Comment on "Rotary Photon Drag Enhanced by a Slow-Light Medium [1]"

The observations reported by Franke-Arnold et al (SCIENCE Reports, 1 July 2011 p. 65) do not provide evidence of slow light enhanced rotary photon drag as claimed, but arise from well-known saturable absorption phenomena consistent with the use of a spectrally broad light source, as described in their theoretical analysis (supporting online material)