Photonics Dictionary: E

An etalon is an optical device that consists of two parallel reflecting surfaces separated by a precise and known distance. It operates based on the principle of optical interference and is used to...

Etaloning is an optical phenomenon that occurs in imaging systems, particularly in devices such as spectrometers, interferometers, and cameras. It is characterized by the appearance of interference...

The engraving of a surface by acid, acid fumes or a tool; a process extensively used in the manufacture of reticles.

An acid used to etch the surfaces of particular materials. For glass, hydrofluoric acid is used either as a liquid or a vapor. Metals are etched by means of suitable acids or other liquids, often to...

A product of the area of a light beam (normal to its direction of propagation) and the solid angle that the beam includes; flux per unit radiance or luminance. Alternative terms: geometric extent,...

The material that has the lowest possible constant melting point of any possible combination of the same components.

A high-frequency approach to the propagation of light in graded-index fibers in which the modal field is represented in terms of an inhomogeneous (evanescent) plane wave with a complex phase, so that...

A sensor generally used for infrared imaging. It consists of two chambers separated by a thin, blackened membrane. An infrared image is formed on the membrane by a lens or mirror and produces...

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 process, either naturally occurring or mechanically induced, whereby water is changed from its liquid state into a vapor.

An event-based image sensor, also known as a dynamic vision sensor (DVS), is a type of digital imaging device designed to capture visual information in a highly efficient and unique way compared to...

In the SI system, prefix meaning 1018. (E).

A factor, F, indicating the increase in shot noise in an avalanche photodiode as compared with the ideal multiplier, which is noiseless. The noise, which results from variations in avalanche gains,...

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...

Excimer laser coronary angioplasty (ELCA) refers to a medical procedure used in the treatment of coronary artery disease. This technique involves the use of an excimer laser to perform angioplasty, a...

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...

1. The process by which an atom acquires energy sufficient to raise it to a quantum state higher than its ground state. 2. More specifically with respect to lasers, the process by which the material...

The difference between the energy of an atom in its ground state and that of the same atom in its excited (quantum) state.

The ratio of the intensities of two specified spectral lines of a source having vastly different excitation energies. This ratio indicates the level of excitation energy in the source.

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...

On the CIE chromaticity diagram, the distance from the achromatic point to the sample point, divided by the distance from the achromatic point through the sample point to the spectrum locus or purple...

The amount of x-rays used to penetrate and diffuse a target sample undergoing electron-probe microanalysis.

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.

In laser pumping, parasitic absorption that occurs at certain wavelengths, decreasing pump efficiency and gain.

In ultraviolet and fluorescence photography, the term applied to the filter used in the photographic system and with the exciting source to screen out ambient radiations and to transmit the exciting...

A small incandescent lamp whose intense beam is focused on the optical soundtrack of a motion picture film. The soundtrack modulates the beam, which in turn is detected by a photocell that produces...

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 single-anode mercury pool tube that is designed to maintain a continuous cathode spot.

The angle between a light ray emerging from an optical system and the optical axis of that system.

In a lens or other optical system, the image of the aperture stop as seen from image space.

Flux leaving a surface per unit area.

The light spectrum formed by an explosive reaction or by the electrical explosion of a metallic wire by a strong current.

In cosmology, a star that exhibits a rapid increase in the magnitude of light, which is followed by a slow decrease in magnitude. The nova and supernova are explosive variables.

In optics, the total radiant energy incident on a surface-per-unit area. It is equal to the integral over time of the radiant flux density. Also known as radiant exposure.