Photonics Dictionary

The unit of force in the mks system that will give 1 kg of mass an acceleration of 1 m/s2.

A bench with instrumentation including a collimator, a microscope, positioners and a nodal slide used to rotate a lens about its second nodal point. The nodal bench is used to determine the cardinal...

Of all the rays passing through a lens from an off-axis object point to its corresponding image point, there is always one ray whose direction in the image space is equal to that in the object space....

The measurement of first- and higher order properties of a lens and its formed image, including effective focal length, back focal length, f number, aberrations, blur patterns, magnification and...

In a communications network, a point at which data are received or from which they are sent. Though the term often is used synonymously with workstation, interconnection points in a network also are...

The unwanted and unpredictable fluctuations that distort a received signal and hence tend to obscure the desired message. Noise disturbances, which may be generated in the devices of a communications...

In a thermal imaging system, the change in temperature that yields a signal-to-noise ratio of unity.

Noise equivalent thermal distance (NETD) is a performance metric used to quantify the sensitivity of thermal imaging systems, including photoacoustic imaging systems. It represents the smallest...

Also referred to as differential interference contrast (DIC) microscopy; Nomarski microscopy is a unique form of microscopy especially suited for the evaluation of surface quality and defects as well...

Any testing method for materials and components that does not damage or destroy the test sample. Some of the methods used are x-ray, ultrasonic, electro-optic and magnetic testing.

A nonlinear crystal is a type of crystal that exhibits nonlinear optical properties when subjected to intense electromagnetic fields, typically from laser light. Unlike linear optical materials,...

A type of radiation detector designed to recognize nonlinear optical effects, such as the Raman effect, by means of a directional, nearly monochromatic light beam; e.g., a laser beam.

A class of optical phenomena that can be viewed only with nearly monochromatic, directional beams of light, such as those produced by a laser. Harmonic generation and the stimulated Raman effect are...

Nonlinear optical materials are substances that exhibit optical properties that are not linearly proportional to the intensity of incident light. In other words, these materials produce optical...

The coupling of laser or light beams via nonlinear optical techniques such as four-wave mixing to achieve spatial variation of the electrical field of the target beam. This technique is also referred...

Nonlinear optics is a branch of optics that studies the optical phenomena that occur when intense light interacts with a material and induces nonlinear responses. In contrast to linear optics, where...

Nonlinear polarization refers to the phenomenon where the polarization of a material responds nonlinearly to an applied electric field. In linear systems, the polarization of a material is directly...

Irregular waves; e.g., light waves, having little coherence and a broad spectrum of frequencies.

A nonradiative transition refers to a process in which an electron or an atom undergoes a change in its energy state without emitting a photon. In contrast to radiative transitions, where a photon is...

A radiometric device or system having uniform responsivity relative to all of the radiation parameters, or relative to one or more specified parameters, throughout all parameter intervals in which...

Nonvolatile memory express (NVMe) is a high-performance, scalable host controller interface designed for accessing solid-state storage devices, such as solid-state drives (SSDs), to leverage the...

Also referred to as the V number in fiber optics; the normalized frequency is a dimensionless quantity, denoted by the symbol V, given by: where a is waveguide core radius, l is wavelength in vacuum,...

The triangle in a chromaticity diagram joining the chromaticities of the NTSC phosphors, and containing all chromaticities which can be produced by additive mixture of their light.

In physics, nuclear fusion refers to the process in which two atomic nuclei come together to form a heavier nucleus, releasing a large amount of energy. This process powers the sun and other stars...

A phenomenon, exploited for medical imaging, in which the nuclei of material placed in a strong magnetic field will absorb radio waves supplied by a transmitter at particular frequencies. The energy...

A chemical detection technique used to measure molecules that have a magnetic dipole moment. The analysis is directed to nucleuses which have a quadrupole moment which leads to an asymmetric electric...

The sine of the vertex angle of the largest cone of meridional rays that can enter or leave an optical system or element, multiplied by the refractive index of the medium in which the vertex of the...

In image acquisition (and sampling theory), the postulate that the pickup sampling frequency must be a minimum of twice as high as the Nyquist rate of brightness change of any detail to be resolved....

The optical element that receives light from the object and forms the first or primary image in telescopes and microscopes. In cameras, the image produced by the objective is the final image. In...

A coarse diffraction grating that is used to form a scale of intensities to determine the relative magnitudes of stars. The grating is placed over the objective of a telescope to form a diffraction...

A common technique in microscopy, oblique illumination is one in which the object is illuminated by a light source that is at an oblique angle (on the side) to the optical axis. This technique is...

A hemispherical covering that is rotatable about a central axis. There is a slit opening along one side wide enough to allow a telescope to be directed at any vertical angle up to 90°.

An acid-resistant, lustrous volcanic glass, usually black or banded.

Refers to the characteristic hue of the ocean according to the presence and concentration of specific minerals or substances, such as chlorophyll. Atmospheric aberrations of color must be corrected...