Steven T. Cundiff

A New Type of Frequency Chain and Its Application to Fundamental Frequency Metrology

A suitable femtosecond (fs) laser system can provide a broad band comb of stable optical frequencies and thus can serve as an rf/optical coherent link. In this way we have performed a direct comparison of the 1S—2S transition in atomic hydrogen at 121 nm with a cesium fountain clock, built at the LPTF/Paris, to reach an accuracy of 1.9×10-14. The same comb-line counting technique was exploited to determine and recalibrate several important optical frequency standards. In particular, the improved measurement of the Cesium D1 line is necessary for a more precise determination of the fine structure constant. In addition, several of the best-known optical frequency standards have been recalibrated via the fs method. By creating an octave-spanning frequency comb a single-laser frequency chain has been realized and tested.

A phase and frequency controlled femtosecond laserfor metrology and single-cycle nonlinear optics

We stabilize the spacing and position of the frequency-domain modes of a femtosecond laser to 2.5 mHz and 2 kHz (in 1 s), respectively.

Control over absolute carrier-envelope phase of ultrafast pulses: complete waveform synthesis

We have established carrier-envelope phase coherence of an ultrafast pulse train extending over 5 minutes. We also discuss results of measuring and controlling the absolute phase of a pulse train emitted directly from an oscillator.

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.