S-LAL18 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.50276\,\lambda^2}{\lambda^2 - 0.0145462} + \frac{0.430224\,\lambda^2}{\lambda^2 - -0.00332784} + \frac{1.34726\,\lambda^2}{\lambda^2 - 93.3508}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.66 \times 10^{-6} + 2(1.08 \times 10^{-8})\,\Delta T + 3(-1.81 \times 10^{-11})\,\Delta T^2 + \frac{4.54 \times 10^{-7} + 2(4.93 \times 10^{-10})\,\Delta T}{\lambda - 0.202}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$