Photonics Dictionary

A tool used to determine the curvature of a lens surface in terms of dioptric power. See lens watch; spherometer.

An instrument that uses optical filtration in order to measure the transmittance for a discrete range or specific number of wavelengths.

Measures the absorption or sample transmittance over a range of specified wavelengths. Sample may be placed within the device and the transmission measured to an accuracy of given percent. The...

The measured change in absorption at a single wavelength while altering experimental parameters such as the incident intensity or pulse width.

Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effects of atmospheric distortions. The Earth's atmosphere can cause light passing through it...

An atomic absorption spectrometer (AAS) is an analytical instrument used to determine the concentration of specific chemical elements in a sample by measuring the absorption of light at...

An atomic clock is a highly precise timekeeping device that uses the vibrations or oscillations of atoms as a reference for measuring time. The most common type of atomic clock uses the vibrations of...

The measured wavelength of the most distinct edge of a spectral band.

In semiconductor physics, the term bandgap refers to the energy range in a material where no electronic states are allowed. It represents the energy difference between the valence band, which is the...

The distance between pupil centers in a two-pupil system, measured perpendicularly to the optic axis.

Beam profiling is a technique used to characterize and analyze the spatial intensity distribution of a laser beam. It involves measuring and visualizing how the optical power or intensity is...

A beamsplitter is an optical device used to divide a beam of light into two or more separate beams, typically by reflecting a portion of the incident light while transmitting the remainder....

The angular width of a radiation beam. With respect to a conical beam of light, it is the vertex angle of the cone. The beamwidth is a measure of the rate of divergence or convergence of a light...

A technique in which a beam of x-rays is directed against a crystal, the atoms of which, because of their lattice arrangement, reflect the ray in the same way as a series of plane surfaces. If the...

Focal, nodal or principal points of a lens. If the respective distances of the object and image are measured from the cardinal points, all thin-lens equations are applicable to thick lenses.

Cathode radiant sensitivity refers to the ability of a photocathode to convert incident radiant energy, typically in the form of light, into an electrical signal. Photocathodes are components used in...

The lens thickness measured at the optical axis.

Circular dichroism (CD) is a spectroscopic technique used to study the structural characteristics of chiral (asymmetric) molecules, particularly biomolecules like proteins, nucleic acids, and certain...

Cold atoms refer to atoms that have been cooled to extremely low temperatures, typically in the microkelvin (µK) to nanokelvin (nK) range, close to absolute zero (0 Kelvin or -273.15°C). At...

A laser warning and countermeasure system containing a sensor that indicates the direction of a laser beam, and analytical instruments to determine pulse code, repetition frequency and wavelength.

The ratio between the object distance and the image distance measured along the principal axis of a lens or mirror. An object at the focal point of a lens has an infinite conjugate ratio; an object...

The measure of departure from a flat surface, as applied to lenses; the reciprocal of radius. Applies to any surface, including lenses, mirrors and image surfaces.

A technique for measuring fiber attenuation or distortion by performing two transmission measurements. One is at the output end of the full length of the fiber. The other is within 1 to 3 m of the...

A multidimensional array of values that is commonly used in programming to describe a time series of image data. Each dimension in the data cube represents a new attribute, while the cells of the...

A measure of the sensitivity of a detector; the reciprocal of noise equivalent power (NEP). See D*.

A detector array refers to a collection of individual detector elements arranged in a two-dimensional grid or matrix format. Each element within the array is capable of detecting electromagnetic...

A detector-Dewar assembly typically refers to a combination of a detector and a Dewar flask used in scientific instruments, particularly in the field of infrared spectroscopy or other applications...

A lidar (light detection and ranging) technique used in pollution monitoring. Two light beams are emitted simultaneously, one at a wavelength that will be absorbed by the target particles, and the...

Diffraction efficiency is a measure of how effectively a diffractive optical element (DOE) or diffraction grating directs light into specific diffraction orders or achieves a desired optical effect....

A diffraction grating is an optical component consisting of a surface with a periodic structure of equally spaced, parallel grooves or rulings. These rulings act as an array of closely spaced slits...

Diffuse reflectance spectroscopy (DRS) is a nondestructive analytical technique used to investigate the optical properties of materials, particularly in the field of spectroscopy. Unlike traditional...

A unit of optical measurement that expresses the refractive power of a lens or prism. In a lens or lens system, it is the reciprocal of the focal length in meters. For example, if a lens has a focal...

A distributed feedback laser (DFB laser) is a type of semiconductor laser diode designed to emit coherent, narrow-bandwidth light with precise control over the wavelength. It achieves this through a...

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.

A spectrophotometer that measures the amount of ozone in the atmosphere through a comparison of solar energy at two wavelengths in the ozone's absorption band. This comparison is achieved by...

The maximum variation in thickness of a lens as measured around a diameter centered on the optical axis. The ETD divided by that diameter yields the wedge of the lens.

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

An Er:YAG laser is a type of solid-state laser that uses a crystal made of erbium-doped yttrium aluminum garnet (Er:Y3Al5O12) as the gain medium. The erbium (Er) ions are introduced into the crystal...

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...

An instrument used to measure the light from a scene to be photographed and to indicate the camera lens and shutter settings required to expose the film correctly. The exposure time required in a...

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 gyroscope (FOG) is a type of gyroscope that uses the interference of light waves to detect changes in orientation or rotation. It operates based on the principle of the Sagnac effect,...