Stable diode lasers for hydrogen precision spectroscopyJ. 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
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 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 Hz.
© EDP Sciences, Springer-Verlag 2008