Phase Change Materials‐Based Bilayer Metasurfaces for Near‐Infrared Photonic Routing

Abstract Photonic routing holds immense significance in the fields of photonic integrated circuits (PICs) for free‐space optical linking. The emergence of programmable metasurfaces with powerful phase regulation capability provides a promising strategy for achieving designated wavefront modulation and thus photonic routing in the optical communication waveband. Here, a bilayer metasurfaces with four‐level codable unit pixels, which realize controllable photonic routing in near‐infrared (NIR) region is reported. The unit pixel of the metasurfaces consists of the underneath amorphous silicon (α‐Si) nanofin and the upper Ge₂Sb₂Te₅ (GST) nano‐antenna, which contribute to the cross‐polarization generation and amplitude modulation of cross‐polarization light, respectively. Each unit pixel can be designated with desired states, thus achieving on‐demand non‐volatile photonic routing for coherent NIR light. In particular, polarization conversion modulation of the tunable metasurfaces comprising identical unit cell with large cross‐polarization switching (≈55%) at ≈1550 nm is demonstrated. Moreover, the metasurfaces with coded unit pixels to realize designated photonic routing are prototyped. The metasurfaces with four‐level programmability portend a new paradigm in NIR photonic routing for PICs.