On-chip ultracompact multimode vortex beam emitter based on vertical modes

Abstract

Free-space orbital angular momentum (OAM) communication is considered as one of the potential alternative on-chip optical interconnect solutions. The number of OAM modes determines the capacity of high-speed communication. However, existing integrated vortex beam emitters have a constraint relationship between the number of OAM modes and the emitter size, rendering it difficult to emit more OAM modes with a small-sized emitter. In view of the above, this study proposes an on-chip ultracompact multimode vortex beam emitter based on vertical modes, which permits more OAM modes without requiring an increase in the size of the emitter. Vertical modes in large-aspect-ratio waveguides are pointed out to enable multimode microrings with small radii because high-order vertical modes can maintain almost the same horizontal wave vector as that of the fundamental mode. Four-mode and five-mode vortex beam emitters with the same radius of 1.5 µm are designed and the effectiveness of these emitters is verified through simulation. Furthermore, a high-efficiency and low-crosstalk approach for high-order vertical mode coupling by varying the waveguide height is presented. This research not only promotes further integration of on-chip optical interconnection, but also provides a new strategy for optical waveguide mode selection in photonic integrated circuits design.

Advances in Meta-Optics and Metasurfaces: Fundamentals and Applications

“…Such OAM-carrying structured light beams have been found to have various significant applications in optics and photonics, such as optical communications [ 188 ], optical trapping [ 189 ], and image processing [ 190 ], etc. Because of their properties of ultra-compact configuration and powerful functionalities for wavefront control, metasurface-based structured-light technologies offer new opportunities for excavating the fundamentals and applications of light beams that are impossible to achieved by conventional optics [ 191 , 192 , 193 , 194 ]. As shown in Figure 7 a, Shuang Zhang et al propose multichannel metalenses via geometrical phase-based metasurfaces composed of metallic nanovoid arrays.…”