Hardo Stoehr

Diode laser with 1 Hz linewidth

We report an ultranarrow-linewidth laser spectrometer at 657 nm, consisting of a diode laser locked in a single stage to a stable high-finesse reference cavity. The system is characterized by comparison with a second independent system. From beat frequency measurements a linewidth below 1.5 Hz (FWHM) and a fractional instability of less than 2 x 10(-15) for 1 s of averaging time are observed.

Influence of chirped excitation pulses in an optical clock with ultracold calcium atoms

We have investigated the influence of frequency chirps of the excitation pulses in a time-domain optical Ramsey-Borde/spl acute/ atom-interferometer used in an optical clock with ultracold calcium atoms. With optical interferometry, we identify a ringing in the excitation pulses to be responsible for the observed frequency shifts. Using these results, the uncertainty of the latest frequency measurement could be reduced to 1.2/spl middot/10/sup -14/.

An improved optical clock with ultracold calcium atoms

We present the latest results of an optical frequency standard with about 10 calcium atoms laser cooled in a two-step procedure. The current fractional uncertainty of about 10 represents one of the most precisely known optical frequencies. Here, we show how this fractional uncertainty can be reduced to about 2 . 10 by eliminating the black body shift of the atomic oven and correcting for the effect of laser chirps.

An optical frequency standard with ultracold calcium atoms

We present latest results of an optical frequency standard with laser cooled calcium atoms. The current fractional uncertainly of 1.2/spl middot/10/sup -14/ makes this one of the most precisely known optical frequencies. Applications and further developments will be discussed.

Improved Optical Frequency Standard with Ultracold Calcium Atoms

We report on latest improvements in an optical frequency standard based on ultracold calcium atoms. First steps towards a clock using atoms trapped in an optical lattice are presented

Diode laser frequency stabilization for a Ca optical clock

Frequency stabilization of extended-cavity diode lasers at 657 nm to the Hz-level is reported. Using the Pound-Drever-Hall technique the lasers are locked to high-finesse Fabry-Perot cavities made of ULE (ultra low expansion glass). The cavities are isolated against vibrations passively with a one stage spring suspension inside an acoustic damping box resting on the optical table. Thus cavity accelerations on the /spl mu/g-level and below are achieved. The temperature of the reference cavities is stabilized by the use of active and passive temperature stabilization.