LiGa(IO₃)₄: An Excellent NLO Material with Unprecedented 2D [Ga(IO₃)₄]^- Layer Synthesized by Aliovalent Substitution

Nonlinear optical (NLO) crystals are indispensable for the solid-state lasers for their ability to expand wavelength spectral to the regions where the directing lasing is difficult or even impossible, yet the rational design of a high-performance NLO crystal remains a great challenge owing to the severe structural and properties' requirements. Herein, a new noncentrosymmetric (NCS) and polar gallium iodate, LiGa(IO3)(4), with a novel 2D anionic layer, is successfully designed and synthesized by the aliovalent substitution strategy based on classic alpha-LiIO3. The 2D [Ga(IO3)(4)](infinity)(-) layer in LiGa(IO3)(4) is built from the GaO6 octahedra and highly polarizable units IO3. Compared with its parent compound, the partial replacement of A-site Li+ cation with main group Ga3+ cation facilitates LiGa(IO3)(4) to possess excellent NLO properties, including the large second-harmonic generation (SHG) response (14 x KH2PO4 (KDP) @ 1064 nm), wide bandgap (4.25 eV), large birefringence (0.23 @ 1064 nm), and wide optical transparency from UV to mid-IR. These reveal that LiGa(IO3)(4) will be a promising NLO crystal.