  Double photo-electron momentum spectra of the Helium atom are calculated
\textit{ab initio} at extreme ultra-violet and near infrared wavelengths. At
short wavelengths two-photon double ionization yields, two-electron energy
spectra, and triply differential cross sections agree with results from recent
literature. At the near infrared wavelength of $780\,nm$ the experimental
single-to-double ionization ratio is reproduced up to intensities of $4\times
10^{14}W/cm^2$, and two-electron energy spectra and joint angular distributions
are presented. The time-dependent surface flux (tSurff) approach is extended to
full 3+3 spatial dimensions and systematic error control is demonstrated. We
analyze our differential spectra in terms of an experimentally accessible
quantitative measure of correlation.
