H-LAF55 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.7392\,\lambda^2}{\lambda^2 - 0.00974401} + \frac{1.16163\,\lambda^2}{\lambda^2 - 111.118} + \frac{0.279488\,\lambda^2}{\lambda^2 - 0.0423325}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-2.76 \times 10^{-6} + 2(1.53 \times 10^{-8})\,\Delta T + 3(-4.05 \times 10^{-11})\,\Delta T^2 + \frac{7.53 \times 10^{-7} + 2(5.1 \times 10^{-10})\,\Delta T}{\lambda - 0.241}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$