Coherent perfect absorber

The concept was first published in the July 26, 2010, issue of Physical Review Letters, by a team at Yale University led by theorist A. Douglas Stone and experimental physicist Hui W.

[4][5] In the September 9, 2010, issue of Physical Review A, Stefano Longhi of Polytechnic University of Milan showed how to combine a laser and an anti-laser in a single device.

[15] In the initial design, identical laser beams are fired onto opposite sides of a cavity consisting of a silicon wafer, a light-absorbing material that acts as a "loss medium".

[11] Necessary conditions for coherent perfect absorption include that the film, when illuminated from one side only, will act as a (lossy) beam splitter, transmitting and reflecting equal fractions of the incident power.

[4] Another potential application is in radiology, where the principle of the CPA might be used to precisely target electromagnetic radiation inside human tissues for therapeutic or imaging purposes.

Coherent perfect absorption arises from destructive interference of transmitted and reflected waves, which traps wave energy within an absorber until it is absorbed.
Real (n) and imaginary (k) parts of the refractive index of strongly doped silicon and the corresponding coherent absorption for a film thickness of 150 nm. [ 10 ]
Constructive interference of mutually coherent counterpropagating waves on a thin material enhances the wave-matter interaction, while destructive interference suppresses it.