Laser

An electronic device that produces an intense and very pure, parallel beam of light known as coherent light. Laser light can be focused to form a powerful cutting and welding tool. it can be used in telecommunications to carry signals along optical fibres. Surgeons and eye specialists also sometimes use laser instruments. The main types of lasers are Ruby crystal lasers, Gas laser and Semiconductor lasers. The ruby laser ca produces only pulses of laser light, The other two types can produce continuous beams . A widely used gas laser uses carbon dioxide. A common semiconductor laser uses gallium arsenide crystals. the word laser stands for light amplification by stimulated emission of radiation.

Gas laser

Source : wikipedia