N-BK7 by Schott

$$n(\lambda) = \sqrt{1 + \frac{1.03961\,\lambda^2}{\lambda^2 - 0.0060007} + \frac{0.231792\,\lambda^2}{\lambda^2 - 0.0200179} + \frac{1.01047\,\lambda^2}{\lambda^2 - 103.561}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[1.86 \times 10^{-6} + 2(1.31 \times 10^{-8})\,\Delta T + 3(-1.37 \times 10^{-11})\,\Delta T^2 + \frac{4.34 \times 10^{-7} + 2(6.27 \times 10^{-10})\,\Delta T}{\lambda - 0.17}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$