Photon Acceleration Using a Time-Varying Epsilon-near-Zero Metasurface
Cong Liu, M. Zahirul Alam, Kai Pang, Karapet Manukyan, Orad Reshef, Yiyu Zhou, Saumya Choudhary, Joel G. Patrow, Anuj Pennathur, Hao Song, Zhe Zhao, Runzhou Zhang, Fatemeh Alishahi, Ahmad Fallahpour, Yinwen Cao, Ahmed Almaiman, Jahan M. Dawlaty, Moshe Tur, Robert W. Boyd, Alan E. Willner
Abstract
A light beam’s frequency can blueshift when the beam travels through a medium that exhibits a time-dependent decrease in the refractive index. Here we show that a metasurface made of a plasmonic antenna array on a thin indium tin oxide (ITO), which exhibits epsilon-near-zero (ENZ) response, can behave as a time-varying medium and change the frequency of a sufficiently strong light beam through self-action effect. Specifically, we observe that a near-resonant optical excitation of the 92 nm thick metasurface leads to an intensity-dependent blueshift of the excitation pulse. We measured a maximum blueshift of ∼1.6 THz with ∼4 GW/cm2 incident intensity. The observed effect using an ITO-based ENZ metasurface has an energy requirement that is up to 200× lower than implementations using ITO alone.