Lasers have become prominent in the modern world; technologies using lasers are found everywhere from the space shuttle to an everyday CD player. Semiconductor lasers are the most inexpensive lasers to produce. Therefore, much effort has been placed on trying to learn more about semiconductor lasers in order to find new uses for them and to extend their capabilities. This study focuses on a simple model of the behavior of a semiconductor laser cavity and a discussion of interesting behavior which can be produced by simple additions to the model.
First, let us look at the fundamental principles of a laser system in terms of physical concepts. The word LASER stands for Light Amplification by Stimulated Emission of Radiation; that is, a laser acts as an amplifier of light waves. Atoms and molecules possess varying energy levels. When they fall to a low energy level from a higher one, the energy difference comes out in the form of light. Conversely, they get excited to a higher level when they absorb light. The difference in energy corresponds to a particular frequency of light. In semiconductors carriers, electron hole pairs, are the excited state. They recombine producing light of a certain frequency.
The light produced stimulates further emission. As this procedure is repeated, certain frequencies reinforce as the light is reflected between the mirrors. Thus a coherent light source (i.e. a light of a single frequency) is produced with a large intensity.