Research

Research at the Department of Optics concerns the interaction of light with matter and the use of optical methods to characterise materials. Work is experimental in the first place, supported by modelling, and it is carried out in the department’s own laboratories and in the University’s shared-access instrumentation centre.

Six directions are described below. Behind each there are named people, specific instruments and papers from the last three years.

Advanced materials for optics and semiconductor optoelectronics

One of the department’s strongest and most active research directions: development and research of GeSn, InGaAs, CIGS, CZTS and other semiconductor materials for radiation sources and detectors, solar cells and optoelectronic devices. Silicon emits light poorly because its band gap is indirect. Alloying germanium with enough tin makes the gap direct, which yields a material that emits and can still be processed on a silicon line — the route to a laser and a photodetector integrated on a chip.

The department studies how photogenerated charge moves in such films: the origin of photoconductivity, the effect of defects and of compositional inhomogeneity, and what happens at grain boundaries. Methods include photoconductivity spectra from 10 K, impedance spectroscopy, scanning probe microscopy and nanosecond laser patterning of the surface. The structures are grown by partners at the University of Arkansas and characterised in Kyiv, together with the Lashkaryov Institute of Semiconductor Physics and Chemnitz University of Technology.

Solar energy

Silicon and germanium do not absorb the long-wavelength part of the solar spectrum, and that energy is simply lost. GeSn with a direct band gap of 0.3–0.8 eV absorbs exactly that range, so a GeSn layer on top of a silicon cell can collect what an ordinary panel lets through.

The work is directed at making such structures manufacturable: plasmonic structures that enhance absorption, thinner semiconductor layers, cheaper deposition methods. The direction is supported by international grants, including NATO, DAAD, DFG and CRDF Global.

Laser spectroscopy and fast processes

A carbon particle struck by an intense nanosecond pulse reaches thousands of kelvin within the pulse duration and emits thermally. The effect is at once a measurement method and a subject in itself: it makes visible how a particle heats, evaporates and transfers heat to its surroundings. The department studies these fast processes in carbon micro- and nanoparticles together with the non-linear luminescence that accompanies them, in collaboration with Shizuoka University.

The same direction includes random lasing. In a strongly scattering medium — a powder, a porous material, a dye suspension — generation occurs without any mirrors: scattering itself takes the part of the resonator. The department studies how such generation interacts with stimulated Raman scattering; this part of the work is led by Vasyl Yashchuk.

Quantum materials and synchrotron research

A direction the department is developing in collaboration with the Kyiv Academic University and within USynC, the Ukrainian synchrotron community. Synchrotron and free-electron-laser methods resolve the electronic structure of quantum materials with a precision that no laboratory source reaches.

Through the community the department has access to European XFEL, the SOLARIS synchrotron and the Paul Scherrer Institute, and its students can take part in measurements at these facilities; the USynC workshop opens the SPO-2026 symposium on 28 September. The direction is led by Serhii Kondratenko.

Optical surface diagnostics

Ellipsometry — the oldest of the department’s lines of work — measures the change in polarisation on reflection and recovers from it the optical constants of a material and the thickness of a film, without destroying the sample. Its applied outcome is plasmonic sensing: a gold film on which the surface plasmon resonance shifts in response to a small number of molecules adsorbed on it.

The same direction covers speckle metrology and fractal analysis. A rough surface illuminated by a laser produces a granular pattern whose statistics are determined by the relief that produced it, so surface texture can be measured from a single image, without contact and without sample preparation. For ceramic materials the differences in fractal characteristics are statistically significant, so the method distinguishes materials and detects defects.

Optical technologies for MilTech

Thermal imaging systems, laser range-finding, night-vision devices, homing heads, optical navigation, computer vision, object detection and tracking are key components of modern MilTech. Students study the principles of optoelectronic devices, digital image processing and the development of optical modules. Training is provided by a dedicated block of elective courses and the department’s branch at the Arsenal enterprise, operating since 1984 and combining education with real engineering tasks.

The research side of the direction is being developed in collaboration with the Kyiv Academic University. It is led by Serhii Kondratenko.

What we measure with

The heaviest instruments sit in the University’s Centre for Microscopy and Laser Spectroscopy, in operation since 2025: electron microscopy, confocal Raman spectroscopy, atomic force microscopy, spectroscopic ellipsometry and thin-film deposition. For a student of the department this means an electron microscope and a Raman spectrometer are equipment they can book while still an undergraduate.

Collaborations

Standing partners abroad: the University of Arkansas (growth of GeSn structures), Chemnitz University of Technology, Shizuoka University and Le Mans Université. In Ukraine the department works most closely with the Lashkaryov Institute of Semiconductor Physics of the National Academy of Sciences. Through the Ukrainian synchrotron community it has access to European XFEL, the SOLARIS synchrotron and the Paul Scherrer Institute.

Funded projects

NATO SPS project G5853, Innovative Solar Cells, and CRDF Global project FSA3-20-66707-0, both led by Serhii Kondratenko. The department also carries out projects supported by the National Research Foundation of Ukraine and by the Ministry of Education and Science of Ukraine. Students are employed on these projects as paid research assistants.

Selected publications