Fig. 4

Optical properties of Pna2₁-Ba₃Mg₃(BO₃)₃F₃. a Powder second-harmonic generation data for Ba₃Mg₃(BO₃)₃F₃ polymorphs at 1064 nm laser radiation. The well-known NLO material KH₂PO₄ (KDP) was used as the reference. The curves are drawn to guide the eyes, and are not fit to the data. The error bars from left to right correspond to sieved crystal particle size ranges: 20–38; 38–55; 55–88; 88–105; 105–150; 150–200; and 200–250 μm. b Transmission spectrum of Pna2₁-Ba₃Mg₃(BO₃)₃F₃ crystal. Transmittance curve (magenta line) between 180 and 2500 nm was collected by a Shimadzu Solid Spec-3700DUV Spectrophotometer. Transmittance curve (black line) between 2500 and 4000 nm was collected by a Shimadzu IRAffinity-1 spectrometer. Inset gives transmittance curves between 170 and 400 nm for Pna2₁-Ba₃Mg₃(BO₃)₃F₃ (red line) and β-BaB₂O₄ (blue line). The ultraviolet cutoff edge of Pna2₁-Ba₃Mg₃(BO₃)₃F₃ is about 184 nm, which is 5 nm shorter than that of β-BBO (189 nm). c The refractive index dispersion curves for the Pna2₁-Ba₃Mg₃(BO₃)₃F₃ crystal. d The refractive index dispersion curves for fundamental (blue lines) and the second-harmonic (red lines) light. Based on the Sellmeier equations, when considering the type I phase-matching condition, n(ω) = n(2ω), the shortest type I phase-matching wavelengths in the xz and xy plane are evaluated to be 310 and 322 nm