The theory behind how lasers work dates back over 100 years. Einstein’s work on the Photoelectric Effect won him the Nobel Prize; not for Relativity as most people assume. Ted Maiman, while at Hughes Aircraft, built the first working laser using synthetic ruby over 50 years ago.
Consequently, lasers have become powerful tools of the modern age and find use in telecommunications, holography, eye surgery and bar code scanners. Several types have even found their way into printing as described below.