H-ZLAF71 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.276155\,\lambda^2}{\lambda^2 - 0.0557996} + \frac{2.02569\,\lambda^2}{\lambda^2 - 0.0120701} + \frac{1.44514\,\lambda^2}{\lambda^2 - 99.8778}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-2.79 \times 10^{-6} + 2(1.48 \times 10^{-8})\,\Delta T + 3(-2.75 \times 10^{-11})\,\Delta T^2 + \frac{8 \times 10^{-7} + 2(8.15 \times 10^{-10})\,\Delta T}{\lambda - 0.275}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$