S-LAM3 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.64259\,\lambda^2}{\lambda^2 - 0.00868246} + \frac{0.239635\,\lambda^2}{\lambda^2 - 0.0351226} + \frac{1.22483\,\lambda^2}{\lambda^2 - 116.604}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-4.66 \times 10^{-6} + 2(9.34 \times 10^{-9})\,\Delta T + 3(-3.89 \times 10^{-11})\,\Delta T^2 + \frac{4.57 \times 10^{-7} + 2(5.81 \times 10^{-10})\,\Delta T}{\lambda - 0.266}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$