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

基于我们的模拟结果，我们用硅制备了H1光子晶体（PhC）腔，并通过测量腔内的光致发光（PL）来表征其光学特性。从测量结果来看，谐振腔的波长和质量因子与数值模拟结果一致。原理上，H1型PhC腔具有两个简并偶极子模式。然而，由于制造误差是可以避免的，模式的谱简并被解除，导致在PL光谱中观察到两个峰。在不同的空腔中，峰劈裂的幅度是不同的。当前样品的结果将作为下一次加工的反馈，以减少加工误差，从而改善模态简并度。另一方面，我们打算在光子晶体上非均质集成二维范德华材料。我们进一步开发了与二维材料相关的技术。特别是，我们使用聚二甲基硅氧烷（PDMS）、蒽和六方氮化硼（hBN）薄片的组合进行了二维材料的剥离和转移。我们还开发了一种新型的光子晶体腔，即光子晶体波导中的二维材料诱导纳米腔。适当宽度的二维材料薄片可以提供小的局部折射率调制，从而在放置二维材料的任何位置诱导PhC波导中腔的形成。通过时域有限差分和有限元仿真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.