S-LAM2 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.7713\,\lambda^2}{\lambda^2 - 0.00976652} + \frac{0.195814\,\lambda^2}{\lambda^2 - 0.0412719} + \frac{1.19488\,\lambda^2}{\lambda^2 - 110.458}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.01 \times 10^{-7} + 2(1.12 \times 10^{-8})\,\Delta T + 3(-3.68 \times 10^{-11})\,\Delta T^2 + \frac{6.07 \times 10^{-7} + 2(6.45 \times 10^{-10})\,\Delta T}{\lambda - 0.245}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$