H-LAF4 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.210645\,\lambda^2}{\lambda^2 - 0.0542759} + \frac{1.75547\,\lambda^2}{\lambda^2 - 0.0112371} + \frac{1.28979\,\lambda^2}{\lambda^2 - 119.852}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[6.53 \times 10^{-7} + 2(1.81 \times 10^{-8})\,\Delta T + 3(-1.59 \times 10^{-10})\,\Delta T^2 + \frac{9.02 \times 10^{-7} + 2(8.16 \times 10^{-10})\,\Delta T}{\lambda - 0.246}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$