Photodiodes and photomultiplier tubes have important applications in the field of photoelectric conversion, but they differ significantly in principle, characteristics, and application scenarios. The following is a detailed comparison of these two devices:

1. Principle

Photodiode: Based on the principle of photoelectric effect, when light is irradiated on semiconductor materials, photons are absorbed by electrons, and their energy is converted into electronic energy. When the photon energy is greater than the semiconductor bandgap energy, electron hole pairs are generated. In a photodiode, these electrons and holes form a potential difference in the P-N junction, thereby generating current.
Photomultiplier tube: based on the theories of external photoelectric effect, secondary electron emission, and electron optics. When light shines on the photocathode, it excites photoelectrons into the vacuum. These photoelectrons enter the doubling system under the action of an electric field, and are further amplified through secondary emission. Finally, they are collected by the anode as a signal output.

2. Characteristics

photodiode:
Fast response speed: usually completed within nanoseconds.
High linearity: There is a good linear relationship between current and light intensity.
High sensitivity: It has a high sensitivity to detecting light.
Low gain: Compared to photomultiplier tubes, its gain is relatively small.
Photomultiplier tube:
Extremely high sensitivity: With extremely high gain and sensitivity, it can detect extremely weak light signals.
High gain: By multi-level multiplication, a gain much higher than that of a photodiode can be obtained.
Slow response speed: Compared to photodiodes, their response speed is slower.

3. Application

photodiode:
Optical communication: As a core device in optical communication, it converts optical signals into electrical signals.
Optoelectronics: used in fields such as spectral analysis, laser ranging, optical imaging, etc.
Photoelectric detection: gas detection, photoelectric sensors, etc.
Lighting: such as solar panels, LED lights, etc.
Photomultiplier tube:
Weak light signal detection: such as celestial photometric measurement, spectral analysis, laser detection, etc.
In optical measuring instruments and spectroscopic analysis instruments, it is used to measure extremely weak radiation power with wavelengths ranging from 200 to 1200 nanometers.
Scintillation counter: Expands the application range of photomultiplier tubes.

Other fields: such as metallurgy, electronics, machinery, chemical engineering, geology, medicine, nuclear industry, astronomy, and space research.

There are significant differences between photodiodes and photomultiplier tubes in terms of principles, characteristics, applications, and manufacturers. Photodiodes have the characteristics of fast response speed, high linearity, and high sensitivity, and are widely used in fields such as optical communication and optoelectronics; The photomultiplier tube, with its extremely high sensitivity and gain, has important applications in the field of weak light signal detection.