Our research group Advanced nanostructures and spin-photonic devices in focused on modelling , design and characterization of thin-film structures, periodic systems and metasurfaces. Our research activities involves study of spintronic structures and spintronic-laser emitters, development of advanced diffractive structures for holographic security applications, study of textured surfaces and structures for photovoltaics, design of devices to control of light polarization.
Theoretical research and optical modelling are supported with experimental equipment in our laboratories. For lagre-scale and complex numerical simulations we use IT4I supercomputing infrastructure and installed numerical tools. Nanostructures are developed in cleanroom laboratory with optical lithography and thin-film deposition. Optical response of studied structures and materials characterized in optical laboratory equipped with spectroscopic and ellipsometric system covering the wide spectral range, from terahertz for near ultraviolet wavelengths. In laboratory of ultra-short laser pulses we study ultrafast dynamic behavior in solids by analysis of laser pulse propagation state change and time delay.
Spin lasers and spin-optoelectronics
Spin lasers are based on multiple thin film of different semi-conducting materials. The emitted light has circular polarization due to the recombination of spin-polarized electron in quantum wells. Combination of the electron spin modulation together with low-dimensional nanostructures directly implemented to the laser thin-film structure opens wide possibilities for applications in semiconductor research, optical telecommunication and information technology. Our main activities are i) modeling of time-dependent dynamical properties of spin-lasers using HPC, ii) design and development of low-dimensional thin film structures for new generation of lasers, iii) theoretical and experimental study of spin-lasers for compact sources of terahertz light and for ultra-fast data transfer. Within this research we collaborate with excellent foreign universitie: EPSRC National Epitaxy Facility, University of Sheffield in United Kingdom, and CNRS Unité Mixte de Physique in France.
Applied holography and metasurfaces
We are focused on preparation of nanostructures using our optical laser lithographic system and a system for deposition of thin films. Optical lithography allows direct writing of a patterned structure with a resolution of up to 300 nm, and a total size of the exposed pattern up to 10x10 cm. After the photoresist is exposed with the designed motive, a photoresist is developed and, if it is required, it may be covered with a thin film (in the order of units or tens of nanometers) in the thin-film deposition reactor. This sputtering deposition system allows us to deposit thin metallic and dielectric films. For special applications and materials, it is possible to prepare thin metallic films using thermal evaporation. A great advantage of our thin-film deposition is that it allows deposition of up to 4 different materials during one single process using deposition in a reactive atmosphere (oxygen, nitrogen). The sputtering deposition system can be further extended with spectroscopic ellipsometry enable us to monitor and check growth processes in the real time.
Optical spectroscopy and ellipsometry
Interaction of light with matter depends on the properties of a studied material and the wavelength of light used in our experiments. If we aim at determining optical properties of a material in a specific region of the electromagnetic spectrum, we perform spectroscopy. Our instrumentation background can cover a wide range of wavelengths from terahertz to near ultraviolet. One of the key pillars of our research activity is focus on characterization of the complex polarization properties of materials using spectroscopic ellipsometry. Our laboratory boasts, among others, unique time-domain terahertz spectroscopy. Unlike common optical methods, it allows not only radiation intensity but also its phase, i.e., full optical response, to be detected. The latest newcomer in our laboratory is a prototype of the Mueller matrix microscope, which is a combination of a conventional optical microscope and spectroscopic ellipsometer. It is exactly this combination that gives the study of polarization properties a brand-new dimension.
Terahertz photonics in time-domain and laboratory of ultrashort laser pulses
The main objective of this research is to develop new structures and sources for emission of the terahertz light with required polarization state. This activity is strongly connected to the equipment in the laboratory of the ultrashort laser pulses. Most of our applications of our laser systems revolve around terahertz time domain spectroscopy, which allows us direct observation of material properties in the spectral range from 100 GHz to 4 THz and higher. In addition, we use ultrashort pulses to develop optical experimental systems implementing pump-probe approach. Thanks to pump-probe technique, it is possible to measure relaxation times in studied material shortly after direct excitation. The pump-probe spectroscopy brings a new possibility in study of effects happening in electron shell of atoms with a very short lifetime. This can be used in scientific areas as electron transfer or manipulation with electron spin and magnetism at nanoscale.
In the frame of the H2020 project s-Nebula (http://s-nebula.eu) we collaborate with 7 foreign research institutions on research focused on development of new terahertz sources based on spintronics effects. The developed sources are further used to develop ellipsometry in terahertz spectral domain.
Our research can be summarized as:
- General terahertz time domain spectroscopy with pump-probe option
- Terahertz time domain ellipsometry
- Development and evaluation of novel sources of terahertz radiation especially new photoconductive antennas with polarization control and terahertz spintronic sources
- Time resolved magnetooptics
- Measurement of radiated terahertz beam properties and development of artefact correction methods