D-LAK70-25 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.615747\,\lambda^2}{\lambda^2 - 0.000310602} + \frac{1.11671\,\lambda^2}{\lambda^2 - 0.0158114} + \frac{1.29437\,\lambda^2}{\lambda^2 - 102.15}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.1 \times 10^{-6} + 2(1.31 \times 10^{-8})\,\Delta T + 3(-3.75 \times 10^{-11})\,\Delta T^2 + \frac{5.42 \times 10^{-7} + 2(6.96 \times 10^{-10})\,\Delta T}{\lambda - 0.177}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$