Abstract

The excitation of atoms by consecutive, phase-coherent, and near resonant laser fields leads to optical Ramsey resonances, which can be interpreted as atom interferences.¹ We report on interference structures observed by excitation of an effusive $\left(\overline{v}=700\text{m}/s\right)$ and a laser cooled ${\left(\overline{v}=35\text{m}/\text{s}\right)}^2$ calcium atomic beam and of Ca atoms stored in a magnetooptical trap (v_rms ≅ 0.5 m/s)3 Three different excitation schemes have been used for the excitation of the different atom sources: Four travelling waves for the effusive and the laser cooled beam, two pulsed counterpropagating beams for the laser cooled beam, and three pulses of standing laser fields for the trapped atoms. Phase shifts of the interferometer can be compensated by corresponding frequency shifts of the exciting laser. Long time separations between the excitations leads to high spectral resolution, which is of great importance for the development of an optical frequency standard. We have observed interference structures with a spectral resolution of 2.5 kHz (FWHM) corresponding to a line-Q of v/Δv ≅ 2 × 10¹¹.

© 1994 IEEE