What is a photodetector?
A photodetector is a device that converts light signals into electrical signals. Its basic operating principle involves the photoelectric effect: when photons hit the light-sensitive element on the detector surface, energy is converted into electrons, which generate current or voltage signals. These signals can then be amplified, processed and analyzed to obtain information about the intensity, frequency and time characteristics of the light signal.
Types of Photodetectors：
- Photodiodes are semiconductor devices with a p-n junction or p-i-n structure (i = intrinsic material) (→p-i-n photodiode) in which light is absorbed in the depletion region and generates a photocurrent. Such devices can be very compact, fast, highly linear, and exhibit high quantum efficiency (i.e., nearly one electron is generated per incident photon) and high dynamic range, provided they are operated in conjunction with suitable electronics. A particularly sensitive type is the avalanche photodiode, which is sometimes even used for photon counting.
- Metal-semiconductor-metal (MSM) photodetectors contain two Schottky contacts instead of a p-n junction. They can be faster than photodiodes, with bandwidths up to hundreds of gigahertz.
- Phototransistors are similar to photodiodes, but exploit the internal amplification of the photocurrent. They are used at lower frequencies than photodiodes.
- Photoconductive detectors are also based on certain semiconductors, such as cadmium sulfide (CdS). They are cheaper than photodiodes, but they are considerably slower, not very sensitive, and exhibit a nonlinear response. On the other hand, they can react to long-wavelength infrared light.
- A phototube is a vacuum tube or gas-filled tube that exploits the photoelectric effect (→ light emission detector).
- A photomultiplier is a special type of phototube that exploits the process of electron multiplication to obtain a greatly increased reactivity. They can also have high speed and large active area. Some of them are based on multichannel plates; they can be more compact than conventional photomultipliers.
- Investigation of new photodetectors based on carbon nanotubes (CNTs) or graphene that can provide very wide wavelength ranges and very fast responses. Methods for integrating such devices into optoelectronic chips are explored.
Applications of Photodetectors:
- In radiometry and photometry, they can be used to measure properties such as optical power, luminous flux, light intensity and irradiance, and can also be combined with other methods to measure properties such as radiometry.
- They are used to measure optical power, for example, in spectrometers, gratings, optical data storage devices, autocorrelators, beam profilers, fluorescence microscopes, interferometers, and various types of optical sensors.
- lParticularly sensitive photodetectors are needed for laser rangefinders, lidar, quantum optics experiments, and night vision devices.
- Particularly fast photodetectors are used in fiber-optic communications, optical frequency metrology, and characterization of pulsed lasers or laser noise.
- lMost two-dimensional arrays containing many identical photodetectors are used as focal plane arrays, mainly for imaging applications. For example, most cameras contain devices such as image sensors.
Suppliers：
Hamamatsu photonics offers a wide range of optoelectronic devices and sensors. On our website you can find the detector that best suits your specific application.
Purchase：
CH379-03 CH375-03 CH360-03
CH282-01 CH132
FAQ
How to check if the photodetector is damaged?
- Appearance inspection: Shell and connection parts: Check if there is obvious damage, cracks on the shell or whether the connection parts are stable. Make sure the physical structure of the detector is intact.
- Electrical connection: Check the electrical connection parts of the detector, including whether the cables or connecting wires are properly connected. Make sure that the electrical contact is good and there is no looseness or rust.
- Voltage check: Use an appropriate meter or test instrument to measure the voltage output of the detector. For some detectors, such as photodiodes, their working status can be confirmed by measuring their voltage when they are working normally.
- Optical signal test: Use a light source (such as a laser or fiber optic light source) to illuminate the photosensitive part of the detector (such as a photodiode). Observe or measure whether the detector outputs the corresponding electrical signal. Photodiodes should produce current or voltage changes under light exposure.
- Spectral response test: If you need to determine the response of the detector within a specific wavelength range, you can use a light source to generate light of different wavelengths and measure the response of the detector. This is especially important for applications with high requirements for specific wavelengths.
- Comparison test: If there is a spare photodetector that is working properly, you can compare it with the suspected damaged detector. This can help confirm if there is a noticeable performance difference or damage.
- Professional testing: If the above methods cannot determine the problem or a more precise evaluation is required, the detector can be sent to a professional optoelectronic device repair center or manufacturer for detailed diagnosis and repair.
For more information, please contact us at:emi-ic.com
