What is the purpose of the laser invention?

Answer 1

Before the LASER was invented the MASER was invented, the difference is that MASERs operate in the microwave radio band instead of the light band.

MASERs were originally invented for use as microwave amplifiers, but they can also be used to produce very powerful narrow bandwidth microwave radiation not available any other way.

The first LASER invented was a ruby flashtube pumped LASER that produced short pulses of red light. The primary uses LASERs were originally put to were as sources of highly coherent narrow bandwidth light (which has many applications). One of the most well known of these applications is holography.

In modern fiber optic communications systems LASER diodes are used as modulated light sources to drive the fiber and LASERs made of doped sections of fiber act as amplifiers, periodically boosting the signal in very long fibers.

Note: the quantum mechanical physics on which both MASERs and LASERs are based was well known long before it was practical to make either and cosmic MASERs had been observed and studied in detail by radio astronomers before the first MASER was built.