Integrated topological photonics with time-reversal symmetry breaking

Abstract

The bottleneck of bandwidth limitation and power dissipation in today's electronic microchips is conflicting with the exceeding demand for information communication and processing. Light, due to its intrinsic high frequency and environment-insensitivity (owing to its charge neutrality), is expected to bring solutions to this fundamental challenge. However, by the same token, certain functionalities in optical information processing will require sophisticated control of light in nanoscale structures interfacing different materials and light-matter interactions. In this regard, the emerging field of topological photonics brings new degree of freedom to realize manipulation of light propagation with unprecedented properties. In this talk, I will present works of integrated topological photonics based on dynamic modulation scheme. Since dynamic modulation breaks time-reversal symmetry, topological photonic states realized in this way are distinctive to those in passive or static dielectric platform. I will introduce two integrated architectures: optoelectronic integration and optomechanical integration. For the optoelectronic integration, external electric drives are applied through the integrated metal electrodes and PN diodes to dynamically modulate the refractive index of silicon photonic structures. By controlling the phase of the electrical modulation, we can realize an effective magnetic field for photons and topological light propagation. These novel manipulations are unreachable in static dielectrics and provide a solution for on-chip optical isolation that is essential for stable and energy efficient optical communication. In the second part of my talk, I will present work in another hybrid architecture that interfaces light and sound: optomechanical crystals. This architecture allows for simultaneously engineering of optical and mechanical properties as well as photon-phonon interactions at nanoscale. Time-reversal symmetry is broken through the radiation-pressure force driven mechanical vibrations, and both topological photonic and phononic states can be realized in this architecture. Combining electron beam lithography and scanning probe microscope tuning, we fabricated cavity-optomechanical circuits on silicon microchips that exhibits optical non-reciprocity, which paves the way towards realizing effective magnetic field for photons and phonons in the cavity-optomechanical architecture. These achievements hold promise for the application of topological photonics for light-based communication and processing in an integrated, chip-scale platform.