Large optical tunability from charge density waves in 1T-TaS2 under incoherent illumination

The next-generation technology poised to revolutionize our society is 3D displays, and tunable nanophotonics is the key. Tunability in optical devices has been achieved in the past by many techniques including electrical doping, chemical doping, mechanical actuation, and optical nonlinearity. However, they all present either fast and small or slow and large tuning response. An unconventional material that can exhibit a large tuning with MHz response is 1T-tantalum disulfide. We observed unity order refractive index change in the visible at room temperature with an in-plane DC bias, AC bias, and moderately intense white light illumination (2.5 Suns). The strong correlations in this material give rise to charge ordering even at room temperatures and result in the large tunability. Using this new optical material, we demonstrate tunable meta-devices operating in the visible.