S-LAL12 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{0.992054\,\lambda^2}{\lambda^2 - 0.0167095} + \frac{0.771378\,\lambda^2}{\lambda^2 - 0.0023675} + \frac{1.18296\,\lambda^2}{\lambda^2 - 105.901}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-2.18 \times 10^{-6} + 2(1.12 \times 10^{-8})\,\Delta T + 3(-3.73 \times 10^{-11})\,\Delta T^2 + \frac{3.25 \times 10^{-7} + 2(4.77 \times 10^{-10})\,\Delta T}{\lambda - 0.27}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$