Share

WIKIPEDIA ARTICLE

From Wikipedia, the free encyclopedia
  (Redirected from Ambient light sensor)
Jump to navigation Jump to search

A photodetector salvaged from a CD-ROM drive. The photodetector contains three photodiodes, visible in the photo (in center).

Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation.[1] A photo detector has a p–n junction that converts light photons into current. The absorbed photons make electron–hole pairs in the depletion region. Photodiodes and photo transistors are a few examples of photo detectors. Solar cells convert some of the light energy absorbed into electrical energy.

Types[edit]

A commercial amplified photodetector for use in optics research

Photodetectors may be classified by their mechanism for detection:[2][unreliable source?][3][4]

  • Photoemission or photoelectric effect: Photons cause electrons to transition from the conduction band of a material to free electrons in a vacuum or gas.
  • Thermal: Photons cause electrons to transition to mid-gap states then decay back to lower bands, inducing phonon generation and thus heat.
  • Polarization: Photons induce changes in polarization states of suitable materials, which may lead to change in index of refraction or other polarization effects.
  • Photochemical: Photons induce a chemical change in a material.
  • Weak interaction effects: photons induce secondary effects such as in photon drag[5][6] detectors or gas pressure changes in Golay cells.

Photodetectors may be used in different configurations. Single sensors may detect overall light levels. A 1-D array of photodetectors, as in a spectrophotometer or a Line scanner, may be used to measure the distribution of light along a line. A 2-D array of photodetectors may be used as an image sensor to form images from the pattern of light before it.

A photodetector or array is typically covered by an illumination window, sometimes having an anti-reflective coating.

Properties[edit]

There are a number of performance metrics, also called figures of merit, by which photodetectors are characterized and compared[2][3]

  • Spectral response: The response of a photodetector as a function of photon frequency.
  • Quantum efficiency: The number of carriers (electrons or holes) generated per photon.
  • Responsivity: The output current divided by total light power falling upon the photodetector.
  • Noise-equivalent power: The amount of light power needed to generate a signal comparable in size to the noise of the device.
  • Detectivity: The square root of the detector area divided by the noise equivalent power.
  • Gain: The output current of a photodetector divided by the current directly produced by the photons incident on the detectors, i.e., the built-in current gain.
  • Dark current: The current flowing through a photodetector even in the absence of light.
  • Response time: The time needed for a photodetector to go from 10% to 90% of final output.
  • Noise spectrum: The intrinsic noise voltage or current as a function of frequency. This can be represented in the form of a noise spectral density.
  • Nonlinearity: The RF-output is limited by the nonlinearity of the photodetector[7]

Devices[edit]

Grouped by mechanism, photodetectors include the following devices:

Photoemission or photoelectric[edit]

Semiconductor[edit]

Photovoltaic[edit]

Thermal[edit]

  • Bolometers measure the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance. A microbolometer is a specific type of bolometer used as a detector in a thermal camera.
  • Cryogenic detectors are sufficiently sensitive to measure the energy of single x-ray, visible and infrared photons.[14]
  • Pyroelectric detectors detect photons through the heat they generate and the subsequent voltage generated in pyroelectric materials.
  • Thermopiles detect electromagnetic radiation through heat, then genetating a voltage in thermocouples.
  • Golay cells detect photons by the heat they generate in a gas-filled chamber, causing the gas to expand and deform a flexible membrane whose deflection is measured.

Photochemical[edit]

Polarization[edit]

Graphene/silicon photodetectors[edit]

A graphene/n-type silicon heterojunction has been demonstrated to exhibit strong rectifying behavior and high photoresponsivity. Graphene is coupled with silicon quantum dots (Si QDs) on top of bulk Si to form a hybrid photodetector. Si QDs cause an increase of the built-in potential of the graphene/Si Schottky junction while reducing the optical reflection of the photodetector. Both the electrical and optical contributions of Si QDs enable a superior performance of the photodetector.[16]

Frequency range[edit]

In 2014 a technique for extending semiconductor-based photodetector's frequency range to longer, lower-energy wavelengths. Adding a light source to the device effectively "primed" the detector so that in the presence of long wavelengths, it fired on wavelengths that otherwise lacked the energy to do so.[17]

See also[edit]

References[edit]

  1. ^ Haugan, H. J.; Elhamri, S.; Szmulowicz, F.; Ullrich, B.; Brown, G. J.; Mitchel, W. C. (2008). "Study of residual background carriers in midinfrared InAs/GaSb superlattices for uncooled detector operation". Applied Physics Letters. 92 (7): 071102. Bibcode:2008ApPhL..92g1102H. doi:10.1063/1.2884264. 
  2. ^ a b Donati, S. "Photodetectors" (PDF). unipv.it. Prentice Hall. Retrieved 1 June 2016. 
  3. ^ a b Yotter, R.A.; Wilson, D.M. (June 2003). "A review of photodetectors for sensing light-emitting reporters in biological systems". IEEE Sensors Journal. 3 (3): 288–303. Bibcode:2003ISenJ...3..288Y. doi:10.1109/JSEN.2003.814651. 
  4. ^ Stöckmann, F. (May 1975). "Photodetectors, their performance and their limitations". Applied Physics. 7 (1): 1–5. Bibcode:1975ApPhy...7....1S. doi:10.1007/BF00900511. 
  5. ^ A. Grinberg, Anatoly; Luryi, Serge (1 July 1988). "Theory of the photon-drag effect in a two-dimensional electron gas". Physical Review B. 38 (1): 87–96. Bibcode:1988PhRvB..38...87G. doi:10.1103/PhysRevB.38.87. 
  6. ^ Bishop, P.; Gibson, A.; Kimmitt, M. (October 1973). "The performance of photon-drag detectors at high laser intensities". IEEE Journal of Quantum Electronics. 9 (10): 1007–1011. Bibcode:1973IJQE....9.1007B. doi:10.1109/JQE.1973.1077407. 
  7. ^ Hu, Yue (1 October 2014). "Modeling sources of nonlinearity in a simple pin photodetector". Journal of Lightwave Technology. 32 (20): 3710–3720. Bibcode:2014JLwT...32.3710H. doi:10.1109/JLT.2014.2315740. 
  8. ^ "Photo Detector Circuit". oscience.info. 
  9. ^ Paschotta, Dr. Rüdiger. "Encyclopedia of Laser Physics and Technology - photodetectors, photodiodes, phototransistors, pyroelectric photodetectors, array, powermeter, noise". www.rp-photonics.com. Retrieved 2016-05-31. 
  10. ^ "PDA10A(-EC) Si Amplified Fixed Gain Detector User Manual" (PDF). Thorlabs. Retrieved 24 April 2018. 
  11. ^ "DPD80 760nm Datasheet". Resolved Instruments. Retrieved 24 April 2018. 
  12. ^ Rizzi, M.; D`Aloia, M.; Castagnolo, B. "Semiconductor Detectors and Principles of Radiation-matter Interaction". Journal of Applied Sciences. 10 (23): 3141–3155. Bibcode:2010JApSc..10.3141R. doi:10.3923/jas.2010.3141.3155. 
  13. ^ "Silicon Drift Detectors" (PDF). tools.thermofisher.com. Thermo Scientific. 
  14. ^ Enss, Christian (Editor) (2005). Cryogenic Particle Detection. Springer, Topics in applied physics 99. ISBN 3-540-20113-0. 
  15. ^ Yuan, Hongtao; Liu, Xiaoge; Afshinmanesh, Farzaneh; Li, Wei; Xu, Gang; Sun, Jie; Lian, Biao; Curto, Alberto G.; Ye, Guojun; Hikita, Yasuyuki; Shen, Zhixun; Zhang, Shou-Cheng; Chen, Xianhui; Brongersma, Mark; Hwang, Harold Y.; Cui, Yi (1 June 2015). "Polarization-sensitive broadband photodetector using a black phosphorus vertical p–n junction". Nature Nanotechnology. 10 (8): 707–713. Bibcode:2015NatNa..10..707Y. doi:10.1038/nnano.2015.112. 
  16. ^ Yu, Ting; Wang, Feng; Xu, Yang; Ma, Lingling; Pi, Xiaodong; Yang, Deren (2016). "Graphene Coupled with Silicon Quantum Dots for High-Performance Bulk-Silicon-Based Schottky-Junction Photodetectors". Advanced Materials. doi:10.1002/adma.201506140. 
  17. ^ Claycombe, Ann (2014-04-14). "Research finds "tunable" semiconductors will allow better detectors, solar cells". Rdmag.com. Retrieved 2014-08-24. 

External links[edit]

Disclaimer

None of the audio/visual content is hosted on this site. All media is embedded from other sites such as GoogleVideo, Wikipedia, YouTube etc. Therefore, this site has no control over the copyright issues of the streaming media.

All issues concerning copyright violations should be aimed at the sites hosting the material. This site does not host any of the streaming media and the owner has not uploaded any of the material to the video hosting servers. Anyone can find the same content on Google Video or YouTube by themselves.

The owner of this site cannot know which documentaries are in public domain, which has been uploaded to e.g. YouTube by the owner and which has been uploaded without permission. The copyright owner must contact the source if he wants his material off the Internet completely.

Powered by YouTube
Wikipedia content is licensed under the GFDL and (CC) license