Definitions

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.

Specified curved optic intended for maximum collection of light, including off-axis rays, before leaving the exit aperture.

A grazing incidence mirror telescope with concentric conic surfaces having a single common point: a paraboloid-hyperboloid combination with two internal reflections.

The phenomenon in which alkali metals are transparent to ultraviolet radiation.

A Cassegrain telescope having a parabolic primary mirror, a spherical secondary mirror and a zero-power doublet in the converging bundle for aberration correction.

An instrument that is used to chart x-ray diffraction patterns, such as an x-ray spectrometer having photographic or other recording implements.

A printing process of electrostatic electrophotography that uses a photoconductive insulating medium, in conjunction with infrared, visible or ultraviolet radiation, to produce latent...

Spherical or chromatic aberration in a lens having a wide aperture. It is present because the refracting power varies for different zones concentric at the axis. This is the residual when the lens...