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BaGeO3: A Mid-IR Transparent Crystal with Superstrong Raman Response
journal contribution
posted on 2020-02-25, 13:35 authored by Songming Wan, Yu Zeng, Yanan Yao, Miriding Mutailipu, Jian Han, Shengjie Jiang, Shujie Zhang, Shilie PanStimulated Raman
scattering processes based on Raman crystals offer a simple and effective
method to generate mid-IR lasers. However, currently available mid-IR
Raman crystals are extremely scarce. Herein, a new type of mid-IR
Raman crystal, BaGeO3, is reported. It crystallizes in
the monoclinic space group C2/c with
Ba2+ cations and [Ge3O9]6– rings as basic building units and features high transparency from
2.5 to 5.5 μm and a Raman response larger than that of diamond.
The BaGeO3 crystal has 45 IR-active modes (22Au + 23Bu) and 42 Raman-active modes (20Ag +
22Bg). The wide mid-IR transparent window is attributed
to the low phonon energy of the second-order IR-active Au ⊗ Bg mode. The strongest Raman band, located at
799 cm–1, arises from the symmetrically stretching
vibration of the [Ge3O9]6– extra-ring Ge–O bonds. The findings provide new insights
into the crystallographic and Raman spectroscopic characteristics
of high-performance mid-IR Raman crystals.