H-ZK6 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.35139\,\lambda^2}{\lambda^2 - 0.00735017} + \frac{0.206957\,\lambda^2}{\lambda^2 - 0.0254398} + \frac{0.961154\,\lambda^2}{\lambda^2 - 99.5133}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[1.08 \times 10^{-7} + 2(1.53 \times 10^{-8})\,\Delta T + 3(-3.29 \times 10^{-11})\,\Delta T^2 + \frac{4.32 \times 10^{-7} + 2(6.25 \times 10^{-10})\,\Delta T}{\lambda - 0.191}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$