GaAs-laser-induced population inversion in the ground-state hyperfine levels of Cs133

This paper describes the achievement of population inversion among the hyperfine levels in the ground state of Cs
¹³³
by optically pumping these atoms with radiation from a GaAs diode laser. The laser output was used to monitor the populations in the two ground-state hyperfine levels as well as to perform the hyperfine pumping. By varying the injection current, a GaAs laser operated CW at about 77°K was used to scan the 8521-Å line of Cs
¹³³
. The intensity of the resonance scattering from cesium vapor served as an indicator of the populations of the two levels involved. Experiments were performed both with neon-filled and with paraflint-coated cells containing the cesium vapor. It was discovered that the diode laser could easily be tuned by manually adjusting the injection current to match either of the hyperfine components of the D
2
optical transition. Possible future applications, including a restudy of the light shifts, the construction of a cesium maser, and the physics of optical pumping with coherent light are discussed.