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Issue Eur. Phys. J. Special Topics
Volume 163, October I 2008
Atomic Clocks and Fundamental Constants
Page(s) 89 - 94
DOI 10.1140/epjst/e2008-00811-y
Published online 25 October 2008

Eur. Phys. J. Special Topics 163, 89-94 (2008)
DOI: 10.1140/epjst/e2008-00811-y

Stable diode lasers for hydrogen precision spectroscopy

J. Alnis1, A. Matveev1, 2, N. Kolachevsky1, 2, T. Wilken1, R. Holzwarth1 and T.W. Hänsch1

1  MPI für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany
2  P.N. Lebedev Physics Institute, Leninsky Prosp. 53, 119991 Moscow, Russia

Janis.Alnis@mpq.mpg.de

Abstract
We report on an external cavity diode laser at 972 nm stabilized to a mid-plane mounted Fabry-Perot (FP) resonator with a finesse of 400000. The 0.5 Hz optical beat note line width between two similar lasers (Allan deviation 2 $\times$ 10-15) is limited by thermal noise properties of two independent FP resonators. The long term drift of the FP resonator and mirror substrates made from Ultra-Low-Expansion glass (ULE) is small and can be well predicted on time intervals up to many hours if the resonator is stabilized at the zero thermal expansion temperature Tc. Using a Peltier element in a vacuum chamber for temperature stabilization allows stabilization of the FP cavity to Tc which is usually below the room temperature. Beat note measurements with a femtosecond optical frequency comb referenced to a H-maser during 15 hours have shown a well defined linear drift of the FP resonance frequency of about 60 mHz/s with residual frequency excursions of less than $\pm 20$ Hz.



© EDP Sciences, Springer-Verlag 2008


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