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Photonics is a branch ofoptics that involves the application ofgeneration,detection, and manipulation oflight in the form ofphotons throughemission,transmission,modulation,signal processing, switching,amplification, andsensing.[1][2]
Photonics is closely related to quantum electronics, where quantum electronics deals with the theoretical part of it while photonics deal with its engineering applications.[1] Though covering all light's technical applications over the wholespectrum, most photonic applications are in the range of visible and near-infrared light.
The termphotonics developed as an outgrowth of the first practical semiconductor light emitters invented in the early 1960s and optical fibers developed in the 1970s.
The word 'Photonics' is derived from the Greek word "phos" meaning light (which has genitive case "photos" and in compound words the root "photo-" is used); it appeared in the late 1960s to describe a research field whose goal was to use light to perform functions that traditionally fell within the typical domain of electronics, such as telecommunications, information processing, etc.[citation needed]
An early instance of the word was in a December 1954 letter fromJohn W. Campbell toGotthard Gunther:
Incidentally, I’ve decided to invent a new science — photonics. It bears the same relationship to Optics that electronics does to electrical engineering. Photonics, like electronics, will deal with the individual units; optics and EE deal with the group-phenomena! And note that you can do things with electronics that are impossible in electrical engineering![3]
Photonics as a field began with the invention of themaser andlaser in 1958 to 1960.[1] Other developments followed: thelaser diode in the 1970s,optical fibers for transmitting information, and theerbium-doped fiber amplifier. These inventions formed the basis for the telecommunications revolution of the late 20th century and provided the infrastructure for theInternet.
Though coined earlier, the term photonics came into common use in the 1980s as fiber-optic data transmission was adopted by telecommunications network operators.[citation needed] At that time, the term was used widely atBell Laboratories.[citation needed] Its use was confirmed when theIEEE Lasers and Electro-Optics Society established an archival journal namedPhotonics Technology Letters at the end of the 1980s.[citation needed]
During the period leading up to thedot-com crash circa 2001, photonics was a field focused largely on optical telecommunications. However, photonics covers a huge range of science and technology applications, including laser manufacturing, biological and chemical sensing, medical diagnostics and therapy, display technology, andoptical computing. Further growth of photonics is likely if currentsilicon photonics developments are successful.[4]
Photonics is closely related tooptics. Classical optics long preceded the discovery that light is quantized, whenAlbert Einstein famously explained thephotoelectric effect in 1905. Optics tools include the refractinglens, the reflectingmirror, and various optical components and instruments developed throughout the 15th to 19th centuries. Key tenets of classical optics, such asHuygens Principle, developed in the 17th century,Maxwell's Equations and the wave equations, developed in the 19th, do not depend on quantum properties of light.
Photonics is related toquantum optics,optomechanics,electro-optics,optoelectronics andquantum electronics. However, each area has slightly different connotations by scientific and government communities and in the marketplace. Quantum optics often connotes fundamental research, whereas photonics is used to connote applied research and development.
The termphotonics more specifically connotes:
The termoptoelectronics connotes devices or circuits that comprise both electrical and optical functions, i.e., a thin-film semiconductor device. The termelectro-optics came into earlier use and specifically encompasses nonlinear electrical-optical interactions applied, e.g., as bulk crystal modulators such as thePockels cell, but also includes advanced imaging sensors.
An important aspect in the modern definition of Photonics is that there is not necessarily a widespread agreement in the perception of the field boundaries. Following a source on optics.org,[5] the response of a query from the publisher of Journal of Optics: A Pure and Applied Physics to the editorial board regarding streamlining the name of the journal reported significant differences in the way the terms "optics" and "photonics" describe the subject area, with some description proposing that "photonics embraces optics". In practice, as the field evolves, evidences that "modern optics" and Photonics are often used interchangeably are very diffused and absorbed in the scientific jargon.
Photonics also relates to the emerging science ofquantum information and quantum optics. Other emerging fields include:
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Applications of photonics are ubiquitous. Included are all areas from everyday life to the most advanced science, e.g. light detection,telecommunications,information processing,photovoltaics,photonic computing,lighting,metrology,spectroscopy,holography,medicine (surgery, vision correction, endoscopy, health monitoring),biophotonics,military technology, laser material processing, art diagnostics (involvinginfrared reflectography,X-rays,ultraviolet fluorescence,XRF),agriculture, androbotics.
Just as applications of electronics have expanded dramatically since the firsttransistor was invented in 1948, the unique applications of photonics continue to emerge. Economically important applications forsemiconductor photonic devices include optical data recording, fiber optic telecommunications,laser printing (based on xerography), displays, andoptical pumping of high-power lasers. The potential applications of photonics are virtually unlimited and include chemical synthesis, medical diagnostics, on-chipdata communication, sensors, laser defense, andfusion energy, to name several interesting additional examples.
Microphotonics and nanophotonics usually includesphotonic crystals andsolid state devices.[8]
The science of photonics includes investigation of theemission, transmission,amplification, detection, andmodulation of light.
Photonics commonly uses semiconductor-based light sources, such aslight-emitting diodes (LEDs),superluminescent diodes, and lasers. Other light sources includesingle photon sources,fluorescent lamps,cathode-ray tubes (CRTs), andplasma screens. Note that while CRTs, plasma screens, andorganic light-emitting diode displays generate their own light,liquid crystal displays (LCDs) likeTFT screens require abacklight of eithercold cathode fluorescent lamps or, more often today, LEDs.
Characteristic for research on semiconductor light sources is the frequent use ofIII-V semiconductors instead of the classical semiconductors likesilicon andgermanium. This is due to the special properties ofIII-V semiconductors that allow for the implementation oflight emitting devices. Examples for material systems used aregallium arsenide (GaAs) andaluminium gallium arsenide (AlGaAs) or othercompound semiconductors. They are also used in conjunction with silicon to producehybrid silicon lasers.
Light can be transmitted through anytransparent medium.Glass fiber orplastic optical fiber can be used to guide the light along a desired path. Inoptical communications optical fibers allow fortransmission distances of more than 100 km without amplification depending on the bit rate and modulation format used for transmission. A very advanced research topic within photonics is the investigation and fabrication of special structures and "materials" with engineered optical properties. These includephotonic crystals,photonic crystal fibers andmetamaterials.
Optical amplifiers are used to amplify an optical signal. Optical amplifiers used in optical communications areerbium-doped fiber amplifiers,semiconductor optical amplifiers,Raman amplifiers andoptical parametric amplifiers. A very advanced research topic on optical amplifiers is the research onquantum dot semiconductor optical amplifiers.
Photodetectors detect light. Photodetectors range from very fastphotodiodes for communications applications over medium speed charge coupled devices (CCDs) fordigital cameras to very slowsolar cells that are used forenergy harvesting fromsunlight. There are also many other photodetectors based on thermal,chemical, quantum,photoelectric and other effects.
Modulation of a light source is used to encode information on a light source. Modulation can be achieved by the light source directly. One of the simplest examples is to use aflashlight to sendMorse code. Another method is to take the light from a light source and modulate it in an externaloptical modulator.[9]
An additional topic covered by modulation research is the modulation format.On-off keying has been the commonly used modulation format in optical communications. In the last years more advanced modulation formats likephase-shift keying or evenorthogonal frequency-division multiplexing have been investigated to counteract effects likedispersion that degrade the quality of the transmitted signal.
Photonics also includes research on photonic systems. This term is often used foroptical communication systems. This area of research focuses on the implementation of photonic systems like high speed photonic networks. This also includes research onoptical regenerators, which improve optical signal quality.[citation needed]
Photonic integrated circuits (PICs) are optically active integrated semiconductor photonic devices. The leading commercial application of PICs are optical transceivers for data center optical networks. PICs fabricated on III-Vindium phosphide semiconductor wafer substrates were the first to achieve commercial success;[10] PICs based on silicon wafer substrates are now also a commercialized technology.
Key Applications for Integrated Photonics include:
Biophotonics employs tools from the field of photonics to the study ofbiology. Biophotonics mainly focuses on improving medical diagnostic abilities (for example for cancer or infectious diseases)[14] but can also be used for environmental or other applications.[15][16] The main advantages of this approach are speed of analysis,non-invasive diagnostics, and the ability to workin-situ.
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