Sellmeier coefficients

Formula (wl is wavelength in micrometers):
n^2 = 1 + K1 wl^2 / (wl^2 - L1) + K2 wl^2 / (wl^2 - L2)

K1 = 1.170244
L1 = 0.008450127
K2 = 109.7225
L2 = 9773.816