title: Coherent perfect absorbers: time-reversed lasers.
abstract: We show that an arbitrary body or aggregate can be made perfectly absorbing at discrete frequencies if a precise amount of dissipation is added under specific conditions of coherent monochromatic illumination. This effect arises from the interaction of optical absorption and wave interference and corresponds to moving a zero of the elastic S matrix onto the real wave vector axis. It is thus the time-reversed process of lasing at threshold. The effect is demonstrated in a simple Si slab geometry illuminated in the 500-900 nm range. Coherent perfect absorbers act as linear, absorptive interferometers, which may be useful as detectors, transducers, and switches.
authors.affiliation: Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA. yidong.chong@yale.edu
authors.forename: Y D
authors.initials: YD
authors.lastname: Chong
authors.forename: Li
authors.initials: L
authors.lastname: Ge
authors.forename: Hui
authors.initials: H
authors.lastname: Cao
authors.forename: A D
authors.initials: AD
authors.lastname: Stone