S-LAH88 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{2.12844\,\lambda^2}{\lambda^2 - 0.011731} + \frac{0.405082\,\lambda^2}{\lambda^2 - 0.0508707} + \frac{1.67918\,\lambda^2}{\lambda^2 - 107.091}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[4.66 \times 10^{-6} + 2(1.07 \times 10^{-8})\,\Delta T + 3(-2.33 \times 10^{-11})\,\Delta T^2 + \frac{9.1 \times 10^{-7} + 2(1.07 \times 10^{-9})\,\Delta T}{\lambda - 0.262}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$