So it takes excited molecules or atoms in it. When a laser amplifies itself, it takes energy out of the medium. Martin - The way that lasers work is that they have to have the material which is in some sort of excited state. And most laser beam powers are limited, since if you don’t put energy into the laser fast enough to excite the atoms in the cavity medium, they can start absorbing light rather than amplifying it.
And this limits the power of the laser beam output. They will absorb some energy rather than reflecting all of it. Hannah - In fact, both mirrors are not perfect. Each bounce of that light losses a little bit of energy. So, that means some energy is lost on each cycle. It needs to have a little bit of light leakage out, otherwise light will be permanently trapped inside that cavity and you’ll never get a shining out of the laser itself. Martin - You need one of the mirrors to be partially reflective. Hannah - And so, given that, can we simply line up more and more parallel mirrors to make an all-powerful laser? Apparently, not. So, the light passes through the medium and gets amplified, bounces off the mirror on the right hand side and then passes all the way down to the left hand side and get amplified and then repeats and bounces backwards and forwards, and as it’s passing through the medium, it gets more and more powerful. Martin - Now a way that you can make the amplification even more powerful is by having parallel mirrors. Martin Austwick from University College London explains how the use of mirrors further amplifies this signal in lasers.
#Laser reflector 3 mirrors full#
That means that in a medium full of excited atoms one photon can get amplified into millions of photons all going in the same direction. Normally, it does it spontaneously in a random direction, but if it’s hit by another photon of light of exactly the same energy, it will release its energy as a second photon which is identical to the first photon and in the same direction. Hannah - So, first up, how does a laser actually work? If you give an atom energy, it can give that energy back out as a photon of light in two different ways. My question for the Naked Scientists is whether you can make an infinitely powerful laser, just using mirrors.
Jay - My name is Jay Shoal and I'm from Greenhithe in Kent.
Hannah - This week, we probe with the powers of reflection.
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