20 February 2018

Difference between spontaneous and stimulated emission

What is called spontaneous emission?

Spontaneous emission is electron drops from an excited state to a lower state. 

Example - emitting a photon.

What is called stimulated emission?

Stimulated emission is a photon of the same frequency that interacts with an electron in an excited state which drops to a lower state. The emitted photon is coherent with the incoming photon.

Example - Laser 

Let us have deep insight into the difference between spontaneous and stimulated emission to know more about this concept. 

Differences between spontaneous and stimulated emission :

  • Where quantum system undergoes a change and jumps to a lower energy state, emitting quanta of energy is called the spontaneous emission Whereas stimulated emission is the process where an external photon of a certain frequency, reacts with the excited electron in an atom and this results in dropping to lower energy state.
  • Spontaneous emission found in LEDs, Fluorescent tubes and stimulated emission found in laser it is the key process for the formation of a laser beam. 
  • There is no population inversion of electrons in LEDs in spontaneous emission whereas population inversion is achieved by various pumping techniques in stimulated emission. 
  • In spontaneous emission, external stimuli are not required and stimulated emission is caused by external stimuli. 
  • Spontaneous emission depends only on the upper level of the electron whereas stimulated emission depends upon the electron being in the upper level but the electron must be started at the upper level. 
  • Only one energy wave is released during spontaneous emission while two energy waves are released during stimulated emission. 
  • Spontaneous emission is the self-emission process of radioactive materials without any influence of radiation whereas a single particle or group of particles initiated emission in radioactive material is called stimulated emission.