S-LAH63 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.89458\,\lambda^2}{\lambda^2 - 0.0102277} + \frac{0.268703\,\lambda^2}{\lambda^2 - 0.0442801} + \frac{1.45706\,\lambda^2}{\lambda^2 - 104.875}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[6.2 \times 10^{-6} + 2(1.43 \times 10^{-8})\,\Delta T + 3(-3.96 \times 10^{-12})\,\Delta T^2 + \frac{8.21 \times 10^{-7} + 2(7.44 \times 10^{-10})\,\Delta T}{\lambda - 0.216}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$