Time-varying gradient metasurface with applications in all-optical beam steering

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Epsilon-near-zero (ENZ) materials exhibit large, subpicosecond nonlinear optical responses.
• Plasmonic metasurfaces offer design flexibility for optical devices.
• Combining ENZ materials with metasurfaces enables advanced optical functionalities.

Purpose of the Study:

• To experimentally investigate a plasmonic gradient metasurface on indium tin oxide (ITO).
• To characterize the dynamic modulation of probe pulse diffraction by a pump pulse near the ENZ region.
• To explore applications in rapidly modulated optical devices.

Main Methods:

• Fabrication of a plasmonic gradient array on a thin ITO layer.
• Experimental characterization of probe pulse diffraction under dynamic modulation by a pump pulse.
• Analysis of angular shifts in diffraction orders.

Main Results:

• Observed angular shifts in diffraction orders attributed to adiabatic wavelength conversion.
• Demonstrated significantly different dynamic responses for different diffraction orders in an asymmetric gradient metasurface.
• Achieved free-space wavelength shifts of 6 nm and 12 nm for +1 and -1 diffraction orders, respectively.

Conclusions:

• The study highlights the potential of ENZ metasurfaces for creating rapidly modulated optical devices.
• Observed phenomena suggest applications in telecommunications, sensing, and reactive beam steering.
• The asymmetric gradient metasurface acts as a blazed diffraction grating with distinct dynamic responses.