Red (660 & 635 nm), green (532 & 520 nm) and blue-violet (445 & 405 nm) lasers
In the lower picture, the light has been collimated.
A laser beam used for welding
An example of an optical collimating lens.
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Diagram of a collimated-light display system, as seen from the side of a flight simulator
A helium–neon laser demonstration. The glow running through the center of the tube is an electric discharge. This glowing plasma is the gain medium for the laser. The laser produces a tiny, intense spot on the screen to the right. The center of the spot appears white because the image is overexposed there.
Diagram of display system that uses collimated light and a real flight simulator
Spectrum of a helium–neon laser. The actual bandwidth is much narrower than shown; the spectrum is limited by the measuring apparatus.
Lidar measurements of lunar topography made by Clementine mission.
Laserlink point to point optical wireless network
Mercury Laser Altimeter (MLA) of the MESSENGER spacecraft
Aleksandr Prokhorov
Charles H. Townes
LASER notebook: First page of the notebook wherein Gordon Gould coined the acronym LASER, and described the elements required to construct one. Manuscript text: "Some rough calculations on the feasibility / of a LASER: Light Amplification by Stimulated / Emission of Radiation. /
Conceive a tube terminated by optically flat / [Sketch of a tube] / partially reflecting parallel mirrors..."
Graph showing the history of maximum laser pulse intensity throughout the past 40 years.
Wavelengths of commercially available lasers. Laser types with distinct laser lines are shown above the wavelength bar, while below are shown lasers that can emit in a wavelength range. The color codifies the type of laser material (see the figure description for more details).
A 50 W FASOR, based on a Nd:YAG laser, used at the Starfire Optical Range
A 5.6 mm 'closed can' commercial laser diode, such as those used in a CD or DVD player
Close-up of a table-top dye laser based on Rhodamine 6G
The free-electron laser FELIX at the FOM Institute for Plasma Physics Rijnhuizen, Nieuwegein
Lasers range in size from microscopic diode lasers (top) with numerous applications, to football field sized neodymium glass lasers (bottom) used for inertial confinement fusion, nuclear weapons research and other high energy density physics experiments.
The US–Israeli Tactical High Energy weapon has been used to shoot down rockets and artillery shells.
Laser application in astronomical adaptive optics imaging

Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers and lidar (light detection and ranging).

- Laser

Laser light from gas or crystal lasers is highly collimated because it is formed in an optical cavity between two parallel mirrors which constrain the light to a path perpendicular to the surfaces of the mirrors.

- Collimated beam
Red (660 & 635 nm), green (532 & 520 nm) and blue-violet (445 & 405 nm) lasers

1 related topic

Alpha

A glass nanoparticle is suspended in an optical cavity

Optical cavity

Arrangement of mirrors that forms a standing wave cavity resonator for light waves.

Arrangement of mirrors that forms a standing wave cavity resonator for light waves.

A glass nanoparticle is suspended in an optical cavity
Types of two-mirror optical cavities, with mirrors of various curvatures, showing the radiation pattern inside each cavity.
Stability diagram for a two-mirror cavity. Blue-shaded areas correspond to stable configurations.
Alignment of a folded cavity using an autocollimator

Optical cavities are a major component of lasers, surrounding the gain medium and providing feedback of the laser light.

Commonly, a pair of curved mirrors form one or more confocal sections, with the rest of the cavity being quasi-collimated and using plane mirrors.