This reference provides an overview of near-Earth laser communication theory developments including component and subsystem technologies, fundamental limitations, and approaches to reach those limits. It covers basic concepts and state-of-the-art technologies, emphasizing device technology, implementation techniques, and system trades. The authors discuss hardware technologies and their applications, and also explore ongoing research activities and those planned for the near future. This new edition includes major to minor revisions with technology updates on nearly all chapters. Hamid Hemmati is an Engineering Director at Facebook Inc. Prior to that he was with the JPL-NASA-Caltech for 28 years working primarily on satellite laser communications technology. From 1983 to 1986 he worked at the NASA Godard Space Flight Center on the COBE spacecraft and on free-space laser communications. As a post-doctoral fellow at NIST – University of Colorado (Boulder, 1981-83), Dr. Hemmati worked on ultra-stable atomic clocks based on laser-cooled trapped ions.