S-TIM35 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.5585\,\lambda^2}{\lambda^2 - 0.0115367} + \frac{0.230767\,\lambda^2}{\lambda^2 - 0.0586096} + \frac{1.84436\,\lambda^2}{\lambda^2 - 162.982}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[4.7 \times 10^{-7} + 2(1.25 \times 10^{-8})\,\Delta T + 3(-3.4 \times 10^{-11})\,\Delta T^2 + \frac{8.29 \times 10^{-7} + 2(1.09 \times 10^{-9})\,\Delta T}{\lambda - 0.289}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$