In an apparatus using optically excited atomic media, such as an atomic frequency
standard, a source providing a controlled emission of light for exciting the D1
and/or D2 resonance lines of an alkali gas, such as rubidium or cesium,
is controlled by an output generated by digital electronics from the light intensity
signal of a light sensor for light transmitted by the alkali gas, an output for
representing ambient temperature, and a light intensity-ambient temperature algorithm
to substantially eliminate changes in light intensity due to light source aging
for the purpose of reducing changes in temperature sensitivity of the apparatus
as a function of time and the light-shift contribution to the frequency aging of
the standard.
