Componentsof a typicallaser:1. Gain medium2. Laser pumpingenergy3. High reflector4. Output coupler5. Laser beam
A laser is a device that emits light (electromagnetic radiation)through a process of optical amplification based onthe stimulated emission of photons. The term "laser"originated as an acronym for Light Amplification byStimulated Emission of Radiation. The emitted laser lightis notable for its high degree of spatial andtemporal coherence.Temporal (or longitudinal) coherence implies a polarizedwave at a single frequency whose phase is correlated over arelatively large distance (the coherence length) along thebeam. A beam produced by a thermal or other incoherentlight source has an instantaneous amplitude and phase whichvary randomly with respect to time and position, and thus avery short coherence length.
Since the early period of laser history,laser research has produced a variety ofimproved and specialized laser types,optimized for different performance goals,including:-new wavelength bands-maximum average output power-maximum peak pulse energy-maximum peak pulse power-minimum output pulse duration-maximum power efficiency-minimum cost
Solid-state lasersSolid-state lasers use a crystalline or glass rodwhich is "doped" with ions that provide therequired energy states. For example, the firstworking laser was a ruby laser, madefrom ruby (chromium-doped corundum).The population inversion is actually maintainedin the "dopant", suchas chromium orneodymium. These materialsare pumped optically using a shorterwavelength than the lasing wavelength, oftenfrom a flashtube or from another laser.
Dye lasersDye lasers use an organic dye as the gainmedium. The wide gain spectrum of availabledyes, or mixtures of dyes, allows these lasers tobe highly tunable, or to produce very short-duration pulses (on the order of afew femtoseconds). Although these tunablelasers are mainly known in their liquid form,researchers have also demonstrated narrow-linewidth tunable emission in dispersiveoscillator configurations incorporating solid-statedye gain media. In their most prevalent formthese solid state dye lasers use dye-dopedpolymers as laser media.
When lasers were invented in 1960, they werecalled "a solution looking for aproblem". Since then, they have becomeubiquitous, finding utility in thousands ofhighly varied applications in every section ofmodern society, including consumerelectronics, information technology, science,medicine, industry, law enforcement,entertainment, and the military.The first use of lasers in the daily lives of thegeneral population was thesupermarket barcode scanner, introduced in1974. The laserdisc player, introduced in 1978,was the first successful consumer product toinclude a laser but the compact disc player wasthe first laser-equipped device to becomecommon, beginning in 1982 followed shortlyby laser printers.
Some other uses are:Medicine:- Bloodless surgery,- laser healing, surgical treatment, kidneystone treatment, eye treatment, dentistryIndustry:-Cutting, welding, material heat treatment,-marking parts, non-contact measurement ofpartsMilitary:- Marking targets, guiding munitions, missiledefence,- -electro-optical countermeasures (EOCM),alternative to radar, blinding troops.Law enforcement:-used for latent fingerprint-detection in the forensic identification field]Laser application in astronomical adaptiveoptics imaging