LAF45 by Hoya

$$n(\lambda) = \sqrt{2.55074 - 0.0128067\,\lambda^2 + 0.0187449\,\lambda^{-2} + 0.000507964\,\lambda^{-4} - 7.28661 \times 10^{-6}\,\lambda^{-6} + 2.19113 \times 10^{-6}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.16 \times 10^{-6} + 2(1.24 \times 10^{-8})\,\Delta T + 3(-3.34 \times 10^{-11})\,\Delta T^2 + \frac{6.09 \times 10^{-7} + 2(4.61 \times 10^{-10})\,\Delta T}{\lambda - 0.205}\right] \Delta T = T - T_0, \quad T_0 = 23\,°\text{C}$$