H-QF50 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.29451\,\lambda^2}{\lambda^2 - 0.00894504} + \frac{0.150752\,\lambda^2}{\lambda^2 - 0.0483714} + \frac{1.08698\,\lambda^2}{\lambda^2 - 113.96}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[4.05 \times 10^{-7} + 2(2.23 \times 10^{-9})\,\Delta T + 3(5.39 \times 10^{-11})\,\Delta T^2 + \frac{5.36 \times 10^{-7} + 2(1.83 \times 10^{-9})\,\Delta T}{\lambda - 0.288}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$