Introduction to Lasers
 

Everyone loves playing with lasers and they are really useful for many experiments in A Level Physics. The monochromatic light of one wavelength is great for showing diffraction and many other wave phenomena.

Atomic Processes (including Stimulated Emission)
 

To understand how lasers work we need to look at the three processes that occur within an atom when it interacts with a photon: absorption, spontaneous emission or even stimulated emission.

Population Inversion
 

In order to allow an in increase in the total number of photons emitted by a sample there needs to be more atoms held in the high energy excited state. Here I explain why.

3 and 4 Level Energy Systems
 

In reality a three or four level energy system is used to allow a population inversion, with the atoms excited by pumping them with an external source of energy.

Laser Construction and the Laser Diode
 

Here I show you the general construction of a laser and also how the small semiconductor laser diodes are constructed. These have hundred of uses and can be found everywhere in the modern world.