Photonics Dictionary

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...

Broadband dielectric mirrors, also known as broadband mirrors, are optical coatings designed to efficiently reflect or transmit light over a broad range of wavelengths. These mirrors are constructed...

A piece of glass with a high refractive index that is fused to the major blank.

The radiation produced when a charged particle traverses a medium that has a refractive index considerably greater than unity. The moving particle has a velocity that exceeds the velocity of light in...

Chalcogenide refers to a class of compounds containing elements from group 16 of the periodic table, which includes sulfur (S), selenium (Se), and tellurium (Te). These elements are known as...

Chip-on-board (COB) lights refer to a type of LED lighting technology where multiple LED chips are directly mounted onto a substrate, typically a printed circuit board (PCB), without the need for...

The monochromatic transparency effect produced by the immersion of a finely powdered substance (e.g., glass or quartz) into a liquid with a similar refractive index.

A transparent powdered solid immersed in a liquid or plastic of similar refractive index but widely different dispersion; used to isolate narrow spectral regions.

The low-refractive-index material that surrounds the core of an optical fiber to contain core light while protecting against surface contaminant scattering. In all-glass fibers, the cladding is...

In fiber optics, the glass that is found around the glass core of the fiber, and that has a lower refractive index than the fiber.

A mode that is confined by virtue of a lower-index medium surrounding the cladding. Cladding modes, in the terminology of mode descriptors, are equivalent to cladding rays in the terminology of...

A mechanism or device, especially a coating with a refractive index equal to or slightly greater than that of an optical fiber's cladding, that removes modes propagating through the cladding by...

The heat-treating method in which the index of refraction of glass is fixed near or at its maximum value by holding the glass for different periods at suitable degrees of heat below the range of...

A liquid, usually of a specific refractive index and dispersion, serving as an interface between two solids to form a complete light transmission system.

The light-conducting portion of an optical fiber, defined by the region of high refractive index.

The least angle of incidence at which total internal reflection takes place. The angle of incidence in a denser medium, at an interface between the denser and less dense medium, at which the light is...

One of the two principal types of optical glass, the other being flint glass. Crown glass is harder than flint glass, and has a lower index of refraction and lower dispersion. Both types are used in...

An organizational method used in optical design computer programs. The technique produces one number (merit function) to measure the state of correction of an optical system. This number, which is...

A photomicrographic recording technique that utilizes dark-field illumination to render an image of an object having a refractive index much like that of the medium holding it. The object may be...

An optical fiber, usually a single-mode fiber, that has an outer cladding with nearly the same index of refraction as the core and an inner cladding with a very low index of refraction.

A compact, folded version of a Dove prism, made of high-index glass with a silvered base and used for image rotation.

A dichroic mirror, also known as a dichroic beamsplitter or interference filter beamsplitter, is an optical device that selectively reflects or transmits light based on its wavelength. Dichroic...

A high-reflectance coating consisting of alternating layers of quarter-wave film of a higher refractive index and lower refractive index than the substrate. Such coatings can be made very specific to...

Differential interference contrast (DIC) microscopy, also known as Nomarski interference contrast microscopy, is an optical imaging technique used in microscopy to enhance the contrast of transparent...

A variation in propagation delay caused by differences in group velocity among modes of an optical fiber. Also called multimode group delay, this effect is commonly due to imperfections or any...

Digital holographic microscopy (DHM) is an advanced imaging technique that combines holography and digital image processing to capture and reconstruct three-dimensional images of objects. This method...

Dispersion refers to the phenomenon where different wavelengths (colors) of light travel at different speeds when passing through a medium. This variation in the speed of light for different colors...

All formulas that present the index of refraction as a function of a wavelength of electromagnetic radiation. Also called dispersion equation, Cauchy formula, Hartmann formula.

A measure of the dispersive properties of a glass. The relative dispersion is defined as: where C, D, and F refer to the material's index of refraction at the three chief Fraunhofer lines in the...

A spectroscope having a divided circle and a means for the rapid reversal of prisms for the measurement of refractive index of the prism for a specific wavelength.

The separation of unpolarized light into two plane-polarized elements by a doubly refracting crystal. When a crystal, such as calcite, is placed between the eye and a pinhole in a card, two bright...

Double-clad fiber (DCF) is a specialized optical fiber that features two concentric cladding layers surrounding a core. The design of double-clad fibers allows them to be used in various...

A change in the refractive index of an optical fiber caused by variation in the length of the fiber core in response to mechanical stress.

An electro-optic deflector is a device that can change the direction of light beams using an electric field. It operates based on the electro-optic effect, which involves the modulation of the...

The change in the refractive index of a material under the influence of an electrical field.

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...

1. The branch of physics that deals with the use of electrical energy to create or manipulate light waves, generally by changing the refractive index of a light-propagating material; 2....

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...

When a block of glass (prism, window, filter, etc.) is placed into a converging light bundle, it increases the physical distance to the point of focus. The equivalent air path for that block of glass...

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...

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 means of determining a prism's index of refraction by placing the prism so that its emergent face is perpendicular to the incident beam. This arrangement permits the determination of the prism's...

In a birefringent material, the index of refraction varies with the direction of vibration of a lightwave. That direction having a low refractive index is the fast axis; at right angles to it is the...

A fiber Bragg grating (FBG) is a type of optical filter that is inscribed or "written" into the core of an optical fiber. It consists of a periodic modulation of the refractive index along the length...

A fiber optic preform is a cylindrical glass rod or tube used as the starting material for manufacturing optical fibers. It serves as the precursor from which optical fibers are drawn. The process of...