PCD40 by Hoya

$$n(\lambda) = \sqrt{2.58445 - 0.00905219\,\lambda^2 + 0.014302\,\lambda^{-2} + 0.000170508\,\lambda^{-4} + 4.96454 \times 10^{-6}\,\lambda^{-6} - 1.29275 \times 10^{-7}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-1.08 \times 10^{-5} + 2(2.42 \times 10^{-9})\,\Delta T + 3(1.57 \times 10^{-11})\,\Delta T^2 + \frac{7.21 \times 10^{-7} + 2(4.29 \times 10^{-10})\,\Delta T}{\lambda - 1.46 \times 10^{-9}}\right] \Delta T = T - T_0, \quad T_0 = 23\,°\text{C}$$