H-ZK9B by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.874919\,\lambda^2}{\lambda^2 - 0.00373965} + \frac{0.709627\,\lambda^2}{\lambda^2 - 0.0163972} + \frac{1.09454\,\lambda^2}{\lambda^2 - 100.204}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-9.86 \times 10^{-7} + 2(1.83 \times 10^{-8})\,\Delta T + 3(-3.36 \times 10^{-11})\,\Delta T^2 + \frac{3.65 \times 10^{-7} + 2(9.55 \times 10^{-11})\,\Delta T}{\lambda - 0.222}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$