The first laser was developed by a man called Charles Townes in the 1950s. It actually didn’t generate light but made microwaves (another part of the electromagnetic spectrum) so it was called a maser.
It worked by using a ruby to produce the microwave beam, this was done by wrapping a spiral bulb around it. This gave of white light which was absorbed by the ruby and the energy was converted into the emitted microwaves.
This early design was very in efficient, but it did work and was the start of laser research.