Laser Beam

Laser beams are electromagnetic waves between 400 nm and 700 nm wavelength, created through stimulated emission. Light is a wave consisting of short wave packets, so called photones. Through stimulated emission an atom is encouraged to emit another photon by an already existing photon. This may be achieved via energy supply from outside ("pumping"): through light irradiation (DPSS lasers) or through electric energy (diode lasers). Furthermore one needs a resonator consisting of two mirrors between which the rays are reflected permanently and thereby getting amplified. One of these mirrors is slightly translucent. The emitting light is the laser beam. In a laser projector these emitted beams are filtered by means of a dichroic filter (that lets pass through only desired wavelengths) and then strike the mirrors of the laser scanner which deflect them. Thus one gets the visible laser beams escaping of the laser outlet of the projector.
Depending on the wavelength the beams have got different colors. Laser light is very concentrated and the beams may be visible over long distances. To get a narrow and sharp beam even over a longer distance (so called collimation) it is essential to have spatial coherence of the waves.