Semiconductor Lasers

Even though more than four decades have passed since the first demonstration of lasing in semiconductors, the pace of development of new and further improved semiconductor lasers continues to be rather high. Judging by their economic impact, semiconductor lasers can be considered today as the most important type of laser. From the beginning, the development of semiconductor lasers has been closely connected with the progress of semiconductor technology and device physics. Hence, the invention of semiconductor heterostructures as well as the straightforward implementation of quantum effects together with improved epitaxial techniques have had a decisive impact on the evolution of these lasers. Besides the physical background and the various device concepts, a proper treatment of semiconductor lasers has to particularly include a description of the relevant materials and their fabrication technology. After a brief review of the conditions for laser action in semiconductors, this article gives an overview of the most relevant semiconductor materials and material systems. Besides the materials, it is also shown that the various choices among the various laser structures makes this laser class well suited for a vast number of applications. The stationary, dynamic, and spectral characteristics of state-of-the-art semiconductor lasers are presented in the next section and a brief discussion on single-frequency and vertical-cavity surface-emitting semiconductor lasers completes this article.