13 February 2008 Single-frequency 389-nm CW coherent light source for optical pumping of metastable 3He atoms
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A hyperpolarized helium-3 (3He) has been researched extensively for application in fields such as polarization analysis, 3He spin filtration for n (p, d) γ, and medical imaging. In the medical field, nuclear magnetic resonant imaging (MRI) using hyperpolarized gas is attracted recently because air space in human lungs can be monitored in detail by aspirating polarized gas. There are two methods of producing hyperpolarized 3He gas: spin-exchange optical pumping (SEOP) and metastability exchange optical pumping (MEOP). It is well known that the way of making polarization by the MEOP method is more shortly and more directly. In this study, however, the metastable 3He atoms provided by hollow cathode discharge are polarized by circularly polarized light. When 3He atoms pumped optically, the 23S-23P transition at the wavelength of 1083nm is leveraged typically. The 3He atom actually has the optical transition 23S→ 23P at 389nm, but the transition has never been used. Therefore, we developed the 389-nm coherent light source to polarize 3He gas by MEOP method. This light source utilized the second harmonic generation (SHG) of continuous-wave Ti:sapphire laser operating at a wavelength of 778nm based on BiB3O6 (BiBO) in an external cavity.
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Shingo Maeda, Shingo Maeda, Yutaka Tabata, Yutaka Tabata, Hiroshi Kumagai, Hiroshi Kumagai, Ataru Kobayashi, Ataru Kobayashi, } "Single-frequency 389-nm CW coherent light source for optical pumping of metastable 3He atoms", Proc. SPIE 6875, Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications VII, 68751B (13 February 2008); doi: 10.1117/12.761518; https://doi.org/10.1117/12.761518

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