H-LAF52 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.225894\,\lambda^2}{\lambda^2 - 0.0391552} + \frac{1.88248\,\lambda^2}{\lambda^2 - 0.0100952} + \frac{1.11307\,\lambda^2}{\lambda^2 - 85.0043}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[7.32 \times 10^{-6} + 2(1.67 \times 10^{-8})\,\Delta T + 3(-2.76 \times 10^{-11})\,\Delta T^2 + \frac{7.23 \times 10^{-7} + 2(7.76 \times 10^{-10})\,\Delta T}{\lambda - 0.219}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$