John Emmett was working at the Naval Research Laboratory in Washington, D.C., and had a Ph.D. from Stanford University, was asked to join Lawrence Livermore National Laboratory's new Laser Division in July 1972. He became associate director of Laser Programs at in 1975, succeeding Carl Hausmann, who became weapons program manager.

Emmett led the LLNL Laser Programs until 1989, guiding and overseeing the construction of a series of successively more powerful lasers, including Nova. In a speech at the dedication of the National Ignition Facility (May 2009), Emmett credited former director Roger Batzel and former associate director Carl Haussmann for seeing the need for an integrated effort. "Before I came to Livermore, the Lab's laser program was 57 Grand Duchies of Fenwick with every program having its own laser fusion effort. Carl and Roger recognized that they all needed to be pulled together into a single program."

Nova fired its last shot in May 1999 after 14 years and more than 14,000 experiments. "Nova has been an extremely successful facility," Emmett said at the time. "It's been a lot more productive than anyone thought it would be."

When Emmett left the lab in 1989, the Laser Programs had grown from 125 employees and a yearly budget of $7 million to a world-renowned team of 1700 people and an annual budget of $275 million.

During his career, Emmett received the E.O. Lawrence award from the Department of Energy and the Fusion Power Associates Leadership Award. After retiring from government research, Emmett lives in Washington state and runs a firm called Crystal Chemistry, which develops gemstone color and clarity enhancement methods.