Ultra-Compact, High-Efficiency Vertical Meta-Grating Couplers for Meta-Photonic Integrated Circuits

• DOI: 10.3390/nano15080583
• Publication Date: 2025-04-11T10:45:31Z
• Authors: Hang Cheng; Jiagui Wu; Yue Wang; Chongchong Ran; Haitang Li; Yu Wang; Yuanhui Li; Sen Zhang; Chunhui Wang; Junbo Yang
• Keywords: Extinction ratio; Beam propagation method; Coupling loss

Vertical meta-grating couplers (VMGCs), while essential for flexible spatial beam coupling in meta-photonic integrated circuits (MPICs), suffer from inherently low efficiency that hinders broader applications. In this study, we introduce an improved adjoint optimization method with high computational and excellent effectiveness. Utilizing method, demonstrate ultra-compact single-polarization VMGC achieving 81.57% a 92 nm 3 dB bandwidth, dual-polarization beam-splitting coupler over 52% both polarizations, bandwidth exceeding 60 nm, ultra-high extinction ratio of 26.4 dB, negligible polarization dependent loss at 1550 nm. To the best our knowledge, achievement represents simulation record to date perfect vertical without bottom reflectors.