength of MoS2 which have the better mode coupling in the vertical direction compared to multilayers HMMs. Moreover, its anisotropic property make the PL of MoS2 led to in-plane confinement and resonance. Therefore, the strong coupling between structure and two-dimensional materials and spontaneous emission enhancement was observed in both experiment and simulation. In the second part, we started to curved the planar 1-D HMM into the concentric planar HMM (CPHMM) because we expected the better resonance in the ring cavity. On one hand, because the concentric structure could support the Whisper Gallery Mode (WGM) resonance compared to one dimensional resonance, the higher spontaneous emission enhancement of MoS2 with CP-HMM was observed than enhancement with P-HMM. On the other hand, by the photoluminescence mapping analysis, the highest happened at the inner edge of CP-HMM than other position of CP-HMM. It meant the energy concentration at the inner edge which led to the stronger mode coupling to the two-dimensional materials led to the higher enhancement. The similar results was also confirmed by the simulation results by Finite Element Method. Therefore, it showed the possibility to develop the ultrasmall light source combing subwavelength cavity and atomic thick two-dimensional materials.