D-LAK52 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.04648\,\lambda^2}{\lambda^2 - 0.0173537} + \frac{0.889911\,\lambda^2}{\lambda^2 - 0.00298398} + \frac{1.23174\,\lambda^2}{\lambda^2 - 87.11}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[1.8 \times 10^{-6} + 2(1.72 \times 10^{-8})\,\Delta T + 3(-5.24 \times 10^{-11})\,\Delta T^2 + \frac{4.52 \times 10^{-7} + 2(1.37 \times 10^{-10})\,\Delta T}{\lambda - 0.229}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$