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Optogalvanic spectroscopy of two-photon dissociation of Tl/sub 2/ at 532 nm producing large population inversion between Tl(7 /sup 2/S/sub 1/2/) and (6 /sup 2/P/sub 3/2/) states

Athar S. Naqvi

Published Mar 1, 1985• 0 citations
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This paper reports the first time achievement of large population inversion between thallium 7 2S1/2 and 6 2P3/2 states through two-photon dissociation of pure Tl2 molecules. The second harmonic of a Nd–YAG laser at 532 nm is used to cause two-photon absorption in Tl2 from ground state Ou− to the repulsive state associated with the atomic 7 2S and 6 2P1/2 states. The relative population of the product atomic species is determined by using a tunable dye laser pumped by the third harmonic of a Nd–YAG laser. The dye laser beam focused for complete spatial and temporal overlap with the photodissociaiton pulse excites the product states to known atomic Rydberg states with subsequent ion detection. Prompt population inversion amounting to 100% is achieved. It is shown that photodissociation transition is mediated through predissociation of the upper bound state to a repulsive state correlated with Tl(7 S1/2) in the region of large internuclear separation.

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Lasing without inversion in three-level systems without external coherent driving

V. Ahufinger, J. Mompart, R. Corbalán

Summary form only given. We study a model for an incoherently pumped laser operating with a Doppler-broadened three-level system placed in a doubly resonant cavity and producing two laser fields, one of them without population inversion. Each laser field couples to only one of the transitions of the three-level medium. We have studied our model for parameters appropriate to two real atomic systems (i) a cascade scheme in atomic /sup 138/Ba looking for lasing with (without) inversion at /spl lambda//sub /spl beta//=554 nm (/spl lambda//sub /spl alpha//=821 nm), and (ii) a V-scheme in atomic /sup 85/Rb with ordinary lasing at /spl lambda//sub /spl alpha//=780 nm and lasing without inversion (LWI) at /spl lambda//sub /spl alpha//=4216 nm. These two cases are qualitatively different in that two-photon processes are responsible for inversionless gain in case (i) while LWI in case (ii) arises from one-photon processes. Moreover, the frequency up-conversion ratio is R=0.67 for the case of /sup 138/Ba and it is R=1.88 for the case of /sup 85/Rb. In spite of the fact that the frequencies of the two laser fields are relatively different, our results show that dual-wavelength lasing extends up to Doppler broadening values typical for optical transitions of atoms in a vapor cell. In case (i) /spl alpha/-lasing occurs without two-photon inversion only for approximately the lower half of the domain of Doppler-broadening values. However, in case (ii) one has LWI in all the domains. Some considerations for a practical realization of the dual-wavelength inversionless-conventional laser are discussed.

Conference on Lasers and Electro-Optics•Aug 29, 2005•1 citation
This paper reports the first time achievement of large population inversion between thallium 7 2S1/2 and 6 2P3/2 states through two-photon dissociation of pure Tl2 molecules. The second harmonic of a Nd–YAG laser at 532 nm is used to cause two-photon absorption in Tl2 from ground state Ou− to the repulsive state associated with the atomic 7 2S and 6 2P1/2 states. The relative population of the product atomic species is determined by using a tunable dye laser pumped by the third harmonic of a Nd–YAG laser. The dye laser beam focused for complete spatial and temporal overlap with the photodissociaiton pulse excites the product states to known atomic Rydberg states with subsequent ion detection. Prompt population inversion amounting to 100% is achieved. It is shown that photodissociation transition is mediated through predissociation of the upper bound state to a repulsive state correlated with Tl(7 S1/2) in the region of large internuclear separation.
Evidence is obtained which demonstrates the potential for developing purely chemical visible lasers based on rapid near-resonant energy transfer from metastable excited triplet states of germanium and silicon monoxide (a/sup 3/ Sigma /sup +/,b/sup 3/ Pi ) to select metal atoms. In this study, the Group IIIA metal atoms were chosen as the energy receptors for the energy transfer-pump sequence. Excited triplet states were generated from the Ge-O/sub 3/, Ge-N/sub 2/, Si-N/sub 2/O, and Si-NO/sub 2/ reactions; the bulk of the experimental results was obtained with a germanium-based system. The energy stored in the long-lived triplet states is transferred to pump X/sup 2/P/sub 1/2/ thallium, indium, and gallium atoms to their lowest lying /sup 2/S/sub 1/2/ states. The authors observe a system of temporal behavior which suggests the creation of a population inversion producing a gain condition and forming the basis for full cavity oscillation on the Tl 7/sup 2/S/sub 1/2/-6P/sub 3/2/ transition at 535 nm.>
Summary form only given. We study a model for an incoherently pumped laser operating with a Doppler-broadened three-level system placed in a doubly resonant cavity and producing two laser fields, one of them without population inversion. Each laser field couples to only one of the transitions of the three-level medium. We have studied our model for parameters appropriate to two real atomic systems (i) a cascade scheme in atomic /sup 138/Ba looking for lasing with (without) inversion at /spl lambda//sub /spl beta//=554 nm (/spl lambda//sub /spl alpha//=821 nm), and (ii) a V-scheme in atomic /sup 85/Rb with ordinary lasing at /spl lambda//sub /spl alpha//=780 nm and lasing without inversion (LWI) at /spl lambda//sub /spl alpha//=4216 nm. These two cases are qualitatively different in that two-photon processes are responsible for inversionless gain in case (i) while LWI in case (ii) arises from one-photon processes. Moreover, the frequency up-conversion ratio is R=0.67 for the case of /sup 138/Ba and it is R=1.88 for the case of /sup 85/Rb. In spite of the fact that the frequencies of the two laser fields are relatively different, our results show that dual-wavelength lasing extends up to Doppler broadening values typical for optical transitions of atoms in a vapor cell. In case (i) /spl alpha/-lasing occurs without two-photon inversion only for approximately the lower half of the domain of Doppler-broadening values. However, in case (ii) one has LWI in all the domains. Some considerations for a practical realization of the dual-wavelength inversionless-conventional laser are discussed.