Single-Frequency 389-nm Coherent Light by Efficient Wavelength Conversion for Magnetic Resonance Imaging of Porous Materials with Nuclear Spin Polarization of 3He Atoms

We report that we developed the efficient 389-nm cw coherent light, corresponding to the optical transition of 2 3 S 1 3 3 P J , for optical-pumping the metastable 3 He atoms by means of the high finesse external cavity with BiBO crystal. We obtained the second harmonic power of 380mW with the maximum conversion efficiency of 56%. To the best of our knowledge, it is the most efficient frequency-doubling based on BiBO crystal recently reached at around 390 nm. In addition, the output power was stable enough to scan the frequency and to perform the spectroscopy.