Coherent perfect absorber

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A coherent perfect absorber (CPA), or anti-laser, is a device which absorbs coherent waves, such as coherent light waves, and converts them into some form of internal energy, e.g. heat or electrical energy. [1] [2] It is the time-reversed counterpart of a laser. [3] Coherent perfect absorption allows control of waves with waves (light with light) without a nonlinear medium. 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. Cao. [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. [6] In February 2011 the team at Yale built the first working anti-laser. [7] [8] It is a two-channel CPA device which absorbs two beams from the same laser, but only when the beams have the correct phases and amplitudes. [9] The initial device absorbed 99.4 percent of all incoming light, but the team behind the invention believe it will be possible to achieve 99.999 percent. [7] Originally implemented as a Fabry-Pérot cavity that is many wavelengths thick, the optical CPA operates at specific optical frequencies. In January 2012, thin-film CPA has been proposed by utilizing the achromatic dispersion of metal-like materials, exhibiting the unparalleled bandwidth and thin profile advantages. [10] Shortly after, CPA was observed in various thin film materials, including photonic metamaterial, [11] multi-layer graphene, [12] single [13] and multiple [14] layers of chromium, as well as microwave metamaterial. [15]

Contents

Coherent perfect absorption arises from destructive interference of transmitted and reflected waves, which traps wave energy within an absorber until it is absorbed. Coherent Perfect Absorption.png
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. Thin film coherent perfect absorber.png
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.

Anti-laser principle and demonstration

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". While light incident on one side would be partially transmitted and reflected, simultaneous illumination of both sides can result in destructive interference of all transmitted and reflected waves. Such complete suppression of transmission and reflection traps the optical energy within the loss medium until it is fully absorbed. The photons bounce back and forth until they are absorbed and transformed into heat. [9] [7] In contrast, a normal laser uses a gain medium which amplifies light instead of absorbing it.

Constructive interference of mutually coherent counterpropagating waves on a thin material enhances the wave-matter interaction, while destructive interference suppresses it. Coherent Perfect Absorption and Coherent Perfect Transmission.png
Constructive interference of mutually coherent counterpropagating waves on a thin material enhances the wave-matter interaction, while destructive interference suppresses it.

Coherent perfect absorption and transmission in thin films

If the absorbing medium is thin in comparison to the wavelength, then constructive interference of mutually coherent waves incident on opposite sides of the absorber will enhance the level of absorption, while destructive interference will suppress it. For an ideal coherent absorber thin film, absorption can be enhanced to 100% and suppressed down to 0%, where absorption can be tuned between these extremes by adjusting the phase difference between the incident waves. [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. Necessary conditions for coherent perfect transmission include that, for illumination from one side, 25% of the incident power is transmitted and reflected each.

Coherent perfect absorption in thin films is ultrafast, absorption of ~10 femtosecond light pulses has been demonstrated, implying that it can offer around 100 THz bandwidth. [16] The demonstration of CPA of single photons [17] indicates that the effect is compatible with arbitrarily low intensities and has led to opportunities for quantum technologies. [14]

While absorption of electromagnetic waves is usually considered, the concept is also applicable to other waves (such as sound waves [18] ) and other phenomena. Indeed, as constructive and destructive interference of waves on a thin material enhance and suppress the wave-matter interaction, any effect of the medium on the wave may be controlled in this way, including polarization effects associated with chirality and anisotropy, [19] as well as refraction [20] and nonlinear optical phenomena. [21]

Applications

Coherent perfect absorbers can be used to build absorptive interferometers, which could be useful in detectors, transducers, and optical switches. [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. [7]

Integration of thin coherent perfect absorbers in waveguides [22] has led to proof-of-principle demonstrations of fast and low-energy all-optical signal processing and cryptography, [23] while integration of CPA with imaging systems [24] has enabled demonstrations of all-optical focusing, [25] pattern recognition & image processing, [26] and massively parallel all-optical signal processing. In principle, such applications can offer extremely high bandwidth and low energy consumption.

Related Research Articles

<span class="mw-page-title-main">Optical rotation</span> Rotation of the plane of linearly polarized light as it travels through a chiral material

Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circular birefringence and circular dichroism are the manifestations of optical activity. Optical activity occurs only in chiral materials, those lacking microscopic mirror symmetry. Unlike other sources of birefringence which alter a beam's state of polarization, optical activity can be observed in fluids. This can include gases or solutions of chiral molecules such as sugars, molecules with helical secondary structure such as some proteins, and also chiral liquid crystals. It can also be observed in chiral solids such as certain crystals with a rotation between adjacent crystal planes or metamaterials.

<span class="mw-page-title-main">Metamaterial</span> Materials engineered to have properties that have not yet been found in nature

A metamaterial is any material engineered to have a property that is rarely observed in naturally occurring materials. They are made from assemblies of multiple elements fashioned from composite materials such as metals and plastics. These materials are usually arranged in repeating patterns, at scales that are smaller than the wavelengths of the phenomena they influence. Metamaterials derive their properties not from the properties of the base materials, but from their newly designed structures. Their precise shape, geometry, size, orientation and arrangement gives them their smart properties capable of manipulating electromagnetic waves: by blocking, absorbing, enhancing, or bending waves, to achieve benefits that go beyond what is possible with conventional materials.

<span class="mw-page-title-main">Electromagnetically induced transparency</span>

Electromagnetically induced transparency (EIT) is a coherent optical nonlinearity which renders a medium transparent within a narrow spectral range around an absorption line. Extreme dispersion is also created within this transparency "window" which leads to "slow light", described below. It is in essence a quantum interference effect that permits the propagation of light through an otherwise opaque atomic medium.

Planar chirality, also known as 2D chirality, is the special case of chirality for two dimensions.

Negative refraction is the electromagnetic phenomenon where light rays become refracted at an interface that is opposite to their more commonly observed positive refractive properties. Negative refraction can be obtained by using a metamaterial which has been designed to achieve a negative value for (electric) permittivity (ε) and (magnetic) permeability (μ); in such cases the material can be assigned a negative refractive index. Such materials are sometimes called "double negative" materials.

A superlens, or super lens, is a lens which uses metamaterials to go beyond the diffraction limit. The diffraction limit is a feature of conventional lenses and microscopes that limits the fineness of their resolution depending on the illumination wavelength and the numerical aperture (NA) of the objective lens. Many lens designs have been proposed that go beyond the diffraction limit in some way, but constraints and obstacles face each of them.

Slow light is the propagation of an optical pulse or other modulation of an optical carrier at a very low group velocity. Slow light occurs when a propagating pulse is substantially slowed by the interaction with the medium in which the propagation takes place.

A fiber laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, thulium and holmium. They are related to doped fiber amplifiers, which provide light amplification without lasing.

Picosecond ultrasonics is a type of ultrasonics that uses ultra-high frequency ultrasound generated by ultrashort light pulses. It is a non-destructive technique in which picosecond acoustic pulses penetrate into thin films or nanostructures to reveal internal features such as film thickness as well as cracks, delaminations and voids. It can also be used to probe liquids. The technique is also referred to as picosecond laser ultrasonics or laser picosecond acoustics.

<span class="mw-page-title-main">Negative-index metamaterial</span> Material with a negative refractive index

Negative-index metamaterial or negative-index material (NIM) is a metamaterial whose refractive index for an electromagnetic wave has a negative value over some frequency range.

<span class="mw-page-title-main">Photonic metamaterial</span> Type of electromagnetic metamaterial

A photonic metamaterial (PM), also known as an optical metamaterial, is a type of electromagnetic metamaterial, that interacts with light, covering terahertz (THz), infrared (IR) or visible wavelengths. The materials employ a periodic, cellular structure.

<span class="mw-page-title-main">Chiral media</span> Applied to electromagnetism

The term chiral describes an object, especially a molecule, which has or produces a non-superposable mirror image of itself. In chemistry, such a molecule is called an enantiomer or is said to exhibit chirality or enantiomerism. The term "chiral" comes from the Greek word for the human hand, which itself exhibits such non-superimposeability of the left hand precisely over the right. Due to the opposition of the fingers and thumbs, no matter how the two hands are oriented, it is impossible for both hands to exactly coincide. Helices, chiral characteristics (properties), chiral media, order, and symmetry all relate to the concept of left- and right-handedness.

A metamaterial absorber is a type of metamaterial intended to efficiently absorb electromagnetic radiation such as light. Furthermore, metamaterials are an advance in materials science. Hence, those metamaterials that are designed to be absorbers offer benefits over conventional absorbers such as further miniaturization, wider adaptability, and increased effectiveness. Intended applications for the metamaterial absorber include emitters, photodetectors, sensors, spatial light modulators, infrared camouflage, wireless communication, and use in solar photovoltaics and thermophotovoltaics.

A flat lens is a lens whose flat shape allows it to provide distortion-free imaging, potentially with arbitrarily-large apertures. The term is also used to refer to other lenses that provide a negative index of refraction. Flat lenses require a refractive index close to −1 over a broad angular range. In recent years, flat lenses based on metasurfaces were also demonstrated.

A plasmonic metamaterial is a metamaterial that uses surface plasmons to achieve optical properties not seen in nature. Plasmons are produced from the interaction of light with metal-dielectric materials. Under specific conditions, the incident light couples with the surface plasmons to create self-sustaining, propagating electromagnetic waves known as surface plasmon polaritons (SPPs). Once launched, the SPPs ripple along the metal-dielectric interface. Compared with the incident light, the SPPs can be much shorter in wavelength.

<span class="mw-page-title-main">Chirality</span> Difference in shape from a mirror image

Chirality is a property of asymmetry important in several branches of science. The word chirality is derived from the Greek χειρ (kheir), "hand", a familiar chiral object.

<span class="mw-page-title-main">Orbital angular momentum of light</span> Type of angular momentum in light

The orbital angular momentum of light (OAM) is the component of angular momentum of a light beam that is dependent on the field spatial distribution, and not on the polarization. It can be further split into an internal and an external OAM. The internal OAM is an origin-independent angular momentum of a light beam that can be associated with a helical or twisted wavefront. The external OAM is the origin-dependent angular momentum that can be obtained as cross product of the light beam position and its total linear momentum.

Quantum metamaterials extend the science of metamaterials to the quantum level. They can control electromagnetic radiation by applying the rules of quantum mechanics. In the broad sense, a quantum metamaterial is a metamaterial in which certain quantum properties of the medium must be taken into account and whose behaviour is thus described by both Maxwell's equations and the Schrödinger equation. Its behaviour reflects the existence of both EM waves and matter waves. The constituents can be at nanoscopic or microscopic scales, depending on the frequency range .

<span class="mw-page-title-main">Electromagnetic metasurface</span>

An electromagnetic metasurface refers to a kind of artificial sheet material with sub-wavelength thickness. Metasurfaces can be either structured or unstructured with subwavelength-scaled patterns in the horizontal dimensions.

Spoof surface plasmons, also known as spoof surface plasmon polaritons and designer surface plasmons, are surface electromagnetic waves in microwave and terahertz regimes that propagate along planar interfaces with sign-changing permittivities. Spoof surface plasmons are a type of surface plasmon polariton, which ordinarily propagate along metal and dielectric interfaces in infrared and visible frequencies. Since surface plasmon polaritons cannot exist naturally in microwave and terahertz frequencies due to dispersion properties of metals, spoof surface plasmons necessitate the use of artificially-engineered metamaterials.

References

  1. ↑ Gmachl, Claire F. (2010). "Laser science: Suckers for light". Nature. 467 (7311): 37–39. Bibcode:2010Natur.467...37G. doi: 10.1038/467037a . PMID   20811446.
  2. ↑ "Behold, the Antilaser". Science News. Archived from the original on 2012-11-15. Retrieved 2010-09-07.
  3. ↑ Longhi, Stefano (2010). "Backward lasing yields a perfect absorber". Physics. 3: 61. Bibcode:2010PhyOJ...3...61L. doi: 10.1103/Physics.3.61 .
  4. 1 2 Chong, Y.; Ge, Li; Cao, Hui; Stone, A. (2010). "Coherent Perfect Absorbers: Time-Reversed Lasers". Physical Review Letters. 105 (5): 053901. arXiv: 1003.4968 . Bibcode:2010PhRvL.105e3901C. doi:10.1103/PhysRevLett.105.053901. PMID   20867918. S2CID   17003350.
  5. ↑ Stefano Longhi (2010). "Backward lasing yields a perfect absorber". Physics. 3: 61. Bibcode:2010PhyOJ...3...61L. doi: 10.1103/Physics.3.61 .
  6. ↑ Stefano Longhi (2010). "PT-symmetric laser absorber". Physical Review A. 82 (3): 031801. arXiv: 1008.5298 . Bibcode:2010PhRvA..82c1801L. doi:10.1103/PhysRevA.82.031801. S2CID   119157414. (Synopsis by Mark Saffman.)
  7. 1 2 3 4 "Scientists Build the World's First Anti-laser". Yale University. 2011-02-17. Archived from the original on 2011-02-21. Retrieved 2011-02-17.
  8. ↑ "Scientists build the world's first anti-laser". BBC. 2011-02-17. Retrieved 2011-02-17.
  9. 1 2 Wan, W.; Chong, Y.; Ge, L.; Noh, H.; Stone, A. D.; Cao, H. (2011). "Time-Reversed Lasing and Interferometric Control of Absorption". Science. 331 (6019): 889–892. Bibcode:2011Sci...331..889W. doi:10.1126/science.1200735. PMID   21330539. S2CID   206531272.
  10. 1 2 Pu, M.; Feng, Q.; Wang, M.; Hu, C.; Huang, C.; Ma, X.; Zhao, Z.; Wang, C.; Luo, X. (17 January 2012). "Ultrathin broadband nearly perfect absorber with symmetrical coherent illumination". Optics Express. 20 (3): 2246–2254. Bibcode:2012OExpr..20.2246P. doi: 10.1364/oe.20.002246 . PMID   22330464.
  11. 1 2 Zhang, J.; MacDonald, K. F.; Zheludev, N. I. (6 July 2012). "Controlling light-with-light without nonlinearity". Light: Science & Applications. 1: e18. arXiv: 1203.6110 . doi: 10.1038/lsa.2012.18 .
  12. ↑ Rao, S. M.; Heitz, J. J. F.; Roger, T.; Westerberg, N.; Faccio, D. (2014). "Coherent control of light interaction with graphene". Optics Letters. 39: 5345–5374. arXiv: 1406.6217 . doi:10.1364/OL.39.005345.
  13. ↑ Goodarzi, A.; Ghanaatshoar, M. (2016). "Controlling light by light: photonic crystal-based coherent all-optical transistor". Journal of the Optical Society of America B. 33: 1594–1599. doi:10.1364/JOSAB.33.001594.
  14. 1 2 Vetlugin, A. N.; Guo, R.; Soci, C.; Zheludev, N. I. (2022). "Deterministic generation of entanglement in a quantum network by coherent absorption of a single photon". Physical Review A. 106: 012402. doi:10.1103/PhysRevA.106.012402. hdl: 10356/170804 .
  15. ↑ Li, S.; Luo, J.; Anwar, S.; Li, S.; Lu, W.; Hang, Z.H.; Lai, Y.; Hou, B.; Shen, M.; Wang, C. (2015). "Broadband Perfect Absorption of Ultrathin Conductive Films with Coherent Illumination: Super Performance of Electromagnetic Absorption". Physical Review B. 91 (22): 220301. arXiv: 1406.1847 . Bibcode:2015PhRvB..91v0301L. doi:10.1103/PhysRevB.91.220301. S2CID   118609773.
  16. ↑ Nalla, V.; Valente, J. F.; Sun, H. I.; Zheludev, N. I. (2017). "11-fs dark pulses generated via coherent absorption in plasmonic metamaterial". Optics Express. 25: 22620. doi: 10.1364/OE.25.022620 . hdl: 10220/43706 .
  17. ↑ Roger, T.; Vezzoli, S.; Bolduc, E.; Valente, J. P.; Heitz, J. J. F.; Jeffers, J.; Soci, C.; Leach, J.; Couteau, C. I.; Zheludev, N. I.; Faccio, D. (2015). "Coherent perfect absorption in deeply subwavelength films in the single-photon regime". Nature Communications. 6: 7031. doi: 10.1038/ncomms8031 . PMC   4455071 .
  18. ↑ Wei, P.; Croënne, C.; Tak Chu, S.; Li, J. (2014). "Symmetrical and anti-symmetrical coherent perfect absorption for acoustic waves". Applied Physics Letters. 104: 121902. doi:10.1063/1.4869462.
  19. ↑ Mousavi, S. A.; Plum, E.; Shi, J.; Zheludev, N. I. (2014). "Coherent control of birefringence and optical activity". Applied Physics Letters. 105: 011906. doi:10.1063/1.4890009. hdl: 10220/46790 .
  20. ↑ Shi, J.; Fang, X.; Rogers, E. T. F.; Plum, E. P.; MacDonald, K. F.; Zheludev, N. I. (2014). "Coherent control of Snell's law at metasurfaces". Optics Express. 22: 21051–21060. doi: 10.1364/OE.22.021051 . hdl: 10220/20668 .
  21. ↑ Rao, S. M.; Lyon, A.; Roger, T.; Clerici, M. P.; Zheludev, N. I.; Faccio, D. (2015). "Geometries for the coherent control of four-wave mixing in graphene multilayers". Scientific Reports. 5: 15399. doi: 10.1038/srep15399 . PMC   4613863 .
  22. ↑ Xomalis, A.; Demirtzioglou, I.; Plum, E.; Jung, Y.; Nalla, V.; Lacava, C.; MacDonald, K. F.; Petropoulos, P.; Richardson, D. J.; Zheludev, N. I. (2018). "Fibre-optic metadevice for all-optical signal modulation based on coherent absorption". Nature Communications. 9: 182. doi: 10.1038/s41467-017-02434-y . PMC   5766546 .
  23. ↑ Xomalis, A.; Demirtzioglou, I.; Jung, Y.; Plum, E.; Lacava, C.; Petropoulos, P.; Richardson, D. J.; Zheludev, N. I. (2019). "Cryptography in coherent optical information networks using dissipative metamaterial gates". APL Photonics. 4: 046102. doi: 10.1063/1.5092216 . hdl: 10220/49488 .
  24. ↑ Papaioannou, M.; Plum, E.; Valente, J.; Rogers, E. T. F.; Zheludev, N. I. (2016). "Two-dimensional control of light with light on metasurfaces". Light: Science & Applications. 5: e16070. doi: 10.1038/lsa.2016.70 . PMC   6059948 .
  25. ↑ Papaioannou, M.; Plum, E.; Rogers, E. T. F.; Zheludev, N. I. (2018). "All-optical dynamic focusing of light via coherent absorption in a plasmonic metasurface". Light: Science & Applications. 7: 17157. doi: 10.1038/lsa.2017.157 . PMC   6060048 .
  26. ↑ Papaioannou, M.; Plum, E.; Zheludev, N. I. (2017). "All-optical pattern recognition and image processing on a metamaterial beam splitter". ACS Photonics. 4: 217. doi: 10.1021/acsphotonics.6b00921 .
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