Frequency Combs 
    High Precision 
Measurements for fundamental Physics



We are part of the group of Prof. T. W. Hänsch and located at the Max-Planck Institute for Quantum Optics

optical synthesizer

This self referenced optical frequency comb allows to synthesize almost any optical frequency. Hence we call such a device an optical synthesizer. It is based on a Ti:Sapphire mode locked laser that emits in the infrared.

fs ring laser

The Ti:Sapphire ring laser of the left picuture in close up. The green pump laser was switched off for this picture. The ring design makes this laser almost immune for optical feedback that could be some trouble in linear laser cavities used for the  same purpose.

non linear interferometer

The nonlinear interferometer used to self reference the optical synthesizer. It is used to measure the comb offset frequency by frequency doubling the red wing of the comb and merge it with the blue wing. A photodetector placed in the merged beam will record the comb offset frequency wich is then stabilized to an atomic clock along with the repetition frequency.

fs ring laser

This cesium atomic clock build by the group of Andre Clairon at BNM-SYRTE/Paris has been brought to out lab to perform the most precise measurement of a hydrogen transition frequency reported yet. It  provided the reference for locking the comb offset frequency and the repetiton rate of our fs laser comb.

hydrogen spectrometer

The hydrogen spectrometer operated by Nikolai Kolachevsky and Mark Fischer. The blue laser light is cretaed by frequency doubling a highly stable dye laser and is subsequently used to drive the 1s-2s transition in a 6K hydrogen beam insiide the vacuum vessel visible on the left side.

fiber frequency comb

An optical synthesizer based on a mode locked fiber laser. The advantage here is there are no part that missallign during operation because of slow temperature variations. Thefore this synthesizer can operate continuously for several days.

photonic crystal fiber

Electron microscopic picture of a photonic crystal fiber made by Philip Russells group at Bath/England. The air channels around the core permit strong nonlinear interaction. We have used this property to broaden or frequency combs such until they cover a complete octave. In this case the simplest form of self referencing described above (frequency doubling of the red wing) becomes possible.

white light laser

A very broad spectrum covering the whole visible and beyond is produced by self phase modulation. The resulting laser beam apears white. The same prcoess takes place i the photonic crystal fiber.

last change August 31 2008