Directional Loss Immune Metasurfaces

ABSTRACT Flexible harnessing and controlling optical loss are central to advancing non‐Hermitian photonics, yet achieving directional and tunable manipulation remains challenging. Here, we demonstrate a dielectric metasurface that exhibits directional loss immunity through the formation of a hybridized mode with strongly unbalanced radiation. The mode arises from the coupling between transverse‐magnetic resonances in silicon pillars and transverse‐electric guided modes in the substrate, yielding a radiation asymmetry exceeding two orders of magnitude between the top and bottom ports. Consequently, reflection under top incidence is continuously tunable by modulating non‐radiative loss, while bottom incidence remains immune to the loss. By balancing radiative and non‐radiative decay channels, the metasurface achieves single‐sided perfect absorption accompanied by a phase singularity. The concept is validated through optical pump terahertz probe experiments, where photocarrier injection dynamically controls loss and confirms the directional loss immunity. Combining structural simplicity with robust functionality, this strategy provides a scalable route to metasurfaces that exploit, rather than circumvent, loss. Our results establish a platform for loss‐resilient photonic systems, with potential applications in sensors, lasers, and non‐reciprocal devices.