H-LAF62 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.68895\,\lambda^2}{\lambda^2 - 0.00969036} + \frac{0.196642\,\lambda^2}{\lambda^2 - 0.0423751} + \frac{1.18909\,\lambda^2}{\lambda^2 - 118.147}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.33 \times 10^{-6} + 2(1.58 \times 10^{-8})\,\Delta T + 3(-3.48 \times 10^{-11})\,\Delta T^2 + \frac{6.21 \times 10^{-7} + 2(5.86 \times 10^{-10})\,\Delta T}{\lambda - 0.262}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$