S-LAL54Q by Ohara

$$n(\lambda) = \sqrt{1 + \frac{0.920085\,\lambda^2}{\lambda^2 - 0.016083} + \frac{0.758646\,\lambda^2}{\lambda^2 - 0.00292059} + \frac{1.07073\,\lambda^2}{\lambda^2 - 85.1211}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[8.26 \times 10^{-6} + 2(1.35 \times 10^{-8})\,\Delta T + 3(1.67 \times 10^{-11})\,\Delta T^2 + \frac{4.28 \times 10^{-7} + 2(4.05 \times 10^{-10})\,\Delta T}{\lambda - 0.205}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$