S-BAH10 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.59034\,\lambda^2}{\lambda^2 - 0.00932734} + \frac{0.138465\,\lambda^2}{\lambda^2 - 0.0427499} + \frac{1.21988\,\lambda^2}{\lambda^2 - 119.252}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.39 \times 10^{-6} + 2(1.19 \times 10^{-8})\,\Delta T + 3(-3.43 \times 10^{-11})\,\Delta T^2 + \frac{5.18 \times 10^{-7} + 2(5.64 \times 10^{-10})\,\Delta T}{\lambda - 0.261}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$