21 February 2018

Difference between LED and laser diode

LASER diode is also known as a laser diode and LED also known as a light emitting diode, both diodes have different characteristics in the way in which they emit light. When a LASER emits converged light, the output of an LED highly diverges. In a LASER diode, the operation of the device may be described by the formation of an electromagnetic standing wave within a cavity (called an optical resonator) which provides an output of monochromatic highly coherent radiation. This explanation on LASER  LED helps to compare the difference between LED and LASER diode. Here this article gives the information about the difference between LED and laser diode, to know more about LED and laser diode.

LED Diode :

  • LED stands for the light emitting diode.
  • LED is small size.
  • LED are longer life, reliable, require little power.
  • Coupling efficiency is very low.
  • Here generation photon by spontaneous emission.
  • Output power is linearly proportional to drive current.
  • LED's produce a divergent and non-coherent light beam.
  • Transmission distance is too much smaller and the response is so fast.
  • Cost is low.
  • The coupling efficiency of LED is very low.
  • A wide range of wavelengths is available, Wavelength is 0.66 to 1.65 micrometer.
  • Drive current for LED is to be maximum about 50 to 100 mA peak.
  • LED has required no extra circuit just because of it is a simple circuit.
  • The data rate is low.
  • Their response is fast.
  • LED's use with the multi-mode fibers.
  • The bandwidth of LED is moderate.
  • Light emitted of LED consist of various colors.
  • The junction area is wider when use LED. 
  • Two types of LED 1)Surface and 2)Edge emitter.
  • LED generally consider an eye shape.
  • Feedback is not required in LED.
LASER Diode :
  • A LASER  diode stands for light amplification by stimulated emission of radiation.
  • Laser's are bigger in size.
  • Laser are longer life, less reliable and also require more power compare LED type of diode.
  • Coupling efficiency is very high.
  • Here generating photon stimulated emission.
  • power is linearly proportional to the current above threshold.
  • The laser produces the monochromatic and coherent light beam.
  • Transmission distance is too much greater and also have the response is faster than LED.
  • Cost is high.
  • The coupling efficiency of the laser is very high compared to LED.
  • Wavelength range is 0.78 to 1.65 micrometer.
  • Require to drive current is Threshold current around - 5 to 40mA.
  • In a laser diode, it has to require an extra circuit for isolation of temperature reaction.
  • The data rate is high.
  • Their response faster than LED.
  • Laser use with single mode and multimode fiber.
  • The bandwidth of the LASER is higher.
  • While LASER consists of single colors.
  • In case of LASER junction area externally small.
  • Two types LASER one type of semiconductor LASER and other types of Gas LASER.
  • LASER must be rendered eye shape especially for ϒ = < 1400 nm 
  • Proper feedback is essential in a laser to treated as an optical source.
So in this above difference, we can conclude that LED and LASER both are generated light, but both diodes are different.

Explore more information:

  1. What are the advantages and disadvantages of laser diode