title: Electrically Tunable Epsilon-Near-Zero (ENZ) Metafilm Absorbers.
abstract: Enhancing and spectrally controlling light absorption is of great practical and fundamental importance. In optoelectronic devices consisting of layered semiconductors and metals, absorption has traditionally been manipulated with the help of Fabry-Pérot resonances. Even further control over the spectral light absorption properties of thin films has been achieved by patterning them into dense arrays of subwavelength resonant structures to form metafilms. As the next logical step, we demonstrate electrical control over light absorption in metafilms constructed from dense arrays of actively tunable plasmonic cavities. This control is achieved by embedding indium tin oxide (ITO) into these cavities. ITO affords significant tuning of its optical properties by means of electrically-induced carrier depletion and accumulation. We demonstrate that particularly large changes in the reflectance from such metafilms (up to 15% P) can be achieved by operating the ITO in the epsilon-near-zero (ENZ) frequency regime where its electrical permittivity changes sign from negative to positive values.
authors.affiliation: Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States.
authors.forename: Junghyun
authors.initials: J
authors.lastname: Park
authors.affiliation: Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States.
authors.forename: Ju-Hyung
authors.initials: JH
authors.lastname: Kang
authors.affiliation: Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States.
authors.forename: Xiaoge
authors.initials: X
authors.lastname: Liu
authors.affiliation: Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Brongersma