Phase grating modulator

A new type of optical modulator is reported in which a phase grating is use d to diffract a beam of light. Piezoelectric elements modulate the phase sh ift between adjacent portions of the grating, and hence control the diffrac tion efficiency. Efficiencies of up to about 17% have been observed, compar ed to the theoretical maximum of about 40% for diffraction into a single or der by a pure square wave phase grating. (C) 1999 American Institute of Phy sics. [S0034-6748(99)03501-7].