Laser
Albert Einstein was the first to have the idea of stimulated emission that could produce a laser. From that point many years were spent to see if the idea worked. At first, people succeeded in making masers and later figured how to make shorter visible wavelengths. It was not until 1959 that the name laser was coined by Gordon Gould in a research paper. The first working laser was put together and operated by Theodore Maiman at the Hughes Research Laboratories in 1960.  Many people started working on lasers at this time, and the question of who would get the patent for the laser wasn't decided until 1987 (Gould won the rights).