[hwillis]

Lasers and masers are not inherently collimated or straight lines. The only thing specific to lasers/masers is that all the light is the same wavelength. Beam, parabolic and phased antennas are all very capable of making much tighter beams than your average laser.

In fact at the limits of performance lasers (and particularly masers) are quite bad at generating straight beams, because they are quite small sources of light and divergence is inversely proportional to the width of the emitter. It is a misconception that they are low-etendue.

[mitthrowaway2]

Lasers are coherent emitters, which means that they behave like a perfect point source and the beam forming is limited only by diffraction. The collimation is limited only by the lens diameter and quality.