does this work out? Answered
production of light with low energy
for this take a long tube with both ends open.Now place a one way mirror in such a way that light passes from outside to inside and the other end with a colored glass except red [primary colors].before this just fill it with active medium or the elements used in laser[make sure that this medium emits any color other than red on exited] Then send red laser light into the tube for few seconds if my guess is right the tube will give a colored light outside Now let me explain it when the red laser light first enters the tube it makes the active medium in it excite and release a colored light along with the red light this passes all through the tube and at the end the colored glass [the same color which the medium emits on exciting] will send the emited light through it and reflects the red colored light back and the process keeps on going as the first one way mirror even reflects the red light back. I have a picture of laser active medium and one way mirrors.
So,energy is consumed only for the first production of light for minute.