Photonics Dictionary

An immersion liquid used to treat polarizing filters to eliminate the effects of surface variations and to minimize the optical path difference between that part of the spectrum that passes through...

A laser that uses a substance in the liquid state, such as an organic dye, as the active lasing medium.

Liquid marble refers to a unique form of microscale liquid encapsulation, where small droplets of liquid are coated with a fine layer of hydrophobic powder, such as silica nanoparticles or Teflon....

A mirror composed of liquid, taking advantage of the parabolic shape of a spinning liquid and the fact that the mirror's focal length can be adjusted by altering the velocity at which the liquid's...

Liquid or fluid optics refers to the use of liquids to create or enhance optical systems. These systems leverage the unique properties of liquids, such as their ability to change shape, refractive...

The pattern, formed by a character generation cathode-ray tube system, in which the characters are made up of wave shapes synthesized by a series of sine and cosine terms.

Lithium triborate (LiB3O5), commonly abbreviated as LBO, is a nonlinear optical crystal widely used in various applications involving frequency conversion of laser light. It is valued for its...

Lithography is a key process used in microfabrication and semiconductor manufacturing to create intricate patterns on the surface of substrates, typically silicon wafers. It involves the transfer of...

A 30-60-90° spectrograph prism that is coated on the surface opposite the 60° angle with a reflecting film.

A mirror employed with a very high incidence angle to form a pair of coherent light sources by reflection, and therefore forming interference bands.

Data communications network in a clearly defined geographical location, and extending no more than a few miles in length. It generally takes in an office building or group of buildings, a campus or...

In coherent optical communications systems, a laser used at the receiving end to produce a steady wave that is combined with the incoming laser signal before detection, generating a composite wave...

A lock-in amplifier is a specialized electronic instrument used to extract and measure small signals embedded in noise or interference. It is particularly useful in fields such as spectroscopy,...

A diagram that uses special symbols called logic symbols to represent the detailed functioning of electronic logic circuits. The symbols do not represent the type of electronics used, but only their...

A long-pass filter is an optical filter that allows longer wavelengths of light to pass through while blocking or attenuating shorter wavelengths. These filters are designed to transmit light with a...

Long-wave infrared (LWIR) refers to a specific range of the infrared spectrum. Infrared radiation is divided into three main categories based on wavelength: near-infrared (NIR), mid-wave infrared...

In fiber optic communications systems, generally one that operates between 1000 and 1700 nm.

In image processing, the memory that stores the values for the point processes. Input pixel values are those for the original image, while output values are those displayed on the monitor as altered...

In fiber optic cable, containment of the fiber or fibers within an outer protective tube in which they can move to some extent. The interstices usually are filled with an insulating material. See...

The Lorentz oscillator model is a theoretical model used in physics to describe the response of a charged particle (such as an electron) to an oscillating electric field. It is particularly employed...

A low-power (2x to 10x) magnifier consisting of a single positive lens assembly.

Low Earth orbit (LEO) refers to a region in space that is relatively close to Earth's surface, typically characterized by altitudes ranging from approximately 180 to 2,000 kilometers (112 to 1,242...

Instrumentation designed to permit the perception, recording or measurement of scenes under conditions of low incident illumination.

Optical fiber that transmits a greater percentage of input light than does high-loss step-index fiber. Low-loss fiber requires higher purity materials and a more sophisticated drawing process and...

A lumen is a unit of measurement used to quantify the amount of luminous flux, which is the perceived power of light. In other words, the lumen measures the total amount of visible light emitted by a...

SI unit of quantity of light.

A complete unit containing a light source, globe, reflector, housing, socket and other necessary components for lighting.

Luminous flux emitted from a surface per unit solid angle per unit of area, projected onto a plane normal to the direction of propagation. Also known as brightness and luminous sterance.

A type of photometer calibrated in luminance units (candles per square unit, or lamberts). In photography an exposure meter contains a luminance meter to record the average luminance of a scene.

Luminescence is the emission of light that occurs without the involved substance undergoing a significant increase in temperature. In other words, it is the production and emission of light by a...

Luminosity refers to the total amount of energy emitted by an astronomical object, typically measured per unit time. It quantifies the intrinsic brightness of the object and is often expressed in...

Pertaining to electromagnetic radiation as perceived by the eye; that is, with the contributions as wavelengths in the visible region weighted according to V(λ), which symbolizes the spectral...

Luminous flux emitted per unit area of a source, expressed as lumens per area.

A measure of the time-integrated amount of flux. It has units of lumen-seconds and might be used to describe such things as the radiant energy that the eye would receive from a photographic flash.

The total luminous flux given out per unit area; i.e., the sum of the luminous emittance and any radiation that is reflected from and/or transmitted through the surface: expressed as lumens per area.

Luminous flux emitted by a source in a given range of directions; the unit of measure is the lumen/steradian, now known as the candela.

A dielectric sphere with an index of refraction that varies with distance from the sphere center. A parallel beam of rays is focused on the lens surface at a point diametrically opposite the...

SI unit of luminous incidence or illuminance, equal to 1 lumen per square meter.

SI unit of light exposure.

The hydrogen-derived, ultraviolet radiation running from 1216 to 512 A, discovered by Theodore Lyman in 1914.

A lymphocyte is a type of white blood cell (leukocyte) that plays a central role in the immune system. Lymphocytes are produced in the bone marrow and mature in the lymphoid organs, such as the...

A type of filter consisting of a series of birefringent crystals and polarizers invented by French astronomer Bernard Lyot for isolating and observing significant wavelengths of solar light.