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Proceedings Paper

Voltage tuning of reflectance from a strongly coupled metasurface-semiconductor hybrid structure (Conference Presentation)
Author(s): Raktim Sarma; Salvatore Campione; Michael Goldflam; Joshua Shank; Sean Smith; Jinhyun Noh; Peide Ye; Michael Sinclair; Ganapathi Subramania; Isaac Ruiz; Stephen Howell; Joel Wendt; Igal Brener
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Paper Abstract

Metasurfaces have been investigated for various applications ranging from beam steering, focusing, to polarization conversion. Along with passive metasurfaces, significant efforts are also being made to design metasurfaces with tunable optical response. Among various approaches, voltage tuning is of particular interest because it creates the possibility of integration with electronics. In this work, we demonstrate voltage tuning of reflectance from a complementary metasurface strongly coupled to an epsilon-near-zero (ENZ) mode in an ultrathin semiconductor layer. Our approach involves electrically controlling the carrier concentration of the ENZ layer to modulate the polaritonic coupling between the dipole resonances of the metasurface and the ENZ mode for modulating the reflectance of the metasurface. The hybrid structure we fabricate is similar to MOSCAP configuration where the complementary metasurface offers a continuous gold top layer for biasing and positive/negative bias to the metasurface leads to accumulation/depletion of carriers in the ENZ layer beneath it. We optimized our structure by using InGaAs as the ENZ material because of its high mobility and low effective mass. This allowed us to reduce the doping requirement and thereby reduce the ionized impurity scattering as well as the reverse bias required to deplete the ENZ layer. For low leakage and efficient modulation of carrier density, we used Hafnia as the gate dielectric. We further added a reflecting backplane below the ENZ layer to enhance the interaction and by applying bias, we achieved spectral shifts of 500 nm and amplitude modulation of 11% of one of the polariton branches at 14 µm.

Paper Details

Date Published: 17 September 2018
Proc. SPIE 10721, Active Photonic Platforms X, 107211E (17 September 2018); doi: 10.1117/12.2321256
Show Author Affiliations
Raktim Sarma, Sandia National Labs. (United States)
Salvatore Campione, Sandia National Labs. (United States)
Michael Goldflam, Sandia National Labs. (United States)
Joshua Shank, Sandia National Labs. (United States)
Sean Smith, Sandia National Labs. (United States)
Jinhyun Noh, Purdue Univ. (United States)
Peide Ye, Purdue Univ. (United States)
Michael Sinclair, Sandia National Labs. (United States)
Ganapathi Subramania, Sandia National Labs. (United States)
Isaac Ruiz, Sandia National Labs. (United States)
Stephen Howell, Sandia National Labs. (United States)
Joel Wendt, Sandia National Labs. (United States)
Igal Brener, Sandia National Labs. (United States)

Published in SPIE Proceedings Vol. 10721:
Active Photonic Platforms X
Ganapathi S. Subramania; Stavroula Foteinopoulou, Editor(s)

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