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Physical Review Letters

Optical Difference-Frequency Generation in Atomic Thallium Vapor

Allen M. Flusberg, THOMAS W. MOSSBERG, Sven R. Hartmann

Published Jan 10, 1977• 49 citations
Publisher

Abstract

Coherent radiation at the 1.28-\ensuremath{\mu}m electric-dipole-forbidden $6^{2}P_{\frac{3}{2}}\ensuremath{-}6^{2}P_{\frac{1}{2}}$ transition in thallium vapor has been produced by the simultaneous application of a magnetic field and two collinear, overlapping laser beams nearly resonant with the $6^{2}P_{\frac{1}{2}}\ensuremath{-}7^{2}S_{\frac{1}{2}}$ and $6^{2}P_{\frac{3}{2}}\ensuremath{-}7^{2}S_{\frac{1}{2}}$ transitions, respectively. The effect of the magnetic field is to mix hyperfine levels---atomic polarization effects are negligible. The optical difference-frequency power generated at low magnetic field varies as the square of the magnetic-field component normal to the laser-beam propagation direction.

DOI
10.1103/physrevlett.38.59

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Self-induced transparency has been observed for the degenerate, $F=3\ensuremath{\rightarrow}4$, hyperfine component of the 1.315-\ensuremath{\mu}m magnetic dipole transition of atomic iodine, at high optical power levels, up to 50 MW ${\mathrm{cm}}^{\ensuremath{-}2}$. For pulse areas approaching $2\ensuremath{\pi}$, the dynamics of the strong coherent resonant self-focusing which accompanies self-induced transparency have been studied with a streak camera to provide time-dependent analysis of the spatial beam profile.
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Nonlinear magneto-optical resonances on the hyperfine transitions belonging to the D2{D}_{2}D2​ line of rubidium were changed from bright to dark resonances by changing the laser power density of the single exciting laser field or by changing the vapor temperature in the cell. In one set of experiments atoms were excited by linearly polarized light from an extended cavity diode laser with polarization vector perpendicular to the light's propagation direction and magnetic field, and laser-induced fluorescence was observed along the direction of the magnetic field, which was scanned. A low-contrast bright resonance was observed at low laser power densities when the laser was tuned to the ${F}_{g}=2\ensuremath{\rightarrow}{F}_{e}=3$ transition of 87{}^{87}87Rb and near to the ${F}_{g}=3\ensuremath{\rightarrow}{F}_{e}=4$ transition of 85{}^{85}85Rb. The bright resonance became dark as the laser power density was increased above 0.6 mW/cm2{}^{2}2 or 0.8 mW/cm2{}^{2}2, respectively. When the ${F}_{g}=2\ensuremath{\rightarrow}{F}_{e}=3$ transition of 87{}^{87}87Rb was excited with circularly polarized light in a second set of experiments, a bright resonance was observed, which became dark when the temperature was increased to around 50${}^{\phantom{\rule{0.16em}{0ex}}\ensuremath{\circ}}$C. The experimental observations at room temperature could be reproduced with good agreement by calculations based on a theoretical model, although the theoretical model was not able to describe measurements at elevated temperatures, where reabsorption was thought to play a decisive role. The model was derived from the optical Bloch equations and included all nearby hyperfine components, averaging over the Doppler profile, mixing of magnetic sublevels in the external magnetic field, and a treatment of the coherence properties of the exciting radiation field.