H-ZBAF21 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.71447\,\lambda^2}{\lambda^2 - 0.0106695} + \frac{0.17292\,\lambda^2}{\lambda^2 - 0.0536257} + \frac{1.37587\,\lambda^2}{\lambda^2 - 127.688}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[1.42 \times 10^{-6} + 2(1.45 \times 10^{-8})\,\Delta T + 3(-2.3 \times 10^{-11})\,\Delta T^2 + \frac{7.19 \times 10^{-7} + 2(8.37 \times 10^{-10})\,\Delta T}{\lambda - 0.256}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$