Control of coherent light and its broad applications

A remarkable synergy has been formed between precision optical frequency metrology and ultrafast laser science. This has resulted in control of the frequency spectrum produced by mode-locked lasers, which consists of a regular “comb” of sharp lines. Such a controlled mode-locked laser is a “femtosecond optical frequency comb generator.” For a sufficiently broad comb, it is straightforward to determine the absolute frequencies of all of the comb lines. This ability has revolutionized optical frequency metrology and synthesis, and it has also led to recent demonstrations of atomic clocks based on optical frequency transitions. In addition, the comb technology is having a strong impact on time-domain applications, including control of the carrier-envelope phase, precision timing synchronization, and synthesis of a single pulse from independent lasers.