Photonics Dictionary

A hologram formed when the light of the illuminating beam is absorbed in correspondence with the recording exposure. In application, absorption holograms are intended for use in satellite...

An absorption peak refers to a sharp increase or spike in the absorption of electromagnetic radiation at a particular wavelength or energy level. It is a distinctive feature in the absorption...

A bulk crystalline optic which permits the propagation of light through a volume of index altered material. The variation in refractive index along the material volume is due to a piezoelectric...

Actinometry refers to the measurement of the intensity of radiation, particularly ultraviolet (UV) radiation or sunlight. It is commonly used in atmospheric science, environmental monitoring, and...

Any fluorescence in which the wavelength of the emitted light differs from that of the absorbed light.

Light-absorbing material that is applied to the back support of any bright image under inspection to prevent the formation of a secondary image.

An atomic absorption spectrometer (AAS) is an analytical instrument used to determine the concentration of specific chemical elements in a sample by measuring the absorption of light at...

An attenuator is an electronic or optical device used to reduce the power or intensity of a signal without significantly affecting its waveform or other characteristics. Attenuators are commonly used...

Autofluorescence refers to the natural emission of fluorescence exhibited by certain biological structures or molecules when exposed to light. Unlike fluorescence that results from the application of...

Brightfield refers to a type of microscopy and imaging technique in which the specimen is illuminated with a white light source, and the image is observed or captured against a bright background. In...

The law stating that the amount of chemical change produced is proportional to the amount of light absorbed. Actually, the change is also dependent on the intensity of light -- a fact named the...

Circular dichroism (CD) is a spectroscopic technique used to study the structural characteristics of chiral (asymmetric) molecules, particularly biomolecules like proteins, nucleic acids, and certain...

Cold atoms refer to atoms that have been cooled to extremely low temperatures, typically in the microkelvin (µK) to nanokelvin (nK) range, close to absolute zero (0 Kelvin or -273.15°C). At...

A dichroic coating, also known as a dichroic filter or dichroic mirror, is an optical coating designed to selectively transmit or reflect certain wavelengths of light while simultaneously absorbing...

Dichroism refers to the property of certain materials to exhibit different colors or absorbance of light depending on the direction of light propagation or polarization. The term is commonly used in...

A shallow, fine-pitch diffraction grating having a precise dielectric overcoating that experimentally has absorbed wavelength-specific incident light that is polarized in the P-plane.

A lidar (light detection and ranging) technique used in pollution monitoring. Two light beams are emitted simultaneously, one at a wavelength that will be absorbed by the target particles, and the...

A diode-pumped solid-state laser (DPSSL) is a type of laser system that uses semiconductor diode lasers to pump energy into a solid gain medium, resulting in the generation of coherent light. This...

A type of erasable data storage device that uses a medium deposited on the disc in two layers, each dyed to absorb a different wavelength of laser light. To record data, the lower layer is heated by...

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...

An Er:YAG laser is a type of solid-state laser that uses a crystal made of erbium-doped yttrium aluminum garnet (Er:Y3Al5O12) as the gain medium. The erbium (Er) ions are introduced into the crystal...

The amount of energy required to raise the energy level of an atom; a necessity if the atom is to radiate energy. High excitation potential is the amount of energy in the upper state of the...

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...

Extreme ultraviolet (EUV) refers to a specific range of electromagnetic radiation in the ultraviolet part of the spectrum. EUV radiation has wavelengths between 10 and 124 nanometers, which...

The study and interpretation of the spectra of substances after they have absorbed the radiant energy emitted by a brief, intense light source.

Fluence is a term used in various scientific and technical disciplines to describe the amount of something per unit area. The specific meaning of fluence can vary depending on the context in which it...

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...

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...

A tube containing mercury vapor and lined with a phosphor. When current is passed through the vapor the strong ultraviolet emission excites the phosphor, which emits visible light. The ultraviolet...

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...

Functional near-infrared spectroscopy (fNIRS) is a non-invasive neuroimaging technique that measures changes in hemoglobin concentration in the brain. It utilizes near-infrared light to penetrate the...

Germicidal ultraviolet (GUV) refers to a specific range of UV radiation that has disinfectant properties capable of killing or inactivating microorganisms, including bacteria, viruses, and fungi. The...

A thermal radiation detector consisting of a small cell with a blackened plastic front face that bulges slightly when heat is received by it. The bulging tilts a small mirror, which, in turn, varies...

A glass filter that transmits visible light while absorbing infrared energy (heat).

Holmium lasers are a type of medical laser that utilizes holmium-doped crystals as the gain medium. The term holmium laser is often associated with a specific type of laser used in urology for...

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...

An infrared detector is a device that is used to detect and measure infrared radiation, which lies beyond the visible spectrum of light. These detectors are utilized in various applications,...

A nonoptical surface, within lenses and lens mounts, that contributes largely to flare by reflecting light into the image space. As a result, such surfaces, so located, are finished with a dull...

An absorbing coating medium between fibers, used in some fused fiber optic plates to absorb unwanted light. Such coatings are sometimes called EMA (extramural absorption).