H-LAK53B by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.03141\,\lambda^2}{\lambda^2 - 0.00395422} + \frac{0.985282\,\lambda^2}{\lambda^2 - 0.0186863} + \frac{1.17066\,\lambda^2}{\lambda^2 - 81.1327}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[1.22 \times 10^{-6} + 2(1.66 \times 10^{-8})\,\Delta T + 3(-2.94 \times 10^{-11})\,\Delta T^2 + \frac{5.17 \times 10^{-7} + 2(4.19 \times 10^{-10})\,\Delta T}{\lambda - 0.196}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$