S-LAM66 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.92094\,\lambda^2}{\lambda^2 - 0.0115075} + \frac{0.219901\,\lambda^2}{\lambda^2 - 0.0547994} + \frac{1.72705\,\lambda^2}{\lambda^2 - 120.134}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.83 \times 10^{-7} + 2(9.65 \times 10^{-9})\,\Delta T + 3(-2.68 \times 10^{-11})\,\Delta T^2 + \frac{7.96 \times 10^{-7} + 2(1 \times 10^{-9})\,\Delta T}{\lambda - 0.263}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$