Stimulated hyper Raman emission and super-fluorescent emission from sodium vapour

Abstract Stimulated hyper Raman scattering at 2.3 μm due to the 4d-4p transition of Na atoms and super-fluorescent emission in the wavelength range from 7680 A due to the A 1 Σ + u -X 1 Σ + g transition of Na 2 molecules were observed when sodium vapour was optically pumped by a N 2 -laser-pumped dye laser radiation with its frequency around the two-photon resonance of the 3s-4d transition of Na atoms. The former was as high as 64% in photon conversion efficiency and its frequency tunability was 26 cm -1 . The pump frequency increase to maximal Raman output was approximately 17 276.6 cm -1 , which was higher than the 3s-4d two-photon resonance frequency (17 274.4 cm -1 ). The latter was continuously observed over the pump wavelength range from 5740 A to 5840 A except the region in which Raman emission was produced. The pulse shape was composed of double peaks; each of them being 5 ns in FWHM and separated by 30 ns. Stimulated hyper Raman emission and super-fluorescent emission have shown different optimum temperatures of Na vapour.