Describe the operating principle of LASER diode with diagram.

Describe the operating principle of LASER diode with diagram.
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2 Answers

Answer :

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When the P-N junction of a laser diode is forward-biased by an external voltage source, electrons move across the junction and recombination occurs in the depletion region which results in the production of photons. As forward current is increased, more photons are produced which drift at random in the depletion region. Some of these photons strike the reflective surface perpendicularly. These reflected photons move back and forth between the two reflective surfaces. The photon activity becomes so intense that at some point, a strong beam of laser light comes out of the partially reflective surface of the diode.

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Answer :

Operating Principle:

There are three main processes in semiconductors that are associated with light:

Light absorption

Spontaneous emission

Stimulated emission

Stimulated emission is different. A light photon entering the semiconductor lattice will strike an electron and release energy in the form of another light photon.

The way in which this occurs releases this new photon of identical wavelength and phase. In this way the light that is generated is said to be coherent.

This type of process is the basic principle on which LASER Diode operates.

Photon, with energy equal to E2 – E1 interacts with an atom in upper energy state, causing it to return to lower energy state with the emission of a second photon.

Second photon has the same phase, frequency and polarization as the first.

It is stimulated emission which gives LASER special properties such as narrow spectral width and coherent output radiation. 

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