Red (660 & 635 nm), green (532 & 520 nm) and blue-violet (445 & 405 nm) lasers
Red (635 nm), blueish violet (445 nm), and green (520 nm) laser pointers
A laser beam used for welding
Trails by a 15 mW green laser pointer in a time exposure of a living room at night
frameless
A 5 mW green laser pointer directed at a palm tree at night. Note that the beam itself is visible through Rayleigh scattering.
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.
Laser level used in construction.
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

A laser pointer or laser pen is a small handheld device with a power source (usually a battery) and a laser diode emitting a very narrow coherent low-powered laser beam of visible light, intended to be used to highlight something of interest by illuminating it with a small bright spot of colored light.

- Laser pointer

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

1 related topic

Alpha

Energy level scheme of SHG process.

Second-harmonic generation

Nonlinear optical process in which two photons with the same frequency interact with a nonlinear material, are "combined", and generate a new photon with twice the energy of the initial photons (equivalently, twice the frequency and half the wavelength), that conserves the coherence of the excitation.

Nonlinear optical process in which two photons with the same frequency interact with a nonlinear material, are "combined", and generate a new photon with twice the energy of the initial photons (equivalently, twice the frequency and half the wavelength), that conserves the coherence of the excitation.

Energy level scheme of SHG process.
Schematic view of the SHG conversion of an exciting wave in a non-linear medium with a non-zero second-order non-linear susceptibility.
An electron (purple) is being pushed side-to-side by a sinusoidally-oscillating force, i.e. the light's electric field. But because the electron is in an anharmonic potential energy environment (black curve), the electron motion is not sinusoidal. The three arrows show the Fourier series of the motion: The blue arrow corresponds to ordinary (linear) susceptibility, the green arrow corresponds to second-harmonic generation, and the red arrow corresponds to optical rectification.
Different types of second-harmonic generation phase-matching of a coherent light for strong conversion. The case of negative crystals.
Diagram of the second-harmonic generation process.
A depiction of the second-harmonic generation setup for measuring the orientation of phenol at the air-water interface.
Cartoon depicting ordered molecules at a small spherical surface. An ultrafast pump laser pumps light with frequency ω which generates light at 2ω from the locally non-centrosymmetric media.
SHG radiation pattern excited with a Gaussian beam, in a homogeneous medium (A), or at an interface between opposite polarities that is parallel to the propagation (B). Only the forward SHG is represented.
SHG radiation pattern in forward (F) and backward (B) from different dipoles arangment: (a) single dipoles, thus F = B ; (b) a small stack of dipoles, F > B ; (c) a large stack of dipoles, F >> B ; (d) the Gouy phase-shift cancels the SHGs, F&B weak
Intensity SHG, phase-matched or not. The medium width is supposed to be much higher than z, the Rayleigh range at 20µm, excitation wavelength of 0.8µm, and optical index of 2.2.

The demonstration was made possible by the invention of the laser, which created the required high intensity coherent light.

Nevertheless, some "green laser pointer" products have become available on the market which omit the expensive infrared filter, often without warning.