The new two-dimensional material graphene was discovered only in 2004. This ‘youngest’ material is stronger than steel, can stretch, and perfectly conducts electricity. These characteristics make breakthroughs in a wide variety of fields – from electronics to construction – possible.
New micro and nano lasers with resonant graphene elements are modeled by a team of researchers from O. Ya. Usikov Institute for Radio Physics and Electronics of the National Academy of Sciences of Ukraine. Their project ‘Electromagnetic modeling of micro and nano lasers with resonant graphene elements, at the threshold of stationary radiation’ was successful in the call ‘Support for Research of Leading and Young Scientists’ of the National Research Foundation of Ukraine and received grant funding from the Foundation before the beginning of russian invasion in Ukraine.
Are Kharkiv researchers safe today? Can they continue their research? What had they managed to do before the start of the full-scale invasion? And for which branches of research and economy are the results of this work important? We asked these questions to the project PI, a Senior Researcher at the Department of Quasi-Optics of the National Academy of Sciences of Ukraine Tetiana Zinenko.
The researcher said that due to intense shelling, most of the team members, like thousands of other Kharkiv residents, were forced to leave the city.
“During the shelling, our institute was badly damaged,” the researcher noted. “Almost all windows were broken, and the heating pipes got frozen. Next winter, there will be no heating in the institution either.”
Today, only one team member remains in Kharkiv. Three male performers and a female team member left for the western regions of Ukraine (they continue to work remotely). Two team members are currently abroad and also work remotely, in particular, they are conducting research on the project.
The project PI said that the project topic is extremely important and promising because the study and improvement of lasers is one of the ‘breakthrough’ areas of physical and engineering sciences. In 2004, researchers began work on modeling the threshold conditions for stable emission of eigenmodes of micro-resonator lasers. Researchers have excellent results, articles in top journals, and awards from international research societies. “But we could not get competitive funding in Ukraine for several years – neither at the National Academy of Sciences of Ukraine nor at the Ministry of Education and Science,” the researcher said.
Tetiana Zinenko explained that electronic circuits in communication and information processing systems are gradually becoming a thing of the past, they are being replaced by optical and terahertz integrated circuits. And lasers (micro and nano-sized light sources) occupy an important place in new optical systems.
The most important elements of any laser are the open cavity and the active zone. Miniature resonators are made of noble metals capable of supporting so-called surface plasmon modes. But all noble metals have significant losses in the visible and infrared wavelength ranges. Because of this, the thresholds of stationary radiation of plasmon modes are quite high. Replacing metal elements with graphene elements can lower these thresholds.
“It is important that graphene is able to support plasmonic modes even in the terahertz wave range,” the researcher continued. “And it means that it can be used in nanodevices and nanosystems of this particular range.”
The cost of technologies for the manufacture of these devices and systems is still extremely high. Preliminary mathematical and electrodynamic modeling will help to reduce development and production costs. This is very important, because there is no extra money in Ukraine, especially now, during the war.
Today, world research is only taking the first steps in theoretical research of nanoscale modes of graphene resonators and lasers, and often moves ‘blindly’. Researchers carrying out the project are sure that their results will allow significant progress in these studies.
Before the start of the war, the researchers managed to derive all the basic equations for the tasks of the project Terms of References. In 2020-2021, the team studied the problems of scattering and absorption of electromagnetic waves in the visible, infrared, and terahertz ranges on dielectric nanowires with graphene shells; on pairs of such nanowires; on nanowires with partial graphene coating; on dielectric disks with graphene disks on the surface; and on lattices of graphene ribbons on dielectric substrates. “These studies are of great independent importance in photonics and optics of terahertz waves. At the same time, the results obtained facilitate further research of the determinant equations for laser eigenvalue problems which we planned for 2022,” added the PI.
According to the results of research in 2020-2021, researchers published seven articles in international Q1 and Q2 journals. During the war months, the project team has published four more papers in journals of the same level. At the end of September, two graduate students from this were awarded travel grants and presented their results at the European Microwave Conference in Milan. And this is truly a brilliant result of Kharkiv researchers!
By the way, the project team is very young. At the time the project was launched, four of the seven performers were under the age of 35.
“Despite challenges of the war, our team remains united, we work and keep in touch with each other,” added Tetiana Zinenko. We hope that the NRFU will recover its funding next year and that we will be able to complete the project. Its results are important for both science and economics. Moreover, in close cooperation with allies, they can be used in defense technologies as well.
Svitlana GALATA
