The first part of this tutorial covers the basic background material necessary for gaining an in-depth understanding of the operating principles of semiconductor diode lasers and light emitters. Following this introductory material, the tutorial focuses on various specific laser designs, including edge emitters and vertical cavity lasers configured for high output power levels. Particular emphasis will be placed on high power diode lasers, including pump lasers for EDFAs and Raman amplifiers, as well as semiconductor optical amplifiers covering the 1300 to 1600 nm spectral region. The tutorial will also cover the critical issues of diode laser reliability, handling, and operation. It will be shown that pump lasers with MTBF values of the order of 100 years are now commercially available.