Long-wavelength Infrared Semiconductor Lasers provides a comprehensive review of the current status of semiconductor coherent sources emitting in the mid-to far-infrared spectrum and their applications. It includes three topics not covered in any previous book: far-infrared emission from photo-mixers as well as from hot-hole lasers, and InP-based lasers emitting beyond two micrometers. Semiconductor lasers emitting at more than two micrometers have many applications such as in trace gas analysis, environmental monitoring, and industrial process control. Because of very rapid progress in recent years, until this book no comprehensive information beyond scattered journal articles is available at present.