Probing the Heavy Quark Content of the Photon Using b Tagging at   Electron Photon Colliders
  We study the prospects for probing the quark content of the photon using b tagging at high energy electron-photon colliders. We find that heavy quark tagging provides a sensitive and effective probe of the quark content of the photon. Using a 500 GeV $e^+e^-$\ NLC in electron-photon mode, the cross section for $eb_{\gamma}\rightarrow eb$\ can be measured to 10\% with b tagging. This is sufficient to differentiate between the various photon structure functions. 
K. Andrew Peterson, M. A. Doncheski and Stephen Godfrey