Polarization-independent electronic varifocal lenses via spatially dual-phase responses

Polarization-independent electrically tunable liquid-crystal (LC) gradient-index spectacles are a major makeover of Benjamin Franklin's most famous invention, bifocal spectacles in 1784. However, response time (∼6 sec) is still a challenge. It motivates us to tackle the challenges of polarization-independent LC GRIN lenses: acceleration of operation and a dilemma between switching speed (response time) and optical phase. In this paper, we demonstrate polarization-independent electronic varifocal lenses via spatially dual-phase response. The mechanism of this lens is based on spatially dual-phase modulation composed of the Kerr phase in the central part and the orientational phase in the rest region. The response time is less than 10 msec as the lens power changes by 1.5 Diopters. In addition, the Kerr phase, proportional to the square of the electric field, is achromatic, but the orientational phase is chromatic. The operating principle is introduced and verified experimentally. The impacts of this study are not only in the application of spectacles but also in machine vision.