Abstract

For the first time by means of two-photon hybrid excitation in the Na₂-Na system, which is distinguished from the usual two-photon excitation in atomic vapor, tunable UV coherent radiation (between 337.6 and 339.1 nm and between 358.0 and 359.6 nm) and tunable infrared stimulated radiation (3.38-3.46 µm) were generated. By optically pumping with a pulsed dye laser scanning from 614.5 to 617.4 nm for sodium vapor in a heat-pipe oven, Na₂ was excited by the first photon absorption from the $X^{\prime }{\Sigma }_g^{+}$ to the $A^{\prime }{\Sigma }_u^{+}$ state. The energy was transferred to Na by Na₂^*-Na collision to populate the levels 3p_1/2,3/2 in Na, which was followed by another photon excitation from the same beam up to near the 5S level, resulting in SERS (3P_1/2-4P and 3P_3/2-4P) and OPSE(5S → 4P and 4P → 4S) radiation. Assuming the detunings of pumping frequency ω₁, from ω(5S,3P_3/2) and ω(5s,3p1/2) to be Δ₁ and Δ₂, respectively, the three UV coherent radiation components were supposed to be generated by the following mixing processes: ω_UV = 2ω₁ − ω(5S − 4P);${\omega }_{UV}^{\prime }=2{\omega }_1-\left[\omega (5S\to 4P)+{\Delta }_1\right];{\omega }_{UV}^{\prime \prime }=2{\omega }_1-\left[\omega (5S\to 4P)+{\Delta }_2\right]$, and also ${\omega }_{UV}^{\prime \prime \prime }=2{\omega }_1-\omega (4P\to 4S)$. The SERS and the UV signals were tuned as the pumping wavelength was tuned. The measured wavelengths agreed well with the calculated values.

© 1986 Optical Society of America