Demonstration of valley spin devices by coupling 2D semiconductors to chiral photonic crystal nanocavities

根据我们的模拟结果，我们用硅制造了 H1 光子晶体 (PhC) 腔，并通过测量腔的光致发光 (PL) 来表征其光学特性。 从我们的测量结果来看，腔谐振波长和品质因数与我们的数值模拟一致。原则上，H1 PhC 腔有两种简并偶极子模式。然而，由于制造误差是可以避免的，模式的光谱简并性被提升，导致在 PL 光谱中观察到两个峰值。峰分裂的幅度因腔体而异。我们当前样品的结果将用作我们下一步制造的反馈，以减少制造误差，从而改善模式简并。另一方面，我们打算在光子晶体上异构集成 2D 范德华材料。我们进一步开发了二维材料相关技术。特别是，我们利用聚二甲基硅氧烷（PDMS）、蒽和六方氮化硼（hBN）薄片的组合进行了二维材料剥离和转移。我们还开发了一种新型光子晶体腔，即光子晶体波导中的二维材料诱导纳米腔。适当宽度的 2D 材料薄片可以提供小的局部折射率调制，以在 PhC 波导中放置 2D 材料的任何位置诱导形成空腔。我们通过FDTD和FEM模拟验证了该方法的可行性。

Based on our simulation results, we have fabricated H1 photonic crystal (PhC) cavities with silicon and characterized their optical characteristics by measuring the photoluminescence (PL) from the cavity. From our measurement results, the cavity resonant wavelengths and quality factor are consistent with our numerical simulations. In principle, the H1 PhC cavity has two degenerate dipole modes. However, as fabrication errors are avoidable, the spectral degeneracy of the modes are lifted resulting in the observation of two peaks in the PL spectra. The magnitude of the peak splitting varies from cavity to cavity. Results from our current sample will be used as feedback for our next fabrication in order to reduce fabrication error and thus improve the mode degeneracies.On the other hand, we intend to heterogeneously integrate 2D van der Waals material on the photonic crystal. We have further developed the technologies related to 2D materials. In particular, we carried out 2D materials exfoliation and transfer using combinations of polydimethylsiloxane (PDMS), anthracene and hexagonal boron nitride (hBN) flakes.We also developed a novel type of photonic crystal cavity, namely the 2D material-induced nanocavity in a photonic crystal waveguide. A 2D material flake of a suitable width can provide a small local refractive index modulation to induce the formation of a cavity in a PhC waveguide at wherever the 2D material is placed. We confirmed the feasibility of such method by FDTD and FEM simulations.