H-LAK53A by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.21007\,\lambda^2}{\lambda^2 - 0.0052168} + \frac{1.19496\,\lambda^2}{\lambda^2 - 83.5558} + \frac{0.806533\,\lambda^2}{\lambda^2 - 0.0200804}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[1.86 \times 10^{-6} + 2(1.36 \times 10^{-8})\,\Delta T + 3(-2.33 \times 10^{-11})\,\Delta T^2 + \frac{5.16 \times 10^{-7} + 2(5.98 \times 10^{-10})\,\Delta T}{\lambda - 0.185}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$