A description is given of a microlens array design, believed to be new, with tunable focal length. Converging or diverging periodic refractive-index distribution is induced in a linear electro-optic wafer through the application of electric field profiles on both sides of the wafer. The transparent electrodes on both sides of the wafer are positioned such that the electrodes on the opposite side compensate the phase delay from the electrodes on the front side of the wafer for a normally incident plane wave, suppressing the intrinsic electrode diffraction for the device without applied voltage. The original technique of the electric field calculation was developed to analyze accurately the induced refractive index inside the wafer. Its focal length changes from 7 mm to infinity at a 1-μm wavelength with an external voltage range of 0-100 V.
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