Acousto-optic control and modulation of optical coherence by electronically synthesized holographic gratings

We introduce a new technique to modify the coherence properties and the far-field intensity distributions of optical fields. Use is made of a combination of Bragg diffraction and Raman–Nath diffraction in an acousto-optic deflector. The high-frequency Bragg grating in the deflector is phase modulated by a synthetic low-frequency Raman–Nath regime grating that has a structure of an optimized phase-only computer-generated hologram. We demonstrate, e.g., electronic control of the state of spatial coherence of light, Gaussian to flat-top conversion, and the generation of arrays of equally intense but mutually incoherent light spots.