Photonics Dictionary

In an optical waveguide,- typically a multimode fiber - the distortion resulting from differential mode delay, i.e. axial rays (modes), with the shortest path length, will have the shortest...

A camera that uses a rotating mirror to project sequential images onto lenses that are arranged in an arc. The reflected images can then be recorded on stationary film. By using an 8-mm frame format,...

A specific form of phase shifting interferometry - commonly referred to as multiple wavelength phase shifting interferometry - this form of interferometry utilizes two short wavelengths to synthesize...

The combination of two or more signals for transmission along a single wire, path or carrier. In most optical communication systems this is referred to as wavelength division multiplexing, in which...

Multispectral imaging is a technique that involves capturing and analyzing images at multiple discrete spectral bands within the electromagnetic spectrum. Unlike hyperspectral imaging, which acquires...

A form of shearing interferometer that contains a simple wedged (plane-parallel) glass plate with a nonzero optical path difference to create interference between split optical wavefronts. The...

Nanoimprint lithography (NIL) is a nanolithography technique used for fabricating nanoscale patterns on a substrate. It is a high-resolution, high-throughput process that involves the mechanical...

Nanophotonics is a branch of science and technology that explores the behavior of light on the nanometer scale, typically at dimensions smaller than the wavelength of light. It involves the study and...

Nanoplasmonics is a branch of nanophotonics that focuses on the study and manipulation of optical phenomena at the nanoscale using plasmonic materials and structures. Plasmonics deals with the...

A defect in infrared systems that appears as a dark circular area on a displayed image, caused by radiation reflecting into a detector. It can be reduced by low-reflective coatings or by altering the...

An imaging system designed to highlight small deviations in a planar reflective object such as a mirror. The system can be used to detect minute flaws or to image faint marks that are made in the...

Nd:YAG laser refers to a solid-state laser that utilizes neodymium-doped yttrium aluminum garnet (Nd:Y3Al5O12) as the gain medium. This type of laser emits light at a wavelength of 1064 nm in the...

A near-eye display (NED) is a type of display technology designed to be positioned close to the user's eyes, typically within a few centimeters. This technology is commonly used in applications such...

A near-infrared (NIR) camera is an imaging device designed to capture images in the near-infrared region of the electromagnetic spectrum. The near-infrared spectrum typically extends from about 700...

A near-infrared (NIR) spectrometer is an analytical instrument used to measure the absorption, transmission, or reflection of light in the near-infrared region of the electromagnetic spectrum....

Near-infrared spectroscopy (NIRS) is a non-invasive analytical technique that uses the near-infrared region of the electromagnetic spectrum to study the absorption of light by molecules in a sample....

The shortest wavelengths of the infrared region, nominally 0.75 to 3 µm.

A light source, such as the sun or an incandescent lamp, that freely penetrates ordinary glass bulbs and emits in the near-ultraviolet (wavelengths ranging from about 300 to 400 nm). A mercury vapor...

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 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...

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...

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...

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

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...

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 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 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,...

Ocular accommodation is the process by which the eye changes its optical power to maintain a clear image (focus) on an object as its distance varies. This process is essential for seeing objects at...

Off-axis paraboloid and ellipsoid mirrors are specialized optical components used in various optical systems, particularly in applications requiring precise focusing, collimation, or imaging of...

A form of high-power microscope objective where the space between the object and the first element is filled with an oil having the same index as that element. This form reduces losses, increases the...

Oleophobic is a term used to describe substances or materials that repel or resist oils. The word oleophobic comes from the Greek words "oleo," meaning oil, and "phobos," meaning fear. Oleophobic...

On-board optics refers to optical systems integrated into devices or platforms for various purposes, such as imaging, navigation, communication, and sensing. These systems are crucial in a wide range...

Also referred to as a funduscope, an ophthalmoscope is a specialized instrument used by ophthalmologists for observing and photographing the fundus (interior) of the eye which includes the retina,...

Optical aberration refers to imperfections or deviations from ideal optical behavior in an imaging system, such as a lens or a mirror. These aberrations can cause distortions, blurring, or other...

A measure of the optical path length for light traveling from the sun or other celestial source through Earth's atmosphere to sea-level relative to the optical path length traveled by light from the...

An optical assembly refers to a collection of optical components that are carefully arranged and aligned to perform a specific function within an optical system. These components may include lenses,...

An instrument used to test lenses by utilizing the optical transfer function. It consists of a HeNe laser, a beamsplitter and two mirrors.

The imaginary line passing through both the centers of curvatures of the optical surfaces of a lens or mirror; the optical centerline for all the centers of an optical element(s) of an optical...

The phenomenon that can render an optical resonator the equivalent of a semiconductor flip-flop. A bistable device will remain stable in two optical states, one of high transmission and another of...