Optical Frequency Standards & Metrology
New types of atomic clock operating at optical rather than microwave frequencies promise significant advances in both science and technology.
All other things being equal, the stability of an atomic clock is proportional to its operating frequency. Visible light has a frequency roughly 100 000 times higher than that of microwaves. This means that clocks based on narrow absorptions at optical, rather than microwave, frequencies should be much more stable.
Optical clocks have many potential applications. These range from improved satellite navigation systems and better tracking of deep space probes to sensitive tests of general relativity and measurements of fundamental physical constants. In future they could even lead to the SI unit of time, the second, being redefined.
The heart of an optical clock is a highly stable reference frequency provided by a narrow optical absorption in an atom or ion. At NPL we are developing clocks based on transitions in single trapped ions and neutral atoms confined in an optical lattice.
- At NPL we are working on a variety of frequency standards based on cold atoms. Reducing the temperature of the atoms or ion used for frequency metrology allows for long measurement cycles and greatly reduces velocity-related shifts of the clock transition frequency.
- Advances in optical frequency standards and metrology are opening up new horizons in fundamental physics. In particular, they provide powerful tools for scientists to make highly precise measurements of fundamental constants.
- NPL offers a routine service for the verification of interferometer system accuracy.