The book is devoted to the problem of obtaining laser radiation in the form of ultrashort pulses, the duration of which approaches the period of a light wave, i.e. it is several femtoseconds. This is one of the most important and relevant areas of modern laser physics. A brief history of research leading to the creation of femtosecond pulse lasers is presented. The principles of operation of lasers are discussed, which allow generating femtosecond pulses and amplifying their power up to the petawatt level. It is shown how the durations of such short laser pulses are measured.