Editing Laser pointer (section)

{{short description|Handheld device that emits a laser beam}}
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[[File:Laser Pointers.jpg|thumb|300px|Red (635&nbsp;nm), blueish violet (445&nbsp;nm), and green (520&nbsp;nm) laser pointers]]

A '''laser pointer''' or '''laser pen''' is a (typically battery-powered) handheld device that uses a  [[laser diode]] to emit a narrow low-power visible [[laser]] beam (i.e. [[Coherence (physics)|coherent]] [[light]]) to highlight something of interest with a small bright colored spot.

The small width of the beam and the low power of typical laser pointers make the beam itself invisible in a clean atmosphere, only showing a point of light when striking an opaque surface. Laser pointers can project a visible beam via scattering from dust particles or water droplets along the beam path. Higher-power and higher-frequency green or blue lasers may produce a beam visible even in clean air because of [[Rayleigh scattering]] from air molecules, especially when viewed in moderately-to-dimly lit conditions. The intensity of such scattering increases when these beams are viewed from angles near the beam axis. Such pointers, particularly in the green-light output range, are used as [[astronomical object]] pointers for teaching purposes.

Laser pointers make a potent signaling tool, even in daylight, and are able to produce a bright signal for potential search and rescue vehicles using an inexpensive, small and lightweight device of the type that could be routinely carried in an [[emergency kit]].

There are significant safety concerns with the use of laser pointers. Most jurisdictions have restrictions on lasers above 5&nbsp;[[Milliwatt|mW]]. If aimed at a person's eyes, laser pointers can cause temporary visual disturbances or even severe damage to vision. There are reports in the medical literature documenting permanent injury to the macula and the subsequent permanent loss of vision after laser light from a laser pointer was shone at a human's eyes.  In rare cases, a dot of light from a red laser pointer may be thought to be due to a [[Laser sight|laser gunsight]].<ref name=princeton/> When pointed at aircraft at night, laser pointers may dazzle and distract pilots, and increasingly strict laws have been passed to ban this.

The low-cost availability of [[infrared]] (IR) diode laser modules of up to 1000&nbsp;mW (1&nbsp;[[watt]]) output has created a generation of IR-pumped, [[Second-harmonic generation|frequency doubled]], green, blue, and violet [[diode-pumped solid-state laser]] pointers with visible power up to 300&nbsp;mW. Because the invisible IR component in the beams of these visible lasers is difficult to filter out, and also because filtering it contributes extra heat which is difficult to dissipate in a small pocket "laser pointer" package, it is often left as a beam component in cheaper high-power pointers. This invisible IR component causes a degree of extra potential hazard in these devices when pointed at nearby objects and people.
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