Preface

The first publication about the discovery of diffraction grating by the American astronomer D. Rittenhouse dates back to 1786. It was not noticed by the scientific community of the day, and in the history of science the optician J. Fraunhofer was considered to be the creator of the diffraction grating (1821). Theoretical studies of this device, characterized by amazing dispersion properties were started by F.M. Schwerd in 1835. In those days, spectral analysis was coming into being. The needs from this new area stimulated making gratings with progressive enhancement of the resolution, and they encouraged relevant theoretical and experimental studies. The outstanding achievements of H.A. Rowland must be mentioned here. He developed a machine capable of making quite fine diffraction gratings (1882). Also, he suggested making ruling lines on a concave spherical surface and as a result spectrum dispersion and sharpness were elevated to a level that had not been seen before. The progress in several scientific and technological fields is to a large extent guided by the performance of the presently available gratings which are so sophisticated that sometimes they seem to have little to do with their predecessors from the 19th century. Polarization converters and phase changers, filters and multiplexers, quantum and solid state oscillators, open quasi-optical dispersion resonators, and power compressors – these are only a few applications of periodic structures, which astonish us (up to now!) by their capabilities for controlled polarization, spatial and frequency selection of signals. Different operating frequency ranges call for gratings differing in characteristic size (length of a period), and in their way of achieving the operating mode. The range is so wide that, say, if one end is a standard echelette optical reflection grating (3600 lines per millimeter on a 40 [cm] × 40 [cm] aluminium sheet) the other could be the antenna array of the unique decameter radio telescope UTR-2 developed and fabricated by the academician S.Ya. Braude’s team at the Institute of Radio Physics and Electronics of the Ukrainian Academy of Sciences in 1966. This antenna field is developed by two multicomponent arrays. The first one, 1800 [m] long and 53 [m] wide, consists of 1440 wideband components making up 6 meridian aligned rows. The other, 900 [m] long and 40 [m] wide, is normal to the first one and carries 6 rows of 600 dipoles. All the dipoles (8 [m] long and 1.8 [m] across wire cylinders) are horizontally arranged at a height of 3.5 [m] and east–west oriented.