Updated Sellmeier equations of β-BaB2O4

We present updated Sellmeier equations for β-BaB₂O₄ based on measurements of the phase-matching angles for second-harmonic (SHG) and sum-frequency generation (SFG) of a Nd:YAG laser-pumped 90° phase-matched RbTiOAsO₄ optical parametric oscillator (OPO) and a Nd:YAG laser in the 0.6407 - 3.1392 μm range. The phase-matching angles predicted by this index formula agree well with the recently published data points of SFG between a Ti:Al₂O₃ laser and Nd:YAG laser-pumped KTiOAsO₄ OPO in the 0.40 -5.3 μm range {G. Tamosauskas et al., Opt. Mater. Express 8, 1410 (2018)] as wellas those for SFG below 0.2048 μm thus far reported in the literature.