Research project

Recent years have seen incredible progress in fundamental research related to photonics. This has been made possible both by new research tools allowing fabrication and characterisation of photonic structures and by the development of advanced methods of computational electrodynamics, which have proved crucial for understanding physical phenomena at the micro- and nanoscale. On these foundations, the concept of metamaterials was born - structures whose unique optical properties are related more to the geometrical arrangement of the subwavelength size of the elements than to the properties of the component materials used. The subject of metamaterials has become one of the most exciting issues in modern optics. Among the many astonishing results are the discovery of negative refraction, optical magnetism, giant chirality, invisibility caps, new types of light sources, and non-electrolytic generation of hydrogen directly from solar energy, artificially designed nonlinearity and the recently discovered effect of passive cooling below ambient temperature.

In the present project, we plan to take the next step, which envisages the development of active metamaterials with tunable optical properties. The basis for our research is the phenomenon related to the formation of a carrier accumulation layer at the interface between a dielectric oxide and a semiconductor. Such a layer is generated if the structure is placed in an external electric field. Recent studies show that an increase in carrier concentration also changes the optical parameters. This local modulation of the coefficient can be as high as unity! However, since the thickness of the accumulation layer is only a few nanometres, its presence practically does not change the interaction of the structure with light. We believe that only by exploiting the phenomena associated with the existence of accumulation layers in metamaterials will we be able to fully exploit their potential.

The main objective of the project is to investigate how electrically controlled accumulation layer formation at ITO-dielectric boundaries affects the linear and nonlinear optical properties of metallic-dielectric-semiconductor multilayer metamaterials. We intend to demonstrate that unique metamaterial features such as e.g. spatial and time-frequency filtering, hyperbolic dispersion, super-resolution imaging, total absorption or nonlinear properties can be modified in the entire VIS and NIR spectral range only by an applied voltage.

The project covers thematically different scientific topics, ranging from linear and nonlinear optics to the concept of metamaterials and semiconductor physics. The issue of electrically tuned metamaterials will be investigated theoretically, numerically and experimentally. The planned research will give us insights into the interactions of light with accumulation layers in multilayer geometries, a deeper understanding of the formation of carrier accumulation layers, a better knowledge of interfacial processes, and will contribute to the development of materials science and fabrication techniques for nanophotonic structures. It is known that the ability to receive, modulate or emit electromagnetic waves is the basis of a myriad of very important technological devices that underpin the modern world. We believe that the basic research concept in this project will contribute to the development of future technologies. In particular, it can be applied to ultrafast light modulators, tunable frequency filters or devices using electrically controlled nonlinear effects.