Observation of new tunable ultraviolet emissions by four-wave mixing in sodium vapor

An observation is reported of several new coherent ultraviolet emissions in the 320-420 nm region from sodium vapor optically pumped by a single pulsed dye laser with wavelengths in the 570-590 nm region. The observed wave mixing simultaneously involves various combinations of the laser pump wave with, respectively, fixed-frequency infrared emissions, tunable stimulated electronic Raman-scattered radiation, or output from four-wave mixing, all of which are generated in the same medium by the same pump wave. The most pronounced tunable outputs are at 330, 333, 343, 383 and 388 nm. Several of the generated UV emissions are found to be resonantly enhanced by electric-dipole forbidden transitions. The frequency conversion efficiencies are estimated to range from 0.01 to 0.0001.