D-LAK5-25 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.602364\,\lambda^2}{\lambda^2 - 3.075 \times 10^{-8}} + \frac{1.15823\,\lambda^2}{\lambda^2 - 0.0158379} + \frac{1.30267\,\lambda^2}{\lambda^2 - 101.976}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[1.76 \times 10^{-6} + 2(1.72 \times 10^{-8})\,\Delta T + 3(-6.77 \times 10^{-11})\,\Delta T^2 + \frac{3.92 \times 10^{-7} + 2(6.44 \times 10^{-10})\,\Delta T}{\lambda - 0.23}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$