CHARTIST

Although nature has provided us a rich palette of materials to engineer devices for control electromagnetic (EM) radiation, this palette is limited. However, the limitations imposed by conventional materials can be overcome because the required functionality can be achieved by assembling an assortment of sub-wavelength entities together. The artificial materials created by structuring on a sub-wavelength scale are called metamaterials. Metamaterials typically consist of two- or three-dimensional arrays of entities (meta-atoms) with subwavelength period and structural features. The freedom in designing of “artificial atoms” enables a delicate tuning of the optical properties using Mie-type resonances. Due to the sub-wavelength periodicity of meta-atoms array, EM properties of metamaterials can often be described in terms of the permittivity, permeability, refraction index, and other uniform-material parameters. Among them a special attention of the research community is currently attracted to the rotatory power, a quantitative measure of metamaterial’s ability to rotate the polarization azimuth of the incident EM wave. A non-zero rotatory power is a feature inherent in chiral metamaterials. The reason for the special attention in chiral media is two-fold. First, chiral media interact with the right- and left- circularly polarized waves differently, which makes chiral metamaterials a unique playground to access fundamental aspects of the light-matter interaction. Second reason is that chiral media can be employed for polarization control. However, a beauty of the chiral metamaterials is that their optical properties go beyond those of chiral crystals and liquids, e.g. they may be engineered to have negative refraction index for one of the circular polarizations.

The main goal of the CHARTIST is to provide chiral metamaterials that pave the way towards THz components having unprecedented tunability and being beyond the state-of the art in terms of the THz radiation control. We will create arrays of meta-atoms, which are deposited on a dielectric or semiconducting substrate. The meta-atom will be designed to maximize THz response and to enable control of this response by intense laser pulses and external static electric fields. Unprecedented tunability will be based on the graphene membrane placed on the array of chiral meta-atoms deposited on the dielectric substrate. By adding a solid electrolyte layer on the top of the membrane we will tune the carrier densities by applying a small gate voltage thus achieving modulation of the polarization and amplitude of the transmitted THz wave. Such a geometry enables also combing the electrical and optical control of the carrier density providing a feasible approach for achieving THz polarization control.

Research Objectives:

• Designing individual chiral meta-atoms to maximize the helicity-sensitive THz response; Performing theoretical, numerical and experimental investigation of multi-layered metasurfaces composed of arrays of chiral meta-atoms in the THz frequency range;
• Development of feasible and easy to use techniques for fabrication of chiral metasurfaces;
• Evaluating the feasibility of the metasurface chirality tuning by external stimuli including irradiation with laser pulses and application of a dc field;
• Revealing implications of the broken time-reversal symmetry on the performance of the chiral metamaterials.

Innovation Objectives:

• Proof of concept experiments and demonstration of metasurfaces and planar structures capable to generate and control the polarization of the THz radiation;
• CHARTIST prototype fabrication; Tests of the fabricated prototype in view of reproducibility and stability in real operational conditions, essential for upscaling from laboratory prototype to the pre-industrial scale; Reaching the TRL4 with the lab validated prototype of metasurface;
• Scalability of the proposed fabricated prototypes check and an analysis of possible pathways from the laboratory to the pre-industrial and industrial scale; Exploitation plan.

Training objectives:

• At personal level, developing a personalized training program in topics and skills needed for the effective realization of the project for each mobile researcher. Giving a special attention to training of ESRs with respect to the preparation of their PhD theses; Special trainings at local level organized by the hosting laboratories;
• At organization level, mini-training courses for combined secondments from/to different partners;
• At project level, dedicated organization of centralized project events (2 Summer Schools / tutorials, mini-courses, Industrial workshop, Satellite Sessions on recognized conferences, Only-ESR workshop and project meetings); Promoting and facilitating the acquisition of complementary skills applicable across sectors and disciplines;
• At network level, establishing a collaborative network of highly skilled ESRs to become future leaders in the metamaterials’ field. ESRs conference organized fully by ESRs and for ESRs only (including those outside the CHARTIST consortium) in the end of project lifecycle.

Action specific long term and midterm objectives:

• Knowledge transfer through “learning by doing and doing by learning” in international context to achieve the project research and innovation objectives and to increase visibility and recognition of the project consortium as a whole on a global level.
• Knowledge transfer in interdisciplinary context (theoretical physics, material science, computational physics, metamaterials, nanoscience and nanotechnology, THz science and technologies) to achieve scientific breakthroughs in the field of chiral metamaterials for THz applications.
• Intersectoral knowledge transfer on the THz science state-of-the-art and European industry needs through mutual visits between CHARTIST academic and industrial partners.
• Career development and New Career opportunities of ESRs and ERs involved in the project implementation through formal (e.g. PhD Thesis) and informal (e.g. new professional and soft skills) indicators, improved employability and career prospects both in and outside academia; Strengthening of Europe’s human capital base in R&I;
• Creation of a start-up to scale up the developed technology under the roof of Business Finland project and in collaboration with Photonics Finland association, increasing in higher impact R&I outputs, more knowledge and ideas converted into products and services.