Laser
A laser was a directed-energy technology utilizing a beam of light, with all wavelengths equal and all particles in phase with one another. Due to this, the photon's motion was almost parallel, which allowed the beam to travel over a great distance with very little increase of the beam's square area, and therefore with little loss of energy per area. The word "laser" is an acronym for Light Amplification by the Stimulated Emission of Radiation. Lasers had a variety of uses in medicine, computers, mining, and power generation, such as laser-induced fusion in fusion reactors.

Examples 
In 1996, both Rain Robinson and  mistook phaser weapons for lasers. ()

Some of the first lasers constructed operated by passing light through natural crystals. These "ancient lasers" then achieved a necessary excitation and emitted a laser beam. Rubindium crystals were capable of producing a laser beam, even with only a low source of light. ()

An industrial laser cannon was used by the laborers of the Orpheus Mining Complex on Luna in 2155. ()

A laser beacon was part of the Starfleet equipment issued aboard the . Lieutenant DeSalle used the laser beacon to attempt to signal the ship visually from the surface of Gothos. ()

A nanopulse laser was an exotic piece of equipment owned by Andromedan androids who aided Harry Mudd in capturing the Enterprise. ()

A tri-laser connector was a type of Eymorg tool used by Doctor McCoy when he reconnected Spock's brain in 2269. ()

Laser weapons also existed, such as the advanced laser pistols and laser cannons used by Starfleet in the 2250s, and the high-energy X-ray lasers mounted aboard Talarian warships. (; )

According to Lt. Sulu in 2269, the laser weapons the Federation possessed were a more advanced model than the laser setting of the Slaver weapon, and their laser had been more powerful for the last century. ()

The Atlec used laser weapons on their ships and once targeted them on the Enterprise-D in an attempt to acquire the Straleb Jewel of Thesia and Thadiun Okona. Picard noted that such lasers would not even penetrate their navigation shields. Starfleet regulations required that a vessel targeted with laser weapons go to yellow alert; it was considered a very old regulation. () 

When Chief Miles O'Brien introduced the game of darts at Quark's Bar, Grill, Gaming House and Holosuite Arcade, Quark failed to understand its appeal because it did not include anything like lasers or holograms. ()

In the Julian Bashir, Secret Agent holoprogram, Hippocrates Noah deployed earthquake-causing lasers around the Earth. ()

Pulse lasers were used as weapons by the Lysian Central Command. Like other laser devices, pulse lasers were not considered very powerful by 24th century Federation standards. ()

The 24th century Federation belief that lasers were obsolete weapons was proved wrong in a catastrophic fashion on the Federation's first contact with the Borg, as the cutting beam aboard a Borg cube proved to be capable of destroying Federation starships with ease. (; ; )

Zefram Cochrane told Commander Riker that he had a hangover either from the whiskey he drank or because of Riker's laser beam, referring to the phaser he'd been stunned with earlier. ()

Appendices

Apocrypha 
The McDonald's video communicator comic "Votec's Freedom" suggests that Starfleet continued to refine laser technology into the 2270s, as Spock cuts a prisoner's chains with his "new ultra laser."

James Blish's conversion of "Patterns of Force" to prose form in Star Trek 12 had Kirk explain to Isak that crystalline rubindium-based laser cutting torches were not weapons, as they had extremely short ranges. Since the Star Fleet Medical Reference Manual lists rubindium as being radioactive, laser cutting torches based upon it can also be presumed to have short useful life expectancies and therefore to be useless as weapons, as prolonged usage would quickly decrystallize the rubindium in the laser element.

External link 
 

de:Laser
Directed energy weapons
Tools