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In 2017, a group of scientists from the US and the Netherlands reported about the existence of a new state of matter, excitonium [1]. The new state is a condensate consisting of excitons and possessing superfluid properties. To confirm the existence of the excitonium, the researchers measured the spectrum of low-energy collective bosonic excitations in crystals at a temperature of about 190 K. The discovery of the excitonium opens a new direction for the development of quantum technologies. Note that it was the works of physicists belonging to the Kyiv scientific schools headed by A.F. Prikhotko and O.S. Davydov, in which excitons in crystals were studied and which were carried out at the Institute of Physics of the Academy of Sciences of the UkrSSR (IP AS UkrSSR), that laid the foundation for the spectroscopy of nonmetallic crystals in the world science [2–5]. The achievements of some Ukrainian physicists have been thoroughly analyzed in a number of papers [6–11]. But the achievements of other Ukrainian scientists are also significant, so that their contribution to the development of physics requires a further detailed analysis. The aim of this work was to

Contribution of Ukrainian Scientists to the Development of Optics