Controlling the Polarization State of Light with Plasmonic Metal Oxide Metasurface

Abstract

Conventional plasmonic materials, namely noble metals, hamper the realization of practical plasmonic devices due to their intrinsic limitations, such as lack of capabilities to tune in real-time their optical properties, failure to assimilate with CMOS-standards, and severe degradation at elevated temperatures. Transparent conducting oxides (TCOs) is a promising alternative as plasmonic material throughout the near- and mid-infrared wavelengths. In addition to compatibility with established silicon-based fabrication procedures, TCOs provide great flexibility in the design and optimization of plasmonic devices since their intrinsic optical properties can be tailored and dynamically tuned. In this work, we experimentally demonstrate metal-oxide metasurfaces operating as quarter-wave plates (QWP) over a broad near infrared (NIR) range from 1.75 to 2.50 µm. We employ zinc oxide highly doped with gallium (Ga:ZnO) as the plasmonic constituent material of the metasurfaces, and fabricate arrays of orthogonal nanorod pairs. Our Ga:ZnO metasurfaces provide a high degree of circular polarization across a broad range of two distinct optical bands in the NIR. Flexible broadband tunability of the QWP metasurfaces is achieved by the significant shifts of their optical bands, and without any degradation in their performance, after a post annealing process up to 450 °C.

Ultrathin and multicolour optical cavities with embedded metasurfaces

“…This has led to a relaxation of Snell's law [2], a pivotal relation in optics, and has enabled an entirely new family of flat optical elements. These elements can provide diverse functionalities for a plethora of applications including light bending devices [2,7], flat lenses [8][9][10][11], holograms [12][13][14][15][16][17], wave-plates, [18][19][20][21][22] as well as devices with chiral [23][24][25][26][27][28] and bianisotropic [29,30] optical response. A typical metasurface generates its functional output in the far field, which requires a separation distance between the metasurface and the location of the detected output.…”

Suppression of near-field coupling in plasmonic antennas on epsilon-near-zero substrates

“…Therefore, loss near the cross-over frequency is small, and TCO films exhibit a permittivity that is naturally near zero without the need for advanced fabrication [24]. An additional advantage of ENZ TCO films is their tunability: the wide range of TCO materials and deposition techniques allow for ENZ wavelengths ranging from near-to mid-infrared wavelengths, and dynamic control-e.g., thermal annealing [25], optical excitation [8][9][10]26,27], electrical bias [28][29][30][31]-can shift the ENZ point by several hundred nanometers. Thus, TCO films are robust and flexible ENZ materials, 2334-2536/18/121557-07 Journal © 2018 Optical Society of America ideal for incorporating ENZ phenomena and applications into modern optoelectronic and photonic devices.…”

Transparent Conductive Oxides and Their Applications in Near Infrared Plasmonics

“…One kind of GZO/ZnO based polarization controlling metasurface acts as a quaterwaveplate (QWP), as shown in Figure . Thanks to LSPR originated from GZO, the reflections for orthogonal direction, x (along with the strip) and y (perpendicular to the strip) are different.…”

“…b) A schematic view of unit cells of the metasurface, where φ is the polarization angle. Reproduced with permission . Copyright 2016, American Chemical Society.…”