Broadband Achromatic Anomalous Mirror in Near-IR and Visible Frequency Ranges
journal contributionposted on 12.06.2017, 00:00 by Andrei Nemilentsau, Tony Low
An anomalous achromatic mirror operating in the near-IR and visible frequency ranges was designed using an array of metal–insulator–metal (MIM) resonators. An incident wave interacting with the MIM resonator experiences phase shift that is equal to the optical path traveled by the gap plasmon excited by the wave. A phase gradient along the mirror surface is created through the difference in plasmon optical paths in the resonators of varying lengths. In a frequency region well below the plasma frequency of metal, the phase gradient is a linear function of frequency, and thus the mirror operates in the achromatic regime; that is, the reflection angle does not depend on the radiation frequency. Using silver–air–silver resonators, we predicted that the mirror can steer a normally incident beam to angles as large as 40° with high radiation efficiency (exceeding 98%) and small Joule losses (below 10%). Our study indicates that it is feasible to create an efficient broadband anomalous mirror.