H-ZBAF4 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.151467\,\lambda^2}{\lambda^2 - 0.0571831} + \frac{1.5402\,\lambda^2}{\lambda^2 - 0.0111587} + \frac{1.18737\,\lambda^2}{\lambda^2 - 120.129}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-5.11 \times 10^{-7} + 2(1.36 \times 10^{-8})\,\Delta T + 3(-2.61 \times 10^{-11})\,\Delta T^2 + \frac{8.17 \times 10^{-7} + 2(8.22 \times 10^{-10})\,\Delta T}{\lambda - 0.257}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$