Abstract

We demonstrate laser beam focusing at 1300 nm with a flat lens with a thickness of less than 100 nm. The lensing exploits large refractive index changes occurring in vanadium dioxide (VO₂) during a phase transition from insulator to metal. The focal length is 35 cm (with much shorter theoretical limits) and is adjustable in real time. Unlike traditional methods used to fabricate flat lenses, this one does not require surface patterning. A theoretical model of the effect will be presented, and the possibilities and limits will be discussed.

© 2014 Optical Society of America