L-LAL12 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.28516\,\lambda^2}{\lambda^2 - 0.00641062} + \frac{0.478334\,\lambda^2}{\lambda^2 - 0.0214815} + \frac{1.21605\,\lambda^2}{\lambda^2 - 100.243}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.27 \times 10^{-7} + 2(8.14 \times 10^{-9})\,\Delta T + 3(-3.58 \times 10^{-11})\,\Delta T^2 + \frac{5.41 \times 10^{-7} + 2(7.88 \times 10^{-10})\,\Delta T}{\lambda - 0.181}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$