S-LAH55V by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.97025\,\lambda^2}{\lambda^2 - 0.00991088} + \frac{0.304894\,\lambda^2}{\lambda^2 - 0.0383202} + \frac{1.39215\,\lambda^2}{\lambda^2 - 97.7785}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.24 \times 10^{-6} + 2(9.97 \times 10^{-9})\,\Delta T + 3(-2.68 \times 10^{-12})\,\Delta T^2 + \frac{6.8 \times 10^{-7} + 2(7.1 \times 10^{-10})\,\Delta T}{\lambda - 0.217}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$