Photonics Dictionary

Nonspecular reflection from a rough surface.

A reflecting surface that scatters radiation that is incident on it, thus producing diffuse reflection.

An optical diffuser is an optical component or material designed to scatter or diffuse light that passes through it. It is used to create a more even or uniform illumination, reduce glare, or soften...

A cosmetic defect on the surface of an optical element. A dig is nearly equal in terms of its length and width. The size is specified numerically by its average diameter in 1/100 of a millimeter;...

The departure of a curved surface from the plane that is tangent to its vertex. See sag.

Also called DLIP, a high-speed, high-resolution processing technique that uses high-power, pulsed laser systems to directly ablate micro- and nanoperiodic structures with different features on large...

A hole filled with dirt such as a polishing abrasive and located in an optical surface. See dig; scratch.

A lens with one surface convex and the other concave, the latter having the greater curvature. It also is known as a diverging meniscus lens.

A diverging lens is a type of lens that causes parallel rays of light to spread out or diverge. It is thinner in the center than at the edges and is commonly referred to as a concave lens. The most...

A primitive crystal possessing two plane surfaces that form a dihedral angle bisected by another plane surface.

A diverging lens with both surfaces concave.

A converging lens with both surfaces convex.

1. A compound lens consisting of two elements. If there is an air space between the elements it is called an "air-spaced doublet.'' If the inner surfaces are cemented together, it is called a...

The flat or angled surface, usually fine-ground, that limits the aperture of a lens or prism surface.

An edge-emitting light-emitting diode is a type of LED structure where light emission occurs primarily along the edge of the semiconductor chip rather than from the surface. Edge-emitting LEDs are...

A weight reducing method whereby material from the rear of a reflector is removed leaving a pattern of ribs normal to the surface in an egg-crate pattern.

An electro-optic modulator (EOM) is a device used to modulate the amplitude, phase, or polarization of light waves using an external electrical signal. Electro-optic modulation is a fundamental...

A type of optical modulator with potential application in optical switching and displays, in which applied voltage causes a change of interfacial tension between mercury and an electrolyte, varying...

Type of solid-state display tube in which the readout surface is coated with a material that changes color when positively or negatively charged.

An advanced magnetic device used in x-ray lithography to beam x-rays onto the surface of silicon wafers used for semiconductor circuits.

The recording of the information contained in a modulated electron beam onto photographic or silicon resin-coated materials. A direct recording method involves the passage of the recording medium...

An electrowetting display (EWD) is a type of electronic display technology that utilizes the principles of electrowetting to control the behavior of colored oil droplets on a hydrophobic surface....

Ellipsometry is an optical technique used to characterize the properties of thin films and surfaces. It is based on the measurement of changes in the polarization state of light reflected or...

The emissivity of a body times the emissive power of a blackbody at the same temperature. For a blackbody, it is the total radiation per unit area of radiating surface.

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...

Epitaxial equipment refers to a set of specialized tools and systems used in the process of epitaxy, which is the growth of crystalline layers on a substrate material. Epitaxial growth is a critical...

In surface height measurement of optics with steep slopes, the use of two short visible wavelengths to synthesize a longer, equivalent wavelength.

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...

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...

Flux leaving a surface per unit area.

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.

The ejection of electrons from the surface of a solid by the absorption of a sufficient amount of photons.

A ray that has a nonisotropic speed in a doubly refracting crystal. It does not necessarily obey Snell's law upon refraction at the crystal surface.

Also termed eye distance. The distance between the vertex of the last optical surface of a visual optical system and the system's exit pupil.

An f-theta lens, also known as an f-theta scan lens or simply an f-theta lens system, is a specialized optical component used in laser scanning systems, particularly in laser marking, engraving, and...

A multiple-beam interferometer, usually consisting of two flat plates, with high reflective ability. The plates are set parallel to one another by spacers so that lightwaves may bounce back and forth...

A highly reflective mirror that is usually flat on one surface and curved on the other, and that has silver, gold or aluminum deposited on glass, providing about 99 percent reflection.

A device in which slab geometry internally compensates for thermal-optic distortion; the solid host material -- glass or Nd:YAG -- is in the form of a rectangular slab with plane parallel faces. The...

1. One of the plane-reflecting surfaces on a multisurfaced polygon. 2. The cleaved end mirror of a laser diode's active region.

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 fiber laser is a type of laser in which the active gain medium is an optical fiber doped with rare-earth ions such as erbium, ytterbium, or neodymium. Fiber lasers generate coherent light through...