S-LAM55 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.85413\,\lambda^2}{\lambda^2 - 0.0108438} + \frac{0.16545\,\lambda^2}{\lambda^2 - 0.0514051} + \frac{1.27255\,\lambda^2}{\lambda^2 - 109.987}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[1.27 \times 10^{-6} + 2(1.14 \times 10^{-8})\,\Delta T + 3(-3.64 \times 10^{-11})\,\Delta T^2 + \frac{6.01 \times 10^{-7} + 2(7.23 \times 10^{-10})\,\Delta T}{\lambda - 0.278}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$