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Quantum Optics and Unit of Length

Department 4.3

Tasks

The Department is responsible for the realization and dissemination of the unit of length "meter" and also deals extensively with the application of quantum and X-ray optical methods for precision measurements.

The meter is defined by the length of the path travelled by light in vacuum during a time interval of  1/299 792 458 of a second. The unit of length is thus linked up with the unit of time via the velocity of light.

To realize and to disseminate the unit of length, the Department provides laser wavelength standards in the visible and near infrared spectral range, whose vacuum wavelengths result from precision measurements of the optical frequency. They are available as the most accurate length standards for interferometry and for the calibration of technical length standards. In addition, new possibilities for the comparison and dissemination of optical frequencies via fiber networks are tested. Within the scope of a research task, investigation is made as to what extent also X-ray wavelengths can be linked up with the laser wavelength standards.

For a consortium of national metrology institutes, the Department is in charge of an international project dealing with the redefinition of the Avogadro constant on the basis of highly enriched silicon-28. Within the scope of this project, the Department has taken on the particular subproject "Precise determination of the 28Si lattice parameter". Transfer of the developed technologies to applications in industry and society is also a part of the Department's tasks.

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