Tunable all-dielectric metasurface for phase modulation of the reflected and transmitted light via permittivity tuning of indium tin oxide

Nanophotonics

article

Ali Forouzmand¹  Mohammad Mahdi Salary¹  Ghazaleh Kafaie Shirmanesh²  Ruzan Sokhoyan²  Harry A. Atwater²  Hossein Mosallaei¹ 

[1] Metamaterials Laboratory, Electrical and Computer Engineering Department, Northeastern University;Thomas J. Watson Laboratories of Applied Physics, California Institute of Technology;Kavli Nanoscience Institute, California Institute of Technology

关键词: all-dielectric nanoantennas;    phase modulators;    metasurfaces;    electro-optical materials;    silicon;    indium tin oxide;   

DOI  :  10.1515/nanoph-2018-0176

学科分类：社会科学、人文和艺术（综合）

来源: De Gruyter

【 摘 要 】

We propose an electrically tunable metasurface, which can achieve relatively large phase modulation in both reflection and transmission modes (dual-mode operation). By integration of an ultrathin layer of indium tin oxide (ITO) as an electro-optically tunable material into a semiconductor-insulator-semiconductor (SIS) unit cell, we report an approach for active tuning of all-dielectric metasurfaces. The proposed controllable dual-mode metasurface includes an array of silicon (Si) nanodisks connected together via Si nanobars. These are placed on top of alumina and ITO layers, followed by a Si slab and a silica substrate. The required optical resonances are separately excited by Si nanobars in reflection and Si nanodisks in transmission, enabling highly confined electromagnetic fields at the ITO-alumina interface. Modulation of charge carrier concentration and refractive index in the ITO accumulation layer by varying the applied bias voltage leads to 240° of phase agility at an operating wavelength of 1696 nm for the reflected transverse electric (TE)-polarized beam and 270° of phase shift at 1563 nm for the transmitted transverse magnetic (TM)-polarized light. Independent and isolated control of the reflection and transmission modes enables distinctly different functions to be achieved for each operation mode. A rigorous coupled electrical and optical model is employed to characterize the carrier distributions in ITO and Si under applied bias and to accurately assess the voltage-dependent effects of inhomogeneous carrier profiles on the optical behavior of a unit cell.

【 授权许可】

CC BY