S-LAH65VS by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.76068\,\lambda^2}{\lambda^2 - 0.00853607} + \frac{0.414129\,\lambda^2}{\lambda^2 - 0.0301826} + \frac{1.33415\,\lambda^2}{\lambda^2 - 98.0942}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.45 \times 10^{-6} + 2(9.57 \times 10^{-9})\,\Delta T + 3(-3.91 \times 10^{-13})\,\Delta T^2 + \frac{6.2 \times 10^{-7} + 2(6.32 \times 10^{-10})\,\Delta T}{\lambda - 0.215}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$