H-LAK72 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.746934\,\lambda^2}{\lambda^2 - 0.00172608} + \frac{1.12653\,\lambda^2}{\lambda^2 - 0.0176391} + \frac{1.11423\,\lambda^2}{\lambda^2 - 110.122}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-6.19 \times 10^{-6} + 2(1.16 \times 10^{-8})\,\Delta T + 3(-2.9 \times 10^{-11})\,\Delta T^2 + \frac{4.99 \times 10^{-7} + 2(8.23 \times 10^{-10})\,\Delta T}{\lambda - 0.225}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$