S-LAL61 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.11073\,\lambda^2}{\lambda^2 - 0.00464181} + \frac{0.859348\,\lambda^2}{\lambda^2 - 0.0192989} + \frac{1.26707\,\lambda^2}{\lambda^2 - 87.3918}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.12 \times 10^{-6} + 2(1.34 \times 10^{-8})\,\Delta T + 3(-3.54 \times 10^{-11})\,\Delta T^2 + \frac{4.23 \times 10^{-7} + 2(4.31 \times 10^{-10})\,\Delta T}{\lambda - 0.226}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$