S-LAL9 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.16196\,\lambda^2}{\lambda^2 - 0.015966} + \frac{0.64486\,\lambda^2}{\lambda^2 - 0.000505502} + \frac{1.25062\,\lambda^2}{\lambda^2 - 93.8284}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.38 \times 10^{-6} + 2(1.14 \times 10^{-8})\,\Delta T + 3(-3.54 \times 10^{-11})\,\Delta T^2 + \frac{3.51 \times 10^{-7} + 2(3.25 \times 10^{-10})\,\Delta T}{\lambda - 0.264}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$