The world's first laser was not developed until 1960, although Albert Einstein described its principle as early as 1917. LASER stands for "light amplification by stimulated emission of radiation". The term laser thus refers to a light source that emits light with specific properties: light that forms a single beam and is monochromatic and coherent. Each laser contains an active medium in which atoms are excited. These then (in most lasers) pass through a resonator, consisting of one transmitting and one non-transmitting mirror, within which it is possible to concentrate sufficient energy and at the same time concentrate the photons into a single beam of light.
Today, there are a large number of types of lasers that are used in almost all areas of human practice: from industrial and scientific applications to toys to simple pointers. Lasers are classified based on the type of active medium, mode, pulse duration, spectral region, or other special characteristics.
