S-YGH51 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.0828\,\lambda^2}{\lambda^2 - 0.0181156} + \frac{0.933989\,\lambda^2}{\lambda^2 - 0.00304158} + \frac{1.32367\,\lambda^2}{\lambda^2 - 91.0353}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.1 \times 10^{-6} + 2(1.13 \times 10^{-8})\,\Delta T + 3(-4.13 \times 10^{-12})\,\Delta T^2 + \frac{5.17 \times 10^{-7} + 2(5.47 \times 10^{-10})\,\Delta T}{\lambda - 0.191}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$