Bridging oxygen atoms in trigonal prism units driven strong second-harmonic-generation efficiency in Sr 3 Ge 2 O 4 Te 3 .

Herein, a novel IR NLO oxytelluride Sr 3 Ge 2 O 4 Te 3 was successfully designed and synthesized through a "partial O-to-Te substitution" strategy. Compared with the parent oxide, Sr 3 Ge 2 O 4 Te 3 not only successfully achieves a phase-matchability transition (from NPM to PM), but also greatly improves the linear and NLO performances, including a wide band gap (2.26 eV), strong SHG response (1.3 × AgGaSe 2 ) and large optical anisotropy (Δ n = 0.152@2090 nm). The analyses of the structure-property relationship and SHG-density indicate that the bridging oxygen in the [O 3 Ge-O-GeTe 3 ] prism unit plays the most important role in the multiplication SHG effect. This work provides some insights into the design and exploration of novel IR NLO materials.