Thin wide range varifocal diffractive Alvarez lenses actuated by dielectric elastomers

We design a thin wide range of varifocal diffractive Alvarez lenses actuated by dielectric elastomers (DEs). The diffractive Alvarez lenses are manufactured by the laser direct writing technique with four etching depths. The diffractive Alvarez lenses consist of two diffractive phase plates, which can move laterally by applying an actuation voltage to the DEs, and then the focal length of the diffractive Alvarez lenses changes. The thickness and the optical aperture of the proposed diffractive Alvarez lenses are 4 mm and 10 mm, respectively. The focal length ratio is up to 10×, where the maximum the minimum focal lengths are 300 mm and 30 mm, respectively. The rise time and fall time are 134 ms and 206 ms. The average diffraction efficiency is 82 % at 532 nm. Such a thin wide range of varifocal diffractive Alvarez lenses promises a potential solution for many applications, such as endoscopes, consumer electronics, and microscopies.