Photonics Dictionary

A dichroic coating, also known as a dichroic filter or dichroic mirror, is an optical coating designed to selectively transmit or reflect certain wavelengths of light while simultaneously absorbing...

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....

The adjustment of the eyepiece of an instrument to provide accommodation for the eyesight differences of individual observers. The axial distance through which the eyepiece must be moved, to provide...

In optics, the production of maxima and minima by the superimposition of two sets of interference fringes from light of two different wavelengths.

A lens mounting with eccentric rings that may be rotated to shift the axis of the lens to a prescribed position.

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.

An electron lens consisting of a homogeneous axial electric field and a magnetic field used in high-quality image tubes for high modulation transfer function and small geometrical distortion...

A device utilizing an electron beam for the observation and recording of submicroscopic samples with the aid of photographic emulsions or other short-wavelength sensors. With the electron microscope,...

An EMCCD (electron-multiplying charge-coupled device) camera is a type of scientific camera specifically designed for low-light imaging applications that require high sensitivity and fast readout...

An emission spectrum is a graphical representation or a characteristic pattern of the wavelengths or frequencies of light emitted by a source, such as an atom, molecule, or celestial object. It shows...

An f-theta lens, also known as an f-theta scan lens or simply an f-theta lens system, is a specialized optical component used in laser scanning systems, particularly in laser marking, engraving, and...

A FAC lens, or fast axis collimation lens, is an optical component used in laser diode systems to collimate the fast axis of laser emission. Laser diodes emit light in two main axes: the fast axis,...

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...

A plane (through the focal point) at right angles to the principal axis of a lens or mirror; that surface on which the best image is formed.

That point on the optical axis of a lens, to which an incident bundle of parallel light rays will converge.

Freeform mirrors refer to reflective optical components that deviate from traditional symmetric or rotationally symmetric shapes, such as spheres or paraboloids. Unlike conventional mirrors, which...

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...

The restricting aperture located at the front of the lens. It is usually defined as the maximum diameter of the entrance cone at the front vertex, for the specified field of view at infinity focus.

Gallium arsenide phosphide (GaAsP) is a semiconductor alloy composed of gallium (Ga), arsenic (As), and phosphorus (P). It is commonly used in the fabrication of optoelectronic devices, particularly...

Gallium arsenide (GaAs) is a compound semiconductor material composed of gallium (Ga) and arsenic (As). It belongs to the III-V group of semiconductors and has a zincblende crystal structure. GaAs is...

The area of optics that deals with the propagation of Gaussian laser beams in free space, or any general medium - i.e. lenses- under the paraxial (small divergence angle) approximations. Gaussian...

1. That branch of optics that illustrates the theory in which q is substituted for sin q in Snell's law. Effective results are achieved if the aperture and field angle are made very small. The...

The physical center of the lens; it is on the axis of the lens, halfway between the front and rear vertex. It is sometimes referred to as the mechanical center of the lens.

In a microscope, the diaphragm located between the Bertrand lens and the eyepiece, which is closed during conoscopic viewing to restrict the interference figures to that of a crystal lying on the...

A GRIN (gradient index) lens is a type of optical lens that utilizes a gradient in refractive index across its volume rather than having a uniform refractive index like conventional lenses. This...

With respect to waveguides, the continuous change in the direction of the axis of the wavelength, during which the axis is perpendicular to the direction of polarization.

The term half bandwidth (HBW) generally refers to the width of a spectral band or frequency range at half of its maximum amplitude. It is commonly used in the context of signal processing, optics,...

1. The value on either the leading or the trailing edge of a laser pulse at which the power is one-half of its maximum value. 2. The wavelength at which a filter is transmitting one-half of its peak...

Indium gallium arsenide (InGaAs) is a semiconductor compound composed of indium (In), gallium (Ga), and arsenic (As). It belongs to the III-V group of semiconductors and is commonly used in...

An infrared lens is an optical component specifically designed and optimized for transmitting, focusing, or manipulating infrared (IR) radiation within the infrared spectrum. These lenses are used in...

The laser damage threshold refers to the maximum level of laser intensity that a material can withstand without experiencing damage. It is a critical parameter in laser applications and is...

Laser parameters are the characteristics that define the behavior and performance of a laser. These parameters can be categorized into several groups: spatial, temporal, spectral, and operational. ...

Lens testing equipment refers to a range of specialized tools and instruments used to evaluate the optical performance, quality, and characteristics of lenses. These instruments are essential for...

A lens is a transparent optical device that focuses or diverges light, allowing it to pass through and form an image. Lenses are commonly used in optical systems, such as cameras, telescopes,...

Lensless microscopy, also known as computational or holographic microscopy, is an imaging technique that captures and reconstructs microscopic images without the use of traditional lenses. Instead of...

An ophthalmic instrument used to measure the magnitude and direction of the maximum and minimum powers of a spectacle lens, and mark the optical center of the lens by an ink dot. When the lens to be...

The line of vision; the optical axis of a telescope or other observation system. The straight line connecting the object and the objective lens of the viewing device.

Linear receive optics typically refers to the optical components and systems used in the reception (detection) of linearly polarized light signals in various applications, such as optical...

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...

Also referred to as the axial ray (or a-ray), a marginal ray originates from the axial point of the object and passes through the edge or margin of the entrance pupil (or aperture stop) of the lens...

A wedge in a rangefinder or heightfinder used to displace the image produced by one telescope so that it coincides with that produced by the other telescope, thus affording a measurement of the...

In optical fiber, sharp but microscopic curvatures that create local axial displacements of a few microns and spatial wavelength displacements of a few millimeters. One frequent cause is longitudinal...

A form of laser output noise that is caused by thermal, mechanical, or acoustical disturbances of the cavity length. Mode sweeping occurs when the length of the laser cavity changes as a result of...