H-LAK4L by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.402313\,\lambda^2}{\lambda^2 - -0.00267679} + \frac{1.24575\,\lambda^2}{\lambda^2 - 0.0131716} + \frac{1.28904\,\lambda^2}{\lambda^2 - 93.3655}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[5.4 \times 10^{-7} + 2(1.54 \times 10^{-8})\,\Delta T + 3(-2.02 \times 10^{-11})\,\Delta T^2 + \frac{4.56 \times 10^{-7} + 2(2.91 \times 10^{-10})\,\Delta T}{\lambda - 0.15}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$