Photonic spin-orbit coupling in optical microcavities

李峰 教授
2019-11-22 (Fri) 10:00

Fabry-Perrot (FP) microcavities with metal or DBR (distributed Bragg reflector)-coated mirrors provide an excellent platform for investigating the collective behavior of confined 2-dimensional photons and polaritons. The TE-TM mode splitting in such cavities acts as an effective magnetic field, leading to photonic spin-orbit (SO) coupling effect that the pseudospin of cavity photons changes anisotropically with their momenta. Such mechanism has led to interesting observations including optical spin-Hall effect, magnetic-monopole-like half solitons, spinor condensate with half-quantum circulation, and polaritonic topological insulators.

In this talk, I will first report the direct measurement of the Berry curvature and quantum metric of the photonic modes of a F-P cavity containing an optically active (OA) organic microcrystal (Perylene). Photonic spin-orbit-coupling induced by the cavity results in the action of a non-Abelian gauge field on photons. The addition of high OA makes emerge geometrically non-trivial bands containing two gapped Dirac cones with opposite topological charges. This experiment performed at room temperature and at visible wavelength establishes the potential of optically active organic materials for implementing non-magnetic and low-cost topological photonic devices. In the second part of the talk, I will present the open-access microcavity system consisting of planar and concave DBR-coated cavity mirrors separated by a micro-sized gap. A combination of the SO coupling and the lateral photonic potential gives rise to new eigenstates of spin vortices and optical Skyrmions. We show that those states provide vector vortex beam lasing with ultrasmall mode volume, whose pseudospin features can be tuned by varying the cavity length. The open-access microcavities can serve as a new platform for investigate photonic SO coupling with increased photonic lifetime and flexible tunability.



Feng Li got his bachelor’s and master’s degree at Tianjin University in China in 2006 and 2008. He got his PhD at CNRS and the University of Nice Sophia-Antipolis in France in 2013, supported by the European Marie-Curie ITN project CLERMONT4. Then he worked as a research associate at the University of Sheffield in UK from January 2014 to May 2017. Feng Li joined Xi’an Jiaotong University as a professor in June 2017, with main research interest in quantum and topological effects induced by light-matter interaction in microcavities and nanostructures.