H-ZK11 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.0534615\,\lambda^2}{\lambda^2 - 0.045643} + \frac{1.58378\,\lambda^2}{\lambda^2 - 0.0091226} + \frac{0.918196\,\lambda^2}{\lambda^2 - 89.3234}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-1.64 \times 10^{-6} + 2(1.58 \times 10^{-8})\,\Delta T + 3(-3.17 \times 10^{-11})\,\Delta T^2 + \frac{4.74 \times 10^{-7} + 2(3.85 \times 10^{-10})\,\Delta T}{\lambda - 0.203}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$