Aperiodic computer-generated volume holograms improve the performance of amplitude volume gratings

We study the performance of amplitude computer-generated volume holograms (CGVH) in terms of efficiency and angular/frequency selectivity. We compare CGVHs to interferometrically-recorded amplitude volume holograms. Theoretical results show that amplitude CGVHs can increase the efficiency as well as the angular and wavelength selectivity relative to optically recorded amplitude volume holograms. We fabricate the CGVHs using femtosecond laser pulse micromachining in the bulk of glass and demonstrate results consistent with the theory. These results show that aperiodic three-dimensional structures provide the degrees of freedom necessary to improve the performance of volume diffractive optics. They suggest that, under certain circumstances, a departure from the Bragg paradigm provides enhanced volume diffraction properties.