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Photonics Dictionary

photocathodes

Photocathodes are specialized materials or surfaces that exhibit the photoelectric effect, wherein the absorption of photons leads to the emission of electrons. When photons with sufficient energy strike a photocathode, they transfer energy to the electrons within the material, enabling them to overcome the surface potential and escape into the surrounding space. This emission of electrons is often referred to as photoemission.

Photocathodes are crucial components in various photonics and optoelectronic devices, particularly in photodetectors, image sensors, and electron sources. They are commonly used in applications such as night vision, photomultiplier tubes, image intensifiers, and electron microscopes.

The performance of a photocathode is determined by several factors, including its quantum efficiency (the fraction of incident photons that result in emitted electrons), spectral response (the range of wavelengths over which photoemission occurs), and electron emission characteristics (such as energy distribution and temporal response).

Photocathodes are typically made from materials with low work functions, which facilitate the emission of electrons when illuminated with photons of appropriate energy. Common materials used for photocathodes include alkali metals (e.g., cesium and potassium), semiconductors (e.g., gallium arsenide), and specialized compounds (e.g., gallium nitride).

In addition to their use in photonics and optoelectronics, photocathodes play a crucial role in particle accelerators and high-energy physics experiments, where they are used to generate and manipulate electron beams for scientific research and industrial applications.
 
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