All articles starting with O

Optical orthogonal codes

Optical orthogonal codes (OOCs) are binary sequences with sharp autocorrelation and low cross-correlation, introduced in 1989 as signature codes letting asynchronous users share one optical channel.

Optical orthogonal frequency-division multiple access

Optical orthogonal frequency-division multiple access, or OFDMA-PON, is a passive optical network scheme in which users share fiber by transmitting on disjoint orthogonal subcarriers instead of taking turns in time slots.

Optical orthogonal frequency-division multiplexing

Optical orthogonal frequency-division multiplexing (O-OFDM) is the application of OFDM, which carries data on many orthogonal subcarriers, to optical links, proposed for long-haul fiber in 2006.

Optical packet switching

Optical packet switching (OPS) is a networking paradigm that routes data packets entirely in the optical domain, pursued since the mid-1990s to overcome electronic routers' bandwidth limits.

Optical parametric amplification

Optical parametric amplification (OPA) is a second-order nonlinear optics technique in which an intense pump laser amplifies a weaker signal beam in a non-centrosymmetric crystal, generating an idler beam.

Optical parametric amplifier

An optical parametric amplifier (OPA) is a device that amplifies a light beam in a nonlinear crystal pumped by a stronger beam, producing tunable light.

Optical parametric chirped pulse amplification

Optical parametric chirped pulse amplification (OPCPA) is a laser technique that amplifies a stretched pulse in a nonlinear crystal pumped by a separate laser, with no stored energy or heat.

Optical parametric oscillator

An optical parametric oscillator (OPO) is a tunable light source similar to a laser, in which a pump photon in a nonlinear crystal splits into signal and idler photons.

Optical particle counter

An optical particle counter is an instrument that measures airborne particle concentration and size by passing air through a light beam and detecting light scattered by individual particles.

Optical path length

Optical path length, or optical distance, is the vacuum distance giving the same light phase change as its actual path, computed as the refractive index integrated along it.

Optical phase conjugation

Optical phase conjugation is a nonlinear optical technique that generates a backward-traveling wave retracing the incoming path, canceling aberrations; first demonstrated in 1972 via stimulated Brillouin scattering.

Optical phased array

An optical phased array (OPA) steers a laser beam with no moving parts by controlling the phases of coherent emitters, often on a chip, for LiDAR and communication.

Optical phenomenon

An optical phenomenon is any observable event involving light, from reflection and refraction to diffraction and polarization, producing natural effects like rainbows, halos, and the blue sky.

Optical phonon

An optical phonon is a quantized lattice vibration in which atoms in a unit cell move against each other while its center of mass stays at rest, measurable by infrared or Raman spectroscopy.

Optical photothermal infrared spectroscopy

Optical photothermal infrared (O-PTIR) spectroscopy, also called mid-infrared photothermal microscopy, is an infrared technique that measures IR absorption with a visible probe laser, reaching sub-micron spatial resolution with FT-IR-comparable spectra.

Optical pooled screening

Optical pooled screening is a cell-biology method that applies pooled perturbations to a mixed cell population, images each cell's phenotype, and identifies each cell's perturbation in place.

Optical profilometry

Optical profilometry is a non-contact optical metrology technique that measures a surface's 3D topography and roughness using light instead of a mechanical probe, with nanometer-scale vertical resolution.

Optical proximity correction

Optical proximity correction (OPC) is a computational lithography technique that pre-distorts photomask geometry, shifting subdivided mask edges so predictable imaging errors produce the intended pattern on the wafer.

Oct 22, 2026

Optical pulling force

The optical pulling force, also called negative radiation pressure, pulls an object toward the light source, reversing ordinary light pressure; such beams are optical tractor beams.

Optical pumping

Optical pumping is a technique in which circularly polarized light transfers angular momentum to atoms, concentrating them in one quantum state. Proposed by Alfred Kastler in 1950, it won him the 1966 Nobel Prize in Physics.

Optical rectification

Optical rectification is a nonlinear optical effect in which intense light induces a static electric polarization, first reported in 1962 and now a leading source of terahertz radiation.

Optical resolution

Optical resolution is the ability of a telescope, microscope, or camera to distinguish fine detail, limited by diffraction at its finite aperture, as quantified by the Rayleigh criterion.

Optical ring resonators

An optical ring resonator, or ring resonator, is a closed-loop waveguide that light circulates around, sustaining resonance; it serves as a filter, modulator, biosensor, laser cavity, and more in photonic integrated circuits.

Optical rotation

Optical rotation, also called circular birefringence, is the rotation of the plane of polarization of linearly polarized light passing through an optically active medium such as quartz or a chiral solution.

Optical rotatory dispersion

Optical rotatory dispersion (ORD) is a spectroscopic method that measures how the rotation of plane-polarized light by a chiral substance depends on wavelength, used to characterize molecular structure and stereochemistry.

Optical sectioning

Optical sectioning is a microscope's ability to image a thin slice within a thick specimen by rejecting light above and below focus; stacked slices form a 3D image.

Optical single-sideband modulation

Optical single-sideband modulation (OSSB) is an optical transmission technique that suppresses one sideband of a modulated carrier, halving optical bandwidth and suppressing chromatic-dispersion-induced power fading.

Optical solar reflector

An optical solar reflector, also called a thermal control mirror, is a passive spacecraft thermal control element that reflects most sunlight while radiating heat away in the infrared.

Oct 22, 2026

Optical soliton molecules

Optical soliton molecules are stable bound states of two or more optical solitons in lasers, named in 2005 by Stratmann and colleagues for their molecular-like internal dynamics.