Definition: devices emitting infrared radiation
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Author: Dr. Rüdiger Paschotta
The term infrared emitters could in principle be applied to any devices emitting infrared light. However, it is typically used for devices which are not lasers – in particular, to the following types of emitters:
Thermal emitters are devices which emit thermal radiation from some heated part. Some of them are special forms of incandescent lamps, sometimes in a very compact form, and may be used as broadband infrared light sources for applications in spectroscopy, for example, where the quite limited brightness is acceptable. Their emission may be more or less constant, but not necessarily with a high precision of calibration. Special designs that of the Nernst lamp and the globar. Sometimes, such sources are equipped with a infrared filter which transmits only infrared light in a certain spectral region.
There are also calibrated blackbody sources, where e.g. a ceramic tube is electrically heated to a high temperature (e.g. 1000 °C), and the corresponding thermal radiation exits at one end.
Besides, there are pulsable thermal emitters, where the radiation is generated by a thin foil with low thermal capacitance. They can allow the modulation of thermal radiation of timescales of a few milliseconds.
Other thermal emitters are larger infrared heaters, sometimes with quite substantial heating powers, for applications in industrial fabrication or in laser printers, for example.
The radiance of thermal emitters is fundamentally limited. Substantially higher radiance is possible with infrared light emitting diodes (LEDs). The output power of those can also be rapidly modulated, and that feature is frequently employed in remote control transmitters, for example.
Typical output powers between a few milliwatts and hundreds of milliwatts, but emitters with multi-watt output are also available.
The output can be somewhat directed, but not as much as with laser diodes.
In terms of laser safety, infrared LEDs are less critical than lasers.
The RP Photonics Buyer's Guide contains 12 suppliers for infrared emitters.
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See also: infrared light, thermal radiation, incandescent lamps
and other articles in the category photonic devices
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