Generation of Optical Harmonics

This article appears in the following collections:The Physical Review Journals Celebrate The International Year of LightThe editors of the Physical Review journals revisit papers that represent important breakthroughs in the field of optics.Letters from the Past - A PRL Retrospective2008 marked PRL’s 50th anniversary. As part of the celebrations a collection of milestone Letters was started. The collection contains Letters that have made long-lived contributions to physics, either by announcing significant discoveries, or by initiating new areas of research.