D-ZLAF50-25 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.281078\,\lambda^2}{\lambda^2 - 0.0346761} + \frac{1.19505\,\lambda^2}{\lambda^2 - 91.8386} + \frac{1.88534\,\lambda^2}{\lambda^2 - 0.00975312}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[4.6 \times 10^{-6} + 2(1.8 \times 10^{-8})\,\Delta T + 3(-2.67 \times 10^{-11})\,\Delta T^2 + \frac{7.73 \times 10^{-7} + 2(3.51 \times 10^{-10})\,\Delta T}{\lambda - 0.181}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$