H-TF3L by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.3561\,\lambda^2}{\lambda^2 - 0.0082337} + \frac{0.192048\,\lambda^2}{\lambda^2 - 0.0410079} + \frac{1.32584\,\lambda^2}{\lambda^2 - 111.799}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[4.34 \times 10^{-6} + 2(1.58 \times 10^{-8})\,\Delta T + 3(-2.17 \times 10^{-11})\,\Delta T^2 + \frac{6.07 \times 10^{-7} + 2(6.66 \times 10^{-10})\,\Delta T}{\lambda - 0.227}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$