Photonics

Source: Wikipedia, the free encyclopedia.
Dispersion of light (photons) by a prism

Photonics is a branch of

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.[citation needed]

An early instance of the word was in a December 1954 letter from John W. Campbell to Gotthard 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 the maser and laser in 1958 to 1960.[1] 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.[

IEEE Lasers and Electro-Optics Society established an archival journal named Photonics Technology Letters at the end of the 1980s.[citation needed
]

During the period leading up to the

optical computing. Further growth of photonics is likely if current silicon photonics developments are successful.[4]

Relationship to other fields

Classical optics

Photonics is closely related to

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 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 term photonics more specifically connotes:

The term

Pockels 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.

Emerging fields

Photonics also relates to the emerging science of quantum information and quantum optics. Other emerging fields include:

Applications

sea mouse (Aphrodita aculeata),[6]
showing colorful spines, a remarkable example of photonic engineering by a living organism

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

photonic computing, lighting, metrology, spectroscopy, 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

fusion energy
, to name several interesting additional examples.

Microphotonics and nanophotonics usually includes

solid state devices.[8]

Overview of photonics research

The science of photonics includes investigation of the

emission, transmission, amplification, detection, and modulation
of light.

Light sources

Photonics commonly uses semiconductor-based light sources, such as

cold cathode fluorescent lamps
or, more often today, LEDs.

Characteristic for research on semiconductor light sources is the frequent use of

compound semiconductors. They are also used in conjunction with silicon to produce hybrid silicon lasers
.

Transmission media

Light can be transmitted through any

.

Amplifiers

Optical amplifiers are used to amplify an optical signal. Optical amplifiers used in optical communications are

Raman amplifiers and optical parametric amplifiers. A very advanced research topic on optical amplifiers is the research on quantum dot
semiconductor optical amplifiers.

Detection

Photodetectors detect light. Photodetectors range from very fast photodiodes 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. There are also many other photodetectors based on thermal, chemical, quantum, photoelectric and other effects.

Modulation

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 a flashlight to send Morse code. Another method is to take the light from a light source and modulate it in an external optical 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 like phase-shift keying or even orthogonal frequency-division multiplexing 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 optical communication systems. This area of research focuses on the implementation of photonic systems like high speed photonic networks. This also includes research on optical regenerators, which improve optical signal quality.[citation needed]

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 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:

  • 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 Gbit/s 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.[11] 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. [citation needed]
  • 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. [citation needed] Mobile platform sensors are enabling us to more directly engage with practices that better protect the environment, monitor food supply and keep us healthy.
  • LIDAR and other phased array 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. [citation needed
    ]

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)[12] but can also be used for environmental or other applications.[13][14] The main advantages of this approach are speed of analysis, non-invasive diagnostics, and the ability to work in-situ.

See also

References