Photonics Dictionary

FTIR (Fourier transform infrared) spectrometer is a powerful analytical instrument used to obtain an infrared spectrum of absorption or emission of a solid, liquid, or gas sample. It operates based...

That image remaining on the detector after the primary stimulus has been removed. In the visual system, the after-image commonly appears as the complementary color of the primary stimulus.

The luminosity that remains in a rarefied gas after an electrodeless discharge has traversed the gas.

In digital data transmission, the representation of a bit by change in amplitude of the outgoing signal. Amplitude shift keying (ASK) is less sensitive than phase-shift keying, but can tolerate...

A type of phase-shift keying using a one-bit delay line.

A write-once optical disc storage system in which the optical head reads continuously while writing to check the accuracy of the stored data. Data recorded erroneously are then rewritten at another...

A dispersion-shifted fiber (DSF) refers to a type of optical fiber designed to minimize the effects of chromatic dispersion, which is the phenomenon where different wavelengths of light travel at...

Phase shift in electromagnetic signals caused by daily variations in the ionosphere, often during sunrise or sunset.

The magnitude, expressed in cycles per second, of the alteration of the wave frequency observed as a result of the Doppler effect.

A gradual change in the output of a circuit or instrument over time.

A technique used in astronomy that requires a radio telescope to be directed at a point in the sky west of the object under observation. The Earth's rotation causes the object to drift through the...

An astronomical scanning technique for capturing images of stars without moving the sensor. To perform a drift scan, a CCD sensor's readout rate must be synchronized with the motion of celestial...

A shift in the direction of the red in the spectral lines of light which, defined by the relativity theory, will have decreased frequencies upon emerging from a highly gravitational field.

Secondary aberrations remaining after the primary (Seidel) aberrations have been corrected.

In digital data transmission, the separation of the two binary states into output at two frequencies.

A technique used to create an achromatic phase shift based on the principle of geometric phase. The phase shift is experienced by a light beam as a result of a cyclic change in its state of...

A plate containing a uniform pattern of transparent holes in an opaque background, the clear area being nearly equal to the opaque area. Used in the printing process.

The gray-colored tones halfway between shadows and highlights in a reproduced image.

Hyperchromic shift refers to an increase in the absorption of light, leading to a higher absorbance, often observed in certain chemical or biological substances upon undergoing a structural change....

The slight difference in wavelength of an element's given spectral line observed in comparing different isotopes of that element.

Laser drift typically refers to a phenomenon where the frequency or wavelength of a laser source gradually changes over time. In the context of lasers, stability in terms of frequency or wavelength...

Optical design software refers to specialized computer programs used by optical engineers, physicists, and designers to simulate, model, analyze, and optimize the performance of optical systems and...

A technique used to generate a phase shift between reference and sample light beams. The phase shift can be performed through the use of a mirror that is moved along the optic axis by a piezoelectric...

A method of coding information in a communications system where the shift in the phase of an electromagnetic wave represents a particular bit or character.

A device that changes the frequency of light by inducing the Raman effect on a beam passing through it.

The displacement of spectrum lines, as determined by the increasing distance between, and the relative velocity of, the observer and a light source, causing the lines to move toward the red portion...

A shift in the apparent position of an object when an optical element is added or removed.

A term describing an antireflection coating that may be applied to optics that cannot tolerate the high temperatures usually required for normal "hard'' coatings. Such coatings lack durability...

Blocking by means of a pitch ring, pitch button or a totally pitched block. Pitch, containing a soft filter, may be used between the optical components to bar lateral movement.

Term applied to radiation composed of particles or photons that will not easily penetrate a material because of their low energy levels.

A filter that creates spherical aberration resulting in an image with a soft outline.

A lens that exhibits spherical aberration when used at large aperture settings, and that forms an image with a slightly blurred outline.

The change in position of the image of a sine wave object from its ideal position. Usually measured in degrees with 360° designating a full cycle of the image.

A slight displacement in the position of a spectral line because of an alteration in frequency, as a result, in turn, of a cause such as the Doppler effect.