Tunable Materials & Metasurfaces

This group aims at designing, fabricating and characterizing dynamically tunable metasurfaces and nanophotonic devices.

Approach

Nanophotonics has enabled tremendous advances in light-matter interaction and opened up new ways to control light at the nanoscale. Recent progress in plasmonics and dielectric metamaterials made possible the design and fabrication of flat optics devices that hold promise to replace conventional bulk optics. At the nanoscale though, a great challenge is to dynamically modulate the physical properties of such devices. This is currently an intense field of research. There are many different ways to dynamically modify the optical response of a nano-device. A non-exhaustive list would include electro-mechanical systems, liquid crystals, thermal modulations, non-linear optics, and piezoelectric effects… In this group we explore some emergent methods to demonstrate tunable nanophotonic devices.

Topics

Phase-change materials-based metasurfaces

Phase-change materials are a class of materials with unique physical properties: their structural arrangement can be controllably modified back and forth on a fast time-scale (sub-nanosecond) by a thermal, electrical or optical external signal. But what makes them unique is that their crystallographic re-arrangement translates into a large refractive index modification (Δn ≥ 1). Such a large and fast refractive index modulation enables controlling and tuning the optical properties of devices at the nanoscale. Among other projects, we are currently investigating: (i) VO2-based metasurfaces for dynamic control of light-matter interaction; (ii) GeSbTe-based pixel arrays for beam-steering and wavefront shaping.

Tunable transparent conductive oxides

Transparent conductive oxides such as ITO present a plasma frequency in the infrared range. Injection of free carriers in the material enables modifying the plasma frequency and therefore the optical dispersion. In other words, their optical properties can be electrically tuned.
In this topic, we investigate the potential of doped oxides thin films with tailored concentrations of free carriers which therefore present a controllably variable plasma frequency. This opens interesting perspectives for the design and fabrication of broadband plasmonic sensors for the mid-IR range.

Hyperbolic metamaterials

Hyperbolic metamaterials (HMMs) are uniaxially anisotropic multilayered structures with dielectric permittivities of opposite signs. In this topic, through a strong collaboration with the Heteroepitaxy & Nanostructure group, we investigate the potential of epitaxially grown functional oxides in multilayer structures. The nanoscale-control over the doping and thicknesses of the different layers enables an ultimate control on the resulting hyperbolic behavior of the HMM. Such devices represent interesting opportunities for flat lensing and control of spontaneous emission.

Staff :

  • Coordinator: Sébastien Cueff
  • Permanent: Lotfi Berguiga, Jean-Louis Leclercq, Xavier Letartre, Serge Mazauric, Christelle Monat, Hai Son Nguyen, Fabio Pavanello, Pedro Rojo Romeo
  • PhD: Jimmy John, Arnaud Taute, Massoumeh Razaghi
INL CNRS
Tunable hybrid metasurface VO2 (brown) /a-Si (blue)