The laser, first operated in 1960, produced light with coherence properties that demanded explanation. While some attempted a treatment within the framework of classical coherence theory, others insisted that only quantum electrodynamics could give adequate insight and generality. The result was a sharp and rather bitter controversy, conducted over the physics and mathematics that were being deployed, but also over the criteria for doing good science. Three physicists were at the center of this dispute, Emil Wolf, Max Born’s collaborator on (...) a canonical text on optics as a branch of classical electromagnetism, Roy J. Glauber, a student of Julian Schwinger and a high-energy particle theorist, and Leonard Mandel, both experimentalist and theorist and versed in the physics of photodetection. The story told here is thus one of three distinct research trajectories and of the explosion that occurred when, pushed into the well-financed field of laser studies, these trajectories collided. (shrink)

It is a commonplace for historians to write that physicists came out of their World War II radar service with microwave engineering superadded to their knowledge of quantum physics. But what exactly was the content of this new amalgam? How fully was it achieved and by what processes? I suggest that one approach to these questions is via a study of noise and coherence in the 1950s. In these years, novel instruments were proposed and/or operated that were of interest for (...) both engineering and physics; among them various forms of the maser. These instruments required the deployment of both engineering and quantum physics concepts. At the same time, they raised problems for both physics and engineering notions of noise. (shrink)