Photonics Dictionary

A unit of frequency equivalent to 1012 cps. Named for Augustin Jean Fresnel, a French physicist known for his work in light and optics.

1. Also known as near-field diffraction. The field of radiation sent through an aperture in an absorbing screen at large distances as compared with the wavelength and the dimensions of the aperture,...

A single band in a group of light and dark bands that can be viewed in the periphery of Fresnel diffraction shadow.

A hologram formed with an object located close to the recording medium.

A Fresnel lens is a type of optical lens that consists of a series of concentric grooves or steps carved into a flat, thin piece of transparent material, typically plastic or glass. This design...

Two plane mirrors that are not wholly located in the same plane. When light from a point source or slit reflects from the two mirrors, interference bands are revealed in the region where the light...

In a lens, the square of the radius of its aperture divided by the product of the focal length and the wavelength. It measures the importance of diffraction in the image formed by the lens. A small...

Fresnel reflection refers to the reflection of light at the interface between two different media with different refractive indices. This phenomenon was named after the French engineer and physicist...

Reflection losses incurred at input and output of optical elements because of the difference in refractive index between glass and the immersion medium.

A method for measuring the index profile of an optical fiber by measuring the reflectance as a function of position on the end face.

A type of quarter-wave retarder in the form of a glass rhomb; light entering the retarder undergoes two total internal reflections, producing a change in phase.

A zone plate in which the zones are alternately transparent and opaque to specific radiation, and coarse enough so that no appreciable diffraction or focusing takes place. The Fresnel zone plate is...

A bright spot or point, due to Fresnel diffraction, that appears at the center of the shadow of a circular object in light originating from a point source. Also referred to as a Fresnel spot or...

1. A lens situated at or near the plane of an internal image to project the aperture of a previous objective or erector upon the aperture of a following lens. 2. A lens at or near the plane of a...

The series of images formed when periodic objects are exposed to collimated monochromatic radiation and that result from Fresnel diffraction.

A system of Japanese origin that utilizes Fresnel lenses and a fiber optic network to transmit sunlight to otherwise inaccessible areas.

A material, often a liquid or cement, whose refractive index is nearly equal to the fiber's core index, used to reduce Fresnel reflection from a fiber end face.

The technology of manipulating light on a micro scale. In optical communications, this is usually accomplished using two or more materials with significantly different indicies of refraction. In most...

A zone plate produced by a computer and having a binary structure that can be etched into a chromium or quartz layer. It often is used in laser machining, in which the machining of small holes with...

The area closest to an aperture or source where the diffraction pattern differs substantially from that observed at an infinite distance, or more specifically, the far field. Also referred to as the...

A projector used to project transparencies. A horizontal 8 x 10-in. stage for writing or laying down preformed transparencies is provided with either an elliptical mirror or a plastic Fresnel lens...

Conceptual formulas that characterize both the transmittance functions of lenses and propagation in the Fresnel zone.

Scalar diffraction theory is a simplified approach used to describe the propagation of electromagnetic waves, particularly light, as they encounter obstacles or apertures. It is termed "scalar"...

Also known as Fresnel reflection. That portion of the incident radiation that is reflected from the surface of a refractive material. It is a function of the refractive index of the material. At...

A resonator often used for mode control in Fresnel number laser cavities that is highly vulnerable to extremely weak external sources of feedback.