Electrically tunable conducting oxide metasurfaces for high power applications.

Area of Science:

• Photonics and optical engineering
• Materials science
• Nanotechnology

Background:

• Active metasurfaces offer dynamic wavefront control at optical frequencies.
• Understanding power-handling limits is crucial for practical applications of metasurfaces.
• Conducting oxide metasurfaces are emerging photonic components with tunable optical properties.

Purpose of the Study:

• To investigate the thermal performance and power-handling limits of gate-tunable conducting oxide metasurfaces.
• To assess the robustness of indium tin oxide (ITO) based metasurfaces under high-power continuous wave (CW) and pulsed laser illumination.
• To explore theoretical improvements in metasurface reflectance using alternative conducting oxides.

Main Methods:

• Experimental characterization of reflective gate-tunable ITO metasurfaces under high irradiance CW laser beams (1.6–9.1 kW/cm²).
• Measurement of optical response and temperature rise under applied electrical bias and laser illumination.
• Theoretical modeling to predict reflectance enhancement by replacing ITO with cadmium oxide (CdO) in the epsilon-near-zero (ENZ) regime.

Main Results:

• ITO metasurfaces exhibited no significant change in optical response up to 9.1 kW/cm² under CW illumination.
• Despite high light absorption (>60%) in the ITO charge layer, the local temperature rise was modest, indicating robustness.
• Theoretical analysis predicted a tenfold increase in reflectance by using CdO instead of ITO in the ENZ regime.

Conclusions:

• Gate-tunable conducting oxide metasurfaces possess the thermal robustness required for high-power optical applications.
• The findings support the use of these metasurfaces in areas such as free-space optical communications, LiDAR, and laser-based additive manufacturing.
• CdO-based metasurfaces offer a promising route for enhanced performance in high-power photonic devices.