2 Popular misconceptions
The representation of lasers in popular culture, especially science-fiction or other action movies, is generally very misleading. For instance, contrary to what appears in movies such as Star Wars, a laser beam is never visible in the vacuum of space and usually does not glow in air either, the ray only glows if some obstacles, such as dust, lie in its path, in much the same way that a sunbeam glows in a dusty atmosphere. Very high intensity beams can be visible in air due to rayleigh scattering or raman scattering.
Some action movies depict security systems using red lasers (and being foiled by the hero, typically using mirrors); the hero may see the path of the beam by sprinkling some flour in the air. It is actually easier to build infrared laser diodes than visible light laser diodes, therefore such systems have no reason to work in visible light.
3 Laser safety
Even low-power lasers with only a few milliwatts of output power can be hazardous to a person's eyesight. At wavelengths which the cornea and the lens can focus well, the coherence and low divergence of laser light means that it can be focused by the eye into an extremely small spot on the retina, resulting in localised burning and permanent damage in seconds or even faster. Lasers are classified into safety classes numbered I (inherently safe) to IV (even scattered light can cause eye and/or skin damage). Laser products available for consumers, such as CD players and laser pointers are usually in class I or II. See also: Laser safety.
4 Common Laser types
For a more complete list of laser types see: List of laser types.
- Gas lasers
- HeNe (543 nm and 633 nm)
- Argon(-Ion) (458 nm, 488 nm or 514.5 nm)
- Carbon dioxide lasers - used in industry for cutting and welding, up to 100 kW possible
- Carbon monoxide lasers - must be cooled, but extremely powerful, up to 500 kW possible
- Excimer gas lasers, producing ultraviolet light, used in semiconductor manufacturing and in LASIK eye surgery; 157 nm (F_2), 193 nm (ArF), 222 nm (KrCl), 248 nm (KrF), 308 nm (XeCl), 351 nm (XeF).
- Commonly used laser types for dermatological procedures including removal of tattoos, birthmarks, and hair: Ruby (694 nm), Alexandrite (755 nm), Pulsed diode array (810 nm), Nd:YAG (1064 nm), Ho:YAG (2090 nm), Er:YAG (2940 nm).
- Semiconductor laser diodes,
- small: used in laser pointers, laser printers, and CD/DVD players;
- bigger: bigger industrial diode laser are available used in the industry for cutting and welding, up to 10 kW possible
- External-cavity semiconductor lasers, e.g. for generating high power outputs with good beam quality, wavelength-tunable narrow-linewidth radiation, or ultrashort laser pulses
- Dye lasers
- Quantum cascade laser s
- Neodymium-doped YAG lasers ( ), a high-power laser operating in the infrared, used for cutting, welding and marking of metals and other materials
- Ytterbium-doped lasers with crystals such as Yb:YAG, Yb:KGW, Yb:KYW, Yb:SYS, Yb:BOYS, Yb:CaF2, or Yb-doped glasses (e.g. fibers); typically operating around 1020-1050 nm; potentially very high efficiency and high powers due to a small quantum defect; highest laser power in ultrashort pulses achieved with Yb:YAG
- Erbium-doped YAG , 1645 nm
- Thulium-doped YAG, 2015 nm
- Holmium-doped YAG, 2096 nm, a efficient laser operating in the infrared, it is strongly absorbed by water-bearing tissues in sections less than a millimeter thick. It is usually operated in a pulsed mode, and passed through optic fiber surgical devices to resurface joints, remove rot from teeth, vaporize cancers, and to pulverize kidney and gall stones.
- Titanium-doped sapphire ( ) lasers, a highly tunable infrared laser, used for spectroscopy;
- Erbium-doped fiber lasers, a type of laser formed from a specially made optical fiber, which is used as an amplifier for optical communications.
