Top-Seeded Solution Crystal Growth and Linear and Nonlinear Optical Properties of Ba₄B₁₁O₂₀F

A single crystal of Ba₄B₁₁O₂₀F (BBOF) with dimensions of 20 × 17 × 12 mm³ was successfully grown using the top-seeded solution growth method. BBOF melts incongruently; as such several flux systems are discussed. The morphologies and growth habits of BBOF crystals grown with differently oriented seeds, [100], [010], and [001], were investigated. Using the [010]-oriented seed, the single crystal exhibits (200) and (010) faces. Rocking curve measurements indicate that the single crystal is of high quality with a full width at half-maximum (fwhm) of 0.017° (61 arcsec) from the (010) reflection. The transmission spectrum and the refractive indices from the UV to the near-infrared region are reported. BBOF is transparent from 190-2500 nm and exhibits a birefringence of 0.0146 at 1064 nm. The type-I phase matching wavelength region was determined based on the fitted Sellmeier equations to the refractive index data. BBOF is type-I phase-matchable with fundamental (second-harmonic) wavelength ranges from 1049-2348 nm (524.5-1174 nm). In addition, the nonlinear optical coefficients for BBOF were measured using the Maker fringe method. For BBOF at 1064 nm, d₃₁ = 1.57 pm/V, d₃₂ = 0.27 pm/V, and d₃₃ = 0.46 pm/V.