Actively Switchable Beam-Steering via Hydrophilic/Hydrophobic-Selective Design of Water-Immersed Metasurface

Liquid immersion on metasurface was earlier demonstrated to realize spectral control. However, it remains a great challenge to achieve tunable phase modulation and versatile beam-steering performance, which are critical for practical optoelectronic devices. Here, a new liquid-immersive mechanism with metasurfaces for active beam-steering is proposed and experimentally realized. Based on the dielectric-on-metal nanostructure with selective hydrophilic/hydrophobic properties, the switchable beam-steering is initiated and successfully presented in the broadband visible regime with a large reflection angle of approximate to +/- 30 degrees. Specifically, the beam diffraction direction is tuned between two opposite-directional channels by water immersion or drying in a repeatable and controllable manner. The proposed straightforward tuning strategy enjoys great convenience in structural patterning and large-area implementation, instead of requiring any complicated contact patterning or external modulation. This study provides an alternative optical platform for switchable beam-steering functionality, which is promising for potential applications in tunable display, directional emission, sensing technologies, etc.