Photonics Dictionary

The time domain is a concept used in signal processing and analysis to describe signals in terms of their behavior over time. In the time domain, signals are represented as functions of time, showing...

The study of the optical properties of living tissue. Increased understanding of the behavior of light in this varied, turbid medium, especially its scattering and absorption characteristics, is...

Topological photonics is a branch of physics and optics that explores the application of topological concepts to the behavior of light in photonic systems. Drawing inspiration from the field of...

A lens having one or more toric surfaces. A toric surface is one having a maximum power in one meridian and a minimum power in a perpendicular meridian. In ophthalmic optics, toric lenses are used to...

A surface that is swept out by revolving a circle about an axis that lies in the plane of the circle but that does not intersect its center. The result is a surface having different curvatures in...

The process whereby a quantum mechanical system alters from one energy level to another. During this process, energy is emitted or absorbed, and it usually takes the form of photons, phonons, or...

Pertaining to materials having the property of reflecting a part and transmitting a part of the incident radiation.

In the context of optics and lasers, a transverse mode refers to a specific spatial pattern of the electric field within the cross-section of a laser beam. These modes represent the different...

Abbreviated TEA CO2 laser. A gas laser that provides shorter pulses and higher peak powers than conventional CO2 lasers. The electrical excitation pulse occurs transversely to the optical axis...

Also known as TEA laser. A coherent optical source with a wide wavelength range in the infrared, visible and ultraviolet that uses an electrical discharge transverse to (across) the optical axis to...

Oscillator device composed of a semiconducting diode in a coaxial resonating cavity. When the biasing current is applied to the diode, high-frequency waves are emitted into the cavity where they are...

The basis of color vision in the human eye. Three types of cones have been identified, each having a unique spectral response (red, green and blue).

With respect to a crystal, having three unequal axes intersecting at angles, only two of which can be equal and only one of which can measure 90°.

Any form of laser; e.g., a dye laser, having an output that can be adjusted over a wide range of wavelengths. Normally the range is about 70 nm wide.

Tungsten diselenide (WSe2) is a member of the transition metal dichalcogenides (TMDs) family, composed of tungsten (W) and selenium (Se). Similar to other TMDs, tungsten diselenide possesses a...

A compound crystal having two or more crystals or crystal sections that, when regularly positioned, are in reverse position relative to the other sections. When viewed, these crystals appear to be...

Twisted intramolecular charge transfer (TICT) is a phenomenon observed in certain organic molecules containing electron-donor and electron-acceptor groups that are linked together within the same...

This results from the simultaneous absorption of two photons, each having half the energy needed for excitation and requiring a high spatial and temporal concentration of photons. The ensuing...

A dark-field microscope used to view extremely small objects. These objects are suspended in a gas or liquid in an enclosure having a black background. A convergent pencil of bright light enters from...

The rays (such as ultraviolet rays) lying past the visible region of the spectrum.

Ultrasonic refers to sound waves with frequencies higher than the upper audible limit of human hearing, typically above 20,000 Hz. These waves are termed ultrasonic because they are beyond the range...

A doubly refracting crystal having a single axis along which there is an absence of double refraction.

A three-terminal semiconductor having only one PN junction and a stable, open-circuit, negative-resistance property.

An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without a human pilot onboard. UAVs are remotely controlled or autonomously operated, and they can be used for various...

Behaving as though characterized by a series of waves having planes of vibration oriented at all possible azimuths.

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

A type of glass contrived by Schott that is highly transparent to ultraviolet radiation.

In optics, the term vacuum typically refers to a space devoid of matter, including air and other gases. However, in practical terms, achieving a perfect vacuum, where there is absolutely no matter...

Van der Waals forces refer to the attractive or repulsive forces between molecules (or parts of molecules) that arise from fluctuations in electron distribution. These forces are relatively weak...

A vibrational transition refers to a change in the vibrational energy of a molecule. Molecules consist of atoms that are connected by chemical bonds, and these atoms are not stationary but are in...

Virtual histology refers to the use of digital technology and computational methods to simulate or recreate histological images and structures without the need for traditional physical slides and...

Visual detection and ranging (ViDAR) is a technology that utilizes optical sensors, such as cameras or other imaging devices, to detect and track objects in the surrounding environment. Unlike...

Having the characteristics of glass.

An electric cell having two electrodes of unlike metals immersed in a solution that chemically affects one or both of them, thus producing an electromotive force.

An optical element having two principal axes, slow and fast, that resolve an incident polarized beam into two mutually perpendicular polarized beams. The emerging beam recombines to form a particular...

A photofluorescent compound that, when used with a scintillating substance, absorbs photons and emits related photons having a greater wavelength. In this way a phototube or photocell may employ the...

An optical element having plane-inclined surfaces. Usually the faces are inclined toward one another at very small angles. Wedges divert light toward their thicker portions, and may be circular,...

Whispering gallery mode (WGM) refers to a phenomenon in wave physics, particularly in optics, where waves, such as light or sound waves, are trapped and circulate along the periphery of a curved...

The random noise having a spectral density that is substantially independent of the frequency over a specified frequency range. White noise is widely used in the random vibration testing of devices.