What is an Infrared Laser Diode?

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  • Written By: Mal Baxter
  • Edited By: Daniel Lindley
  • Last Modified Date: 27 February 2017
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An infrared laser diode is an electronic component that converts electric current into electromagnetic radiation; this emits a wavelength between visible light and microwave radiation. These devices provide light used for solid state laser pumping in optical fiber networks, scientific spectral analysis, materials processing, and numerous other uses. Laser diodes range from single milliwatt (mW) to 10 mW, or are arrayed as diode-pumped solid state (DPSS) lasers of several kilowatts (kW).

These components feature a high yield of power from low operating currents and multiple beam configuration. Using semiconducting material as reflective end facets, photons stimulated by continuous reflection collide with atoms to generate the powerful release of more photons. This creates intense light rays that may be directed through a collimating, or ray-straightening, lens, or infrared (IR) filter. Applications include disc players, computer drives, and communications networks.

Another application for the infrared laser diode is in the use of free space optical communication links, which are essentially optical transmissions that pass through the open air. With transmission rates around 4 gigabits per second (Gb/s), this can provide an inexpensive alternative for servicing telecommunications in areas where digging optical fiber infrastructure is cost-prohibitive. Atmospheric conditions and beam dispersions affect such placements, however. Wavelengths around 1,330 nanometers (nm) provide the least dispersion, while 1,550 nm allow the best transmissions. An infrared transmitter might use IR laser diodes or light-emitting diodes (LED), and normally operates in temperature ranges of -10° to 60°C, compared to visible diodes at -10° to 50°C.

Diodes are small electronic devices that emit light energy by passing a current over a semiconductor, as in light-emitting diodes. As the atoms fall into gaps in the material, they emit a small amount of energy in the form of a light particle, or photon. The resulting glow can be modulated in different wavelengths or colors of light by configuration of the gaps, and directed through lenses and filters to modify intensity. Infrared (IR) is the portion of the electromagnetic (EM) band higher than radio waves and just under rainbow red, invisible to the naked eye. It is the heat radiation captured by night vision and thermal imaging devices.

IR radiation is stimulated by thermal agitation when radiation strikes an object. This type of radiation moves in a straight line as light, not as thermal convection or electrical conduction. An infrared laser diode intensifies this non-visible light to deliver rapid digital transmissions in everything from cameras to missile systems.

Diode-pumped infrared lasers are employed to engrave metal and construct circuit boards. Long-wave IR lasers are less affected by atmospheric conditions than short-wave IR, and so are more often employed in communications. Infrared laser diode technology is used in surgery and target acquisition missile systems in military applications. It is used to detect gas, and it allows a desktop computer mouse to track surfaces at 20 times the resolution of LED imaging. Laser sights on guns use IR laser diodes to generate an invisible targeting dot to be detected using night vision devices.

Light emitted from an infrared laser diode is dangerous for direct viewing. The human eye has no heat receptors to warn the nervous system of exposure to the dangerous burning effect. An infrared sensitive camera or phosphor plate can assist in determining the optical path of an IR laser. While some lasers direct their collimated beams through infrared filters to eliminate this risk, manufacturing processes sometimes result in faulty or missing IR filters; thus it is safer to simply avoid direct eye exposure to all laser beams.


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