What is laser pumping?

Question

I am having trouble understandingt exactly what this term mean. Can you explain it in layman terms? What i am guessing it means is having a laser do work on molecules by exchanging energy

Answer 1

You put energy into a bunch of atoms/molecules/etc in the laser material so that the electrons are in a higher energy state - this is pumping,by analogy of moving water uphill. You can pump the laser by an external flashlight (in the first lasers) by laser light from another higher energy laser, from electrical energy etc - depending on the laser design.

The electrons want to get back to the lowest energy state (lazy little chaps your average electron). But they need something to trigger the decay. Laser materials are chosen so that the higher energy level is locally stable - it needs a little bit more energy to tip it over the edge and allow it fall back to the lower level.

A single photon comes in and provides this extra kick - the electron falls and the extra energy is given off by emitting a photon, this photon knocks off the next electron and so on. Because the electrons are all falling from the same higher energy level back to the same lower one they all emit the same energy photon - so lasers have a single wavelength.