Mgr. Hynek Němec, Ph.D.

I’m interested in three mutually related research areas:

• Charge transport and their terahertz response in semiconductor nanostructures. Charge transport in complex nanostructures is influenced by a plethora of processes, including namely charge motion inside individual nanoparticles and charge transfer among the nanoparticles. While measurements of dc conductivity contain information on the process with the worst conductivity (which is typically the charge transfer among nanoparticles), measurements of terahertz conductivity spectra selectively monitor charge motion inside the nanoparticles. Our interpretation of the terahertz spectra is based on combined semi-classical simulations of charge motion, and effective medium approximation [Adv. Opt. Mater. 7, 1900623 (2019)].
• Photonic structure and metamaterials for terahertz spectral range. Terahertz radiation may be used for wireless communications transferring large amounts of data. The applications require a large number of key elements allowing manipulation with the terahertz radiation. In our research, we focused on the development of tunable resonant structures; for example, we achieved an artificial (effective) magnetic activity in TiO₂ microspheres at terahertz frequencies [Appl. Phys. Lett. 100, 061117 (2012)].
• Developments of methods in time-domain terahertz spectroscopy. While measurements of terahertz transmission and reflection spectra is nowadays a routine task performed using commercial setups, an accurate and reliable analysis of these spectra is still not fully mastered. For example, in the work [Opt. Exp. 24, 10157 (2016)] we explained the fundamental influence of the depth-profile of the excitation beam on the retrieval of terahertz photoconductivity from reflection terahertz spectra.