H-ZBAF20 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.155463\,\lambda^2}{\lambda^2 - 0.0500497} + \frac{1.22205\,\lambda^2}{\lambda^2 - 119.802} + \frac{1.66612\,\lambda^2}{\lambda^2 - 0.0102206}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.21 \times 10^{-6} + 2(1.68 \times 10^{-8})\,\Delta T + 3(-1.66 \times 10^{-11})\,\Delta T^2 + \frac{8.01 \times 10^{-7} + 2(3.97 \times 10^{-10})\,\Delta T}{\lambda - 0.22}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$