Electrically tunable conducting oxide metasurfaces for high power applications

Abstract

Active metasurfaces designed to operate at optical frequencies are flat optical elements that can dynamic, subwavelength-scale wavefront control of reflected or transmitted light. The practical and fundamental power-handling limits of active metasurfaces at high pulse energies and high average powers determine the potential applications for these emerging photonic components. Here, we investigate thermal performance limits of reflective gate-tunable conducting oxide metasurfaces illuminated with high power density laser beams, for both continuous wave (CW) and pulsed laser illumination. Our gate-tunable metasurfaces use indium tin oxide (ITO) as an active material, which undergoes an epsilon-near-zero (ENZ) transition under applied electrical bias. We experimentally show that under CW illumination, there is no significant change in the electrically tunable metasurface optical response for high irradiances ranging from 1.6 kW/cm2 to 9.1 kW/cm2 when the illuminating laser beam diameter is 7 μm. Even under an applied bias, when over 60% of the incoming light is absorbed in a 1 nm–thick charge accumulation layer within ITO, the local temperature rise in the metasurface is modest, supporting its robustness for high-power applications. Additionally, we theoretically show that in the ENZ regime, the metasurface reflectance can be increased by a factor of 10 by replacing the active ITO layer with cadmium oxide (CdO). Thus conducting oxide metasurfaces can tolerate the power densities needed in higher power applications, including free space optical communications, to light detection and ranging (LiDAR), as well as laser-based additive manufacturing.

Sol–Gel Barium Titanate Nanohole Array as a Nonlinear Metasurface and a Photonic Crystal

“…Moreover, the large transparency window of BTO and the freedom to structure it on transparent insulating substrates enables to utilize the NUV and VIS spectrum range with minimized damage from absorption at high optical powers. The increased field in the electro‐optic medium or in the nanohole cavities can be particularly beneficial for high‐speed beam steering metasurfaces [ 43 ] or advanced nanohole array sensors. [ 31 ] This high‐throughput fabrication platform is advantageous for improving the fabrication flexibility required for application optimized nonlinear photonic devices.…”

High-quality-factor space–time metasurface for free-space power isolation at near-infrared regime

“…However, it is shown that the interelement coupling between the adjacent unit cells is significant under TM polarization in comparison to TE, which leads to cross talk and undesired sidelobes 73 – 75 …”

“…However, it is shown that the interelement coupling between the adjacent unit cells is significant under TM polarization in comparison to TE, which leads to cross talk and undesired sidelobes. [73][74][75] In order to get better insight into the radiative properties of the resonant modes, we employ the multipole decomposition up to the fourth order, tied by electric and magnetic octupoles, to calculate the contribution of each multipole in the scattering response. For this purpose, we have conducted a theoretical analysis based on multipole decomposition method developed for light scattering.…”

Plasmonic polymer nanoantenna arrays for electrically tunable and electrode-free metasurfaces

“…2,8 Electrically tunable metasurfaces have attracted particular attention because they can be readily integrated with existing optoelectronic devices, exploiting the technical maturity of the modern electronics industry. [9][10][11][12][13] Recently, highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) based polymer nanoantennas have shown unique potential as a building block of electrically tunable metasurfaces working in the infrared spectral range. [14][15][16][17][18][19] Therein, the redox states of the PEDOT nanoantennas were controlled by electrochemical doping and dedoping, resulting in changes in both charge carrier concentration and mobility, and consequently nanooptical responses.…”

“…2,8 Electrically tunable metasurfaces have attracted particular attention because they can be readily integrated with existing optoelectronic devices, exploiting the technical maturity of the modern electronics industry. 9–13…”