S-LAM61 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.73883\,\lambda^2}{\lambda^2 - 0.00980244} + \frac{0.150937\,\lambda^2}{\lambda^2 - 0.043318} + \frac{1.12118\,\lambda^2}{\lambda^2 - 101.215}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.38 \times 10^{-6} + 2(1.36 \times 10^{-8})\,\Delta T + 3(-3.69 \times 10^{-11})\,\Delta T^2 + \frac{6.21 \times 10^{-7} + 2(6.44 \times 10^{-10})\,\Delta T}{\lambda - 0.235}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$