We disclose acousto-optic modulators that include: (a) an optical element configured to receive an input optical beam that propagates along a first direction; and (b) a transducer extending along the first direction and positioned on one or more surfaces of the optical element, the transducer having a transducer material positioned between two electrodes configured to apply a potential difference across the transducer to cause the transducer to generate an acoustic waveform propagating in a second direction in the optical element, and the input optical beam undergoing diffraction in a region of the optical element that includes the acoustic waveform. The transducer extends along a third direction orthogonal to the first and second directions, and at least one of the transducer material and the electrodes has a maximum length L along the third direction and is shaped so that the acoustic waveform has a reduced phase variation within a central region of length L of the waveform in the third direction, relative to a phase variation within a central region of length L in the third direction of an acoustic waveform generated by a rectangular transducer.