The invention relates to the technical field of atomic clocks, and discloses a fountain type cold
atomic clock. On one hand, an
atomic energy state selection mechanism is changed into an
optical pumping state selection mechanism, an
atomic state selection structure and a
fluorescence detection structure can be combined into one, and then a state selection
microwave cavity structure commonly used for the fountain type cold
atomic clock can be removed, so that the overall height of a
physical system structure is greatly reduced, the size and the weight of the
atomic clock are effectively reduced, and movement, popularization and use are facilitated; and on the other hand, due to the fact that the atomic
utilization rate is greatly improved through the
optical pumping state selection, the number of atoms used for
microwave inquiry is multiplied, the
signal-to-
noise ratio of a
spectral line is increased, then the index influence caused by the fact that the
line width of the
spectral line is increased due to height reduction is counteracted, the index potential of the accuracy and the stability is equivalent to that of a current fountain type cold atomic
clock, and the performance of the atomic
clock cannot be affected due to height reduction.