Coherent perfect absorber
Encyclopedia
A Coherent perfect absorber (CPA), or anti-laser, is a device which absorbs coherent light and converts it to some form of internal energy such as heat or electrical energy. It is the time reversed counterpart of a laser
. The concept was first published in the July 26, 2010, issue of Physical Review Letters
, by a team at Yale University
led by theorist W. J. Page. In the September 9, 2010, issue of Physical Review A
, Stefano Longhi of Politecnico di Milano showed how to combine a laser and an anti-laser in a single device. In February 2011 the team at Yale built the first working anti-laser. It is a two-channel CPA device which absorbs the output of two lasers, but only when the beams have the correct phases and amplitudes. The initial device was able to absorb 99.4 percent of all incoming light, but the team behind the invention believe it will be possible to increase this number to 99.999 percent.
wafer, a light-absorbing material that acts as a "loss medium." The wafer aligns the light waves from the lasers so they become trapped, causing most of the photon
s to bounce back and forth until they are absorbed and transformed into heat. Furthermore, many of the remaining light waves are cancelled out by interfering with each other. In contrast a normal laser uses a gain medium
which amplifies light instead of absorbing it.
detectors, transducers, and optical switches. 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.
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
. The concept was first published in the July 26, 2010, issue of Physical Review Letters
Physical Review Letters
Physical Review Letters , established in 1958, is a peer reviewed, scientific journal that is published 52 times per year by the American Physical Society...
, by a team at Yale University
Yale University
Yale University is a private, Ivy League university located in New Haven, Connecticut, United States. Founded in 1701 in the Colony of Connecticut, the university is the third-oldest institution of higher education in the United States...
led by theorist W. J. Page. In the September 9, 2010, issue of Physical Review A
Physical Review A
Physical Review A: Atomic, Molecular and Optical Physics is a peer-reviewed scientific journal that is published twelve times per year by the American Physical Society in print, online, and CD formats. The main focus of interest is atomic, molecular and optical physics. The editor-in-chief is...
, Stefano Longhi of Politecnico di Milano showed how to combine a laser and an anti-laser in a single device. In February 2011 the team at Yale built the first working anti-laser. It is a two-channel CPA device which absorbs the output of two lasers, but only when the beams have the correct phases and amplitudes. The initial device was able to absorb 99.4 percent of all incoming light, but the team behind the invention believe it will be possible to increase this number to 99.999 percent.
Design
Identical lasers are fired into a cavity containing a siliconSilicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
wafer, a light-absorbing material that acts as a "loss medium." The wafer aligns the light waves from the lasers so they become trapped, causing most of the photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s to bounce back and forth until they are absorbed and transformed into heat. Furthermore, many of the remaining light waves are cancelled out by interfering with each other. In contrast a normal laser uses a gain medium
Active laser medium
The active laser medium is the source of optical gain within a laser. The gain results from the stimulated emission of electronic or molecular transitions to a lower energy state from a higher energy state...
which amplifies light instead of absorbing it.
Applications
Coherent perfect absorbers can be used to build absorptive interferometers, which could be used indetectors, transducers, and optical switches. 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.