Photonics Dictionary: N

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 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.

Literally, neodymium:yttrium-aluminum-garnet. A cylindrical rod of yttrium-aluminum-garnet doped with neodymium that is the active medium of the Nd:YAG laser, a highly serviceable solid-state device...

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...

In optics, the process of combining two lenses having equal and opposite powers to produce a result having no power.

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...

A telescope with a concave paraboloidal objective mirror and a small plane (diagonal) mirror that reflects rays from the primary mirror laterally outside the tube where the image is viewed with an...

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 prism invented by William Nicol in 1828 that is made of calcite, the end faces of which are ground to an angle of 68° between one vertical side and the end surface. The prism is cut diagonally...

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...

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 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 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...

Any noise or current fluctuation that prevents precise measurement of the signal current. Both dark current and signal current have random fluctuations that affect the arrival of pulses. Thermal...

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

The amount of spatial noise detected equivalent to the output emission location of the giving source.

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.

Zone of laser operation in which the direct, reflected or scattered light exceeds the laser's MPE and (by ANSI standards) requires the use of protective eyewear.

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...

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...

Also known as a gray body; a nonselective radiator is a thermal radiator that has a constant spectral emissivity with respect to wavelength throughout the spectral range being considered. The...

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...

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...

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...

A filtering device that detects what is new in a scene of interest. Often compared to that of a temporal high pass filter, these filters will remove elements that appear repeatedly throughout an...

That branch of spectroscopy that applies to the study of interactions between energy and atomic nuclei. The simultaneous application of a strong magnetic field and the radiation from a...

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...

A lens used in the optical testing of an aspheric surface. It converts a spherical wavefront into one that precisely matches the surface under test. When the wavefront is reflected from that surface,...

Commonly performed in spectroscopy, the optical null process is a method for radiation detection whereby physical detectors are used to rapidly interchange the intensity between a reference beam and...

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...

Expression of the nondimensional coefficient of the heat transfer in a convection process.