Four-wave mixing in potassium involving quadrupole excitation and emission

The stimulated 331.1-nm emission in the K(5D → 4S) quadrupole transition has been studied after excitation by two tunable dye laser waves, one of which is in the K(4S → 3D) quadrupole transition. A four-wave mixing mechanism has been shown to be responsible for the UV emission based on intensity, temperature, and spectral measurements. The measured conversion efficiency is compared with the calculated value.