Arbitrary designer mode convertor and on-chip OAM generator with configurable topological charge using waveguide-integrated metasurface

Leveraging waveguide-integrated metasurface platform, designer mode convertors capable of exclusively exciting arbitrary high-order modes with high-purity reaching 98% are proposed. We also report on-chip scalable broadband vortex-beam-generators with configurable topological charge from -3 to +3.

1. Integrated designer mode convertors to selectively excite arbitrary waveguide modes

Photonic integrated circuits are hatching as a promising candidate to circumvent the electrical bottleneck manifested conventional electronics integration. Recent years have witnessed an enormous interest in translating the concept of meta-optics into the fundamental building block of optical waveguides [1],[2] to largely enrich the design library of conventional waveguide devices and enable novel functionalities [3]. Previous researchers have applied geometric metasurface on top of waveguides for polarization demultiplexing of circular polarizations [4]-[6]. However, the coupled optical fields are hybrid modes, which cannot be controlled at will and one certain mode-of-interest cannot be exclusively excited. The mode dispersion of these coupled hybrid modes will greatly limit communication speed.