H-QF3 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.31974\,\lambda^2}{\lambda^2 - 0.00962234} + \frac{0.106724\,\lambda^2}{\lambda^2 - 0.053425} + \frac{1.1224\,\lambda^2}{\lambda^2 - 121.815}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-1.78 \times 10^{-6} + 2(1.49 \times 10^{-8})\,\Delta T + 3(-4.97 \times 10^{-11})\,\Delta T^2 + \frac{7.15 \times 10^{-7} + 2(4.63 \times 10^{-10})\,\Delta T}{\lambda - 0.244}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$