Woo Aran, Sung Junghyun, Gong Su-Hyun
Opt Express. 2021 Mar 29;29(7):10688-10697. doi: 10.1364/OE.419711.
Understanding the chiral light-matter interaction offers a new way to control the direction of light. Here, we present an unprecedently long-range transport of valley information of a 2D-layered semiconductor via the directional emission through a dielectric waveguide. In the evanescent near field region of the dielectric waveguide, robust and homogeneous transverse optical spin exists regardless of the size of the waveguide. The handedness of transverse optical spin, determined by the direction of guided light mode, leads to the chiral coupling of light with valley-polarized excitons. Experimentally, we demonstrated ultra-low propagation loss which enabled a 16 µm long propagation of directional emission from valley-polarized excitons through a ZnO waveguide. The estimated directionality of exciton emission from a valley was about 0.7. We confirmed that a dielectric waveguide leads to a better performance than does a plasmonic waveguide in terms of both the directional selectivity of guided emission and the efficiency of optical power reaching the ends of the waveguide when a propagation length is greater than ∼10 µm. The proposed dielectric waveguide system represents an essential platform for efficient spin/valley-photon interfaces.
理解手性光与物质的相互作用为控制光的传播方向提供了一种新方法。在此，我们展示了二维层状半导体谷信息通过介质波导的定向发射实现了前所未有的长程传输。在介质波导的倏逝近场区域，无论波导尺寸如何，都存在稳健且均匀的横向光学自旋。由导光模式方向决定的横向光学自旋的手性，导致光与谷极化激子的手性耦合。在实验中，我们展示了超低的传播损耗，使得谷极化激子通过ZnO波导实现了16 μm长的定向发射传播。从谷发出的激子发射的估计方向性约为0.7。我们证实，当传播长度大于约10 μm时，在导波发射的方向选择性和到达波导末端的光功率效率方面，介质波导比等离子体波导具有更好的性能。所提出的介质波导系统是高效自旋/谷 - 光子界面的重要平台。
