Free electron lasers

Patent Granted A free-electron laser (FEL), is a type of laser that uses very-high-speed electrons that move freely through a magnetic structure,[1] hence the term free electron as the lasing medium.[2][not in citation given] The free-electron laser has the widest frequency range of any laser type, and can be widely tunable,[3] currently ranging in wavelength from microwaves, through terahertz radiation and infrared, to the visible spectrum, ultraviolet, and X-ray.