L-LAL15 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.0796\,\lambda^2}{\lambda^2 - 0.00470048} + \frac{0.731872\,\lambda^2}{\lambda^2 - 0.0198616} + \frac{1.17111\,\lambda^2}{\lambda^2 - 87.036}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[9.24 \times 10^{-6} + 2(1.32 \times 10^{-8})\,\Delta T + 3(-3.57 \times 10^{-11})\,\Delta T^2 + \frac{5.77 \times 10^{-7} + 2(5.66 \times 10^{-10})\,\Delta T}{\lambda - 0.206}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$