Frequency-stabilized lasers: a parochial review

It is hoped that this article will serve as a useful introduction to the art of stabilized lasers, especially for those who are joining this sport from other fields. It has become clear that pre- stabilization of the laser on the non-saturable resonance of a stable cavity is a good strategy: with adequate feedback system design, one can effectively replace the intrinsic noise of the laser with the measurement noise of the stabilizer system. By now sub-Hertz frequency control and optical phase locking have been demonstrated with most of these tunable sources. The ready access to modulation of the diode laser can lead to a very simple but impressive source, while the external stabilizer approach is attractive for dye and optically pumped solid-state sources. Current work on amplitude-stabilization of the laser pump may lead to reduction of the intrinsic solid state laser noise as well. With the current explosion of interest in atom trapping techniques we can look forward to major progress in the narrow-line laser/super- sharp absorber high resolution spectroscopy business. Applications range from atomic clocks to cold atom collision physics to tests of special relativity. The combination of ultra-stable lasers with cold atom interferometry will be especially powerful in offering new tests of atomic charge neutrality and of time reversal invariance via new limits on atomic electric dipole moments. Remarkably, a practical instrument for oil and gas prospecting might be based on a laser-diode/atom-interferometric measurement of local g .