## Overview
This topic covers the process of stimulated emission and how this leads to coherent light emission. The structure of lasers is studied, including how a population inversion is attained. The advantages and disadvantages of different types of laser are compared.
## Working Scientifically
Questions set on this unit will assess learner’s abilities to apply scientific knowledge to practical contexts; to process and analyse data using appropriate mathematical skills; to present data in appropriate ways.
## Mathematical Skills
There are a number of opportunities for the development of mathematical skills in this unit. These include; visualising and representing 2D and 3D forms including 2D representations of 3D objects.
## How Science Works
There are opportunities within this topic for learners to communicate information and ideas in appropriate ways using appropriate terminology; to consider applications and implications of science and evaluate their associated benefits and risks.
### Learners should be able to demonstrate and apply their knowledge and understanding of:
(a) the process of stimulated emission and how this process leads to light emission that is coherent
(b) the idea that a population inversion (N2 > N1) is necessary for a laser to operate
(c) the idea that a population inversion is not (usually) possible with a 2-level energy system
(d) how a population inversion is attained in 3 and 4-level energy systems (e) the process of pumping and its purpose
(f) the structure of a typical laser i.e. an amplifying medium between two mirrors, one of which partially transmits light
(g) the advantages and uses of a semiconductor laser i.e. small, cheap, far more efficient than other types of laser, and it is used for CDs, DVDs, telecommunication etc