Li2MTeO6 (M=Ti, Sn): Mid‐Infrared Nonlinear Optical Crystal with Strong Second Harmonic Generation Response and Wide Transparency Range

Oxide crystals have been widely used in nonlinear optics (NLO) in the ultraviolet–visible and near‐infrared regions. Most traditional oxide crystals are restricted to the mid‐infrared region due to their narrow transmission window. Hence, attempting to extend infrared cutoff wavelength of oxides has attracted much attention. Herein, we report two new tellurates Li2TiTeO6 (LTT) and Li2SnTeO6 (LST) with broad transparent regions of 0.38–6.72 and 0.38–6.86 μm, respectively, as excellent candidates for mid‐infrared NLO applications. Both LTT and LST crystallize in the orthorhombic space group Pnn2. The LTT crystal exhibits intense powder second‐order generation efficiency (26×KDP) under the fundamental wavelength of 1064 nm. First‐principles calculations and dipole moments were used to illustrate the results of the powder second‐harmonic generations based on the crystal structures. Our results provide a novel oxide NLO crystal with a strong SHG and wide transparency range. They also pave a way for the design of new oxide mid‐IR NLO crystals. New tellurate LTT and LST crystals were obtained by a TSSG method with a broad transparent region of 0.38–6.72 and 0.38–6.86 μm for MIR NLO applications. Both LTT and LST belong to the space group Pnn2, with an almost identical structure. The LTT crystal exhibits intense powder SHG response. First‐principles calculations and dipole moments were used to illustrate the results of the powder SHG based on the crystal structures.