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Proceedings Paper

Field-effect modulation of the local density of optical states in a reflectarray metasurface (Conference Presentation)
Author(s): Ghazaleh Kafaie Shirmanesh; Ruzan Sokhoyan; Seunghoon Han; Harry A. Atwater

Paper Abstract

During recent years, advances in the design of arrays of subwavelength optical elements with special electromagnetic properties have enabled quasi two-dimensional structures that control and manipulate electromagnetic phase, amplitude and polarization. Active control of the response of metasurfaces is possible using transparent conducting oxides such as Indium Tin Oxide (ITO) as a tunable active material [1]. Changing the complex permittivity of ITO by applying a voltage yields modulation of reflected wave phase and amplitude. To achieve this, we designed subwavelength antenna arrays consisting of a gold back reflector and gold fishbone antennas. Planar dielectric layers containing a gate tunable layer of ITO are sandwiched between the back reflector and the antenna. The obtained structure shows resonance around 1.5 µm. As a result, based on the 1.54 µm photoluminescence emission of Er doped Al2O3 films, we embedded trivalent erbium ions as quantum emitters inside an alumina host within the metasurface in order to enhance the local density of optical states (LDOS). Simulations indicate the designed structure shows a significant LDOS enhancement (of order of hundreds). By applying a bias between the antenna and the ITO layer, across an HfO2 gate dielectric, we can control the permittivity of ITO and hence dynamically modulate the decay rate of quantum emitters embedded within the structure. In this way, we can achieve LDOS enhancement modulation of about 325%. 1. Y. W Huang, H. W. H. Lee, R. Sokhoyan, R. Pala, K. Thyagarajan, S. Han, D. P. Tsai, H. A. Atwater, “Gate-tunable conducting oxide metasurfaces”. (arXiv:1511.09380).

Paper Details

Date Published: 9 November 2016
PDF: 1 pages
Proc. SPIE 9920, Active Photonic Materials VIII, 992018 (9 November 2016); doi: 10.1117/12.2238835
Show Author Affiliations
Ghazaleh Kafaie Shirmanesh, California Institute of Technology (United States)
Ruzan Sokhoyan, California Institute of Technology (United States)
Seunghoon Han, California Institute of Technology (United States)
Samsung Advanced Institute of Technology (Korea, Republic of)
Harry A. Atwater, California Institute of Technology (United States)

Published in SPIE Proceedings Vol. 9920:
Active Photonic Materials VIII
Ganapathi S. Subramania; Stavroula Foteinopoulou, Editor(s)

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