S-LAH63Q by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.96723\,\lambda^2}{\lambda^2 - 0.0110456} + \frac{0.194954\,\lambda^2}{\lambda^2 - 0.0497137} + \frac{1.25386\,\lambda^2}{\lambda^2 - 104.844}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-2.81 \times 10^{-6} + 2(9.15 \times 10^{-9})\,\Delta T + 3(-8.1 \times 10^{-12})\,\Delta T^2 + \frac{7.5 \times 10^{-7} + 2(7.86 \times 10^{-10})\,\Delta T}{\lambda - 0.243}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$