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

基于我们的模拟结果，我们用硅制作了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。从我们的测量结果来看，腔体的谐振波长和品质因数与数值模拟是一致的。在原理上，H1PHC腔有两个简并的偶极模。然而，由于制造误差是可以避免的，模式的光谱简并被解除，导致在光致发光光谱中观察到两个峰。在不同的腔中，峰分裂的大小不同。为了减少制作误差，改善模式简并，我们将把当前样品的结果作为下一步制作的反馈。另一方面，我们打算在光子晶体上异质集成2D van der Waals材料。我们进一步发展了与2D材料相关的技术。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2D材料的剥离和转移，并开发了一种新型的光子晶体腔，即2D材料在光子晶体波导中诱导的纳米腔。适当宽度的2D材料薄片可以提供小的局部折射率调制，以在放置2D材料的任何地方诱导PHC波导中的空腔的形成。通过FDTD和有限元模拟，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.