Laser stand for Light Ampliction by stimulated emmision of radiation. laser is monochromatic light , monochromatic light consists on one color.having one wavelength it is also called coherent light.even LED emmits incoherent light.the symbol of laser are as in fig same like LED.
Construction of LASER DIODE
Laaer diode consists on a pn junction which is formed by two layers of doped gallium arsenide.on the one side of pn junction there is highly reflective end and partially reflective end at the other side.
Working Principle of Laser Diode
When Laser diodis forward biased by source , electrons moving in pn junction becauof electron- hole pair recombinaton.
As electrons falls in holes in the procesa of recmbination,it releases a photons.this generated photons strike an atom ,causing another photons to be released.due to increae in forward current ,more electrons entering in depletion layer and be a reason more photons emmitted.
The emmitted electrons randomly drifteing in depletion region and strike the reflected surface prependicularly.these reflected photons move witjin depletion layer striking atoms and emmiting more photons causof avelenche effect.these alprocess called stimulated emmision. Due to this back and forth movement of photons increases the generation of photons till very intense beam laser light emitts from the partially reflective end of the Pn Junction.
LASER diode used in
- pick up system of CD compact disk players
- Laser printers
- fiber optic system