The Semiconductor Laser
Apart from light-emitting diodes, semiconductor lasers are the most important application of optoelectronic semiconductor devices at present. Compared with other laser media such as gases, molecules in solution or other solids, they offer by far the highest conversion efficiency from electric energy to emitted light energy (up to 50%). In a semiconductor laser the injected electric current is directly transformed into a population inversion without intermediate steps such as the optical pumping via a discharge used in gas lasers. Moreover, semiconductor lasers can be extremely compact, which is a crucial feature for applications in compact disc players, laser printers, and in telecommunication systems (where the most important emission wavelengths are around 1.3 μm and 1.55μm). We can distinguish between two main (technologically relevant) geometric configurations: edge emitters and the even more compact vertical-cavity surface-emitting lasers (VCSELs), both of which are shown in Fig. 13.1.
KeywordsSpontaneous Emission Carrier Density Semiconductor Laser Gain Coefficient Photon Density
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