Optics for modulating multiple beams using an asymmetric multilevel phase grating and a multichannel acousto-optic modulator

Asymmetric multilevel phase gratings for generating even numbered beams have been designed, assuming that their phase patterns are formed by overlapping plural binary-phase patterns, each of which has an arbitrary phase height. The grating for four beams, which produces uniform and high intense diffraction orders of the minus first to the plus second order, is fabricated. The efficiency is 75.5%, although the theoretical efficiency is 79.9%. It is also demonstrated that the optics in which the beams from the grating are fed into a multichannel acousto-optic modulator through a Fourier-transform lens makes their successful modulation possible for pulse signals of 20-ns pulse duration.