Photonics Dictionary

An electron-gun system is an assembly used to generate and control a focused beam of electrons. Electron guns find applications in various fields, including cathode ray tubes (CRTs), electron...

The bands of spectral lines representing the electronic transition in a molecule.

A study of the energies and wavelengths of radiation emitted by atoms and molecules when particular physical conditions are applied to them.

An emission spectrum is a graphical representation or a characteristic pattern of the wavelengths or frequencies of light emitted by a source, such as an atom, molecule, or celestial object. It shows...

Enantiomers are a pair of molecules that are non-superimposable mirror images of each other, similar to left and right hands. They are stereoisomers, meaning they have the same molecular formula and...

An enzyme-linked immunosorbent assay (ELISA) is a laboratory technique used to detect and measure the presence of specific substances, such as antibodies, antigens, proteins, hormones, or other...

Epitaxial deposition is a process used in semiconductor manufacturing and materials science to grow a thin crystalline layer, known as an epitaxial layer, on a substrate. The term epitaxial refers to...

A well controlled thin films technique for growing films with good crystal structure in ultra high vacuum environments at very low deposition rates. Epitaxy methods are well known for the growing of...

Common name for a variety of adhesives used for lens bonding, fiber optic splicing and other photonics applications. The term is actually a prefix denoting the presence of an epoxide group in a...

Coating carried out in a sealed chamber evacuated by a mechanical pump in series with an oil diffusion pump to a pressure less than 10-4 mm of mercury, measured by a vacuum gauge. At such a low...

A contraction of "excited dimer." The term refers to an excited species made by combination of two identical atoms or molecules, one of which is excited and one of which is at a ground...

An excimer laser is a type of ultraviolet laser that emits short pulses of light in the ultraviolet spectrum. The term excimer is derived from excited dimer, reflecting the nature of the gain medium...

The term "excimer," strictly used, refers to excited species made by combination of two identical moieties, atoms or molecules. Excited complexes that do not fall into this category are...

The stationary state of an ion, atom or molecule, above the ground state that is produced by the interaction with the radiation field or another ion, atom or molecule. See ground state.

An exciton is a quasiparticle that represents the bound state of an electron and a hole in a solid-state material, typically a semiconductor or an insulator. In simpler terms, an exciton is a paired...

A femtosecond laser is a type of laser that emits ultrashort pulses of light with durations on the order of femtoseconds, where one femtosecond is equal to 10-15 seconds. These lasers are capable of...

A technique developed to measure the molecular weight of macromolecules by analyzing the spontaneous fluctuations that occur in the inherent thermodynamic concentration of solute molecules in a...

Fluorescence is a type of luminescence, which is the emission of light by a substance that has absorbed light or other electromagnetic radiation. Specifically, fluorescence involves the absorption of...

A powerful method, referred to as FCS, for determining the average diffusion coefficients of fluorescent molecules in solution or membranes. FCS measurements rely on recording the transition of...

Fluorescence lifetime refers to the average time it takes for a fluorophore, a molecule that absorbs light at one wavelength and emits it at another, to return to its ground state after being excited...

Fluorescence lifetime imaging (FLIM) is an advanced imaging technique that provides information about the lifetime of fluorescence emissions from fluorophores within a sample. Unlike traditional...

Fluorescence microscopy is a specialized optical imaging technique used in biology, chemistry, and materials science to visualize and study specimens that exhibit fluorescence. Fluorescence is the...

Fluorescent proteins are proteins that exhibit the property of fluorescence, which is the ability to absorb light at a specific wavelength and emit light at a longer wavelength. These proteins are...

A fluorophore is a molecule or a portion of a molecule that has the ability to emit light upon excitation by an external energy source, such as ultraviolet or visible light. The process by which a...

Förster resonance energy transfer (FRET) is a mechanism describing the transfer of energy between two closely spaced fluorescent molecules. This phenomenon is named after the German scientist...

The principle that electronic energy transitions occur at such speeds that the nuclei of the atoms in the molecular system remain stable during the transfers.

Short-lived molecular or atomic particles, with an unpaired electron, that play an important part in many photochemical reactions.

A free-electron laser (FEL) is a type of laser that generates coherent, high-intensity electromagnetic radiation by using a beam of accelerated electrons as the lasing medium. Unlike traditional...

FTIR (Fourier transform infrared) spectrometer is a powerful analytical instrument used to obtain an infrared spectrum of absorption or emission of a solid, liquid, or gas sample. It operates based...

Molecules composed entirely of carbon, in the form of a hollow sphere, ellipsoid or tube. Also called buckyballs. Cylindrical fullerenes are called carbon nanotubes or buckytubes.

Gallium arsenide phosphide (GaAsP) is a semiconductor alloy composed of gallium (Ga), arsenic (As), and phosphorus (P). It is commonly used in the fabrication of optoelectronic devices, particularly...

The positive ion current created in an electron tube as a result of the collisions between electrons and residual gas molecules.

The conduction of electricity in a gas as a result of the ions generated by collisions between electrons and gas molecules.

In chemistry, a halide refers to a chemical compound containing one or more halogen atoms bonded to another element. The halogens are a group of elements in the periodic table that includes fluorine...

The combination of more than one type of small-molecule monomer into a polymer.

High harmonic generation (HHG) refers to a nonlinear optical process in which intense laser light interacts with a gaseous medium, typically an atom or a molecule, to produce harmonics of the...

Histochemical staining is a laboratory technique used in biology and medicine to visualize specific chemical components within biological tissues. This technique involves the application of various...

The perpendicular orientation of the molecular axes of the nematic molecules in a nematic crystal, relative to the electrode plates.

The broadening of a laser's line width in a way that affects every atom (or molecule), and thus the whole system, in the same manner. Examples are collision broadening, and natural or intrinsic...

The parallel orientation of the molecular axes of the nematic molecules in a nematic crystal, relative to the electrode plates.

A hydrogel is a three-dimensional network of polymer chains that are hydrophilic, meaning they have a strong affinity for water. This network structure allows hydrogels to absorb and retain large...

A photoreceptor material used in solar cells and in drums for laser printers and high-speed copiers because of its high quantum efficiency over a wide spectral band, high data-rate capability and...

Hydrophilic is a term used to describe substances or materials that have an affinity for water. The word hydrophilic comes from the Greek words "hydro," meaning water, and "philos," meaning loving or...

Hydrophobic is a term used to describe substances or materials that repel or do not readily interact with water. The word hydrophobic comes from the Greek words "hydro," meaning water, and "phobos,"...

Hyperchromic shift refers to an increase in the absorption of light, leading to a higher absorbance, often observed in certain chemical or biological substances upon undergoing a structural change....

In the context of optical materials, the term "impurity level" refers to the presence of foreign atoms or molecules within the material that deviate from its regular or intrinsic composition. These...

In vitro is a Latin term that translates to "in glass." In scientific contexts, particularly in biology and medicine, it refers to experiments or procedures conducted outside of a living organism,...