Photonics Dictionary: N

A ghost image that has the reverse lightness relations of the original image. This phenomenon is a common optical illusion that takes place in the human visual system, following long exposures to an...

When a stereo pair of images is switched so that the right eye sees the left image and the left eye the right, the stereo image perceived will be reversed in terms of relative object depth.

An artificial material, engineered to have a negative refractive index value, such that light or any other form of electromagnetic radiation bends in the opposite direction than it would in ordinary...

A negatively charged elementary particle. See electron.

A form of liquid crystal with an appearance of moving, threadlike structures, particularly visible when observed in thick specimens with polarized light. During this phase, the molecules of the...

Glass containing small quantities of neodymium oxide that is used as a filter plate in color television or as a lasing medium (Nd:glass) in solid-state lasers.

A cold-cathode tube containing neon and designed to visually determine a potential difference or field.

An electron tube containing neon gas that uses the transmission of an electric current through the gas to ionize the neon and produce a luminous red discharge.

A Nernst glower, also known simply as a Nernst lamp or Nernst filament, is a type of incandescent lamp or radiant heater based on the Nernst effect. It was invented by the German physicist and...

A network interface card (NIC), also known as a network adapter or LAN adapter, is a hardware component that allows computers to connect to a local area network (LAN) and communicate with other...

A computing paradigm that attempts to process information in a manner similar to that of the brain; it differs from artificial intelligence in that it relies not on pre-programming but on the...

Neuromorphic refers to the design and development of computing systems or devices that are inspired by the structure and functioning of the human brain and nervous system. The term is derived from...

A neuromorphic vision sensor is a type of imaging device designed to mimic the structure and functioning of the human visual system. Inspired by the biological principles of the human eye and brain,...

A light filter that equally decreases the intensity of all wavelengths of light without altering the relative spectral distribution of the energy.

A strip or annulus of glass coated with a semitransparent material such as inconel. The coating thickness, and as a result its transmission, varies linearly as a function of distance. The neutral...

Prediction based on observations of nuclear masses in the valley of stability that indicates the maximum number of electrons that will bind with a given number of protons in progressive order along...

The nondestructive analysis and recording of industrial components based on the absorption of relatively low-energy neutrons by material having low atomic numbers. The visible image formed by the...

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

An instrument devised by Nichols and Hull for use in the measurement of radiation pressure. The device has two small silvered, glass mirrors that are suspended, in the way of a torsion balance, by a...

A device that uses low-level visible radiation or infrared radiation to produce a visual image of a night scene. These devices may rely on the amplification of existing visible light by...

A device consisting of a disc with a spiral arrangement of holes that is used to convert visible patterns into electrical patterns. Light is reflected from the subject and focused through a vertical...

Unit of measurement of brightness (luminance) equal to one candela per square meter.

A nitrogen vacancy (NV) refers to a specific type of defect or impurity in a crystal lattice where a nitrogen atom replaces a carbon atom adjacent to a vacancy (an empty lattice site) in the diamond...

A television system used for seeing in the dark, particularly with the use of infrared rays.

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...

At a given modulation frequency, wavelength, and for a given effective noise bandwidth, the radiant power that produces a signal-to-noise ratio of 1 at the output of a given detector.

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...

An assembly of optical fibers that will not transmit coherent images or information because the relationship of the fibers on either end of the assembly is random; Noncoherent fiber bundles are...

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.

Radiation that does not produce free electrons and ions, or electrically charged particles.

An optical crystal that possesses a strong nonlinear dielectric response function to optical radiation. A material with a strong second-order nonlinearity must not possess a center of symmetry. See...

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...

Derivative of the half-tone screen process involving the fabrication of a binary pulse-width modulated copy of the continuous-level input using a halftone screen and spatial-filtering single...

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...

Direct conversion of a photon from one wavelength to a lower energy photon of another wavelength(s) due to inelastic scattering. In an optical waveguide, nonlinear scattering is usually not important...

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 color whose hue is not produced by a single wavelength in the visible spectrum, but is instead produced by mixing the longest (red) and shortest (blue) wavelengths of the spectrum such as any...

Light striking a surface at an angle perpendicular to the surface.

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,...

Also referred to as a band-stop or band rejection filter; a notch filter is a filter that is designed to screen out a very narrow band of radiation by transmitting most wavelengths with little...