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Engineering Physics

Semiconductor Laser


Diode LASER is one of the effective lasers, its working is based on p-n junction diode. In general, p-n junction diode is made of by silicon or germanium crystals while LED and semiconductor LASER by GaAs or Ga As P material.

Silicon and germanium show the thermal properties when electron and hole recombination take place while in LED and semiconductor laser Ga As shows the optical properties for the same action. It means photon emit when one electron and hole recombination takes place.

Both n and p-type semiconductors are highly doped and normally represented by n+ and p+ .

The electron starts to flow from n-side conduction band to the p-side valence band. When they recombine in the depletion region a photon emits. The device remains in forwarding bias and the value of current decide the spontaneous or stimulated emission process. Below the threshold value of the current spontaneous emission dominates while beyond that stimulated emission.

The LED light is the result of spontaneous emission while semiconductor laser light is the result of stimulated emission. The forward biasing current determine the population inversion.


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  1. Tapas Sharma

    Nice informative video,Helps students to score good marks in engineering Physics

    1. Dr Sushil Kumar

      Thank you Tapas for your time and kind feedback.

  2. Dipin Gandhi

    A very instructive way of learning physics practically through experiments.

    1. Dr Sushil Kumar

      Thank you Dipin Gandhi, hope you are doing great at your end. Best wishes always.

  3. Shivang0308

    Great initiative

    1. Dr Sushil Kumar

      Thank you Shivang.
      best wishes always.

  4. Aashima Malhotra

    Excellent and very informative 👍

    1. Dr Sushil Kumar

      Thank you Ashima madam for your kind words.

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