2. (2R)-8-Benzyl-2-[(S)-hy-droxy(phen-yl)meth-yl]-8-aza-bicyclo-[3.2.1]octan-3-one
Krzysztof Brzezinski, Ryszard Lazny, Michal Sienkiewicz, Sławomir Wojtulewski, Zbigniew Dauter Acta Crystallogr Sect E Struct Rep Online. 2012 Jan;68(Pt 1):o149-50. doi: 10.1107/S1600536811053190. Epub 2011 Dec 17.
The crystal of the title compound, C(21)H(23)NO(2), was chosen from a conglomerate formed by a racemic mixture. An intra-molecular hydrogen bond is formed between hy-droxy group and heterocyclic N atom of the aza-bicyclo-[3.2.1]octan-3-one system. The crystal structure is stabilized by C-H⋯O inter-actions between aliphatic C-H groups and the carbonyl O atom. For the title chiral crystal, the highly redundant and accurate diffraction data set collected with low energy copper radiation gave a Flack parameter of 0.12 (18) for anomalous scattering effects originating from O atoms.
3. 321 W high-efficiency continuous-wave green laser produced by single-pass frequency doubling of narrow-linewidth fiber laser
Mengqi Su, Yang You, Zhao Quan, Hui Shen, Qiurui Li, Wansheng Liu, Yunfeng Qi, Jun Zhou Appl Opt. 2021 May 1;60(13):3836-3841. doi: 10.1364/AO.422514.
In this study, a high-power continuous-wave green laser for copper processing is investigated. The laser is produced by single-pass second-harmonic generation (SHG) of a narrow-linewidth fiber laser. Based on Sellmeier equations, the factors (e.g., fundamental wave linewidth, temperature, and angle) that decide LBO noncritical phase matching are theoretically analyzed for optimizing the SHG setup. A narrow-linewidth polarization-maintained fiber laser is used as the fundamental laser with a linewidth of 20 GHz and polarization extinction ratio of greater than 15 dB. Type I noncritical phase-matching LBO is used as the nonlinear crystal in the SHG. A green laser (up to 321 W) is obtained from a 784 W fundamental laser with a conversion efficiency of 40.9%. The green laser is near-diffraction-limited and has a $ M^{2} $ factor of 1.07.
