Photonics is a branch of optics that involves the application of generation, detection, and manipulation of light in form of photons through

emission Emission may refer to: Chemical products * Emission of air pollutants, notably: **Flue gas, gas exiting to the atmosphere via a flue ** Exhaust gas, flue gas generated by fuel combustion ** Emission of greenhouse gases, which absorb and emit radi ...

transmission Transmission may refer to: Medicine, science and technology * Power transmission ** Electric power transmission ** Propulsion transmission, technology allowing controlled application of power *** Automatic transmission *** Manual transmission *** ...

modulation In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the ''carrier signal'', with a separate signal called the ''modulation signal'' that typically contains informatio ...

, signal processing, switching, amplification, and sensing. Though covering all light's technical applications over the whole spectrum, most photonic applications are in the range of visible and near- infrared light. The term photonics developed as an outgrowth of the first practical semiconductor light emitters invented in the early 1960s and optical fibers developed in the 1970s.

History

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. Photonics as a field began with the invention of the laser in 1960. Other developments followed: the laser diode in the 1970s, optical fibers for transmitting information, and the erbium-doped fiber amplifier. These inventions formed the basis for the telecommunications revolution of the late 20th century and provided the infrastructure for the Internet. Though coined earlier, the term photonics came into common use in the 1980s as fiber-optic data transmission was adopted by telecommunications network operators. At that time, the term was used widely at Bell Laboratories. Its use was confirmed when the IEEE Lasers and Electro-Optics Society established an archival journal named Photonics Technology Letters at the end of the 1980s. During the period leading up to the dot-com crash circa 2001, photonics as 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, and optical computing. Further growth of photonics is likely if current silicon photonics developments are successful.

Relationship to other fields

Classical optics

Photonics is closely related to optics. Classical optics long preceded the discovery that light is quantized, when Albert Einstein famously explained the photoelectric effect in 1905. Optics tools include the refracting lens, the reflecting mirror, and various optical components and instruments developed throughout the 15th to 19th centuries. Key tenets of classical optics, such as Huygens 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.

Modern optics

Photonics is related to quantum optics,

optomechanics Optomechanics is the manufacture and maintenance of optical parts and devices. This includes the design and manufacture of hardware used to hold and align elements in optical systems, such as: * Optical tables, breadboards, and rails * Mirro ...

, electro-optics, optoelectronics and

quantum electronics Quantum optics is a branch of atomic, molecular, and optical physics dealing with how individual quanta of light, known as photons, interact with atoms and molecules. It includes the study of the particle-like properties of photons. Photons have b ...

. 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 term ''photonics'' more specifically connotes: * The particle properties of light, * The potential of creating signal processing device technologies using photons, * The practical application of optics, and * An analogy to electronics. The term optoelectronics connotes devices or circuits that comprise both electrical and optical functions, i.e., a thin-film semiconductor device. The term electro-optics came into earlier use and specifically encompasses nonlinear electrical-optical interactions applied, e.g., as bulk crystal modulators such as the Pockels cell, but also includes advanced imaging sensors.

Emerging fields

Photonics also relates to the emerging science of quantum information and quantum optics. Other emerging fields include: * Optoacoustics or photoacoustic imaging where laser energy delivered into biological tissues will be absorbed and converted into heat, leading to ultrasonic emission. *

Optomechanics Optomechanics is the manufacture and maintenance of optical parts and devices. This includes the design and manufacture of hardware used to hold and align elements in optical systems, such as: * Optical tables, breadboards, and rails * Mirro ...

, which involves the study of the interaction between light and mechanical vibrations of mesoscopic or macroscopic objects; * Optomics, in which devices integrate both photonic and atomic devices for applications such as precision timekeeping, navigation, and metrology; * Plasmonics, which studies the interaction between light and plasmons in dielectric and metallic structures. Plasmons are the quantizations of plasma oscillations; when coupled to an electromagnetic wave, they manifest as

surface plasmon polariton Surface plasmon polaritons (SPPs) are electromagnetic waves that travel along a metal–dielectric or metal–air interface, practically in the infrared or visible-frequency. The term "surface plasmon polariton" explains that the wave involves bot ...

s or

localized surface plasmon A localized surface plasmon (LSP) is the result of the confinement of a surface plasmon in a nanoparticle of size comparable to or smaller than the wavelength of light used to excite the plasmon. When a small spherical metallic nanoparticle is irra ...

s. *

Polaritonics Polaritonics is an intermediate regime between photonics and sub-microwave electronics (see Fig. 1). In this regime, signals are carried by an admixture of electromagnetic spectrum, electromagnetic and lattice vibrational waves known as phonon-pol ...

, which differs from photonics in that the fundamental information carrier is a polariton. Polaritons are a mixture of photons and phonons, and operate in the range of frequencies from 300 gigahertz to approximately 10

terahertz Terahertz or THz may refer to: * Terahertz (unit), a unit of frequency, defined as one trillion (1012) cycles per second or 1012 hertz * Terahertz radiation, electromagnetic waves within the ITU-designated band of frequencies from 0.3 to 3 terahe ...

. *

Programmable photonics Program, programme, programmer, or programming may refer to: Business and management * Program management, the process of managing several related projects * Time management * Program, a part of planning Arts and entertainment Audio * Progra ...

, which studies the development of photonic circuits that can be reprogrammed to implement different functions in the same fashion as an electronic FPGA

Applications

Applications of photonics are ubiquitous. Included are all areas from everyday life to the most advanced science, e.g. light detection, telecommunications,

information processing Information processing is the change (processing) of information in any manner detectable by an observer. As such, it is a process that ''describes'' everything that happens (changes) in the universe, from the falling of a rock (a change in posit ...

, photovoltaics, photonic computing, lighting,

metrology Metrology is the scientific study of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in Fran ...

spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...

, holography, medicine (surgery, vision correction, endoscopy, health monitoring), biophotonics, military technology, laser material processing, art diagnostics (involving InfraRed Reflectography, Xrays, UltraViolet fluorescence, XRF), agriculture, and robotics. Just as applications of electronics have expanded dramatically since the first transistor was invented in 1948, the unique applications of photonics continue to emerge. Economically important applications for semiconductor photonic devices include optical data recording, fiber optic telecommunications, laser printing (based on xerography), displays, and

optical pumping Optical pumping is a process in which light is used to raise (or "pump") electrons from a lower energy level in an atom or molecule to a higher one. It is commonly used in laser construction to pump the active laser medium so as to achieve populat ...

of high-power lasers. The potential applications of photonics are virtually unlimited and include chemical synthesis, medical diagnostics, on-chip data communication, sensors, laser defense, and fusion energy, to name several interesting additional examples. * Consumer equipment: barcode scanner, printer, CD/DVD/Blu-ray devices, remote control devices * Telecommunications:

optical fiber communication Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of infrared light through an optical fiber. The light is a form of carrier wave that is modulated to carry information. Fiber is pref ...

s, optical down converter to microwave *

Renewable Energy Renewable energy is energy that is collected from renewable resources that are naturally replenished on a human timescale. It includes sources such as sunlight, wind, the movement of water, and geothermal heat. Although most renewable energy ...

Solar power systems A photovoltaic system, also PV system or solar power system, is an electric power system designed to supply usable solar power by means of photovoltaics. It consists of an arrangement of several components, including solar panels to absorb and co ...

* Medicine: correction of poor eyesight, laser surgery, surgical endoscopy, tattoo removal * Industrial manufacturing: the use of lasers for welding, drilling, cutting, and various methods of surface modification * Construction: laser leveling, laser rangefinding, smart structures * Aviation: photonic

gyroscope A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rota ...

s lacking mobile parts * Military: IR sensors, command and control, navigation, search and rescue, mine laying and detection * Entertainment: laser shows, beam effects, holographic art *

Information processing Information processing is the change (processing) of information in any manner detectable by an observer. As such, it is a process that ''describes'' everything that happens (changes) in the universe, from the falling of a rock (a change in posit ...

* Passive daytime radiative cooling * Sensors:

LIDAR Lidar (, also LIDAR, or LiDAR; sometimes LADAR) is a method for determining ranges (variable distance) by targeting an object or a surface with a laser and measuring the time for the reflected light to return to the receiver. It can also be ...

, sensors for consumer electronics *

Metrology Metrology is the scientific study of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in Fran ...

: time and frequency measurements,

rangefinding A rangefinder (also rangefinding telemeter, depending on the context) is a device used to measure distances to remote objects. Originally optical devices used in surveying, they soon found applications in other fields, such as photography an ...

* Photonic computing: clock distribution and communication between

computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...

printed circuit board A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in Electrical engineering, electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a L ...

s, or within optoelectronic

integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...

s; in the future:

quantum computing Quantum computing is a type of computation whose operations can harness the phenomena of quantum mechanics, such as superposition, interference, and entanglement. Devices that perform quantum computations are known as quantum computers. Though ...

Microphotonics and nanophotonics usually includes photonic crystals and solid state devices.

Overview of photonics research

The science of photonics includes investigation of the

, amplification, detection, and

of light.

Light sources

Photonics commonly uses semiconductor-based light sources, such as light-emitting diodes (LEDs),

superluminescent diode A superluminescent diode (SLED or SLD) is an edge-emitting semiconductor light source based on superluminescence. It combines the high power and brightness of laser diodes with the low coherence of conventional light-emitting diodes. Its emission ...

s, and lasers. Other light sources include

single photon sources Single-photon sources are light sources that emit light as single particles or photons. These sources are distinct from coherent light sources (lasers) and thermal light sources such as incandescent light bulbs. The Heisenberg uncertainty principle ...

, fluorescent lamps,

cathode ray tube A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms ( oscilloscope), pictu ...

s (CRTs), and plasma screens. Note that while CRTs, plasma screens, and organic light-emitting diode displays generate their own light,

liquid crystal display A liquid-crystal display (LCD) is a flat panel display, flat-panel display or other Electro-optic modulator, electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liqui ...

s (LCDs) like TFT screens require a backlight of either

cold cathode fluorescent lamp A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet, ul ...

s or, more often today, LEDs. Characteristic for research on semiconductor light sources is the frequent use of III-V semiconductors instead of the classical semiconductors like silicon and

germanium Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors s ...

. This is due to the special properties of III-V semiconductors that allow for the implementation of light emitting devices. Examples for material systems used are

gallium arsenide Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a Zincblende (crystal structure), zinc blende crystal structure. Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monoli ...

(GaAs) and aluminium gallium arsenide (AlGaAs) or other compound semiconductors. They are also used in conjunction with silicon to produce

hybrid silicon laser A hybrid silicon laser is a semiconductor laser fabricated from both silicon and group III-V semiconductor materials. The hybrid silicon laser was developed to address the lack of a silicon laser to enable fabrication of low-cost, mass-producible s ...

Transmission media

Light can be transmitted through any transparent medium. Glass fiber or plastic optical fiber can be used to guide the light along a desired path. In

optical communication Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices. The earliest basic forms of optical communication date b ...

s optical fibers allow for

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 include photonic crystals,

photonic crystal fiber Photonic-crystal fiber (PCF) is a class of optical fiber based on the properties of photonic crystals. It was first explored in 1996 at University of Bath, UK. Because of its ability to confine light in hollow cores or with confinement charact ...

s and metamaterials.

Amplifiers

Optical amplifier An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback fr ...

s are used to amplify an optical signal. Optical amplifiers used in optical communications are erbium-doped fiber amplifiers,

semiconductor optical amplifier An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from ...

Raman amplifier Raman amplification "Raman effect"
. ''

optical parametric amplifiers. A very advanced research topic on optical amplifiers is the research on

quantum dot Quantum dots (QDs) are semiconductor particles a few nanometres in size, having light, optical and electronics, electronic properties that differ from those of larger particles as a result of quantum mechanics. They are a central topic in nanote ...

semiconductor optical amplifiers.

Detection

Photodetectors detect light. Photodetectors range from very fast

photodiode A photodiode is a light-sensitive semiconductor diode. It produces current when it absorbs photons. The package of a photodiode allows light (or infrared or ultraviolet radiation, or X-rays) to reach the sensitive part of the device. The packag ...

s for communications applications over medium speed charge coupled devices ( CCDs) for digital cameras to very slow solar cells that are used for energy harvesting from

sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...

. There are also many other photodetectors based on thermal, chemical, quantum, photoelectric and other effects.

Modulation

Modulation In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the ''carrier signal'', with a separate signal called the ''modulation signal'' that typically contains informatio ...

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 a

flashlight A flashlight ( US, Canada) or torch ( UK, Australia) is a portable hand-held electric lamp. Formerly, the light source typically was a miniature incandescent light bulb, but these have been displaced by light-emitting diodes (LEDs) since the ...

to send

Morse code Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one of ...

. Another method is to take the light from a light source and modulate it in an external optical modulator. 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 like

phase-shift keying Phase-shift keying (PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency reference signal (the carrier wave). The modulation is accomplished by varying the sine and cosine inputs at a ...

or even

orthogonal frequency-division multiplexing In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital commun ...

have been investigated to counteract effects like dispersion that degrade the quality of the transmitted signal.

Photonic systems

Photonics also includes research on photonic systems. This term is often used for

systems. This area of research focuses on the implementation of photonic systems like high speed photonic networks. This also includes research on

optical regenerator Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviole ...

s, which improve optical signal quality.

Photonic integrated circuits

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 were fabricated on III-V

indium phosphide Indium phosphide (InP) is a binary semiconductor composed of indium and phosphorus. It has a face-centered cubic ("zincblende") crystal structure, identical to that of GaAs and most of the III-V semiconductors. Manufacturing Indium phosphide ca ...

semiconductor wafer substrates were the first to achieve commercial success; PICs based on silicon wafer substrates are now also a commercialized technology. Key Applications for Integrated Photonics include: * Data Center Interconnects: Data centers continue to grow in scale as companies and institutions store and process more information in the cloud. With the increase in data center compute, the demands on data center networks correspondingly increase. Optical cables can support greater lane bandwidth at longer transmission distances than copper cables. For short-reach distances and up to 40 Gbps data transmission rates, non-integrated approaches such as vertical-cavity surface-emitting lasers can be used for optical transceivers on multi-mode optical fiber networks. Beyond this range and bandwidth, photonic integrated circuits are key to enable high-performance, low-cost optical transceivers. * Analog RF Signal Applications: Using the GHz precision signal processing of photonic integrated circuits, radiofrequency (RF) signals can be manipulated with high fidelity to add or drop multiple channels of radio, spread across an ultra-broadband frequency range. In addition, photonic integrated circuits can remove background noise from an RF signal with unprecedented precision, which will increase the signal to noise performance and make possible new benchmarks in low power performance. Taken together, this high precision processing enables us to now pack large amounts of information into ultra-long distance radio communications. * Sensors: Photons can also be used to detect and differentiate the optical properties of materials. They can identify chemical or biochemical gases from air pollution, organic produce, and contaminants in the water. They can also be used to detect abnormalities in the blood, such as low glucose levels, and measure biometrics such as pulse rate. Photonic integrated circuits are being designed as comprehensive and ubiquitous sensors with glass/silicon, and embedded via high-volume production in various mobile devices. Mobile platform sensors are enabling us to more directly engage with practices that better protect the environment, monitor food supply and keep us healthy. *

and other

phased array In antenna theory, a phased array usually means an electronically scanned array, a computer-controlled array of antennas which creates a beam of radio waves that can be electronically steered to point in different directions without moving th ...

imaging: Arrays of PICs can take advantage of phase delays in the light reflected from objects with three-dimensional shapes to reconstruct 3D images, and Light Imaging, Detection and Ranging (LIDAR) with laser light can offer a complement to radar by providing precision imaging (with 3D information) at close distances. This new form of machine vision is having an immediate application in driverless cars to reduce collisions, and in biomedical imaging. Phased arrays can also be used for free-space communications and novel display technologies. Current versions of LIDAR predominantly rely on moving parts, making them large, slow, low resolution, costly, and prone to mechanical vibration and premature failure. Integrated photonics can realize LIDAR within a footprint the size of a postage stamp, scan without moving parts, and be produced in high volume at low cost.

Biophotonics

Biophotonics employs tools from the field of photonics to the study of biology. Biophotonics mainly focuses on improving medical diagnostic abilities (for example for cancer or infectious diseases) but can also be used for environmental or other applications. The main advantages of this approach are speed of analysis, non-invasive diagnostics, and the ability to work in-situ.

References

{{Authority control Optics