Elements of Quantum Optics gives a broad coverage of the basic elements necessary to understand and carry out research in laser physics and quantum optics. It presents a variety of theoretical tools and important results for two-level and semiconductor media, many of which could only be found in the original literature of in specialized monographs up to now. The text revearls the close connection between many seemingly unrelated topics, such as probe absorption, four-wave mixing, optical instabilities, resonance fluorescence and squeezing. The third edition includes new chapters on atom optics and cavity quantum electrodynamics, as well as expanded discussion of quantum mechanics, system-reservoir interactions and second quantization.