Study of angular responses of mixed amplitude-phase holographic gratings: shifted Borrmann effect

We present theoretical results for angular responses of transmitted and dif fracted beams in mixed amplitude-phase holographic gratings. Experimental r esults for gratings recorded in photographic emulsions and developed withou t a bleaching bath, with diffraction efficiencies of >20%, are also present ed. The model shows an angular shift between minimum transmittance and maxi mum diffraction efficiency when both index modulation and absorption coeffi cient modulation are present. Also, the Borrmann effect was found outside t he Bragg angle. This method can be extended to a study of the mechanism of image formation in materials such as bacteriorhodopsin and azo-dye-doped po lymers that exhibit both types of modulations (index and absorption). (C) 2 001 Optical Society of America.