Difference between LED and LASER

Parameter	LED	LASER
Wavelength Content : A monochromatic source consists of radiation of a single wavelength or a very small range of wavelength.	Large	Small (desirable; more monochromatic)
Spectral Width/Line Width : The wavelength interval over which the magnitude of all the spectral components is greater than or equal to a specified fraction of the total magnitude, Here, the fraction is (0.707)*P	50 nm	< 5 nm
Principle of Emission	Spontaneous; random photon emission (hence, not directional)	Stimulated
Coherence : A constant phase difference between two waves	Incoherent; since emission is spontaneous	Coherent; since emission is stimulated; same phase as the stimulating photon
Output Power	Low	High
Directionality	Low	Highly directional
Speed of Operation	Slow	Faster
Numerical Aperture : determines the output pattern	Higher	Lower
Ease of Use	Easier to use; less complex circuitry	Complex circuitry; needs thermal & optical stabilization circuits due to light amplification
Lifetime	Long	Shorter
Cost	Cheaper	Expensive