fotokatoodi

A fotokatoodi, or photocathode, is an electrode that emits electrons when struck by photons, a process known as the photoelectric effect. This phenomenon is fundamental to the operation of various light-sensitive devices. The material used for the photocathode is crucial, as its work function determines the minimum photon energy required to eject electrons. Common materials include alkali metals like cesium and antimony, often in combination with other elements to achieve desired spectral sensitivity and quantum efficiency.

Photocathodes are essential components in photomultiplier tubes, image intensifier tubes, and photodetectors. In these devices, the emitted electrons are amplified or detected to register the presence and intensity of light. The sensitivity of a photocathode is measured by its quantum efficiency, which is the ratio of emitted electrons to incident photons at a specific wavelength. Different photocathode materials have distinct spectral response curves, meaning they are more sensitive to certain wavelengths of light than others.

The fabrication of photocathodes involves carefully depositing thin films of photoemissive materials onto a transparent substrate, such as glass. The purity and uniformity of these films are critical for optimal performance. Photocathodes are used in a wide range of applications, including scientific research, medical imaging, industrial inspection, and security systems, wherever accurate and sensitive detection of light is required.