Investigations of Laser Pumped Gas Cell Atomic Frequency Standard

摘要

Recently it has been suggested that the performance characteristics of a rubidium gas cell atomic frequency standard might be improved by replacing the standard rubidium discharge lamp with a single mode laser diode. Since the short term stability of the rubidium frequency standard is limited by the shot noise of the photodetector, an increased signal to noise ratio, from the more efficient laser diode pumping, might significantly improve the short term performance. Because the emission wavelength of the laser diode can be tuned, improved long term performance could be attained through the control of the light shift effect. However, work done by Lewis et al at NBS Boulder indicates that a new source of instability is present in the laser pumped clock; the frequency instability of the laser induces instability in the frequency standard. We have been investigating various aspects of the laser pumped gas cell atomic clock. Our investigations include effects due to laser intensity, laser detuning and the choice of the particular atomic absorption line. Our studies indicate that the performance of the gas cell clock may be improved by judicious choice of the operating parameters of the laser diode.