title: Superabsorbing, Artificial Metal Films Constructed from Semiconductor Nanoantennas.
abstract: In 1934, Wilhelm Woltersdorff demonstrated that the absorption of light in an ultrathin, freestanding film is fundamentally limited to 50%. He concluded that reaching this limit would require a film with a real-valued sheet resistance that is exactly equal to R = η/2 ≈ 188.5Ω/□, where [Formula: see text] is the impedance of free space. This condition can be closely approximated over a wide frequency range in metals that feature a large imaginary relative permittivity εr″, that is, a real-valued conductivity σ = ε0εr″ω. A thin, continuous sheet of semiconductor material does not facilitate such strong absorption as its complex-valued permittivity with both large real and imaginary components preclude effective impedance matching. In this work, we show how a semiconductor metafilm constructed from optically resonant semiconductor nanostructures can be created whose optical response mimics that of a metallic sheet. For this reason, the fundamental absorption limit mentioned above can also be reached with semiconductor materials, opening up new opportunities for the design of ultrathin optoelectronic and light harvesting devices.
authors.affiliation: Geballe Laboratory for Advanced Materials , 476 Lomita Mall, Stanford, California 94305-4045, United States.
authors.forename: Soo Jin
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Geballe Laboratory for Advanced Materials , 476 Lomita Mall, Stanford, California 94305-4045, United States.
authors.forename: Junghyun
authors.initials: J
authors.lastname: Park
authors.affiliation: Geballe Laboratory for Advanced Materials , 476 Lomita Mall, Stanford, California 94305-4045, United States.
authors.forename: Majid
authors.initials: M
authors.lastname: Esfandyarpour
authors.affiliation: Geballe Laboratory for Advanced Materials , 476 Lomita Mall, Stanford, California 94305-4045, United States.
authors.forename: Emanuele F
authors.initials: EF
authors.lastname: Pecora
authors.affiliation: Geballe Laboratory for Advanced Materials , 476 Lomita Mall, Stanford, California 94305-4045, United States.|CREOL, The College of Optics and Photonics, University of Central Florida , 4000 Central Florida Boulevard, Orlando, Florida 32816, United States.
authors.forename: Pieter G
authors.initials: PG
authors.lastname: Kik
authors.affiliation: Geballe Laboratory for Advanced Materials , 476 Lomita Mall, Stanford, California 94305-4045, United States.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Brongersma
keywords: Metafilm; Mie resonance; germanium nanobeam; light absorption; semiconductor nanoantenna