@conference{6918, author = {John Hall and M. Taubman and Scott Diddams and B. Tiemann and Jun Ye and L.-S. Ma and D. Jones and Steven Cundiff}, title = {Stabilizing and measuring optical frequencies}, abstract = {Many factors are coming together to make this an exciting time in the development of optical frequency standards. These include improved strategies for interrogation of the resonant quantum reference sample, improved accuracy and control of the modulation process, demonstration of an external modulation-removal strategy, and a rich field of new possibilities for frequency measurement, particularly the arrival of broad optical comb generation techniques. Frequency-domain methods based on broad femtosec laser combs are very promising, as made clear by the work of Udem and Hänsch. We easily see beats at 805 nm with optical comb lines whose center is at 840 nm, a 16 THz interval. Adjustment of the laser compensation broadens the comb to >140 nm width at – 3 dB ! Stabilization of both optical center frequency and pulse rate has been implemented. Interesting combs are also generated near 1060 nm with Kourogi’s modulator-in-a-cavity approach, augmented by an intracavity LiNbO3 crystal which provides OPO gain and frequency connection to the stable pump. So far, about 15 000 coherent comb lines are generated, limited by uncompensated dispersion in the OPO cavity. Useful data regarding S/N necessary for accurate counting and a powerful adaptive Phase-Tracking Filter/Oscillator are discussed. }, year = {1999}, journal = {unknown}, month = {09/1999}, publisher = {World Scientific, Singapore}, address = {Innsbruck, Austria}, isbn = {978-981-02-4160-5}, note = {JILA Pub. 6392}, }