This is the third, revised and extended edition of the acknowledged «Lectures on Quantum Optics» by W. Vogel and D.-G. Welsch. It offers theoretical concepts of quantum optics, with special emphasis on current research trends. A unified concept of measurement-based nonclassicality and entanglement criteria and a unified approach to medium-assisted electromagnetic vacuum effects including Van der Waals and Casimir Forces are the main new topics that are included in the revised edition. The...