S-LAH92 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{2.1044\,\lambda^2}{\lambda^2 - 0.0108532} + \frac{0.358346\,\lambda^2}{\lambda^2 - 0.0443406} + \frac{1.6301\,\lambda^2}{\lambda^2 - 123.25}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.15 \times 10^{-6} + 2(9.26 \times 10^{-9})\,\Delta T + 3(8.39 \times 10^{-14})\,\Delta T^2 + \frac{8.47 \times 10^{-7} + 2(8.87 \times 10^{-10})\,\Delta T}{\lambda - 0.242}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$