S-LAM73 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.86353\,\lambda^2}{\lambda^2 - 0.0107621} + \frac{0.255216\,\lambda^2}{\lambda^2 - 0.0487249} + \frac{1.23399\,\lambda^2}{\lambda^2 - 117.125}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-6.89 \times 10^{-6} + 2(7.66 \times 10^{-9})\,\Delta T + 3(-9.97 \times 10^{-12})\,\Delta T^2 + \frac{8.33 \times 10^{-7} + 2(8.98 \times 10^{-10})\,\Delta T}{\lambda - 0.247}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$