Conical diffraction from a multi-crystal cascade: experimental observations

The cascade conical diffraction phenomenon from up to four crystals is experimentally demonstrated. Less than one year ago M.V. Berry predicted that the focus pattern of conical diffraction from an N-crystal cascade is the superposition of 2 (N-1) single-crystal concentric conical diffraction patterns (rings), whose ring radii are a combination of those from the individual crystals in cascade. The experimental observations presented here are in full agreement with these theoretical predictions.