What is the significance of having coherent light in a laser?

[Jye]

I understand that stimulated emissions produce coherent photons. What happens as a result of their coherence? My guess is that the laser beam does not spread out as much allowing it to travel further. Also, what is the property of a laser that allows the beam to travel great distances?

 

[berkeman]

I understand that stimulated emissions produce coherent photons. What happens as a result of their coherence? My guess is that the laser beam does not spread out as much allowing it to travel further. Also, what is the property of a laser that allows the beam to travel great distances?

Welcome to the PF.

Can you try Hyperphysics or Wikipedia to read a bit more about lasers? You may find the answer there. After you have read some more about lasers, post here to tell us what you have learned, and you will be able to ask a much more specific question after doing that reading.

 

[Jye]

The laser beam is highly collimated as the mirrors in the laser are perpendicular. Therefore only diverges minimally. Is this what allows the laser to travel great distances?

If a laser beam is coherent does this mean that all the photons in the front of beam strike a surface at the same time?

 

[Jye]

Am I correct?