ALL-SEMICONDUCTOR METASURFACES

DURATIONS:
The duration of the PhD is three years. It will be funded at 100% by the European Research Council.

CONTEXT:
Optical devices are generally designed considering light propagation in refractive materials. To achieve a desired wavefront, one often needs to carefully adjust many optical components disposed along the beam path to control the beam properties during propagation. Although filters and mirrors respectively select the wavelength and control the propagation direction of radiation in a very simple manner, the control of the other quantities such as the amplitude, the phase and the state of polarization necessitates more sophisticated devices. Those are generally designed to only achieve a specific purpose at a given wavelength or on a relatively narrow band of frequencies. Recent progress in the fields of nanophotonics and metamaterials has enabled the development of metasurfaces[1-3]; these are two-dimensional ultrathin and ultraflat optical components resembling artificial Huygens-like interfaces. They are composed of resonant nano-engineered sub-wavelength optical resonators that enable an unprecedented control of the wavefront over large bandwidths and subwavelength propagation distances.
RESEARCH SUBJECT, WORK PLAN:
The visible spectrum is a natural frequency range for the human beings, and any new technology in optics that pretends to have considerable technological impact would have to be available for visible wavelengths. Therefore, to be a significant engineering method, control of light with nanostructured materials have to be available at optical wavelengths, i.e. in the visible and UV. It is also important to control light very efficiently and eventually to be able introduce light modulation capabilities. In this thesis, the candidate will tackle these challenges and create efficient tunable metasurfaces and other type of ultrathin metamaterials at visible wavelengths.
Fortunately, any material with a sub-wavelength size in the propagation direction that can “catch and release” the electromagnetic field with a controllable phase shift can be a good candidate for the design of metasurfaces. Pioneering works used metallic optical resonators such as plasmonic nano-antennas in the mid infrared region [1-3]. Metallic antennas have similar resonant behavior from the visible to the radio spectral ranges, making this approach of molding wave fronts with antennas applicable to a large part of the electromagnetic spectrum. Enhanced optical performances can be obtained by designing metasurfaces with high index dielectrics [4]. CRHEA has fabrication tools which are suitable for depositing different dielectric materials such as such as SiO2, Si3N4 and other types of dielectrics on metallic films. Moreover, CRHEA is world renowned for the growth of large gap semiconductors which will be specifically developed for the design and the fabrication of active metasurfaces. During his/her Thesis, the candidate will design different types of optical interfaces, he/she will perform nanofabrication using state-of-the-art CRHEA nanofabrication facility and he/she will perform material electrical and optical characterization of devices for particular applications.
KEYWORDS:
Nanophotonics, Metamaterials, Metasurfaces, Electromagnetic Boundary Conditions, Wavefront engineering, Nano-resonators, Surface/mantle cloak, Flat optics, Finite element methods.
APPLICANTS SKILLS:
The applicant must be highly motivated and enthusiastic student, with a Master degree either in optics and photonics, or applied mathematics, or electrical engineering. He must have good skills/understanding in electromagnetics and/or photonics. We encourage the application of candidates with strong background in applied mathematics. The applicant should also be willing to carry out nanofabrication and optical experiments.
SELECTED PUBLICATIONS:
[1] Light Propagation with Phase Discontinuities: Generalized Laws of Reflection and Refraction, N. Yu, P. Genevet, M. A. Kats, F. Aieta, J.P. Tetienne, F. Capasso, and Z. Gaburro, Science 334, 333-337 (2011)
[2] Holographic optical metasurfaces: a review of current progress, P. Genevet and F. Capasso, Reports of Progress in Physics, 78 (2), 024401 (2015)
[3] Flat Optics: Controlling Wavefronts with Optical Antenna Metasurfaces, N. Yu, P. Genevet, F. Aieta, M. A. Kats, R. Blanchard, G. Aoust, J-P. Tetienne, Z. Gaburro, and F. Capasso IEEE Journal of Selected Topics in Quantum Electronics, DOI:10.1109/JSTQE.2013.2241399 (2013).
[4] Multiwavelength Achromatic metasurface optical components by dispersive phase compensation, F. Aieta, M.A. Kats, P. Genevet, and F. Capasso, Science, 347, 1342-1345 (2015).