Li 2 MTeO 6 (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 the nonlinear optical (NLO) field in the ultraviolet-visible and near-infrared region. Most of the traditional oxide crystals are restricted in the mid-infrared region due to their narrow transmission window. Hence, attempting to extend infrared cutoff wavelength of oxide has attracted much attention. In our work, we reported two new tellurate Li 2 TiTeO 6 (LTT) and Li 2 SnTeO 6 - (LST) with broad transparent region 0.38-6.72 and 0.38-6.86 μm, respectively, which could be excellent candidates for the mid-infrared NLO application. Both LTT and LST are crystallized in the orthorhombic space group P nn 2. The LTT crystal exhibits intense powder second-order generation efficiency (26×KDP) under the fundamental wavelength of 1064 nm. The 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. It also paves a way to design new oxide mid-IR NLO crystals.