Photonics

Photonics is a field within optics that focuses on using light—specifically, photons—for tasks like generating, detecting, and controlling it through processes such as emission, transmission, modulation, signal processing, switching, amplification, and sensing. Despite its common usage, experts don’t universally agree on a precise definition for photonics or how it differs from related areas like optics. The field grew out of the first practical semiconductor light emitters from the early 1960s and the optical fibers developed in the 1970s. Professional groups, including the IEEE Photonics Society, help advance photonics research, engineering, and applications.

The term "photonics" comes from the Greek word "phos," meaning light, and emerged in the late 1960s to describe research aimed at using light for tasks traditionally handled by electronics, such as telecommunications and information processing. An early mention appeared in a 1954 letter from John W. Campbell to Gotthard Gunther, where Campbell proposed inventing a new science called photonics, drawing an analogy to how electronics relates to electrical engineering. The field truly began with the invention of the maser and laser between 1958 and 1960, followed by the laser diode in the 1970s, optical fibers for data transmission, and the erbium-doped fiber amplifier. These breakthroughs fueled the late 20th-century telecommunications revolution and laid the groundwork for the Internet. Although coined earlier, "photonics" became common in the 1980s as telecom networks adopted fiber-optic data transmission, especially at Bell Laboratories. Its use solidified when the IEEE Lasers and Electro-Optics Society launched the journal *Photonics Technology Letters* in the late 1980s. Before the dot-com crash around 2001, photonics was heavily focused on optical telecommunications, but it now spans a wide range of applications, including laser manufacturing, biological and chemical sensing, medical diagnostics and therapy, display technology, and optical computing.

Photonics is closely tied to classical optics, which existed long before the discovery that light is quantized—Albert Einstein explained the photoelectric effect in 1905. Classical optics relies on tools like refracting lenses, reflecting mirrors, and other components developed from the 15th to 19th centuries, and its key principles, such as Huygens Principle from the 17th century and Maxwell’s Equations from the 19th, don’t require quantum properties of light. In modern contexts, photonics relates to quantum optics, optomechanics, electro-optics, optoelectronics, and quantum electronics, though each term has slightly different meanings in scientific, government, and market settings. Quantum optics often implies fundamental research, while photonics suggests applied research and development. Specifically, photonics emphasizes the particle nature of light, the potential for signal processing devices using photons, practical optical applications, and an analogy to electronics. Optoelectronics refers to devices or circuits with both electrical and optical functions, like thin-film semiconductors. Electro-optics, an older term, covers nonlinear electrical-optical interactions, such as bulk crystal modulators like the Pockels cell, as well as advanced imaging sensors. There’s no widespread agreement on the boundaries of photonics; for instance, a query from the publisher of *Journal of Optics: A Pure and Applied Physics* to its editorial board about renaming the journal revealed significant differences in how "optics" and "photonics" describe the field, with some suggesting that "photonics embraces optics." In practice, "modern optics" and "photonics" are often used interchangeably in scientific jargon.

Photonics also connects to emerging fields like quantum information and quantum optics. Other developing areas include optoacoustics or photoacoustic imaging, where laser energy absorbed by biological tissues converts to heat and produces ultrasonic emissions; optomechanics, which studies light’s interaction with mechanical vibrations in mesoscopic or macroscopic objects; optomics, integrating photonic and atomic devices for precision timekeeping, navigation, and metrology; and plasmonics, which examines how light interacts with plasmons in dielectric and metallic structures.