English translation of the paper "Electromagnetic field inside a plane-parallel layer in the resonant absorption regime" (1962) by A. P. Khapalyuk: Pioneering study on coherent perfect absorption

In 1962, Belarusian physicist A. P. Khapalyuk has published the paper [Doklady Akademii nauk BSSR, volume 6, issue 5, pages 301-304] devoted to the effect of resonant absorption of light in a layer of matter. This work can be considered as a first study of the phenomenon known today as coherent perfect absorption (CPA). Unfortunately, the paper by A. P. Khapalyuk was published in a local journal in Russian and is almost unknown to the English-language scientific community. Here, we give the first translation of this paper into English, accompany it with the introductory remarks including some biographical information on A. P. Khapalyuk and put it in the context of modern CPA studies.