H-LAK50A by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.759438\,\lambda^2}{\lambda^2 - 0.00223197} + \frac{1.16057\,\lambda^2}{\lambda^2 - 91.0466} + \frac{0.923361\,\lambda^2}{\lambda^2 - 0.0158591}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[5.6 \times 10^{-7} + 2(1.06 \times 10^{-8})\,\Delta T + 3(-4.91 \times 10^{-11})\,\Delta T^2 + \frac{3.57 \times 10^{-7} + 2(6.22 \times 10^{-10})\,\Delta T}{\lambda - 0.245}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$